Patients’ self-reported adherence to capecitabine on XELOX treatment in metastatic colorectal cancer: findings from a retrospective cohort analysis

BACKGROUND: Capecitabine plus oxaliplatin (XELOX) has been established as a first-line treatment for metastatic colorectal cancer. Adherence is particularly important with capecitabine to maintain appropriate curative effect. In this study, we monitored the adherence to capecitabine on XELOX treatment and investigated which factors might decrease compliance. METHODS: The study included 242 consecutive patients who received XELOX treatment for metastatic colorectal cancer between October 2009 and March 2012. Adherence to capecitabine was checked by pharmacists with a patient-reported treatment diary at a pharmaceutical outpatient clinic. Adherence rate was defined as the number of times that a patient took capecitabine in a 14-day cycle/28 prescribed doses. We retrospectively surveyed median relative dose intensities of capecitabine and the factors deteriorating adherence across eight cycles from electronic patient records and examined differences in compliance rates according to age. RESULTS: The study included 144 male and 98 female patients. The overadherence rate was 1.5% (n=23). The median adherence rate was 93.5% (n=242) in the first cycle of XELOX treatment, which gradually rose to 96.1% (n=148) in the eighth cycle. The median relative dose intensity of capecitabine was 79.2%. The main factors contributing to decreased adherence to capecitabine were diarrhea (22.5%, 352 instances) and nausea/vomiting (13.8%, 215 instances). The rate of missed dose was 12.1%. Analysis of adherence issues in relation to patient age showed a trend toward worse adherence to capecitabine therapy in the group of patients aged ≥80 years (hazard ratio =3.83; 95% confidence interval 2.48–5.91, P<0.001 versus 70–80 years group and versus <70 years group, chi-square test). CONCLUSION: Patient-reported adherence to capecitabine on XELOX treatment in clinical practice is high but adversely affected by side effects. Patients aged 80 years or more exhibit a significant decrease in compliance compared with younger patients.