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

Background/Aim: Few patients with breast cancer experience tumor progression during neoadjuvant systemic therapy (NST), but their poor outcome is similar to that of patients who fail to achieve a pathological complete response (pCR). No previous reports have compared patients with pCR, non-pCR, and progression during NST to determine the survival outcomes. Patients and 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 the Kaplan???Meier methods. Results: Of the 595 patients who received NST, 167 (28.1%) had pCR (pCR group), 404 (67.9%) did not attain 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 ratio (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 groups (HR=15.8, 95%CI=9.2-27.1, p<0.01). Conclusion: The PD group had the poorest survival outcome even after recurrence, thus warranting new treatment strategies.