Review of clinical studies finds some evidence that cannabis-based medicines reduce cancer pain | Research

The takeaway

Five clinical studies spanning 1975 to 2014 found some evidence that THC and CBD formulations reduce cancer-related pain, though most studies were small and optimal dosing remains unclear.

Read this if you want to know what clinical evidence exists for cannabis in managing cancer pain.

Pain relief reported with as little as 2.7mg THC + 2.5mg CBD daily

What the researchers found

The review identified five clinical studies evaluating THC or CBD for cancer pain. THC oil capsules, THC:CBD oromucosal spray (nabiximols), and THC oromucosal sprays all showed some evidence of pain reduction in cancer patients.

Doses ranged from 2.7 to 43.2 mg/day THC and 0 to 40 mg/day CBD. One study found significant pain relief at doses as low as 2.7-10.8 mg THC combined with 2.5-10.0 mg CBD. Higher THC doses correlated with increased pain relief in some but not all studies.

Reported side effects included drowsiness, low blood pressure, mental clouding, and nausea/vomiting.

Why it matters

Cancer pain is often inadequately managed with standard treatments, and patients who do not respond to opioids need alternatives. This review gathers the limited but growing clinical evidence that cannabis-based medicines may fill this gap, particularly for chronic and neuropathic cancer pain.

The numbers in context

Five clinical studies reviewed (1975-2014). THC doses: 2.7-43.2 mg/day. CBD doses: 0-40 mg/day. Significant relief reported at doses as low as 2.7-10.8 mg THC + 2.5-10.0 mg CBD. Side effects: drowsiness, hypotension, mental clouding, nausea.

How the study worked

Selective review of literature published on Medline between 1975 and 2017. The search identified five clinical studies evaluating THC or CBD for cancer pain, ranging from small pilot studies to double-blind placebo-controlled trials.

What this study cannot tell us

Selective rather than systematic review, so study selection may be biased. Only five studies were included, most with small sample sizes. The studies span decades during which cannabis formulations and pain assessment methods changed substantially. Conflicting evidence on dose-response relationships.

How to read the evidence

Selective review of five clinical studies. Summarizes existing evidence but the underlying studies were generally small and used varied methods.

When this study was published

Published in 2017. Additional clinical trials on cannabinoids for cancer pain have been conducted since this review.

The bigger picture

Despite decades of anecdotal use, the clinical evidence for cannabis in cancer pain remains surprisingly thin. Only five studies met inclusion criteria across 40+ years of literature. The field needs larger, well-designed trials to move beyond the current state of "some evidence" to clearer clinical guidance.

Questions still open

What is the optimal THC:CBD ratio for cancer pain? Can cannabinoids reduce opioid requirements in cancer patients? Would modern high-quality cannabis products perform better than the formulations tested in earlier studies?

Common questions

Does cannabis work for cancer pain?

The five studies reviewed found some evidence of pain reduction, but the evidence is limited by small sample sizes and inconsistent results. Cannabis-based medicines appear most promising for patients who have not responded well to standard analgesics, particularly for neuropathic pain components.

What side effects were reported?

The most common side effects included drowsiness, low blood pressure, mental clouding, and nausea/vomiting. These are consistent with known effects of THC and generally manageable, but they may limit the doses that patients can tolerate.

Read the original research

A selective review of medical cannabis in cancer pain management.

Annals of palliative medicine, 6(Suppl 2), S215-S222

View on PubMed ↗Publisher’s paper ↗

Citation

Blake, Alexia; Wan, Bo Angela; Malek, Leila; DeAngelis, Carlo; Diaz, Patrick; Lao, Nicholas; Chow, Edward; O'Hearn, Shannon. (2017). A selective review of medical cannabis in cancer pain management.. Annals of palliative medicine, 6(Suppl 2), S215-S222. https://doi.org/10.21037/apm.2017.08.05