Nodal pCR and overall survival following neoadjuvant chemotherapy for node positive ER+/Her2- breast cancer

The role of neoadjuvant chemotherapy (NAC) in node-positive (N+) ER+/HER2- breast cancer (BC) is debated, given low total pathologic complete response (pCR) rates. However, the rate and impact of nodal pCR is unknown. We sought to evaluate nodal pCR rates and the impact on overall survival (OS). Further, we sought to validate the association between nodal pCR with age and Ki67.

We queried the National Cancer Database for cN + ER+/HER2- BC patients treated with NAC and surgery. Data from 2010 to 2018 were used to evaluate nodal pCR and OS, with multivariable Cox proportional hazards modeling for OS, as well as Ki67 for the years 2018-2019.

From 2010 to 2018, we identified 19,611 cN + ER+/HER2- BC patients treated with NAC. While total pCR occurred in only 7.4%, nodal pCR rates were nearly double (14.3%). Nodal pCR (+/- breast pCR) was seen in 21.7% and associated with 5-year OS rate of 86.1% (95% CI: 84.9-87.4%) versus 77.1% (95% CI: 76.3-77.9%) in patients without nodal pCR (p < 0.001). On multivariable analysis, nodal pCR had better OS (adjusted HR 0.57, 95% CI 0.52-0.63, p < 0.001) across all age groups. Of 2,444 patients with available Ki67, those with age < 50 and Ki67 ≥ 20% had the highest nodal pCR at 31.6%.

In cN + ER+/HER2- BC treated with NAC, nodal pCR is common, associated with age and Ki67, and prognostic for OS. These data strongly suggest that for cN + patients, eradication of nodal disease is critical for OS, and total pCR may not be the optimal measure of NAC benefit.