Effect of elective internal mammary node irradiation on disease-free survival in women with node-positive breast cancer

The benefit of internal mammary node irradiation (IMNI) among women with node-positive breast cancer is not known. A multicenter study in South Korea included patients after breast-conserving surgery or mastectomy with axillary lymph node dissection. The patients were randomized to regional nodal irradiation along with breast or chest wall irradiation with or without IMNI. IMNI did not significantly improve7-year disease-free survival among all patients. Ad hoc subgroup analysis showed that the subgroup with mediocentrally located tumors had better 7-year disease-free and overall survival with IMNI compared to without IMNI.