Tags:  Cannabis; THC; anti-cancer agents; glioblastoma

 

The problem:  There have been conflicting reports on whether (and how) how cannabis can be used in the treatment of cancer. Although the evidence is increasingly strong that cannabis can alleviate many cancer-related symptoms, its role in cancer treatment is less clear.

 

Why do this study?   The aim of this review is to provide a brief summary of the current literature regarding the medical use of cannabis in cancer treatment.

 

The review:  Preclinical data (from cell culture, animal models etc) regarding the effects of cannabis on cancer have been largely positive. For instance, tetrahydrocannabinol (THC) can bind to the cannabinoid receptors (CB1/2) on the surface of cancer cells and promote cancer cell death. However, clinical trials have been sparse and controversial. Synthetic cannabidiol (CBD) was demonstrated to be safe and possibly effective against solid tumors in a popular clinical trial with 119 patients with advanced cancer; CBD was the only treatment for 28 of them. Reductions in tumor size was reported, although only two complete reports were published. In a pilot phase I study of 9 patients with glioblastoma, intracranial THC administration was safe and some patients responded with reduced tumor growth rate. In phase II trials in 21 patients with recurrent glioblastoma, when a cannabis extract (nabiximols) was added along with current therapy, moderate relief in terms of 1-year survival was observed; the 1-year survival rate was 83% with nabiximols vs 56% with placebo (p = 0.042).

 

Conclusions:  The studies on the effect of cannabis in cancer are still in their infancy. The anti-cancer ability of cannabis is not strongly supported by current clinical trials.

 

What does this study add?  This article gives a brief overview of the clinical trials that have been performed with cannabis or cannabis-related products.

 

Funder:  Not provided.

 

Author conflicts:  None.

 

Commentary: Cannabinoids and related products (like THC) are frequently used for treatment of chemotherapy-induced nausea and vomiting. On the other hand, despite strong support for the anticancer effects of cannabis from case reports and blogs, clinical trial data supporting this is still very preliminary. Most of the clinical trials to evaluate the effectiveness of cannabis and related products in cancer have been performed in a small number of patients, making it difficult to interpret negative results.  Equally important, there are some risks of using cannabis, including the possibility that cannabinoids can increase serum levels of anti-cancer drugs and may decrease the effectiveness of immunotherapy. Nevertheless, this is an excellent review of a complex topic by two of the leaders in the field.