Outcomes of early-stage breast cancer patients treated with sequential anthracyclines-taxanes in relationship to relative dosing intensity: a secondary analysis of a randomized controlled trial

PurposeTo assess the impact of relative dosing intensity (RDI) on the outcomes of breast cancer patients referred for adjuvant anthracycline-taxane chemotherapy.MethodsThis is a secondary analysis of the outcomes of patients in the comparator arm of the BCIRG005 study who received adjuvant adriamycin/cyclophosphamide (AC)-docetaxel regimen. Overall survival was assessed according to RDI through Kaplan-Meier analysis. Univariate and multivariate analyses of parameters affecting overall survival were then conducted through Cox regression analysis.ResultsKaplan-Meier analysis of overall survival according to RDI for the AC-docetaxel regimen (<90 vs.90%) was conducted and it showed that RDI<90% is associated with worse overall survival (P=0.006). In univariate Cox regression analysis, the following parameters significantly affected overall survival (P<0.05): age, T stage, lymph node ratio, hormone receptor status, and grade of the disease and RDI for AC-docetaxel regimen. When these factors were included in multivariate analysis, the following factors were associated with worse overall survival: age less than 40years (P<0.0001), greater T stage (P<0.0001), greater lymph node ratio (P<0.0001), negative hormone receptor status (P=0.001), high grade (P<0.0001) and RDI90% (P=0.015). Formal interaction testing between RDI and hormone receptor status has a non-significant P value (P=0.794).ConclusionLower RDI for the whole anthracycline-taxane protocol is associated with worse patient survival. Every effort should be exercised to avoid unnecessary dose reductions and/or interruptions among early breast cancer patients receiving adjuvant anthracycline-taxane chemotherapy.