Products with equal balance of THC+ CBD seem to be particularly effective, data indicate

Medicinal cannabis can safely relieve cancer pain, while curbing the total number of meds and opioids taken, suggest the results of a multicentre registry study, published online in BMJ Supportive & Palliative Care.

Products with an equal balance of the active ingredients tetrahydrocannabinol (THC) and cannabidiol (CBD), rather than a dominance of either one, seem to be particularly effective, the data indicate. 

The findings prompt the researchers to conclude that medicinal cannabis is a safe and complementary treatment when conventional drugs fail to touch cancer pain.

Over half of patients undergoing anticancer treatment and two thirds of those with advanced or terminal disease experience pain, say the researchers.

Powerful opioids along with other meds, such as anti-inflammatory and anticonvulsant drugs, are usually prescribed for pain relief. 

But 1 in 3 patients will still experience pain, added to which the side effects of opioids include nausea, sleepiness, constipation, and respiratory depression, point out the researchers.

They therefore wanted to find out if medicinal cannabis could safely and effectively relieve cancer pain, while at the same time reducing the total number of meds and opioids taken.

They studied the treatment responses of 358 adults with cancer whose details were submitted to a multicentre registry—the Quebec Cannabis Registry in Canada—over a period of 3.5 years (May 2015 to October 2018).

The patients’ average age was 57; nearly half (48%) were men; and the 3 most common cancer diagnoses were genitourinary, breast, and bowel. Pain was the most frequently reported (72.5%) symptom that prompted a prescription of medicinal cannabis.

THC-dominant, THC:CBD-balanced, and CBD-dominant products were authorised in 24.5%, 38%, and 16.5% of patients, respectively. Taking the product by mouth was the most frequently recommended route (59%). 

Patients’ pain intensity, symptoms, total number of drugs taken, and daily morphine consumption were monitored quarterly for 1 year.

Pain intensity was rated, using validated measures, on a sliding scale from none (zero) to the worst possible (10), and pain relief from none (0%) to complete (100%), with two summary measures of overall pain severity and pain interference over the preceding 24 hours.

Medicinal cannabis seemed to be safe and well tolerated, with only 15 moderate to severe side effects reported by 11 patients, 13 of which were regarded as minor. The 2 most common side effects were sleepiness, reported by 3 patients, and fatigue, reported by 2. 

Two serious side effects (pneumonia and a cardiovascular event) were deemed unlikely to have been linked to medicinal cannabis. Only 5 patients stopped taking medicinal cannabis because of side effects.

“The particularly good safety profile of [medicinal cannabis] found in this study can be partly attributed to the close supervision by healthcare professionals who authorised, directed, and monitored [the] treatment,” highlight the researchers.

Statistically significant decreases were observed at 3, 6 and 9 months for worst and average pain intensity, overall pain severity, and pain interference [with daily life].

Overall, THC:CBD balanced products were associated with better pain relief than either THC-dominant or CBD-dominant products. 

The total number of drugs taken also fell consistently at all the subsequent quarterly check-ups, while opioid use fell over the first three check-ups.

This is an observational study, and as such, can’t establish cause, caution the researchers. What’s more, a significant number of patients were lost to follow up over the course of the 12 months while information on the use of other prescribed meds was limited to addition or discontinuation, they acknowledge. 

Nevertheless, they conclude: “Our data suggest a role for [medicinal cannabis] as a safe and complementary treatment option in patients with cancer failing to reach adequate pain relief through conventional analgesics, such as opioids.”


Notes for editors
Medical cannabis is effective for cancer-related pain: Quebec Cannabis Registry results doi 10.1136/spcare-2022-004003
Journal: BMJ Supportive & Palliative Care

Funding: Canadian Consortium for the Investigation of Cannabinoids; Collège des Médecins du Québec; Canopy Growth Corporation

Link to Academy of Medical Sciences press release labelling system

Externally peer reviewed Yes
Evidence type: Observational
Subjects: People