Prescription cannabinoids, informally medicinal cannabis, can safely relieve cancer pain, while decreasing the number medications used, including opioids, suggest the results of a new multicenter registry study from Canada, published online in BMJ Supportive & Palliative Care.
According to investigators, cannabinoid products with an equal balance of the active ingredients tetrahydrocannabinol (THC) and cannabidiol (CBD), rather than a dominance of either one, appear particularly effective.
The findings prompt the researchers to conclude that medicinal cannabis is a safe and complementary treatment for patients undergoing treatment for cancer when relief from conventional medications is suboptimal.
Opioids have long been the gold standard for cancer pain management although other drug classes, including anti-inflammatory and anticonvulsant drugs, also are used.
Pain relief with opioid analgesics, however, is not always optimal, with one-third of patients treated for cancer reporting insufficient relief, study authors report. In addition, opioids are associated with well-known side effects, including nausea, somnolence, and constipation and respiratory depression is a risk at high doses.
Physicians, including 61.5% of general practitioners, are increasingly fielding patient requests to consider medical cannabis for relief of pain and other cancer-related symptoms, authors say. Prescription synthetic cannabinoids (ie, nabilone, dronabinol and nabiximols) have been studied for the management of cancer-related pain and for chemotherapy-induced nausea and vomiting and anorexia. The authors also cite research on the potential for cannabinoids to reduce opioid consumption in cancer pain management.
Thus, the Canadian research team set out to study further the efficacy and safety of medical cannabis for cancer pain management as well as the potential for the treatments to reduce the use of opioid medications, tapping data on participants in the large, prospective, multicenter Quebec Cannabis Registry (QCR).
QCR data were gathered for 358 adults with cancer for 3.5 years (May 2015–October 2018). Participants were referred by general practitioners or specialists and enrolled by physicians across the province of Quebec who agreed to prescribe medicinal cannabis within the QCR research framework.
Specific products authorized for participant treatment were THC-dominant (24.5%), THC:CBD-balanced (38%), and CBD-dominant (16.5%); oral administration was the route most frequently recommended (59%).
Outcomes associated with medicinal cannabis use were measured using the Brief Pain Inventory),Revised Edmonton Symptom Assessment System, the Medication Quantification Scale (MQS), and morphine equivalent daily dose (MEDD).
Pain intensity was rated, using validated measures, on a 0 to 10 scale with 0 reflecting no pain and 10 indicating the worst possible pain. Pain relief was measured from none (0%) to complete (100%). Two summary measures assessed overall pain severity and pain interference over the preceding 24 hours.
Average age of participants was 57 years and 48% were men. 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.
According to study findings, 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 somnolence, 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,” write study authors.
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] (P<.01 for all).
Overall, THC:CBD balanced products were associated with better pain relief than either THC-dominant or CBD-dominant products.
Review of MQS scores found decreases in number of drugs taken compared with baseline at all quarterly follow-ups (for 10%, 23.5%, 26.2% and 31.6% of patients). Decreases in MEDD scores as compared with baseline were reported at 3-month, 6-month and 9-month follow-ups in 11.1%, 31.3% and 14.3% of patients, respectively.
The study’s observational nature, the authors write, does not permit establishment of cause and effect. Other limitiations they mention inlcuded loss to follow up of a significant number of patients over the 12 months as well as addition or discontinuation being the only information available on use of other medications.
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.”
Reference: Aprikan S, Kasvis P, Vigano M et al. Medical cannabis is effective for cancer-related pain: Quebec Cannabis Registry Results. BMJ Support Palliat Care. 2023. Published online ahead of print May 2, 2023. doi:10.1136/spcare-2022-004003