The Effect Of Internal Mammary Lymph Node Irradiation After Modified Radical Mastectomy In Patients With Stage Ⅱ-Ⅲ Breast Cancer

Objective Regional nodal irradiation(RNI)can improve the prognosis of breast cancer patients,whether internal mammary lymph node irradiation(IMNI)could improve the prognosis is still controversial.The purpose of this study is to investigate the effect of internal mammary lymph nodes irradiation after modified radical mastectomy.Methods A retrospective analysis was performed on 74 patients who received IMNI from January 2015 to August 2018,and 74 patients who did not receive IMNI were matched by propensity score matching(PSM).The primary end point was disease-free survival(DFS),recurrence pattern and mean dose of heart and lung.The secondary endpoint was overall survival(OS).DFS and OS were evaluated with Kaplan–Meier method.Differences between two groups were compared with the log-rank test(p < 0.05 considered significant).Multivariate analysis was performed by the Cox regression model.Results The prescription irradiation dose was 50Gy/25F/5W,and the median follow-up time was 34 months(range: 18-63 months).The 2-year disease-free survival rates of internal mammary node irradiation(IMNI)group and non-IMNI group were 91.8% and 75.7%,respectively(p <0.05).The 2-year overall survival rates were 97.2% and 97.2%,respectively(p >0.05).IMNI is an independent prognostic factor for DFS.Subgroup analysis showed that tumors located in the inner or central quadrant,ER positive or stage Ⅲ patients could benefit from internal mammary lymph node irradiation.Conclusion:The 2-year DFS of tumors located in the inner or central quadrant,ER positive or stage Ⅲ breast cancer patients after modified radical mastectomy can be improved by chest wall irradiation with RNI(including IMNI).