First in the Nation: Stereotactic Radiotherapy for Early-Stage Breast Cancer
Topics in This Article
A stereotactic radiotherapy device developed specifically to treat early-stage breast cancer is making its worldwide debut at the University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center (UM GCCC) in Baltimore. The GammaPod aims high doses of external beam radiation at the tumor site with state-of-the-art precision that spares healthy tissue. Compared to other forms of partial breast irradiation, this new approach has the advantage of being noninvasive and faster: Treatment takes days, not weeks.
UM GCCC is currently the only center in the United States offering this treatment, and early-stage breast cancer patients treated at one of the cancer centers within the University of Maryland Cancer Network have direct access to this treatment option. "With this breast-specific treatment system, we deliver high-dose radiation to a tumor while minimizing damage to normal breast tissue and—even more importantly—to major organs such as the heart and lungs," says William F. Regine, MD, FACR, FACRO, the Isadore and Fannie Schneider Foxman Chair and professor of radiation oncology at the University of Maryland School of Medicine (UM SOM). GammaPod was developed by Regine and colleague Cedric Yu, DSc, FAAPM, the Carl M. Mansfield, MD, Professor in Radiation Oncology at UM SOM.
Created for Breast Cancer Patients
One of the things that makes the GammaPod special is that it was designed completely around the treatment of breast cancer, says Elizabeth Nichols, MD, assistant professor of radiation oncology and clinical director of the UM SOM Department of Radiation Oncology.
"One of the guiding principles behind stereotactic radiotherapy is that we need to know exactly where our target is at all times," Nichols says. However, breast tissue moves as patients breathe, and large, pendulous breasts might lie differently from one day to the next.
"Part of the reason the GammaPod technology came about and can be successful is that it offers an immobilization device, or a way to fixate the breast so that it doesn't move while we're delivering treatment," says Nichols.
The GammaPod achieves that with an integrated breast-cup system, consisting of a custom-fitted inner cup, a rigid outer cup, and a silicone flange. The flange connects the two cups and adheres to the skin. A fiducial wire sends coordinates to a computer so it can map the breast. Vacuum pressure pulls the breast into the inner cup and holds it in place.
"It's not painful," Nichols says. She tells patients the device applies less pressure than commercial breast pumps.
To keep the heart and lungs away from the gamma rays, the device treats patients in the prone position. Gravity separates the breast from the chest wall.
On treatment day, patients stand against the GammaPod table wearing the breast cup, which locks into a hole in the device. The table rotates them into a prone position, and a separate computed tomography machine scans the breast. It sends images to the GammaPod treatment-planning system, which uses computational geometry to chart a path that covers the target while avoiding healthy tissue. Once the radiation oncologist finalizes the treatment plan, patients return to the GammaPod, which positions them for treatment.
Same Radiation, but Better Aim and Fewer Sessions
The GammaPod delivers the same effective radiation dose as conventional treatment, but in fewer sessions at a higher dose per session.
"It's the same radiation that we've always given, but it's delivered in a more focused way," says Nichols. During treatment, 25 rotating sources of cobalt radiation form a limitless number of arcs, all converging within the breast at the planned target.
"We don't see the hot spots that we typically see with whole breast radiation, or even with other forms of partial breast radiation," Nichols says. "The dose is more uniform throughout the whole target."
A Targeted Approach for the Right Patients
According to Nichols, women who have a single tumor less than about 3 centimeters in size are eligible for GammaPod treatment. The device might not fit those with very small or very large breasts. Women who are extremely obese or who cannot lie comfortably on their bellies cannot undergo GammaPod treatment.
Good Early Outcomes
The GammaPod received US Food and Drug Administration clearance in 2017, based on findings from a clinical trial conducted at the UM GCCC. Nichols, a lead investigator in that trial, said radiation devices go through a different process than do chemotherapy drugs.
The study enrolled 17 patients, age 60 and over, who had undergone lumpectomy for stage 1 or 2 breast cancer. Study personnel were able to fit 15 of them with the immobilization unit. Those patients received one boost to the tumor bed from the GammaPod before receiving their regular whole-breast radiation.
"What that trial showed is that the device is safe and feasible to use," says Nichols. Furthermore, a survey found patients to be highly satisfied with GammaPod treatment.
"One of the biggest things that patients really appreciated was the fact that it was shortening the overall treatment course," she says.
"Women undergoing traditional radiation typically need 16 to 35 sessions," says Yu. "The GammaPod has the potential to significantly shorten the treatment time to a few sessions or possibly even one treatment, saving patients time and money."
Nichols notes that all of the preclinical studies that compared GammaPod radiation plans to other radiation plans deemed the GammaPod better for delivering radiation to the target and not the heart and lungs. Moreover, the device dispenses much less radiation to the skin than brachytherapy does.
Researchers have not yet determined how well the GammaPod controls local recurrence.
"If we're using the same type of radiation, we have no reason to think that local control should be different than with our other therapies," Nichols says. Furthermore, in studies, partial breast radiation compares favorably with whole breast radiation for preventing recurrence.
Beneficial Effect on Quality of Life
Nichols does not expect the GammaPod to improve the already high survival rate for early-stage breast cancer, but it should enhance patients' quality of life in multiple ways. First, it may lessen fatigue and skin reactions. Second, fewer treatments means less time off from work and other activities, reducing stress for patients. Third, because some women choose mastectomy to avoid disruptive daily radiation treatments, the shorter course of GammaPod care offers an important option that might help them keep their breast.
Partnering with Referring Physicians
Patients who want to receive GammaPod treatment need not give up their primary breast-health team.
"We want to develop great partnerships with our referring physicians, and we're happy to work with them as part of their team," says Nichols.
For more information about GammaPod, or to refer a patient, call 410-328-6080.
