Omitting Regional Nodal Irradiation after Response to Neoadjuvant Chemotherapy

Regional nodal irradiation (RNI) is well established for patients with positive axillary nodes at diagnosis but its role after neoadjuvant chemotherapy has not been well studied, particularly in patients with a pCR.

Patients with breast cancer with a clinical stage of T1 to T3, N1, M0 and a nodal pCR after neoadjuvant chemotherapy were randomly assigned to receive RNI or not. The primary endpoint was invasive breast cancer recurrence.

1641 patients were included and at a median follow-up of 5 years, 109 primary end-point events had occurred. RNI did not significantly increase the invasive breast cancer recurrence–free interval. There were 11 isolated regional recurrences in the non-irradiated group and 4 in the irradiated group but no improvement in locoregional recurrence–free interval, distant recurrence–free interval, disease-free survival, or overall survival. No deaths related to protocol-specified therapy were reported, and RT toxicity was very low.

The addition of RNI did not decrease the risk of invasive breast cancer recurrence or death from breast cancer. 

The EBCTCG meta-analysis of RNI reported that its effects on breast cancer mortality were only seen after a minimum of 5 years. There is a possibility of an improvement in longer term outcomes in the future following RNI and much longer follow-up in this important trial is needed to address this.