Researchers at Fox Chase Cancer Center have showed that combining endocrine therapy and radiation therapy for breast conservation of women with hormone-receptor positive (HR+) invasive breast cancer may not be necessary for all patients affected by the disease.
The results, presented at the American Society for Radiation Oncology’s 56th Annual Meeting, showed that low-risk patients over 65 years old with small tumors could achieve the same survival rates after treatment with adjuvant radiation therapy without endocrine therapy.
“When they’re treated with adjuvant radiation therapy alone, elderly women with small, low risk tumors may have acceptable results. 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”, Colin T. Murphy, MD, Radiation Oncologist at Fox Chase and lead author on the study said in a Fox Chase Cancer Center press release.
Even though recent clinical trial results had demonstrated that endocrine therapy alone could accomplish positive outcomes in elderly women with low risk, early stage HR+ breast cancer, the effects of radiation therapy alone had not been tested yet in this particular population of patients.
“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,” Dr. Murphy explained in the press release.
The team analyzed the medical records of 504 patients older than 65 years of age and diagnosed with invasive, estrogen- or progesterone-positive breast cancer, which had been treated at Fox Chase between 1981 and 2011. These patients had undergone breast-conserving surgery and radiation therapy to remove tumor ranged from 0.1 to 5 centimeters. From the total number of patients, 62% had been treated with both radiation and endocrine therapy, while the rest had received radiation therapy alone.
Several clinical outcomes were measured, such as local control, regional control, freedom from distant metastasis, disease-free survival and overall survival, with results demonstrating no significant differences in any of the studied outcomes at a 10-year follow-up.
However, larger tumor size was associated with an increased risk for distant metastasis, independently of the treatment group.
After 10 years of follow-up, patients treated with radiation alone had an estimated disease-free progression rate of 92% compared to 91% in patients treated with radiation and endocrine therapy.
Additionally, the team observed that patients who did not adhere to endocrine therapy were five times more likely to have metastasis and disease progression when compared to other patients.
“In elderly women who have other medical problems, adding an additional medication for their breast cancer may not be feasible. 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?’” concluded Dr. Murphy.