Impact of Radiation on Locoregional Control in Women with Node-Positive Breast Cancer Treated with Neoadjuvant Chemotherapy and Axillary Lymph Node Dissection: Results from ACOSOG Z1071 Clinical Trial

Purpose: Use of adjuvant radiation therapy (RT) after neoadjuvant chemotherapy (NAC) in node-positive breast cancer (BC) is highly variable. In ACOSOG Z1071, RT after NAC was used at the discretion of treating physicians. Herein, we report the impact of RT and pathologic response on locoregional recurrence (LRR) after NAC. Methods and Materials: ACOSOG Z1071 enrolled women with cT0-4N1-2 BC treated with NAC from 2009 to 2011. Patients underwent sentinel node surgery and completion axillary lymph node dissection. The RT was at the discretion of the treating physicians. Patient outcomes were analyzed as a function of clinical-pathologic factors and use of RT. Results: Of 701 eligible patients, mastectomy was performed in 423 (59.6%) and breast-conserving surgery in 277 (40.4%). After NAC, residual disease was observed in 506 (72.2%), and 195 (27.8%) had a pathologic complete response. Of the patients, 591 (85.3%) received adjuvant RT and 102 (14.7%) did not. Median follow-up was 5.9 years. Forty-three patients (6.1%) experienced LRR, 145 (20.7%) experienced distant metastasis, and 142 (20.4%) died. Patients with pathologic complete response had the best LRR-relapse-free survival (hazard ratio [HR], 0.32; 95% confidence interval, 0.12-0.81; P = .016), distant metastasis–free survival (HR, 0.31; 95% CI, 0.19-0.52; P < .0001), BC-specific survival (HR, 0.34; 95% CI, 0.19-0.59; P = .0001) and overall survival (HR, 0.39; 95% CI, 0.240-0.63; P = .001) compared to patients with residual disease after NAC. Patients with triple-negative BC had a higher LRR rate compared to those with hormone receptor–positive BC (HR, 5.91; 95% CI, 2.80-12.49). There was a trend toward lower LRR with the use of postmastectomy and regional nodal RT, but there was no impact on overall, disease-free, or BC-specific survival. Conclusion: In the ACOSOG Z1071 trial, in which the use of RT after NAC was at the discretion of the treating physicians, RT was associated with a trend toward decreased LRR. There was no association of RT with overall survival, BC-specific survival, or Disease Specific Survival. Triple-negative BC was associated with higher locoregional relapse rates.