Impact of pathologic response and individual prognosis after neoadjuvant treatment in patients with early HER2+ and triple-negative breast cancer

Background: Pathologic complete response (pCR) after neoadjuvant treatment (NAT) is prognostic for recurrence-free survival (RFS) and overall survival (OS) in breast cancer (BC). We assessed prognostic factors for RFS and OS in patients with pCR compared to residual disease (RD) in HER2+ and triple-negative breast cancer (TNBC). Methods: We retrospectively evaluated patients with early HER2+ BC or TNBC who underwent surgery following NAT at Dana-Farber Cancer Institute and who had data on pCR (ypT0/is, ypN0), RD, RFS, and OS. Clinical tumor size (cT), nodal status (cN), and subtype were assessed using Cox models and Kaplan-Meier methods (p < .05 significant). Results: 863 patients (median age 50.2, range 21.0-85.4) underwent surgery from 2016 to 2021, with a median follow-up of 3.5 years. Three-year RFS was 87% overall, 93% in HER2+, and 80% in TNBC cohorts. Among 374 pCR patients (43.3%), 3-year RFS was 98%, compared to 79% in 489 RD patients (56.7%). In HER2+ BC, 3-year RFS was 99% for pCR vs. 87% for RD, while in TNBC it was 97% for pCR vs. 72% for RD. Higher cT, positive cN, TNBC subtype, and RD were associated with poorer RFS and OS. In pCR, 3-year RFS was numerically higher in cT1-2 compared to cT3-4 and in cN0 compared to cN+ (not significant). In RD, higher cT, positive cN, and TNBC subtype remained associated with poorer outcomes. Multivariate analysis found no associations in pCR patients. Conclusion: Patients experiencing pCR had better outcomes. cT, cN, and subtype were prognostic only in patients with RD.