Retrospective evaluation of adjuvant capecitabine dosing patterns in triple negative breast cancer

Background The CREATE-X trial demonstrated that adjuvant capecitabine was effective in prolonging survival in high-risk triple-negative breast cancer (TNBC) patients. However, the recommended dose is generally not well tolerated by the US population. The goal of this study is to analyze dosing patterns in an ethnically diverse cohort to better characterize tolerability and inform future dosing guidelines. Methods In our single-center retrospective study, we evaluated safety and tolerability in TNBC patients undergoing adjuvant capecitabine treatment. The primary endpoint, relative dose intensity (RDI) across eight cycles, was examined alongside subgroup analyses based on age, race, BMI, and initial dose. Secondary endpoints include capecitabine-related side effects and survival. Results 67 patients who completed adjuvant capecitabine at University of Chicago Medicine (UCM) between January 2017 and November 2022 were eligible. The mean RDI across eight cycles of treatment was 60.2% (95% CI: 0.554–0.650). When compared to the CREATE-X trial, the RDI in our population was significantly lower (0.602 vs. 0.787, p < 0.001). There was no statistically significant difference in average RDI across eight cycles for patients stratified by age, BMI, race, or initial starting dose. The most frequently reported adverse events were hand-foot syndrome (73%), diarrhea (27%), and fatigue (22%), consistent with prior studies. Conclusions Our data demonstrates that a significant portion of patients have a lower tolerated dose of capecitabine in comparison to the recommended adjuvant dose. Acknowledging the limitations of our single-center analysis, RDI was not significantly affected by age, race, BMI, or initial starting dose.