Factors associated with medication adherence trajectory among patients treated with oral anticancer drugs: a multicentre cohort study.

PURPOSE: Optimal medication adherence to oral systemic anticancer therapies (SACTs) is critical for effective cancer management. However, the factors influencing adherence, particularly in relation to the longitudinal course of the disease, remain poorly understood. This study aimed to identify factors associated with medication adherence trajectories among patients initiating oral SACTs. METHODS: A multicentre cohort study was conducted among patients initiating oral SACTs and enrolled in a multidisciplinary risk management programme during day hospitalisation. Medication adherence trajectories were identified using group-based trajectory modelling (GBTM), based on scores from a validated six-item medication adherence questionnaire. Factors associated with trajectory allocation were examined using bias-reduced multinomial logistic regression. RESULTS: A total of 135 participants were included, of whom 71 provided at least two adherence scores for trajectory modelling. Three latent groups of adherence trajectories were identified: (i) continuous optimal adherence (73.2%), (ii) improving adherence (9.9%), and (iii) declining adherence (16.9%). In multivariate analysis, subjects belonging to the declining adherence group were more likely to belong to the low-income category. CONCLUSION: GBTM identified three distinct and clinically relevant patterns of oral SACT adherence trajectories among outpatients followed during day hospitalisation. Understanding the factors influencing these trajectories provides a dynamic perspective on the complex phenomenon of medication adherence and highlights actionable factors to support tailored health interventions.