Ten-Year Outcomes of Patients With Breast Cancer With Cytologically Confirmed Axillary Lymph Node Metastases and Pathologic Complete Response After Primary Systemic Chemotherapy.

Importance: The long-term effect of axillary pathologic complete response (pCR) on survival among women with breast cancer treated with primary systemic chemotherapy (PST) is unknown.
Objective: To assess the long-term effect of axillary pCR on relapse-free survival (RFS) and overall survival (OS) in women with breast cancer with cytologically confirmed axillary lymph node metastases treated with PST.
Design, Setting, and Participants: We retrospectively analyzed the effect of axillary pCR on 10-year OS and RFS among all women who received a diagnosis of breast cancer stages II to III with cytologically confirmed axillary metastases between 1989 and 2007 who received PST at a large US comprehensive cancer center. Women were stratified by post-PST axillary status, and survival outcomes were estimated and compared according to response in the breast and axilla.
Main Outcomes and Measures: Outcomes of interest were RFS and OS.
Results: Of 1600 women treated, median (range) age at diagnisis was 49 (21-86) years. A total of 454 (28.4%) achieved axillary pCR. These patients were more likely to have human epidermal growth factor receptor 2 (HER2)-positive and triple-negative disease (P < .001), pCR in the breast (P < .001), high-grade tumors (P < .001), and lower clinical and pathologic T stage (P = .002). Ten-year OS rates were 84% (95% CI, 79%-88%) and 57% (95% CI, 54%-61%) (P < .001) and 10-year RFS rates 79% (95% CI, 74%-83%) and 50% (95% CI, 46%-53%) (P < .001) for patients with axillary pCR and residual axillary disease, respectively. For patients with axillary pCR, 10-year OS rates were 90% (95% CI, 84%-94%) for those with breast pCR and 72% (95% CI, 61%-80%) for those with residual breast disease (P < .001). For patients with residual axillary disease, 10-year OS rates were 66% (95% CI, 56%-74%) for patients with and 56% (95% CI, 52%-60%) for patients without breast pCR (P = .02). Of patients receiving HER2-targeted therapy for HER2-positive disease, 67.1% (100 of 149) achieved axillary pCR; 10-year OS rates were 92% (95% CI, 84%-96%) and 57% (95% CI, 20%-82%) (P = .003) and 10-year RFS rates 89% (95% CI, 81%-94%) and 44% (95% CI, 18%-68%) (P < .001) for those with axillary pCR and residual axillary disease, respectively.
Conclusions and Relevance: Axillary pCR was associated with improved 10-year OS and RFS. Patients with axillary and breast pCR after PST had superior long-term survival outcomes. Patients undergoing HER2-targeted therapy for HER2-positive disease had high rates of axillary pCR, and those with axillary pCR had excellent 10-year OS.