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

Purpose: 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).

Methods And Materials: 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.

Results: 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.

Conclusions: 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.