Association between radiosensitivity and molecular subtypes in patients with early-stage breast cancer and lymph node-negative status

Previous studies have reported that the use of radiotherapy (RT) following breast conserving surgery (BCS) had similar clinical outcomes when compared with that of mastectomy (1,2). The Early Breast Cancer Trialists’ Collaborative Group (EBCTCG), which performed a meta-analysis of 10,801 breast cancer patients’ data obtained from 17 randomized trials comparing RT with no RT after BCS, revealed that RT decreased the risk of locoregional and distant recurrences at 10 years, from 35.0% to 19.3%, and subsequently resulted in an increased survival of 3.8% at 15 years. RT also resulted in an absolute recurrence reduction of 15.4% (10 years, no RT vs. RT; 31.0% vs. 15.6%, P<0.00001), as well as an absolute mortality reduction of 3.3% (15 years, no RT vs. RT; 20.5% vs. 17.2%, P=0.005) in patients with lymph node (LN)-negative status (3). When analyzing the variables of clinicopathological features associated with recurrence in LN-negative patients, the authors demonstrated that the 10-year recurrence was approximately 10% after RT even in patients with T1 lesions or low-grade histology (3). These findings indicate that further investigations of potential markers associated with the radio resistance in LN-negative patients with early-stage breast cancer are warranted.