Is elective nodal irradiation beneficial in patients with pathologically negative lymph nodes after neoadjuvant chemotherapy and breast-conserving surgery for clinical stage II-III breast cancer? A multicentre retrospective study (KROG 12-05)

Background: To evaluate the effects of elective nodal irradiation (ENI) in clinical stage II-III breast cancer patients with pathologically negative lymph nodes (LNs) (ypN0) after neoadjuvant chemotherapy (NAC) followed by breast-conserving surgery (BCS) and radiotherapy (RT). Methods: We retrospectively analysed 260 patients with ypN0 who received NAC followed by BCS and RT. Elective nodal irradiation was delivered to 136 (52.3%) patients. The effects of ENI on survival outcomes were evaluated. Results: After a median follow-up period of 66.2 months (range, 15.6-127.4 months), 26 patients (10.0%) developed disease recurrence. The 5-year locoregional recurrence-free survival and disease-free survival (DFS) for all patients were 95.5% and 90.5%, respectively. Pathologic T classification (0-is vs 1 vs 2-4) and the number of LNs sampled (<13 vs ≥13) were associated with DFS (P=0.0086 and 0.0012, respectively). There was no significant difference in survival outcomes according to ENI. Elective nodal irradiation also did not affect survival outcomes in any of the subgroups according to pathologic T classification or the number of LNs sampled. Conclusions: ENI may be omitted in patients with ypN0 breast cancer after NAC and BCS. But until the results of the randomised trials are available, patients should be put on these trials.