Adjuvant chemotherapy for breast cancer after preoperative chemotherapy: A propensity score matched analysis

Although identified to be at a higher risk of relapse, no consensus exists on the treatment of breast cancer (BC) patients with no pathological complete response after neoadjuvant chemotherapy (NAC). The benefit of adjuvant chemotherapy (ADJ) in this context has scarcely been studied. We evaluated the benefit of administrating adjuvant chemotherapy in a real life cohort of BC patients with invasive residual disease after NAC. 1199 female BC patients with T1-3NxM0 invasive tumors receiving NAC at Institut Curie from 2002 to 2012 were included in the analysis. 1061 had been treated by NAC only, whereas 138 had received additional adjuvant chemotherapy after NAC (FUN protocol: 5-FU-Vinorelbine). We compared disease-free survival (DFS) and overall survival (OS) rates between patients having received NAC only and patients having received NAC+ADJ. To ensure comparability of our populations, we used a propensity score (which defines the probability of treatment assignment conditional on observed baseline covariates) and matched each patient having received NAC+ADJ (n = 138) with a patient having received NAC only that had a similar propensity score value. Before propensity score matching, DFS and OS rates were significantly lower in the NAC+ADJ group compared to NAC only, after 3 years, 5 years and 10 years follow-up (p<0.01). After one-to-one PS matching, the two groups were comparable (n = 276 patients; 138 patients in each group). No significant difference was found regarding DFS (p = 0.87) or OS (p = 0.59) rates, neither in global population, nor by pathological subtype. Although our study did not show a benefit of administrating ADJ with FUN protocol (5-Florouracil- Vinorelbine) to BC patients with residual disease after NAC, further studies are warranted to determine the impact of other adjuvant regimens. Thereby, patients with little chance of responding to particular regimens could avoid the toxicity of futile therapy, and be study participants in evaluations of novel treatment strategies.