Rupak Das, PhD

Rupak Das, PhD


Department of Human Oncology

I am a professor in the Department of Human Oncology with roles in the clinic, teaching and research. In the clinic, I focus primarily on treating cancer patients with brachytherapy and targeted therapy. This includes high-dose-rate brachytherapy treatment of breast, prostate and gyneocological patients and low-dose-rate brachytherapy of choroidal melanoma. I am also involved in using targeted therapies—TheraSphere to treat liver cancer and Xofigo to treat prostate cancer.

My research focuses on the advancement and technological implementation of applicators for the delivery of brachytherapy treatment to different sites and the implementation of imaging devices in implantation and dosimetry.

In addition to my clinical and research roles, I teach graduate students, medical students and residents in our department and in the UW School of Veterinary Medicine.


Resident, University of Florida, Radiation Oncology Physics (1997)

PhD, Ohio University, Nuclear Physics (1988)

MS, Calcutta University, Solid State and Electronics (1982)

BA/BS, Calcutta University, Physics Honors (1976)

Academic Appointments

Professor, Human Oncology, Medical Physics (2009)

Associate Professor, Human Oncology, Medical Physics (2003)

Assistant Professor, Human Oncology, Medical Physics (1997)

Selected Honors and Awards

Teacher of the Year Award, the Association of Residents in Radiation Oncology (2014)

Fellow, American Association of Physicists in Medicine (2010)

Best Paper Award, ClearPath & MammoSite Catheters: Optimal Breast Brachytherapy Technique Hybrid Approach, 12th International Conference, Optimal use of Advanced Radiotherapy in Multimodality Oncology, Rome, Italy (2007)

Teacher of the Year Award, the Association of Residents in Radiation Oncology (2002)

Resident's Training Grant, American Association of Physicists in Medicine Physics (2001)

Resident's Training Grant, American Association of Physicists in Medicine Physics (1999)

Scholars Program Grant, Radiological Society of North America (1998)

Junior Investigator Travel Award for the Annual American Physical Society Meeting, Baltimore, Md. (1986)

National Scholar, Calcutta University (1979)

Boards, Advisory Committees and Professional Organizations

Working group on Medical Physics Training Program (2011–2015)

Task Group on Operative Interstitial Lung Brachytherapy (2011–2012)

Chair, Task Group on Dosimetric Comparisons for Accelerated Partial Breast Irradiation, A Joint Task Group of American Association of Physicists in Medicine and American Brachytherapy Society (2008–2010)

Working Group on Practice Guidelines on Intensity Modulated Radiation Therapy, American Society of Therapeutic Radiation Oncology (2007–2010)

Working Group on Coordination of Medical Physics Residency Program, American Association of Physicists in Medicine (2007–2015)

Scientific Committee for Annual Meetings, American Brachytherapy Society (2007–2012)

Integrating the Health Care Enterprise- Radiation Oncology (IHE-RO) Committee, American Society of Therapeutic Radiation Oncology (2007-2011)

Awards Selection Committee, American Association of Physicists in Medicine (2007–2011)

Education and Training of Medical Physics Committee, American Association of Physicists in Medicine (200–2013)

Scientific Committee for Annual Meetings, American Society of Therapeutic Radiation Oncology (2005-2010)

Radiation Physics Committee, American Society of Therapeutic Radiation Oncology (2004-2011)

Scientific Committee for Annual Meetings, American Association of Physicists in Medicine (2003–2010)

Examiner, Oral Boards, American Board of Radiology (2002–2014)

Working Group (New Item Development) of American Board of Radiology (2000–2004)

High Energy Brachytherapy Dosimetry Committee, American Association of Physicists in Medicine, European Society of Therapeutic Radiation Oncology and The Canadian Organization of Medical Physicists (2003–2010)

Research Focus

Image-Guided Brachytherapy, Targeted Therapy with Unsealed Sources

  • Low cardiac and left anterior descending coronary artery dose achieved with left-sided multicatheter interstitial-accelerated partial breast irradiation. Brachytherapy
    Witt JS, Gao RW, Sudmeier LJ, Rosenberg SA, Francis DM, Wallace CR, Das RK, Anderson BM
    2019 Jan - Feb; 18 (1): 50-56
    • More

      PURPOSE: Studies have shown that an additional mean dose of 1 Gy to the heart can increase the relative risk of cardiac events. The purpose of this study was to quantify the dose delivered to the heart and left anterior descending artery (LAD) in a series of patients with left-sided breast cancer (BC) or ductal carcinoma in situ treated with multicatheter-accelerated partial breast irradiation (MC-APBI) at a single institution.

      METHODS AND MATERIALS: Patients with left-sided BC or ductal carcinoma in situ treated consecutively from 2005 to 2011 with MC-APBI were retrospectively identified. Cardiac and LAD contours were generated for each patient. Cardiac dosimetry and distance to the planning target volume were recorded. Patient health records were reviewed and cardiac events were recorded based on Common Terminology Criteria for Adverse Events version 4.0.

      RESULTS: Twenty consecutive patients with left-sided BC treated with MC-APBI were retrospectively identified. Median followup was 41.4 months. Mean equivalent dose in 2 Gy fractions delivered to the heart and LAD were 1.3 (standard deviation: 0.7, range: 0.2-2.9) and 3.8 (standard deviation: 3.0, range: 0.4-11.3) Gy, respectively. There was an inverse linear relationship (R2 = 0.52) between heart-to-lumpectomy cavity distance and mean heart equivalent dose in 2 Gy fractions. One patient (5%) experienced symptomatic cardiac toxicity.

      CONCLUSIONS: MC-APBI consistently delivers average doses to the heart and LAD that are similar to those achieved in most series with deep inspiration breath-hold and lower than free-breathing radiotherapy techniques. Distance from the heart to the lumpectomy cavity and the availability of other heart-sparing technologies should be considered to minimize the risk of cardiac toxicity.

      View details for PubMedID 30262411
  • Novel use of ViewRay MRI guidance for high-dose-rate brachytherapy in the treatment of cervical cancer. Brachytherapy
    Ko HC, Huang JY, Miller JR, Das RK, Wallace CR, De Costa AA, Francis DM, Straub MR, Anderson BM, Bradley KA
    2018 Jul - Aug; 17 (4): 680-688
    • More

      PURPOSE: To characterize image quality and feasibility of using ViewRay MRI (VR)-guided brachytherapy planning for cervical cancer.

      METHODS AND MATERIALS: Cervical cancer patients receiving intracavitary brachytherapy with tandem and ovoids, planned using 0.35T VR MRI at our institution, were included in this series. The high-risk clinical target volume (HR-CTV), visible gross tumor volume, bladder, sigmoid, bowel, and rectum contours for each fraction of brachytherapy were evaluated for dosimetric parameters. Typically, five brachytherapy treatments were planned using the T2 sequence on diagnostic MRI for the first and third fractions, and a noncontrast true fast imaging with steady-state precession sequence on VR or CT scan for the remaining fractions. Most patients received 5.5 Gy × 5 fractions using high-dose-rate Ir-192 following 45 Gy of whole-pelvis radiotherapy. The plan was initiated at 5.5 Gy to point A and subsequently optimized and prescribed to the HR-CTV. The goal equivalent dose in 2 Gy fractions for the combined external beam and brachytherapy dose was 85 Gy. Soft-tissue visualization using contrast-to-noise ratios to distinguish normal tissues from tumor at their interface was compared between diagnostic MRI, CT, and VR.

      RESULTS: One hundred and forty-two fractions of intracavitary brachytherapy were performed from April 2015 to January 2017 on 29 cervical cancer patients, ranging from stages IB1 to IVA. The median HR-CTV was 27.78 cc, with median D90 HR-CTV of 6.1 Gy. The median time from instrument placement to start of treatment using VR was 65 min (scan time 2 min), compared to 105 min using diagnostic MRI (scan time 11 min) (t-test, p < 0.01). The contrast-to-noise ratio of tumor to cervix in both diagnostic MRI and VR had significantly higher values compared to CT (ANOVA and t-tests, p < 0.01).

      CONCLUSIONS: We report the first clinical use of VR-guided brachytherapy. Time to treatment using this approach was shorter compared to diagnostic MRI. VR also provided significant advantage in visualizing the tumor and cervix compared to CT. This presents a feasible and reliable manner to image and plan gynecologic brachytherapy.

      View details for PubMedID 29773331
  • Clinical implementation of a novel Double-Balloon single-entry breast brachytherapy applicator. Brachytherapy
    Anderson BM, Wallace CR, De Costa AA, Das RK
    2017 Nov - Dec; 16 (6): 1239-1245
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      PURPOSE: The purpose of the study was to describe the clinical utilization of a novel Double-Balloon applicator for accelerated partial breast irradiation (APBI).

      METHODS AND MATERIALS: The Double-Balloon single-entry breast applicator contains a single central treatment catheter, as well as four peripheral catheters that can be differentially loaded to customize radiation dose coverage. An inner balloon is filled with up to 7-30 cm3 of saline to increase separation between the peripheral catheters, and an outer balloon is filled with up to 37-115 cm3 of saline to displace breast tissue from the peripheral catheters. Treatment planning objectives include coverage of the breast planning target volume to a minimum of V90 > 90%, limiting dose heterogeneity such that V200 < 10 cm3 and V150 < 50 cm3, and limiting maximum dose to skin (<100% of prescription dose) and ribs (<145% of prescription dose).

      RESULTS: High-dose-rate APBI was delivered to 11 women using this device (34 Gy in 10 twice daily fractions). The mean V90 was 98.2% (range 94.2-99.4%). The mean skin Dmax with the Double-Balloon applicator was 83.3% (range 75.6-99.5%). The mean breast V200 was 5.8 cm3 (range 2.3-10.2 cm3), and the mean breast V150 was 32.9 cm3 (range 25.0-41.7 cm3). Pretreatment quality assurance was performed using CT prior to each morning fraction and ultrasound prior to each afternoon fraction.

      CONCLUSIONS: The Double-Balloon applicator can be easily introduced into a previously existing brachytherapy program. APBI plans created with this applicator achieve excellent planning target volume coverage, while limiting skin dose and maintaining breast V200 < 10 cm3.

      View details for PubMedID 28844820
  • Simulation study of high-dose-rate brachytherapy for early glottic cancer. Brachytherapy
    Hoffman MR, McCulloch TM, Mohindra P, Das R, Geurts M, Harari PM
    2016 Jan-Feb; 15 (1): 94-101
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      PURPOSE: External beam radiation therapy (EBRT) is effective for early glottic cancers, with cure rates of ∼90% for T1 tumors. EBRT has strengths but also disadvantages including radiation to healthy tissues and duration of 5-7 weeks. With advances in laryngeal framework surgery, new devices can provide reliable, minimally invasive access to the larynx. Such devices could be modified to insert brachytherapy catheters. Brachytherapy could provide focused radiation while limiting dose to normal structures in the larynx and neck. As a preliminary step, we performed simulations comparing EBRT to high-dose-rate brachytherapy to assess if this approach could provide dosimetric advantage.

      METHODS AND MATERIALS: One- and 2-catheter brachytherapy simulations were performed for 3 patients with T1 glottic carcinoma. Percentage of dose delivered to the target and adjacent structures was compared with conventional EBRT using 3D and intensity-modulated radiation therapy approaches.

      RESULTS: Percentage of structures exposed to 50% of the dose was lower for brachytherapy compared with 3D EBRT and intensity-modulated radiation therapy, particularly for the cricoid and contralateral arytenoid. Dose was also lower for the carotid-internal jugular vein complexes compared with 3D EBRT. Dose profiles did not differ significantly between 1- and 2-catheter simulations.

      CONCLUSION: Brachytherapy can decrease radiation to normal tissues including laryngeal cartilages and carotid-internal jugular vein complexes. Recent advancements allowing catheter placement may afford the potential to decrease radiation to healthy tissues with decreased treatment time. However, careful, stepwise evaluation of feasibility and outcomes in model systems is required before recommending this approach for such high cure rate cancers in humans.

      View details for PubMedID 26614234
  • Essentials and guidelines for clinical medical physics residency training programs: executive summary of AAPM Report Number 249. J Appl Clin Med Phys
    Prisciandaro JI, Willis CE, Burmeister JW, Clarke GD, Das RK, Esthappan J, Gerbi BJ, Harkness BA, Patton JA, Peck DJ, Pizzutiello RJ, Sandison GA, White SL, Wichman BD, Ibbott GS, Both S
    2014 May 08; 15 (3): 4763
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      There is a clear need for established standards for medical physics residency training. The complexity of techniques in imaging, nuclear medicine, and radiation oncology continues to increase with each passing year. It is therefore imperative that training requirements and competencies are routinely reviewed and updated to reflect the changing environment in hospitals and clinics across the country. In 2010, the AAPM Work Group on Periodic Review of Medical Physics Residency Training was formed and charged with updating AAPM Report Number 90. This work group includes AAPM members with extensive experience in clinical, professional, and educational aspects of medical physics. The resulting report, AAPM Report Number 249, concentrates on the clinical and professional knowledge needed to function independently as a practicing medical physicist in the areas of radiation oncology, imaging, and nuclear medicine, and constitutes a revision to AAPM Report Number 90. This manuscript presents an executive summary of AAPM Report Number 249.

      View details for PubMedID 24892354
  • Cervical brachytherapy technique for locally advanced carcinoma of the cervix in a patient with septate uterus. J Contemp Brachytherapy
    Platta CS, Wallace C, Gondi V, Das R, Straub M, Al-Niaimi A, Applegate G, Bradley KA
    2014 Mar; 6 (1): 76-81
    • More

      PURPOSE: To describe an approach to cervical brachytherapy in a patient with congenital septate uterus and locally advanced cervical carcinoma.

      MATERIAL AND METHODS: The patient is a 34-year-old female with septate uterus presenting with pelvic pain. Workup demonstrated a stage IIB cervical adenocarcinoma with imaging evidence of an involved right external iliac lymph node. The patient received whole pelvic radiation, with concurrent weekly cisplatin (40 mg/m(2)), to a dose of 45 Gy in 25 fractions followed by a parametrial boost of 5.4 Gy and an additional nodal boost of 9 Gy.

      RESULTS: The patient was initiated on cervical brachytherapy following fraction 23 of pelvic radiation. To conform to her septated uterus, a Rotte-Y tandem was used. Additionally, 2 CT-compatible ovoids were placed in the vaginal apex to enhance dose distribution and coverage of the target volume. Each fraction of brachytherapy was performed with CT-based planning. A high-risk clinical target volume (HR-CTV) and normal structures were defined and constrained per American Brachytherapy Society (ABS) and Groupe Européen de Curiethérapie/European Society for Therapeutic Radiology and Oncology (GEC-ESTRO) guidelines. The brachytherapy dose was 27.5 Gy in 5 fractions of 5.5 Gy each, prescribed to the HR-CTV.

      CONCLUSIONS: Herein, we report the first documented case of cervical brachytherapy in a patient with septate uterus and locally advanced cervical carcinoma. Using CT-guided planning, in conjunction with the ABS and GEC-ESTRO guidelines, the patient was effectively treated with adapted cervical brachytherapy, meeting criteria for HR-CTV coverage and normal tissue tolerances.

      View details for PubMedID 24790625
  • Adjuvant and definitive radiation therapy for primary carcinoma of the vagina using brachytherapy and external beam radiation therapy. J Contemp Brachytherapy
    Platta CS, Anderson B, Geye H, Das R, Straub M, Bradley K
    2013 Jun; 5 (2): 76-82
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      PURPOSE: To report the outcomes of patients receiving vaginal brachytherapy and/or external beam radiation therapy (EBRT) for primary vaginal cancer.

      MATERIAL AND METHODS: Between 1983 and 2009, 63 patients received brachytherapy and/or EBRT for primary tumors of the vagina at a single tertiary center. Patient data was collected via chart review. The Kaplan-Meier method was used to calculate actuarial pelvic local control (LC), disease-free survival (DFS), overall survival (OS), and severe late toxicity rates. Acute and late toxicities were scored according to the Common Terminology Criteria for Adverse Events version 3 (CTCAE v3.0).

      RESULTS: Median follow up was 44.2 months. Patients with early stage disease (stages I and II) had significantly improved 5-year OS when compared to patients with locally advanced disease (stages III and IVA) (73.3 vs. 34.4%, p = 0.032). Patients with greater than 1/3 vaginal involvement had significantly worse prognosis than patients with tumors involving 1/3 or less of the vagina, with the later having superior DFS (84.0 vs. 52.4%, p = 0.007) and LC (86.9 vs. 60.4%, p = 0.018) at 5-years. Age, histology, and brachytherapy technique did not impact treatment outcomes. The 5-year actuarial grade 3 or higher toxicity rate was 23.1% (95% CI: 10.6-35.6%). Concurrent chemotherapy had no impact on outcomes or toxicity in this analysis.

      CONCLUSIONS: Success of treatment for vaginal cancer depends primarily on disease stage, but other contributing factors such as extent of vaginal involvement and tumor location significantly impact outcomes. Treatment of vaginal cancer with primary radiotherapy yields acceptable results with reasonable toxicity rates. Management of this rare malignancy requires a multidisciplinary approach to appropriately optimize therapy.

      View details for PubMedID 23878551
  • Locoregional recurrence following accelerated partial breast irradiation for early-stage invasive breast cancer: significance of estrogen receptor status and other pathological variables. Ann Surg Oncol
    Cannon DM, McHaffie DR, Patel RR, Adkison JB, Das RK, Anderson BD, Geye HM, Bentzen SM, Cannon GM
    2013 Oct; 20 (11): 3446-52
    • More

      BACKGROUND: Understanding risk factors for locoregional recurrence (LRR) after accelerated partial breast irradiation (APBI) can help to guide patient selection for treatment with APBI. Published findings to date have not been consistent. More data are needed as these risk factors continue to be defined.

      METHODS: A total of 277 women with early-stage invasive breast cancer underwent lumpectomy and were treated adjuvantly at our institution with APBI using high-dose rate brachytherapy. APBI was delivered using multicatheter interstitial brachytherapy (91 %) or single-entry catheter brachytherapy (9 %) to a dose of 32-34 Gy in 8-10 twice daily fractions. Failure patterns and risk factors for recurrence were analyzed.

      RESULTS: With a median follow-up of 61 months, the 5-year locoregional control rate was 94.4 %. Negative estrogen receptor (ER) status was strongly associated with LRR on multivariate analysis (p < 0.005). Lobular histology, the presence of an extensive intraductal component, and lymphovascular invasion also were significant but to a lesser degree than ER-negative status. Patients with multiple risk factors were at highest risk for LRR. Age was not significantly associated with increased risk for LRR.

      CONCLUSIONS: The presence of specific pathological features, particularly ER negative status, was associated with increased risk of LRR in this cohort of women treated with APBI. Further investigation is warranted to determine whether patients with adverse pathological risk factors are at higher risk of LRR after APBI than after conventional whole breast irradiation (WBI), as these same features also may place women at risk for LRR after WBI.

      View details for PubMedID 23709055
  • Dose calculation for photon-emitting brachytherapy sources with average energy higher than 50 keV: report of the AAPM and ESTRO. Med Phys
    Perez-Calatayud J, Ballester F, Das RK, Dewerd LA, Ibbott GS, Meigooni AS, Ouhib Z, Rivard MJ, Sloboda RS, Williamson JF
    2012 May; 39 (5): 2904-29
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      PURPOSE: Recommendations of the American Association of Physicists in Medicine (AAPM) and the European Society for Radiotherapy and Oncology (ESTRO) on dose calculations for high-energy (average energy higher than 50 keV) photon-emitting brachytherapy sources are presented, including the physical characteristics of specific (192)Ir, (137)Cs, and (60)Co source models.

      METHODS: This report has been prepared by the High Energy Brachytherapy Source Dosimetry (HEBD) Working Group. This report includes considerations in the application of the TG-43U1 formalism to high-energy photon-emitting sources with particular attention to phantom size effects, interpolation accuracy dependence on dose calculation grid size, and dosimetry parameter dependence on source active length.

      RESULTS: Consensus datasets for commercially available high-energy photon sources are provided, along with recommended methods for evaluating these datasets. Recommendations on dosimetry characterization methods, mainly using experimental procedures and Monte Carlo, are established and discussed. Also included are methodological recommendations on detector choice, detector energy response characterization and phantom materials, and measurement specification methodology. Uncertainty analyses are discussed and recommendations for high-energy sources without consensus datasets are given.

      CONCLUSIONS: Recommended consensus datasets for high-energy sources have been derived for sources that were commercially available as of January 2010. Data are presented according to the AAPM TG-43U1 formalism, with modified interpolation and extrapolation techniques of the AAPM TG-43U1S1 report for the 2D anisotropy function and radial dose function.

      View details for PubMedID 22559663
  • Outcomes after accelerated partial breast irradiation in patients with ASTRO consensus statement cautionary features. Int J Radiat Oncol Biol Phys
    McHaffie DR, Patel RR, Adkison JB, Das RK, Geye HM, Cannon GM
    2011 Sep 01; 81 (1): 46-51
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      PURPOSE: To evaluate outcomes among women with American Society for Radiation Oncology (ASTRO) consensus statement cautionary features treated with brachytherapy-based accelerated partial breast irradiation (APBI).

      METHODS AND MATERIALS: Between March 2001 and June 2006, 322 consecutive patients were treated with high-dose-rate (HDR) APBI at the University of Wisconsin. A total of 136 patients were identified who met the ASTRO cautionary criteria. Thirty-eight (27.9%) patients possessed multiple cautionary factors. All patients received 32 to 34 Gy in 8 to 10 twice-daily fractions using multicatheter (93.4%) or Mammosite balloon (6.6%) brachytherapy.

      RESULTS: With a median follow-up of 60 months, there were 5 ipsilateral breast tumor recurrences (IBTR), three local, and two loco-regional. The 5-year actuarial rate of IBTR was 4.8%±4.1%. The 5-year disease-free survival was 89.6%, with a cause-specific survival and overall survival of 97.6% and 95.3%, respectively. There were no IBTRs among 32 patients with ductal carcinoma in situ (DCIS) vs. 6.1% for patients with invasive carcinoma (p=0.24). Among 104 patients with Stage I or II invasive carcinoma, the IBTR rate for patients considered cautionary because of age alone was 0% vs. 12.7% in those deemed cautionary due to histopathologic factors (p=0.018).

      CONCLUSIONS: Overall, we observed few local recurrences among patients with cautionary features. Women with DCIS and patients 50 to 59 years of age with Stage I/II disease who otherwise meet the criteria for suitability appear to be at a low risk of IBTR. Patients with tumor-related cautionary features will benefit from careful patient selection.

      View details for PubMedID 20732760
  • Point/counterpoint. Most residency programs for radiation oncology physicists do not reflect the heightened importance of medical imaging. Med Phys
    Zhu XR, Das RK, Orton CG
    2010 May; 37 (5): 1939-41
  • American Society of Radiation Oncology recommendations for documenting intensity-modulated radiation therapy treatments. Int J Radiat Oncol Biol Phys
    IMRT Documentation Working Group, Holmes T, Das R, Low D, Yin FF, Balter J, Palta J, Eifel P, FASTRO
    2009 Aug 01; 74 (5): 1311-8
    • More

      Despite the widespread use of intensity-modulated radiation therapy (IMRT) for approximately a decade, a lack of adequate guidelines for documenting these treatments persists. Proper IMRT treatment documentation is necessary for accurate reconstruction of prior treatments when a patient presents with a marginal recurrence. This is especially crucial when the follow-up care is managed at a second treatment facility not involved in the initial IMRT treatment. To address this issue, an American Society for Radiation Oncology (ASTRO) workgroup within the American ASTRO Radiation Physics Committee was formed at the request of the ASTRO Research Council to develop a set of recommendations for documenting IMRT treatments. This document provides a set of comprehensive recommendations for documenting IMRT treatments, as well as image-guidance procedures, with example forms provided.

      View details for PubMedID 19616738
  • A dosimetric comparison of MammoSite and ClearPath high-dose-rate breast brachytherapy devices. Brachytherapy
    Dickler A, Seif N, Kirk MC, Patel MB, Bernard D, Coon A, Dowlatshahi K, Das RK, Patel RR
    2009 Jan-Mar; 8 (1): 14-8
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      PURPOSE: A new form of partial breast irradiation (PBI), ClearPath (CP) breast brachytherapy, has been introduced. We present our results of a dosimetric comparison of MammoSite (MS) and CP PBI.

      METHODS AND MATERIALS: The dimensions of the CP device were reconstructed onto the MS planning CT scans for 15 previously treated patients. The mean %V(100), %V(150), %V(200) (percent of the PTV that received 100%, 150%, and 200% of the prescription dose, respectively), ipsilateral breast %V(50) (percent of the ipsilateral normal breast that received 50% of the prescription dose), ipsilateral lung %V(30) (percent of the ipsilateral lung that received 30% of the prescription dose), the heart %V(5) (percent of the heart that received 5% of the prescription dose), and the maximum skin point dose per fraction were then determined for each patient using the two methods of balloon-based PBI.

      RESULTS: The mean %V(100) was 96.5% vs. 96.5%, the mean %V(150) was 42.1% vs. 42.9% (p=ns), and the mean V(200) was 11.4% vs. 15.2% (p<.05) for the MS and CP methods, respectively. The mean ipsilateral breast %V(50) was 19.8% vs.18.0% (p<.05), the mean ipsilateral lung %V(30) was 3.7% vs. 2.8% (p<.05), the mean heart %V(5) was 57.0% vs. 54.3% (p<.05), and the maximum skin point dose per fraction was 312.2 and 273.6cGy (p<.05) for the MS and CP methods, respectively.

      CONCLUSIONS: The MS and CP methods of PBI offer comparable target volume coverage; however, the CP device achieves increased normal tissue sparing.

      View details for PubMedID 18955018
  • Multicatheter hybrid breast brachytherapy: a potential alternative for patients with inadequate skin distance. Brachytherapy
    Beriwal S, Coon D, Kim H, Haley M, Patel R, Das R
    2008 Oct-Dec; 7 (4): 301-4
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      PURPOSE: The purpose of this study was to determine whether the ClearPath (CP) multicatheter hybrid device was able to achieve acceptable dosimetry in patients in whom the proximity of the breast surgical cavity to the skin precluded treatment with intracavitary MammoSite (MS) brachytherapy.

      METHODS AND MATERIALS: The study consisted of 11 patients who had the MS catheter placed and who were subsequently not treated due to inadequate skin distance. A phantom scan of the CP multicatheter hybrid device was superimposed on the MS CT scan and a dosimetric comparison was performed.

      RESULTS: The median MS balloon size, diameter, and minimum skin distance were 40 cc, 4.1cm, and 5mm, respectively. The D(90), V(100), V(150), and V(200) with MS vs. CP were 95.29% vs. 97.06%, 88.8% vs. 91.3%, 35.7% vs. 38.0%, and 9.4% vs. 9.6%, respectively. The median maximum skin dose was 5.5 Gy vs. 3.9 Gy (p <.0001). The median dose homogeneity index (DHI) was 0.60 vs. 0.59 (p=.09). The median maximum rib, heart, and lung dose were 2.17 Gy vs. 2.18 Gy, 2.17 Gy vs. 2.18 Gy, and 0.50 Gy vs. 0.56 Gy, respectively.

      CONCLUSION: The hybrid CP catheter reduced the skin dose significantly without compromising the planning target volume coverage, DHI, or dose to other critical organs. The use of this device has the potential to increase the applicability of accelerated partial breast brachytherapy (APBI) in patients with a surgical cavity close to skin compared with balloon brachytherapy.

      View details for PubMedID 18771962
  • Clinical outcome analysis in "high-risk" versus "low-risk" patients eligible for national surgical adjuvant breast and bowel B-39/radiation therapy oncology group 0413 trial: five-year results. Int J Radiat Oncol Biol Phys
    Patel RR, Christensen ME, Hodge CW, Adkison JB, Das RK
    2008 Mar 15; 70 (4): 970-3
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      PURPOSE: To report the local control and overall survival outcomes after lumpectomy followed by accelerated partial breast irradiation in high-risk patients as defined by the current inclusion criteria for the National Surgical Adjuvant Breast and Bowel B-39/Radiation Therapy Oncology Group 0413 Intergroup trial.

      METHODS AND MATERIALS: Between 2000 and 2005, 273 women with early-stage breast cancer were treated using either multicatheter interstitial brachytherapy (n=247) or MammoSite (n=26). Patients received 32-34 Gy in 8-10 twice-daily fractions using high-dose-rate 192Ir brachytherapy. All patients met the initial inclusion criteria for the Intergroup trial and were separated into two groups: high-risk patients (representing the cohort that remained eligible for the Intergroup trial) who satisfied one or more of the "high-risk" criteria (age<50 years, estrogen receptor negative, and/or positive lymph nodes; n=90), and low-risk patients who comprised the remainder of the cohort (n=183). The outcomes of the two cohorts were analyzed and compared.

      RESULTS: The median follow-up of the entire cohort was 48.5 months. No significant difference was found in outcomes at 5 years between the low- and high-risk groups, with a local control rate of 97.8% vs. 93.6%, crude local recurrence rate of 2.2% (n=4) vs. 4.4% (n=4), and overall survival rate of 92.1% vs. 89.5%, respectively.

      CONCLUSION: At 5 years, no statistically significant difference was found in outcomes for patients deemed to be at greater risk in the current National Surgical Adjuvant Breast and Bowel B-39/Radiation Therapy Oncology Group 0413 Intergroup trial. These clinical data support the inclusion of this "high-risk" population in this important ongoing study.

      View details for PubMedID 18313521
  • A dosimetric comparison of accelerated partial breast irradiation techniques: multicatheter interstitial brachytherapy, three-dimensional conformal radiotherapy, and supine versus prone helical tomotherapy. Int J Radiat Oncol Biol Phys
    Patel RR, Becker SJ, Das RK, Mackie TR
    2007 Jul 01; 68 (3): 935-42
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      PURPOSE: To compare dosimetrically four different techniques of accelerated partial breast irradiation (APBI) in the same patient.

      METHODS AND MATERIALS: Thirteen post-lumpectomy interstitial brachytherapy (IB) patients underwent imaging with preimplant computed tomography (CT) in the prone and supine position. These CT scans were then used to generate three-dimensional conformal radiotherapy (3D-CRT) and prone and supine helical tomotherapy (PT and ST, respectively) APBI plans and compared with the treated IB plans. Dose-volume histogram analysis and the mean dose (NTD(mean)) values were compared.

      RESULTS: Planning target volume coverage was excellent for all methods. Statistical significance was considered to be a p value <0.05. The mean V100 was significantly lower for IB (12% vs. 15% for PT, 18% for ST, and 26% for 3D-CRT). A greater significant differential was seen when comparing V50 with mean values of 24%, 43%, 47%, and 52% for IB, PT, ST, and 3D-CRT, respectively. The IB and PT were similar and delivered an average lung NTD(mean) dose of 1.3 Gy(3) and 1.2 Gy(3), respectively. Both of these methods were statistically significantly lower than the supine external beam techniques. Overall, all four methods yielded similar low doses to the heart.

      CONCLUSIONS: The use of IB and PT resulted in greater normal tissue sparing (especially ipsilateral breast and lung) than the use of supine external beam techniques of 3D-CRT or ST. However, the choice of APBI technique must be tailored to the patient's anatomy, lumpectomy cavity location, and overall treatment goals.

      View details for PubMedID 17467923
  • Dosimetric prerequisites for routine clinical use of photon emitting brachytherapy sources with average energy higher than 50 kev. Med Phys
    Li Z, Das RK, DeWerd LA, Ibbott GS, Meigooni AS, Pérez-Calatayud J, Rivard MJ, Sloboda RS, Williamson JF, American Association of Physicists in Medicine (AAPM), European Society for Therapeutic Radiology and Oncology (ESTRO)
    2007 Jan; 34 (1): 37-40
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      This paper presents the recommendations of the American Association of Physicists in Medicine (AAPM) and the European Society for Therapeutic Radiology and Oncology (ESTRO) on the dosimetric parameters to be characterized, and dosimetric studies to be performed to obtain them, for brachytherapy sources with average energy higher than 50 keV that are intended for routine clinical use. In addition, this document makes recommendations on procedures to be used to maintain vendor source strength calibration accuracy. These recommendations reflect the guidance of the AAPM and the ESTRO for its members, and may also be used as guidance to vendors and regulatory agencies in developing good manufacturing practices for sources used in routine clinical treatments.

      View details for PubMedID 17278487
  • Image-guided breast brachytherapy: an alternative to whole-breast radiotherapy. Lancet Oncol
    Patel RR, Das RK
    2006 May; 7 (5): 407-15
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      Lumpectomy and whole-breast radiotherapy (ie, breast-conservation treatment) are accepted as viable alternatives to mastectomy in locoregional management of breast cancer. These techniques are used to keep morbidity to a minimum, optimise cosmesis, and maintain treatment outcomes. Pathological and clinical data suggest that most recurrences of cancer in the ipsilateral breast are in the vicinity of the index lesion, and that remote recurrences are uncommon, whether or not whole-breast radiotherapy is delivered. These data lend support to the idea of partial-breast radiotherapy. Such a restricted treatment volume allows safe delivery of an accelerated hypofractionated regimen over a shortened course of 1 week. This technique differs from that of standard whole-breast tangential external-beam radiotherapy and necessitates investigation of accelerated partial-breast irradiation (APBI). Several techniques of APBI are being investigated; however, most experience, and the most favourable early outcomes, has been obtained with image-guided breast brachytherapy. This review highlights the rationale and outcomes of brachytherapy techniques.

      View details for PubMedID 16648045
  • Quality assurance of treatment plans for interstitial and intracavitary high-dose-rate brachytherapy. Brachytherapy
    Das RK, Bradley KA, Nelson IA, Patel R, Thomadsen BR
    2006 Jan-Mar; 5 (1): 56-60
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      PURPOSE: Quality assurance for complex high-dose-rate (HDR) treatment planning has always been a challenge to the physics community because of the time constraint between HDR planning and the delivery of the treatment. This study proposes an efficient, precise, and easy method for checking the complex computer calculation.

      METHODS AND MATERIALS: Posttreatment, three-dimensional dose-volume study was performed for 98 patients with 128 new treatment plans along with 30 library plans. Volumes covered by the 100% isodose line, source activity (Ci), total dwell time (s), and the prescription dose (100%) were recorded. Variation of R(V) defined as (irradiated time x activity/elongation factor x prescribed dose) with volume was studied for different catheter systems.

      RESULTS: Parametric fit of R(V) with volume for three different systems that cover most of the interstitial and intracavitary brachytherapy implants agrees within +/-6%.

      CONCLUSIONS: The excellent agreement of R(V) derived from this simplistic point source model with three-dimensional dose calculations for individual HDR treatment plans clearly establishes that for an implant with known number of catheters, the time needed to deliver a prescribed dose to a given prescription volume can be easily predicted.

      View details for PubMedID 16563998
  • Optimization of conformal avoidance: a comparative study of prone vs. supine interstitial high-dose-rate breast brachytherapy. Brachytherapy
    Hui SK, Das RK
    2005; 4 (2): 137-40
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      PURPOSE: Several recent studies indicate high-dose-rate (HDR) breast brachytherapy as an alternative to standard external beam radiation therapy for partial breast irradiation with high dose conformality to the target. However, this article presents an exploration of the possibility of achieving higher conformal avoidance of sensitive structures through detailed and comparative 3D CT-based anatomical dose distribution of a patient in supine and prone positions.

      METHODS AND MATERIALS: A patient treated with accelerated partial breast HDR breast brachytherapy in the supine position was selected for two CT-based analyses, one in the supine and one in the prone position. The optimized plan (Nucletron HDR planning station) for each position was achieved using graphical optimization with local adjustment of isodose lines to cover the planned target volume (PTV, lumpectomy with 2 cm margin) with 100% of the prescribed dose (34 Gy in 10 fractions) while minimizing the hot spots. Cumulative dose-volume histograms (DVH) were analyzed for the PTV, lung, skin, pectoral muscle, and chest wall.

      RESULTS: The PTV received 100% of prescribed dose in both the prone and supine positions. A significant (>40%) dose reduction was achieved in the lung in the prone treatment position. Similar dose reductions were also achieved for prone pectoral muscle, chest wall, and breast skin, irradiating less volume with high doses. Pectoral muscle, lumpectomy, and the breast skin showed prominent differences in shape and displacement in the prone compared with the supine position.

      CONCLUSION: CT-based treatment planning allowed calculations of volumetric dose distribution to the target and all sensitive structures with proper visualization and volumetric delineation of organs of interest. The treatment plan shows significant dose reduction may be possible in various sensitive structures if the patient is treated with HDR brachytherapy in the prone position.

      View details for PubMedID 15893267
  • Helical tomotherapy as a means of delivering accelerated partial breast irradiation. Technol Cancer Res Treat
    Hui SK, Das RK, Kapatoes J, Oliviera G, Becker S, Odau H, Fenwick JD, Patel R, Kuske R, Mehta M, Paliwal B, Mackie TR, Fowler JF, Welsh JS
    2004 Dec; 3 (6): 639-46
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      A novel treatment approach utilizing helical tomotherapy for partial breast irradiation for patients with early-stage breast cancer is described. This technique may serve as an alternative to high dose-rate (HDR) interstitial brachytherapy and standard linac-based approaches. Through helical tomotherapy, highly conformal irradiation of target volumes and avoidance of normal sensitive structures can be achieved. Unlike HDR brachytherapy, it is noninvasive. Unlike other linac-based techniques, it provides image-guided adaptive radiotherapy along with intensity modulation. A treatment planning CT scan was obtained as usual on a post-lumpectomy patient undergoing HDR interstitial breast brachytherapy. The patient underwent catheter placement for HDR treatment and was positioned prone on a specially designed position-supporting mattress during CT. The planning target volume (PTV) was defined as the lumpectomy bed plus a 20 mm margin. The prescription dose was 34 Gy (10 fx of 3.4 Gy) in both the CT based HDR and on the tomotherapy plan. Cumulative dose-volume histograms (DVHs) were generated and analyzed for the target, lung, heart, skin, pectoralis muscle, and chest wall for both HDR brachytherapy and helical tomotherapy. Dosimetric coverage of the target with helical tomotherapy was conformal and homogeneous. "Hot spots" (> or =150% isodose line) were present around implanted dwell positions in brachytherapy plan whereas no isodose lines higher than 109% were present in the helical tomotherapy plan. Similar dose coverage was achieved for lung, pectoralis muscle, heart, chest wall and breast skin with the two methods. We also compared our results to that obtained using conventional linac-based three dimensional (3D) conformal accelerated partial breast irradiation. Dose homogeneity is excellent with 3D conformal irradiation, and lung, heart and chest wall dose is less than for either HDR brachytherapy or helical tomotherapy but skin and pectoral muscle doses were higher than with the other techniques. Our results suggest that helical tomotherapy can serve as an effective means of delivering accelerated partial breast irradiation and may offer superior dose homogeneity compared to HDR brachytherapy.

      View details for PubMedID 15560722
  • 3D CT-based high-dose-rate breast brachytherapy implants: treatment planning and quality assurance. Int J Radiat Oncol Biol Phys
    Das RK, Patel R, Shah H, Odau H, Kuske RR
    2004 Jul 15; 59 (4): 1224-8
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      PURPOSE: Although accelerated partial breast irradiation (APBI) as the sole radiation modality after lumpectomy has shown promising results for select breast cancer patients, published experiences thus far have provided limited information on treatment planning methodology and quality assurance measures. A novel three-dimensional computed tomography (CT)-based treatment planning method for accurate delineation and geometric coverage of the target volume is presented. A correlation between treatment volume and irradiation time has also been studied for quality assurance purposes.

      METHODS AND MATERIALS: Between May 2002 and January 2003, 50 consecutive patients underwent an image-guided interstitial implant followed by CT-based treatment planning and were subsequently treated with APBI with a high-dose-rate (HDR) brachytherapy remote afterloader. Target volume was defined as the lumpectomy cavity +2 cm margin modified to >/=5 mm to the skin surface. Catheter reconstruction, geometric optimization, and manual adjustment of irradiation time were done to optimally cover the target volume while minimizing hot spots. Dose homogeneity index (DHI) and percent of target volume receiving 100% of the prescription dose (32 Gy in 8 fractions or 34 Gy in 10 fractions) was determined. Additionally, the correlation between the treatment volume and irradiation time, source strength, and dose was then analyzed for manual verification of the HDR computer calculation.

      RESULTS: In all cases, the lumpectomy cavity was covered 100%. Target volume coverage was excellent with a median of 96%, and DHI had a median value of 0.7. For each plan, source strength times the treatment time for every unit of prescribed dose had an excellent agreement of +/-7% to the Manchester volume implant table corrected for modern units.

      CONCLUSIONS: CT-based treatment planning allowed excellent visualization of the lumpectomy cavity and normal structures, thereby improving target volume delineation and optimal coverage, relative to conventional orthogonal film dosimetry. Using the Manchester volume implant table calculated irradiation time can be used as quality assurance for the HDR computed time. Thus dosimetric quality assurance and adequate target volume coverage can be concurrently confirmed, allowing prospective evaluation and optimization of implants.

      View details for PubMedID 15234059
  • The impact of mid-treatment MRI on defining boost volumes in the radiation treatment of glioblastoma multiforme. Technol Cancer Res Treat
    Manon R, Hui S, Chinnaiyan P, Suh J, Chang E, Timmerman R, Phan S, Das R, Mehta M
    2004 Jun; 3 (3): 303-7
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      Radiation therapy is a central modality in the treatment of glioblastoma multiforme (GBM). Integral to adequate radiation therapy delivery is the appropriate determination of tumor volume and extent at the time treatment is being delivered. As a matter of routine practice, radiation therapy treatment fields are designed based on tumor volumes evident on pre-operative or immediate post-operative MRIs; another MRI is generally not obtained for planning boost fields. In some instances the time interval from surgery to radiotherapy initiation is up to 5 weeks and the boost or "cone-down phase" commences 4-5 weeks later. The contrast enhanced T1 MRI may not be a totally reliable indicator of active tumor, especially in regions where such blood-brain barrier breakdown has not occurred. Moreover, these volumes may change during the course of treatment. This may lead to a geographic miss when mid-treatment boost volumes are designed based on a pre-radiotherapy MRI. The goal of this study is to examine how a mid-treatment MRI impacts the delineation and definition of the boost volume in GBM patients in comparison to the pre-treatment MRI scan, particularly when the tumor-specific agent Motexafin-Gadolinium is used.

      View details for PubMedID 15161323
  • Craniospinal treatment with the patient supine. Med Dosim
    Thomadsen B, Mehta M, Howard S, Das R
    2003; 28 (1): 35-8
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      Radiotherapy of the craniospinal axis in young children is frequently complicated by the need for access to the patient's airway for sedation and anesthesia delivery or by frequent, unanticipated movement. Positioning the patient supine, instead of in the conventional prone position, allows the use of immobilization facemasks with body molds and more positive patient fixation, and improved airway access. The procedure for establishing the various fields differs from the prone approach. In this paper, we describe the methodology to achieve successful supine positioning.

      View details for PubMedID 12747617
  • Anatomic variation of prescription points and treatment volume with fractionated high-dose rate gynecological brachytherapy. J Appl Clin Med Phys
    Elhanafy OA, Das RK, Paliwal BR, Migahed MD, Sakr HA, Elleithy M
    2002; 3 (1): 1-5
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      The purpose of this report is to evaluate the geometric movement (relative to the bony pelvis) and dose variation of brachytherapy reference points in the same patient at repeated high-dose rate (HDR) intracavitary implants. A study was also concluded to find the variation in treatment volume from repeated fractions. Twenty-five consecutive cervical cancer patients (all stages) treated with external beam and fractionated HDR intracavitary implants at the University of Wisconsin were reviewed. Each brachytherapy insertion had a different plan generated prior to treatment delivery. ICRU #38 prescription points (A, B, P, bladder, and rectum) were used. Dose volume histogram was generated and treated volume to the prescription dose was recorded for each fraction. Motion analysis of the various points (from a common origin) in subsequent fractions relative to the first fraction revealed a shift of 2-9 mm in a single plane. Vector analysis revealed the magnitude of the average shift ranged from 10-13 mm. These shifts resulted in a dose difference of >20% for the bladder and rectum points, but < than 8% for the other points. Dose volume histograms revealed that with the change in the anatomy of the cervix and upper vagina during a patient's course of treatment, the treatment volume changes considerably. Thirty-six percent of all patients (9/16) had a reduction in the size of the ovoid during the treatment course. Sixty percent of all patients (15/25) had volume changes <10%. Sixty-two and one half percent of patients (10/16) who did not undergo a reduction of avoid size during the entire course of the treatment had volume change <10%. Since there is a change in the anatomy of the cervix and upper vagina during the course of a treatment along with the irreproducibility of the packing, there is movement of the absolute position of the prescription points between fractions, thus emphasizing the importance of individual dosimetry. Moreover, due to the same reasons, there are significant changes in the treatment volume among implants for the same patient. Volume reduction caused by reduction in ovoid size alone could not be extracted from this study.

      View details for PubMedID 11817998

Contact Information

Rupak Das, PhD

600 Highland Avenue,
Madison, WI 53792