Medical cannabis treatment non-adherence among oncology patients: A prospective cohort analysis in Israel

Oncology patients frequently experience distressing symptoms. Medical cannabis (MC) is increasingly used, yet real-world MC discontinuation remains insufficiently characterized. This study aimed to identify baseline factors associated with voluntary MC non-adherence over six months among oncology patients.

Voluntary MC non-adherence was defined as patient-initiated discontinuation due to perceived ineffectiveness and/or MC-related adverse effects (AEs) at any follow-up point. Patients who continued MC through scheduled follow-ups were classified as adherent. Death, clinical recovery, and loss to follow-up were not classified as voluntary non-adherence events and were excluded from the primary adherence analysis.

Of 324 patients who initiated MC and completed baseline assessments, 186 were eligible for non-adherence analysis. At six months, 126/186 (68%) remained adherent and 60/186 (32%) were non-adherent. Among non-adherent patients, discontinuation was attributed to perceived ineffectiveness in 24/60 (40%) and MC-related AEs in 36/60 (60%). In bivariate analyses, non-adherence was more frequent among patients without prior cannabis experience (12% vs. 26%; p < 0.05), with less positive MC-attitudes scores (median 16 vs. 18; p < 0.001), and, among women, lower Female Sexual Function Index scores (median 10 vs. 24; p < 0.005). Penalized multivariable logistic regression associated bladder cancer, stomach cancer, and cardiac comorbidity with higher odds of non-adherence, whereas mood-related MC use and more positive MC-attitudes scores were associated with lower odds.

Voluntary MC non-adherence in oncology was associated with diagnostic, clinical, and psychosocial factors. These exploratory findings may identify patients requiring closer counseling, but require validation in larger prospective studies accounting for competing risks and socioeconomic barriers.