Regional Nodal Irradiation for Clinically Node-Positive Breast Cancer Patients With Pathologic Negative Nodes After...

Area of Science:

• Oncology
• Radiation Oncology
• Surgical Oncology

Background:

• Neoadjuvant chemotherapy (NAC) is increasingly utilized for operable breast cancer (BC).
• Optimal radiation therapy (RT) fields for patients with clinically node-positive (cN1) disease who convert to pathologically node-negative (ypN0) after NAC remain under investigation.
• The NSABP B-51 trial is currently accruing patients to address this question.

Purpose of the Study:

• To compare outcomes between whole breast (WB) radiation therapy (RT) with or without regional nodal irradiation (RNI) in cN1, ypN0 breast cancer patients.
• To evaluate the impact of RNI on survival in patients treated with breast conservation and sentinel lymph node biopsy (SLNB) after NAC.

Main Methods:

• Retrospective analysis of National Cancer Database from 2006-2015.
• Included breast cancer patients with cN1 disease who received NAC, lumpectomy, and SLNB, and were ypN0.
• Compared overall survival between WB RT alone versus WB + RNI using Kaplan-Meier and multivariable Cox proportional hazards analysis, with and without propensity score weighting.

Main Results:

• Regional nodal irradiation (RNI) use increased from 48.13% to 62.13% between 2006 and 2015.
• The 10-year survival rates were 83.6% for WB RT alone and 79.5% for WB + RNI (P = .14).
• Multivariable analysis showed no significant survival benefit with the addition of RNI (HR 0.80; 95% CI, 0.58-1.11; P = .19), even after propensity score adjustment.

Conclusions:

• For women with cN1 breast cancer who convert to ypN0 after NAC and breast-conserving surgery with SLNB, more extensive RNI may not offer a long-term survival advantage.
• Prospective validation through trials like NSABP B-51 is crucial to confirm these findings.