Patient reported medication-related problems, adherence and waste of oral anticancer medication over time

Objectives: Patients on oral anticancer therapy regularly experience medication-related problems (MRPs), potentially leading to non-adherence and medication waste. Most studies reporting these experiences have cross-sectional designs. The aim of our study was to explore patient reported MRPs, adherence and waste of oral anticancer medication over time. Methods: A prospective longitudinal quantitative interview study with 4 months follow-up was performed among patients on oral anticancer medication (mainly tyrosine kinase inhibitors, (anti)hormonal therapy, pyrimidine antagonists) using a semi-structured questionnaire. Patients from two Dutch university medical centres were included from March to December 2022 after informed consent was given. Four interviews were performed with 1 month in between. All interviews were audiotaped, after which the data were entered into an electronic case report form. The primary outcome was the mean number of MRPs per patient per interview round. Secondary outcomes were the proportion of patients with at least one MRP, types of MRPs, perceived non-adherence, medication waste (both in general and specifically for anticancer medication), costs of anticancer medication waste, and factors associated with medication waste as mentioned by the patient. Descriptive statistics were used to analyse the data. Results: Forty patients were included with a mean (SD) age of 64 (9) years; 43% were male. The mean number of MRPs per patient was 2.1 in the first interview and 1.2, 1.0 and 0.9 in the second, third and fourth interviews, respectively. Adverse drug reactions were the most frequently reported type of MRPs (30 (75%) patients in the first interview and 19 (65%) in the last interview). Unintentional non-adherence was regularly reported, especially in the first interview. Medication changes were frequent and associated medication waste was mentioned in all interviews. Conclusions: Many patients using oral anticancer treatment report MRPs and this number remains substantial over time.