Only 8 studies exist on cannabis use during radiation therapy, with some benefits but high bias risk

Of 48 records screened, only 8 clinical studies met criteria. These suggested cannabinoids may reduce anxiety before starting radiation, manage nausea and vomiting comparable to standard care, reduce glioma relapse symptoms, and provide symptom relief over 3 years after head and neck radiation (but not during or immediately after). Six of 8 studies had high risk of bias. Side effects included drowsiness, dry mouth, and substantial rates of dizziness, fatigue, and disorientation.

Scoping review following PRISMA-ScR guidelines, searching multiple databases for clinical studies of cannabis use in patients undergoing radiation therapy. Risk of bias assessed using Cochrane RoB 2.0 and ROBINS-I frameworks.

An estimated 20% of Canadian cancer patients already use cannabis during treatment. Oncology professionals feel too uninformed to counsel patients, and this review confirms the evidence gap is real.

The 3-year delayed symptom relief finding for head and neck radiation is intriguing: cannabinoids may address long-term radiation side effects (chronic pain, swallowing difficulties) rather than acute treatment effects. This distinction could shape future research.

8 studies total (very limited evidence); 6 had high bias risk; heterogeneous cancer types and radiation protocols; no studies measured long-term cannabis consumption impact; included studies predate modern radiation techniques.