Patients with early-stage breast cancer often opt for breast-conserving surgery followed by radiotherapy with a lumpectomy cavity boost—an extra dose of radiation to the tumor bed, the area of greatest risk of recurrence.
A lumpectomy cavity boost reduces the chances of recurrence, but it also increases the risk of damage to healthy tissues, including the heart and lungs.
Radiation oncologists have historically relied on CT scans just before treatment or surrogates for the lumpectomy cavity, such as surgery scars, to position patients to minimize toxic side effects.
With the ViewRay MRIdian treatment machine, the Department of Human Oncology (DHO) now has an additional means of treating patients—real-time MRI monitoring during the radiation delivery.
Dr. Bethany Anderson, DHO assistant professor, is leading a clinical trial to determine whether the use of real-time MRI to position patients can further improve the accuracy of lumpectomy cavity boosts.
“What’s unique about the ViewRay system is that we can see the cavity throughout treatment and watch it moving,” Anderson says. “We can stop treatment if the target moves outside the treatment target area. Viewing daily MRI images also gives us a chance to do adaptive re-planning to account for anatomic changes.”
The benefits of viewing MRI images during treatment were evident with one of the first patients in this clinical trial. The patient had a large hematoma in her breast during the initial treatment simulation. On the day of her first lumpectomy cavity boost fraction, the hematoma was significantly smaller. In this case, use of real-time MRI helped minimize delivery of radiation to surrounding healthy breast tissue.
The clinical trial began in January 2015 and will enroll 50 patients with invasive breast cancer or ductal carcinoma in situ who have had breast conserving surgery and will receive standard of care radiation treatment with a lumpectomy cavity boost.
Anderson expects the use of MRI information may enable a more accurate determination of changes to the lumpectomy cavity between treatments, which could lead to smaller treatment margins—and, therefore, fewer long-term side effects.