A new study on breast cancer challenges the current medical treatment guideline for women with hormone-receptor positive (HR+) invasive breast cancer by showing that combination treatment with endocrine and radiation therapy as part of breast conservation surgery may not be necessary for all patient populations with this type of cancer. This study was conducted by Colin T. Murphy, MD, Radiation Oncologist at Fox Chase, Temple University Health System in Philadelphia, senior author on the study, and colleagues and presented during the American Society for Radiation Oncology’s 56th Annual Meeting on September 14. The other authors involved in this study were Gary Eastwick, Tianyu Li, Matthew Johnson, Lori Goldstein, Elin Sigurdson, Richard Bleicher, Jennifer Shih and Penny Anderson.
The results of this study suggest that low-risk patients over 65 years old with small tumors after treatment only with adjuvant radiation therapy, without taking endocrine therapy, and patients taking the combination therapy, endocrine and radiation, may have similar survival rates. “When they’re treated with adjuvant radiation therapy alone, elderly women with small, low risk tumors may have acceptable results,” said Dr. Colin T. Murphy. “Once their tumors start to get bigger, however, we identified an increasing risk for metastasis, and those people likely need to be on endocrine therapy.” added Dr. Colin T. Murphy.
The conclusions from a recent phase III clinical trial suggested that older women with low risk, early stage HR+ breast cancer treated with endocrine therapy only, without radiation, can have satisfactory results. However, Dr. Murphy commented that the outcomes due to the treatment with radiation only, without endocrine therapy, on this type of cancer patients have not been addressed yet. “There are scant data comparing radiation therapy versus radiation and endocrine therapy in this low risk elderly population, and that’s what we were trying to do here,” said Dr. Murphy.
Dr. Murphy and colleagues analyzed the medical reports of 504 patients older than 65 years diagnosed with invasive, estrogen- or progesterone-positive breast cancer, treated at Fox Chase between 1981 and 2011, to compare the outcomes from different therapy strategies. All the women had done breast-conserving surgery and radiation therapy, and the size of the tumors were observed to be between 0.1 and 5 centimeters. These patients were divided in two groups according to the type of therapy administered, 311 (62%) were treated with the combination therapy, radiation and endocrine, and had a median age of 71, while the rest 193 (38%) were treated with radiation only and had a median age of 72. Importantly, patients treated with radiation only had smaller, lower-grade tumors and fewer positive surgical margins than patients treated with the combination therapy. The researchers analyzed a number of clinical outcomes, including local and regional control, absence of distant metastasis, survival without disease, and overall survival, and concluded that there was little or no difference in frequencies between the two groups during the 10-year follow-up. The patients treated with combined therapy were in “a slightly higher risk group than radiation alone,” said Dr. Murphy. Moreover, the researchers recognized that larger tumor size is a predictor of increased risk for distant metastasis or shorter survival without disease in both treatment groups. At the time of follow-up, 26 out of 31 patients with metastatic disease had tumors larger than 1 centimeter. They also found that patients who did not adhere to the prescribed endocrine therapy (adherence was defined as taking endocrine therapy for 5 years or at the time of the most recent follow-up) had poor outcomes.
Ten years after treatment, patients treated with radiation alone had an estimated disease-free progression rate of 92%, while patients treated with combination therapy had a rate of 91%. On the other hand, the disease-free progression rate of patients who did not adhere to endocrine therapy was very low, at 72%. These patients had five and four times higher probability, respectively, to experience metastasis and disease progression as other patients. Overall, non-adherence to prescribed endocrine therapy was the strongest predictor of both distant metastasis and disease progression. Dr. Murphy stresses that broad conclusions should not be made from this study, since it was done retrospectively. He added that in the future, a phase III clinical trial should be done were the outcomes between patients treated with combination therapy, radiation and endocrine, and treated with just endocrine therapy should be compared.
Finally, he concluded that for each patient, the standard treatment should be adjusted with the goal of improving the patient quality of life “In elderly women who have other medical problems, adding an additional medication for their breast cancer may not be feasible,” said Dr. Murphy. “The question is, ‘for women with a low risk breast cancer, what’s the minimal extent of therapy we can deliver to minimally disrupt an elderly woman’s quality of life and still result in an acceptable cancer outcome?”added Dr. Murphy.