Characterization of pathologic complete response to neoadjuvant chemotherapy among breast cancer patients in the...

Neoadjuvant chemotherapy (NAT) is often used for patients with node-positive breast cancer to facilitate downstaging regardless of tumor biology. However, pathologic complete response (pCR) rates can vary according to patient and tumor factors and may not be uniform in the breast and axilla. We sought to identify clinicopathologic and treatment-specific factors predictive of NAT response in the breast and axilla and their impact on overall survival (OS).

Patients with clinical stage II-III breast cancer undergoing NAT between 2018 and 2021 were selected from the National Cancer Database and grouped by breast cancer subtype. We used multinominal logistic regression to evaluate tumor and nodal response to NAT and Cox proportional hazard regression to assess OS.

Of 57,058 patients identified, 17,616 (30.9%) achieved pCR in both the breast and axilla. HER2+ patients had higher rates of pCR (61%) than triple negative patients (37.7%) and ER+/HER2- patients (9.9%). Triple negative patients had a higher proportion of nodal response with residual primary tumor (ypN0/ypT+, 35.9%) compared to other groups, and ER+/HER2-patients had higher proportions of incomplete breast and axillary response (ypT+/ypN+, 67.3%), P < .001. Patients under 50 years had 21% increased likelihood of pCR compared to patients aged ≥50 (P < .001). Compared to privately insured patients, those with non-private insurance had lower likelihood of complete response, with uninsured patients having worst outcomes (OR, 0.80 [95% CI, 0.70, 0.92]). Of all patients achieving pCR, HER2+ patients had the highest OS and had improved survival compared to other groups regardless of neoadjuvant response (HR, 0.66 [0.58, 0.74]). Triple negative patients had the lowest OS (HR, 1.89[1.76, 2.02]). Factors negatively affecting survival included Black race, non-metropolitan residence, lymphovascular invasion, higher pretreatment cT/cN stage, and non-private insurance.

HER2+ breast cancer was more likely to result in a pCR to neoadjuvant therapy and conferred a survival advantage over ER+/HER2-and triple-negative patients. Several clinical and sociodemographic risk factors were associated with partial response to therapy and differential survival between groups. Patients without a pCR were more likely to have a pCR in the axilla versus the breast.