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

To assess the impact of relative dosing intensity (RDI) on the outcomes of breast cancer patients referred for adjuvant anthracycline–taxane chemotherapy.

This 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.

Kaplan–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 40 years (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 RDI ≤ 90% (P = 0.015). Formal interaction testing between RDI and hormone receptor status has a non-significant P value (P = 0.794).

Lower 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.