Proton radiation is on par with photon radiation for treating breast cancer, according to research presented September 30 at the American Society of Radiation Oncology (ASTRO) annual meeting in San Francisco.
In her talk, Shannon MacDonald, MD, from the Southwest Florida Proton Center in Three Oaks reported her team’s findings. The researchers found that health-related quality of life was “excellent” and similar among women undergoing either treatment. However, fewer women who underwent proton radiation reported shortness of breath.
“Health-related quality of life as we all know is a very important endpoint for patients,” MacDonald said. “This is the largest randomized trial for proton therapy versus photon therapy to date.”
Photon-based radiation eliminates cancer tumors, but scatters bits of radiation that can lead to side effects. Proton therapy meanwhile uses proton beams, which deposit less radiation when targeting tumors, according to previous research.
MacDonald and colleagues compared patient-reported quality of life outcomes for women who underwent either photon-based or proton-based radiation for breast cancer treatment. They designed their study, RadComp, to test whether proton therapy could reduce side effects while maintaining the high degree of cancer control achieved with photon therapy. While a primary outcome of RadComp is comparing major cardiac events stemming from either treatment, MacDonald said that data will not be available until the next “three to five to seven years.”
The initial results included data from 1,239 women from 32 U.S. centers who were prospectively enrolled into the RadComp trial. The women had nonmetastatic breast cancer. The team randomly assigned the women to receive either proton therapy (n = 624) or photon therapy (n = 615). And of the total women, 69.6% underwent mastectomy, 80.6% had few cardiovascular risk factors, and 61.8% presented with left-sided or bilateral cancer. All participants received radiation to their internal mammary lymph nodes.
The researchers also had the women complete several validated health-related quality-of-life questionnaires before treatment, at the end of their radiation, and at one and six months after treatment.
The team reported no clinically meaningful differences between either treatment arm for the following questionnaires: Patient-Reported Outcomes Information System (PROMIS) Fatigue score, Satisfaction with Breast Cosmetic Outcome score, Breast-Q total score, and Fact-B trial outcome index score.
However, proton therapy had more success for the Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE) score when shortness of breast was evaluated (odds ratio [OR], 0.74). But this finding did not remain significant after correction for multiple comparisons. However, MacDonald said this finding deserves additional research.
For the Functional Assessment of Chronic Illness Therapy (FACIT) score, women were more likely to recommend proton therapy more than women in the photon therapy arm (OR, 0.13, p < 0.001). Furthermore, women were more likely to choose proton therapy compared to women in the photon arm being asked if they would do the same (OR, 0.11, p < 0.001).
MacDonald said these findings should be interpreted in the context of an unblinded study. She added that the team will report on loco-regional control and major cardiac events in future analyses.
In an accompanying expert perspective, Jose Bazan, MD, from the City of Hope National Medical Center in Duarte, CA, said the results highlight the importance of radiation oncologists monitoring shortness of breath in patients undergoing treatment.
“The findings … suggest that it is not yet time to move the needle toward protons in the treatment of regional lymph node irradiation for breast cancer,” Bazan said. “Of course, [we] are really looking forward to the primary endpoint of the major cardiac events and the cancer control outcomes. As it stands, x-ray should remain the prominent modality.”
