Association of Low Nodal Positivity Rate Among Patients With ERBB2-Positive or Triple-Negative Breast Cancer and Breast Pathologic Complete Response to Neoadjuvant Chemotherapy.

Importance: A recent publication reported that of 527 patients with clinically node-negative (cN0) cT1/cT2 triple-negative breast cancer (TNBC) or ERBB2-positive disease treated with neoadjuvant chemotherapy (NAC), 100% of those who achieved a breast pathologic complete response (pCR) had pathologic node negativity (pN0). Eliminating axillary surgery in these patients has been suggested as safe based on these results.

Objective: To evaluate nodal positivity rates in patients with cT1/cT2 N0 ERBB2-positive disease and TNBC with a breast pCR after NAC using the National Cancer Database (NCDB), which included academic and community settings.

Design, Setting, and Participants: This retrospective study reviewed data from the NCDB from January 1, 2010, through December 31, 2015. Participants included patients with cN0/cN1 cT1/cT2 breast cancer who received NAC followed by surgery. Pathologic nodal positivity rates by breast pCR were compared in cN0 and cN1 disease, within each tumor subtype (ERBB2-positive, TNBC, and hormone receptor-positive/ERBB2-negative). Data were analyzed from September 13, 2017, through January 30, 2018.

Exposures: Neoadjuvant chemotherapy followed by surgery.

Main Outcomes and Measures: The pathologic nodal positivity rate after NAC (ypN) specifically in patients with cT1/cT2 cN0 ERBB2-positive disease or TNBC who achieve a breast pCR after NAC.

Results: A total of 30 821 patients with cT1/cT2 cN0/cN1 breast cancer treated with NAC and surgical resection (99.6% female; mean [SD] age, 52.0 [11.5] years) were identified. Of 6802 patients with cN0 ERBB2-positive disease, 3062 (45.0%) achieved breast pCR and of those, 49 (1.6%; 95% CI, 1.2%-2.1%) were ypN positive. In 6222 patients with cN0 TNBC, 2315 (37.2%) achieved breast pCR, and of those, 36 (1.6%; 95% CI, 1.1%-2.1%) were pathologic node positive after NAC. Rates of ypN positivity were higher in patients with cN0 and residual disease in the breast; 632 of 3740 (16.9%) with ERBB2-positive disease and 492 of 3907 (12.6%) with TNBC with residual disease in the breast were node positive (P < .001). Among 4164 patients with cN1 ERBB2-positive disease, 1801 (43.3%) achieved breast pCR, with 223 of those (12.4%) being ypN positive. In 3293 patients with TNBC, 1229 (37.3%) achieved breast pCR, with 173 of these (14.1%) being ypN postive. Breast pCR rates were lower in hormone receptor-positive/ERBB2-negative disease (646 of 5069 [12.7%] for cN0; 711 of 5271 [13.5%] for cN1) and ypN positivity rates were 26 of 646 (4.0%) in cN0 vs 217 of 711 (30.5%) in cN1 disease with breast pCR and 1464 of 4423 (33.1%) in cN0 disease vs 3775 of 4560 (82.8%) in cN1 disease with residual disease in the breast.

Conclusions and Relevance: In this study, the highest rates of breast pCR were seen in ERBB2-positive disease and TNBC. In patients with cN0 ERBB2-positive disease or TNBC with breast pCR, the nodal positivity rate was less than 2%, which supports consideration of omission of axillary surgery in this subset of patients.