Outcomes of metastatic breast cancer patients in relationship to disease-free interval following primary treatment of localized disease; a pooled analysis of two clinical trials

The aim of the current study is to assess the impact of disease-free interval (DFI) following treatment of primary localized breast cancer on the outcomes of patients with subsequent metastatic breast cancer treated with first-line docetaxel chemotherapy. This study is a combined analysis of patient-level raw data of 604 metastatic breast cancer patients referred for docetaxel first-line chemotherapy in two clinical trials. Overall survival and time to progression were evaluated according to DFI through Kaplan-Meier analysis. Multivariate analysis of factors affecting overall survival and time to progression was then conducted through Cox regression analysis. For the overall cohort, shorter DFI is associated with worse overall survival (P < 0.0001). When classified by the hormone receptor status, the shorter interval was associated with worse overall survival in both hormone receptor positive and negative patients (P = 0.009; P = 0.018; respectively). Likewise, shorter DFI is associated with shorter time to progression (P < 0.0001) in the overall cohort. When classified by the hormone receptor status, the shorter interval was associated with shorter time to progression for hormone receptor negative but not positive patients (P = 0.001; P = 0.070; respectively). In multivariate Cox regression analysis, the following factors were associated with worse overall survival: shorter DFI (P < 0.0001), poorer ECOG performance score (P = 0.008) and lower body mass index (P = 0.018). Likewise, in multivariate Cox regression analysis, the following factors were associated with shorter time to progression: shorter DFI (P < 0.0001) and hormone receptor negative status (P = 0.025). Shorter DFI was associated with worse overall survival and shorter time to progression among patients receiving first-line docetaxel chemotherapy.