Adjustments in relative dose intensity (RDI) for FECD chemotherapy in breast cancer: A population analysis.

547Background: Reductions in RDI of adjuvant chemotherapy for breast cancer (BC) has been associated with inferior survival. However, earlier studies may be confounded by uncharacterized BC subtype(s) (TNBC, HER2+) and non-taxane chemotherapy regimens (CMF, AC). This retrospective study evaluates survival (DFS/OS) outcomes for patients receiving RDI reductions for FECD adjuvant chemotherapy in Alberta, Canada. Methods: Patients with stage I-III, ER +/-, HER2- BC receiving adjuvant FECD chemotherapy from 2007-2014 were identified using the Alberta Cancer Registry. RDI of individual chemotherapeutics (cycle 1-6) were recorded. Average RDI was stratified by <85% vs ≥85% of total dose. Subgroup analysis for early (cycle 1-3) versus late (cycle 4-6) RDI reductions were evaluated. Events (recurrence/death) from any cause were identified. Results: FECD patients (n=1304) receiving an average RDI <85% (range 25-84%) compared to ≥85% demonstrated a significant decline in DFS (79% vs 85%; p<0.01) and OS (82% vs 89%;...