Breast cancer played a prominent role at this year's ASTRO Annual Meeting-with 35 oral presentations dedicated to breast cancer, including interim results of a randomized trial presented in the plenary session. In addition, there were 130 poster presentations dedicated to breast cancer treatment.
In the Plenary Session, Dr. Timothy Whelan presented preliminary toxicity results of the Canadian RAPID trial, which compared whole breast irradiation over four to six weeks with accelerated partial breast irradiation (APBI) delivered over one week, all with external beam radiation. His study results showed a lower rate of good-to-excellent cosmetic outcome in the partial breast group compared with the whole breast group, as reported by patients, physicians, and nurses grading the cosmetic outcome. Longer follow-up and more specific details regarding APBI will hopefully help to identify factors associated with poorer cosmetic outcome.
In a study of detailed cardiac evaluations performed in patients undergoing radiation for breast cancer, Dr. Charles Simone, in an analysis of data from an NCI randomized trial, showed that cardiac toxicity was not increased in patients treated for left-sided cancers. These data should be reassuring, demonstrating that with careful modern treatment planning patients can safely receive radiation to the left side without compromising cardiac function.
In two separate but similar studies evaluating the large SEER database, Dr. Randi Cohen from the University of Maryland and Dr. Mariam Korah from University of Southern California reported that women over age 70 treated with radiation to the breast following breast-conserving surgery had improved outcomes compared with women not receiving radiation. While there are limitations to these analyses, they demonstrate the importance of weighing both the risks and potential benefits of radiation following breast-conserving surgery, even in elderly women.
In an RTOG trial of patients with low-risk ductal carcinoma in situ, randomized to radiation vs. observation, Dr. Beryl McCormick reported that radiation significantly lowered the local relapse rate at seven years from 6.4 percent in the observation arm to 0.7 percent in the radiation arm. Even in this low-risk group of patients, radiation significantly lowered the local relapse rates. However, absolute local relapse rates were relatively low in both arms and patients need to weigh all of the factors in their decision-making.
Also featured in oral presentations were several papers demonstrating potential technologic advances in the radiation treatment of breast cancer including technologic developments in IMRT (intensity modulated radiation therapy) for breast cancer, proton beam radiation for breast cancer, and prone breast irradiation.
Dr. Etin-Osa Osa from NYU reported on a prospective trial of prone accelerated whole breast irradiation delivered over three weeks with promising results. Dr. Alphonse Taghian from Massachusetts General Hospital presented a prospective dose escalation trial of partial breast irradiation demonstrating acceptable toxicity with twice-daily treatment of 4 Gy to a total of 36 Gy.
Dr. Shannon MacDonald from Massachusetts General Hospital reported the first clinical experience using proton beam radiation therapy following mastectomy in patients with an unfavorable anatomy, demonstrating excellent sparing of the cardiac and pulmonary structures with acceptable toxicity.
Finally, as we progress into the era of molecular medicine and personalized treatment, several oral presentations were dedicated to molecular profiling of breast cancer and how the molecular profiles can potentially help to guide local-regional management and decision-making. Dr. Anthony Fyles from Princess Margaret Hospital in Canada reported high local control rates in women with very favorable luminal A subtype breast cancers treated by observation without radiation.
Dr. Pauline Truong from British Columbia demonstrated that women with triple-negative, early-stage, node-negative breast cancers treated by mastectomy have low rates of recurrence and may not require radiation therapy. However, Dr. Atif Khan from the Cancer Institute of New Jersey reported that triple-negative breast cancer patients treated by mastectomy, with one to three lymph nodes involved, have high rates of local relapse and should be considered for post-mastectomy radiation.
Dr. Robert Prosnitz from the University of Pennsylvania. in an analysis of more than 3,000 patients with molecular profiling of their tumors, concluded that molecular subtype was a significant predictor in women with all stages of breast cancer regardless of age or pathology.
These and other presentations in the oral and poster sessions demonstrated significant progress in research related to the role of radiation therapy in the management of breast cancer.