SAN DIEGO – Adding radiation therapy after lumpectomy reduced the risk of recurrent breast cancer within 10 years by nearly 15% and reduced the overall chance of dying from the disease within 15 years by nearly 4%, results from a large long-term analysis demonstrated.
During a Nov. 1 press briefing at the annual meeting of the American Society for Radiation Oncology, Sarah C. Darby, Ph.D., presented the findings on behalf of the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG) that reviewed the medical records of 10,906 women who participated in 17 randomized trials of radiation therapy after breast-conserving surgery with a median follow-up of 9.5 years.
Every 5 years since 1985, the 400-plus members of the EBCTCG worldwide have shared their data, said Dr. Darby, professor of medical statistics at Oxford University’s Clinical Trial Service Unit and Epidemiological Studies Unit. The combination of moderate gains in treatment and screening has led to a halving of breast cancer mortality among women aged 35-69 years in the United States and in the United Kingdom since the late 1980s, she said.
Among all 10,906 women evaluated in the current analysis, Dr. Darby reported that adding radiation therapy reduced the 10-year risk of breast cancer recurrence by 14.6% (from 37.3% to 22.7%) and the 15-year risk of death from the disease by 3.7% (from 25.4% to 21.7%).
Of the 7,334 women with pathology-confirmed node-negative disease, adding radiation therapy reduced the 10-year risk of isolated locoregional recurrence by 15.4% (from 22.5% to 7.1%) and the 10-year risk of any recurrence by 14.5% (from 33.4% to 18.9%).
Certain factors associated with node-negative disease were associated with a greater benefit from radiation therapy. For example, among women with estrogen receptor–positive tumors in trials where tamoxifen use was planned, radiation therapy reduced the 10-year risk of recurrence for women aged 40 years and younger by 35% (from 55% to 20%). At the same time, radiation therapy reduced the 10-year risk of recurrence for women aged 70 and older with low-grade tumors by only 5% (from 11% to 6%).
Of the 1,108 women studied who had pathology-confirmed node-positive disease, radiation therapy reduced the 10-year risk of recurrence by 17.7% (from 64.5 to 46.8%) and reduced their 15-year risk of death by 7.8% (from 51.2% to 43.4%).
Dr. Darby said that she had no relevant financial conflicts to disclose.