Recent results from the NRG-NSABP B-51/RTOG 1304 clinical study showed that the addition of regional nodal irradiation (RNI) does not decrease the rates of invasive breast cancer recurrence in patients whose positive axillary nodes at presentation convert to negative following neoadjuvant chemotherapy. These results were recently published in the New England Journal of Medicine.

The study enrolled 1,641 patients stratified by type of surgery (mastectomy, lumpectomy), hormone receptor status (ER-positive and/or PgR-positive; ER- and PgR-negative), HER2 status, adjuvant chemotherapy use, and pathologic complete response (pCR) in the breast, then randomized to RNI vs. No RNI.

Anti-HER2 therapy was required for patients with HER2+tumors, as was endocrine therapy, for patients with hormone-sensitive tumors. The primary endpoint was invasive breast cancer recurrence-free interval (IBCRFI). Final analysis was planned after 172 events or 10 years post-study initiation.

At the time-driven analysis, 109 IBCRFI events (63% of the planned 172) were confirmed. RNI did not significantly improve IBCRFI (HR=0.88, 95%CI 0.60-1.28; p=0.51, five-year point estimates: No RNI:91.8%, RNI:92.7%) and did not improve secondary endpoints of loco-regional recurrence-free interval, distant recurrence-free interval, disease-free survival, or overall survival.

“Although numerous prior clinical trials have demonstrated benefit from RNI in patients with positive axillary lymph nodes who undergo surgery first, this trial evaluated RNI in patients who presented with node-positive breast cancer but whose axillary lymph nodes converted to pathologically negative after neoadjuvant chemotherapy.

“Our study results demonstrate that pCR in axillary lymph nodes predicts for no benefit from RNI. We will continue follow-up for evaluation of longer-term outcomes for these patients,” stated Eleftherios Mamounas, MD, of AdventHealth Cancer Institute, and the lead author of the NRG-NSABP B-51/RTOG 1304 manuscript.

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NRG Oncology