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

The takeaway

A scoping review found only 8 clinical studies on cannabis use during radiation therapy, suggesting possible benefits for anxiety, nausea, and long-term symptom relief, but 6 of 8 had high risk of bias.

Radiation oncologists, cancer patients undergoing radiation, and supportive care researchers.

Only 8 studies exist; 20% of cancer patients already use cannabis

What the researchers found

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.

Why it matters

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 numbers in context

48 records screened; 8 included; 6 had high bias risk; ~20% of Canadian cancer patients use cannabis; side effects: drowsiness, dry mouth, dizziness, fatigue, disorientation.

How the study worked

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.

What this study cannot tell us

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.

How to read the evidence

Preliminary: only 8 studies identified, 6 with high bias risk; the evidence base is critically thin.

When this study was published

Published 2020.

The bigger picture

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.

Questions still open

Should oncologists recommend cannabis for long-term radiation side effects rather than during treatment? Would CBD alone (avoiding THC side effects) be effective?

Common questions

Can cannabis help during radiation treatment?

The limited evidence suggests possible benefits for pre-treatment anxiety and nausea, but not for immediate radiation side effects. Long-term symptom relief (3+ years after head and neck radiation) was noted. However, 6 of 8 studies had high bias risk.

What side effects occur from cannabis during cancer treatment?

Drowsiness and dry mouth were most common. Substantial rates of dizziness, fatigue, and disorientation were also reported, which could compound radiation-related fatigue.

Read the original research

Cannabis and Radiation Therapy: A Scoping Review of Human Clinical Trials.

Journal of medical imaging and radiation sciences, 51(2), 342-349

View on PubMed ↗Publisher’s paper ↗

Citation

Rosewall, Tara; Feuz, Carina; Bayley, Andrew. (2020). Cannabis and Radiation Therapy: A Scoping Review of Human Clinical Trials.. Journal of medical imaging and radiation sciences, 51(2), 342-349. https://doi.org/10.1016/j.jmir.2020.01.007