Entire Versus Medial Supraclavicular Nodal Irradiation for Patients With High-Risk Node-Positive Breast Cancer

Abstract

We aimed to examine whether elective inclusion of the posterolateral supraclavicular node (SCL) region to the standard medial SCL target volume improves SCL control and survival outcomes in patients with high-risk node-positive breast cancer undergoing regional nodal irradiation (RNI). We retrospectively reviewed 544 consecutive women with high-risk breast cancer treated with postoperative chest wall/breast and RNI in our center from January 2015 to December 2016. High-risk features were defined as clinical or pathologic stage N2-3b disease. Patients were classified into the medial SCL irradiation (M-SCLI) group and the entire SCL irradiation (E-SCLI) group, which included both the medial and the posterolateral SCL region. SCL recurrence (SCLR), disease-free survival (DFS), and overall survival (OS) were estimated and compared. Propensity-score matching (PSM) and multivariate cox regression were used for analysis. The median follow-up time was 64.2 months. Before PSM, there was no significant difference in the cumulative incidence of SCLR between the 2 groups, with 5-year rates of 2.0% in the M-SCLI group and 0.6% in the E-SCLI group (P = .1). After PSM, there was also no significant difference in the cumulative incidence of SCLR (2.1% vs 0.5%; P = .2). Only 2 patients had recurrence in the posterolateral SCL region, with 1 patient in each group. Similarly, there was no significant difference in DFS and OS between the M-SCLI and E-SCLI group both before PSM (5-year rates of 78.5% vs 78.8%, P = .8; 92.2% vs 90.0%, P = .2) and after PSM (76.7% vs 77.2%, P = .8; 91.5% vs 88.4%, P = .1). Multivariate analysis demonstrated that E-SCLI was not independently prognostic for DFS and OS. E-SCLI does not appear to be associated with improved SCL control and survival outcomes in high-risk node-positive breast cancer. These data do not support the routine use of E-SCLI in N2-3b disease. We initiated a multicenter randomized controlled phase 3 study comparing M-SCLI and E-SCLI to further validate these results.