The potential role of phytocannabinoids and the endocannabinoid system (ECS) in confining malignant tumors is among the most discussed topics in the field of medical cannabis.

There are countless anecdotes from patients and even clinical studies (usually small ones) about the effect of cannabinoids on controlling different cancer types. Many patients also believe that cannabis and its derivatives are effective tools for fighting against cancer. Hence, many cancer patients want to use cannabis to treat their disease.

The state of evidence

It should be noted that there is not enough clinical evidence about the efficacy of cannabinoids on cancer in humans; however, there is plenty of evidence from preclinical studies indicating that cannabinoids and ECS can potentially play a role in treating cancers.

A review by Dr. Hinz and Dr. Ramer published in the British Journal of Pharmacology has summarized the current state of evidence about the interactions (and possible therapeutic effects) between the ECS and tumors as the followings:

Source: Hinz B, Ramer R. Anti-tumour actions of cannabinoids. Br J Pharmacol. 2019;176(10):1384-1394.

• Up-regulation of some ECS components (e.g., receptors, endogenous ligands,…) has been reported in several preclinical studies; however, the functional implication of this phenomenon has not been understood.
• Cannabinoid can show their antineoplastic effect in several ways:
  • Cannabinoids can control tumoural growth by inhibiting cell proliferation or promoting apoptosis.
  • Cannabinoids may also control the invasiveness of cancerous cells that may improve patients’ outcomes. For instance, activation of CB1 receptors by 2-AG inhibited prostate cancer cell invasion.
  • Data from animal studies showed that cannabinoids could inhibit angiogenesis by down-regulation of proangiogenic factors such as VEGF.
  • There is also some evidence that cannabinoids may boost the immune response to tumors to control cancerous cells’ growth.
• The best clinical evidence about the effectiveness of cannabinoids on cancer comes from a randomized placebo-controlled phase II trial on THC and CBD in treating Glioblastoma Multiform on 21 patients. Patients who received cannabinoids had significantly higher one-year survival (83% vs. 53%).
• Cannabinoids can also enhance the effectiveness of existing chemotherapeutic agents. For instance, CBD and THC increase the cytotoxicity of several chemotherapeutic agents such as cytarabine, doxorubicin, mitoxantrone, carmustine, temozolomide, bortezomib, carfilzomib, and cisplatin.

In summary, the current evidence does not support the use of cannabinoids and cannabis-based medications as therapeutic options for treating cancer in clinical settings; however, cannabinoids and the ECS are a plausible target for developing new medications that can be added to our arsenal to the fight against cancer.

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