THURSDAY, June 5, 2025 (HealthDay News) — For patients with node-positive breast cancer who become pathologically tumor-free with negative axillary nodes (ypN0) after neoadjuvant chemotherapy, the addition of adjuvant regional nodal irradiation does not reduce the risk for invasive breast cancer recurrence or death, according to a study published in the June 5 issue of the New England Journal of Medicine.

Eleftherios P. Mamounas, M.D., from the AdventHealth Cancer Institute in Orlando, Florida, and colleagues examined whether regional nodal irradiation improves outcomes in patients with biopsy-proven, node-positive breast cancer who reach ypN0 status after neoadjuvant chemotherapy. Participants with T1 to T3, N1, M0 breast cancer who achieved ypN0 status were randomly assigned to receive regional nodal irradiation or no regional nodal irradiation (772 and 784 individuals, respectively). The interval of freedom from invasive breast cancer recurrence or death from breast cancer was examined as the primary end point.

The researchers found 109 primary end point events after a median follow-up of 59.5 months (50 events in the irradiation group and 59 events in the no-irradiation group). There was no significant increase in the invasive breast cancer recurrence-free interval in the regional nodal irradiation group. Point estimates of survival free from the primary end-point events were 92.7 and 91.8 percent in the irradiation and no-irradiation groups, respectively. No increase in the locoregional recurrence-free interval, distant recurrence-free interval, disease-free survival, or overall survival was seen with regional nodal irradiation. There were no deaths related to protocol-specific therapy, nor were there unexpected adverse events.

“The results of our trial indicate that patients with positive axillary lymph nodes who reach stage ypN0 after neoadjuvant chemotherapy have low rates of disease recurrence and do not receive a statistically significant benefit from regional nodal irradiation at five years,” the authors write. “These results support a shift in treatment strategy in that regional nodal irradiation can be tailored in patients treated with neoadjuvant chemotherapy on the basis of their pathological nodal response.”

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