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Medicinal Cannabis and Cancer: what is new??

Posted by Manuela Boyle on 28 June 2021
Medicinal Cannabis and Cancer: what is new??
Cannabinoids are defined as chemical compounds that interact with the cannabinoid receptors, which in humans include CB1, predominantly expressed on neurons in the brain and central nervous system, and CB2 expressed in non-neuronal tissues such as immune cells. Cancer cells can express these receptors as well, and studies are mixed as to whether it can indicate a better or worse prognosis compared to cells that do not have the receptors. But the effects of cannabinoids on cancer are not limited to interaction with these receptors as several studies have documented effects that are not prevented by blocking these receptors. THC is the cannabinoid classically associated with the psychoactive and appetite-stimulating effects, although it is not exclusively so. Cannabidiol is another cannabinoid that also has been studied for anti-cancer effects and is often referred to as CBD.

The FDA has approved several drugs that we will call cannabinoid-based (i.e. they are not naturally derived but synthetic): dronabinol (Marinol and Syndros, delta-9-THC), and nabilone (Cesamet, THC-similar). As of June 25, 2018, the FDA approved Epidiolex (cannabidiol naturally derived from cannabis) for two rare and severe forms of epilepsy, marking the first time a non-synthetic cannabinoid has been approved in the United States. However, the first regulatory approval for a naturally-derived cannabis product in North America was given by Health Canada for nabiximols (Sativex) for symptomatic relief of neuropathic pain (2005) and muscle spasticity (2010) from multiple sclerosis. Nabiximols is a formulated extract of C. sativa with a THC:CBD ratio of 1:1 as well as other cannabinoid and non-cannabinoid components.

Terpenoids and flavonoids are responsible for the color and aroma of plants and also serve biological functions.

An hypothesis that has received a lot of attention is that cannabis has benefits on cancer that is maximized by an 'entourage effect', meaning that all the individual components of the plant work together to create an effect that's greater than the effect of any one component. Blasco-Benito et al published in 2018 a study that compared the antitumor effects of THC alone compared to a whole plant extract and found that the extract was more potent than THC in cell culture and animal models of ER+, HER+ and triple negative breast cancer. Likewise, the extract was synergistic with tamoxifen, lapatinib and cisplatin chemotherapy in those respective cancer types. The authors also identified that the enhanced potency of the extract did not appear to be due to the 5 most abundant terpenes in the extract, consistent with the theory that the potency was due to the cannabinoid content. 

In another Taha et al conducted a retrospective observational study and reviewed the charts of 140 patients with advanced melanoma, non-small cell lung cancer and renal cell carcinoma who received nivolumab. 89 patients received nivolumab and 51 patients received cannabis with nivolumab. The authors found that the only significant factor that lowered the response rate to immunotherapy was cannabis (37.5% for nivolumab, 15.9% who received both (odds ratio 3.13; 95% CI 1.24-8.13, p=0.02). However, progression-free survival and overall survival was not effected by cannabis. Since this is a retrospective study and subject to numerous confounding factors, it is mainly a precautionary study that warrants additional research before making any definitive conclusions.



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Author:Manuela Boyle
Tags:NewsEvidence Based ResearchCancer


  • The Institute for Functional Medicine
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