Retrospective study of predictors of response to neoadjuvant systemic therapy and survival in patients with cN1 breast cancer

Patients with clinically node-positive (cN1) breast cancer represent a heterogeneous population with evolving axillary management strategies. A retrospective study at MD Anderson Cancer Center (Houston, TX) investigated whether extent of axillary nodal involvement in associated with survival in cN1 disease. The study included 825 patients with cT1-4N1M0 breast cancer and biopsy-proven axillary metastasis. All patients underwent axillary ultrasound (AUS) prior to neoadjuvant systemic therapy (NST) and again before surgery. Most patients had cT2-3 (75.6%), HR+/HER2- (73%), ductal (89.7%) carcinoma. A total of 529 patients (64.1%) had 1-3 abnormal nodes on pretreatment AUS, whereas 35.9% had > 3 abnormal nodes.Definitive axillary surgery consisted of ALND in 83.3% and SNB or targeted axillary dissection in 16.7%. Pathologic complete response (pCR) rate (breast and nodes) was 22.7%; breast-only and nodal-only pCR rates were 6.4% and 11.8%, respectively. At median follow-up of 5.6 years, 5-year overal survival, breast cancer-specific survival, and event-free survival were 92%, 94%, and 91%, respectively. Achieving pCR was prognostic across all survival outcomes. On multivariable analysis, age, triple-negative subtype, cT4 tumors, lack of pCR, and > 3 abnormal nodes on pretreatment AUS were independent predictors of worse outcomes. The authors conclude that among patients with cN1 breast cancer receiving NST and surgery, long-term survival outcomes were excellent. Extent of pretreatment nodal involvement by AUS was prognostic.