Chronic cannabis use in breast cancer survivors: A questionnaire study of Israeli patients

Introduction: As many as 90% of BC survivors suffer from long term sequelae, and many use or used cannabis during or after treatment to alleviate symptoms. Little is known about the effects of chronic cannabis use in this population. We aimed to study the patterns and effects of chronic cannabis use in BC survivors. Materials and methods: this is a single center cohort study. Participants were patients aged 30–75, diagnosed with stage 1–3 BC and prescribed medical cannabis. Patients were included if they completed chemotherapy at least 6 months before study entry and did not experience disease recurrence during follow up. Patients were interviewed over the phone regarding the patterns and effects of cannabis use. Results: Twenty-one patients were included. At the time of interview all patients increased their cannabis dose from 20 grams per month to an average of 47.6 grams per month. The positive effects reported were improved mood (76%), sleep (62%), pain (52%), neuropathy (29%) and appetite (5%). Adverse effects were increased appetite (10%), sleepiness (10%), cognitive adverse effects (10%), nausea (5%), mood adverse effects (5%) and gait problems (5%). Six patient (29%) reported themselves as being addicted to cannabis. Conclusion: In this cohort, long term cannabis use was associated with adverse effects, dose increments and risk of addiction. Further study is needed to better understand the safety of chronic cannabis use in BC survivors.