Whole-Breast Irradiation Following Breast-Conserving Surgery for Invasive Breast Cancer

Irradiation of the whole breast in women who have undergone breast-conserving surgery (BCS) has long been a standard of care in the treatment of early breast cancer. This practice is predominantly based on the local control and survival gains demonstrated by the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG) meta-analyses [1, 2]. These are based on data from 10,801 women treated in 17 randomised trials of BCS plus or minus whole-breast irradiation (WBI) and demonstrate that the addition of WBI to BCS approximately halves the risk of local recurrence at 10 years (from 35% to 19%) and reduces the risk of breast cancer death at 15 years by around one sixth (from 25% to 21%). In women with pathologically node-negative disease (n = 7287), the risk of local recurrence was reduced from 31% to 16% at 10 years and the risk of breast cancer death from 21% to 17% at 15 years. In women with node-positive breast cancer (n = 1050), radiotherapy reduced the 10-year risk of local recurrence from 64% to 43% and the 15-year risk of breast cancer death from 51% to 43%. Consistent with previous meta-analyses, the prevention of four local recurrences at 10 years prevented one breast cancer death at 15 years.