Impact of Tumor Progression on Survival during Neoadjuvant Chemotherapy in Breast Cancer: A Cohort Study

Abstract Background: Although few patients with breast cancer experience tumor progression during neoadjuvant systemic therapy (NST), their extremely poor outcomes are similar to patients who fail to achieve pathological complete response (pCR). No reports have compared patients with pCR, non-pCR, and progression during NST to determine the survival outcomes.Methods: This retrospective chart review of patients with stage I–III breast cancer was conducted between January 2001 and December 2018. pCR was defined as no invasive cancer or in situ residuals in the breast and lymph nodes (ypT0 ypN0). Disease-free survival (DFS) and overall survival (OS) were estimated using Kaplan–Meier methods.Results: Of the 595 patients who received NST, 167 (29.2%) had pCR (pCR group), 404 (70.8%) responded to NST but did not have pCR (non-pCR group), and 24 (4.0%) experienced tumor progression during NST (PD group). The median DFS was 6.0 months, 154.0 months, and not reached in the PD, non-pCR, and pCR groups, respectively. The PD group had significantly shorter DFS than patients without tumor progression in the pCR and non-pCR groups [hazard ratios (HR) 13.0, 95% CI: 8.1–21.0, p < 0.01]. The median OS was 13.6 months (95% CI: 10.4–35.5) in the PD group and was not reached in the pCR and non-pCR (non-PD) groups. The OS was significantly poorer in the PD group than in the non-PD group (HR 15.8, 95% CI: 9.2–27.1, p < 0.01).Conclusion: The PD group had the poorest survival outcomes even after recurrence, thus warranting new treatment targets.