Radiotherapy in Older Women With Low-Risk Breast Cancer: Why Did Practice Not Change?

Abstract

Radiotherapy after breast-conserving surgery reduces the risk of breast cancer recurrence and death as a result of breast cancer. In the most recent update of the Early Breast Cancer Trialists’ Group metaanalysis, radiotherapy lowered the risk of breast cancer recurrence by about one half and lowered the risk of breast cancer death by one sixth. 1,2 However, the absolute benefit of radiotherapy depended on the baseline risk of recurrence and was smaller in patients with a lower risk of recurrence. This concept raises the question of whether radiotherapy after breast-conserving surgery can be safely omitted if the absolute risk of recurrence is low. The CALGB 9343 trial directly addressed this question in the subset of older women with low-risk breast cancer. 2 This study enrolled more than 600 women age 70 years and older who had clinical stage 1 estrogen receptor–positive breast cancer and who were treated with breast-conserving surgery. Patients were randomly assigned to tamoxifen alone or tamoxifen plus radiotherapy. This study showed that there was no significant difference in the rates of subsequent mastectomy, distant metastases, or overall survival between the two groups. At the time of the initial study publication in 2004, the median follow-up was five years and the rate of local or regional recurrence was 1% in the group that received radiation and 4% in the group that did not. With longer follow-up of 10.5 years, the only significantly different outcome was local recurrence with a difference of 2% in the irradiated group and 9% in those women who did not receive adjuvant radiotherapy. 3 On the basis of these findings, the National Comprehensive