Can Cannabis Cure Cancer? The Truth Behind the Hype
Social media is full of anecdotal tales of people using cannabis to cure all sorts of ailments including cancer. These stories of hope and positivity are shared to such an extent that they become facts in the minds of many, but is this justified?
Prior to conducting detailed research of my own, my impression was that medicinal cannabis may have a use in managing the symptoms of cancer and the side effects of treatment, but I was deeply sceptical about any claims relating to a cure.
So I decided to conduct some detailed analysis of the current research, if only to ensure that I know how to respond when someone asks me (for the one-hundredth time) “Have you tried cannabis for your cancer?”
Here’s what I found out…
What is medicinal cannabis?
The cannabis plant is a highly complex species in which nearly 500 different chemicals have been identified, 80-100 of these belonging to a class of compounds called cannabinoids (1). Cannabinoids hold special interest in the medical field as they have the potential to exert effects on living cells by interacting with cannabinoid receptors found on the surface of cells of the central nervous system (i.e. the brain and the spinal cord), the immune system and more generally throughout the body.
The two main cannabinoids that have yielded the most promise in a medicinal setting are THC (delta-9-tetrahydrocannabinol) and CBD (cannabidiol). These compounds are the active constituents of the three cannabis-based drugs that are licensed in the UK - Epidiolex (for epilepsy), Nabilone (for chemotherapy-induced sickness) and Sativex (for multiple sclerosis).
Despite the huge volume of anecdotal evidence claiming that cannabis can have a curative role in cancer, there are currently no cannabis-based drugs licensed to treat the spread of the disease. The only legal route for people seeking cannabis to control the spread of cancer is to buy cannabis oils from the growing number of online and over-the-counter suppliers.
The current state of research
Pharmaceutical companies are reluctant to invest in research into cannabis because of the unlikelihood of achieving a patent for these naturally occurring chemical compounds. Medical research, especially clinical research (i.e. research carried out on humans) is formidably expensive. Without the prospect of a patentable product, there is no commercial viability and no prospect of a return for shareholders.
Although there have been some small-scale clinical trials sponsored by universities and government bodies, the majority of studies have focused on human cell cultures and animals (usually mice and rats) because these laboratory-based experiments are far cheaper. Whilst these have shown some anti-tumour effects, killing cancer cells in a laboratory is not the same as killing cancer cells in a person. Cancer is such a complex and individual disease with over 200 different variants that the only way to guarantee the efficacy of any treatment is to conduct rigorous clinical research.
Numerous laboratory studies have demonstrated the anti-tumour effects of cannabinoids for a wide variety of cancer types including lymphoma (cancer of the immune system), lung, prostate, breast, skin, and pancreatic cancer (2). It is believed that this effect is achieved by the cannabinoids activating two cannabinoid receptors - CB1 and CB2, inducing apoptosis (programmed cell death) and interfering with the pathways that allow tumours to grow.
This hypothesis is backed up by a study conducted in 2005 which concluded that cancer cells that expressed (i.e. produced on their surface) a low number of CB1 and CB2 receptors were resistant to the anti-tumour effects of cannabinoids. In fact, low CB1 And CB2 cancer cells exposed to cannabinoids actually grew faster than those in the control group. It is believed that this is due to the known immunosuppressive effect of THC (3).
It appears then, that the ability of cannabinoids to accelerate or decelerate the growth of cancer cells can be explained by the varying levels of CB1 and CB2 expression found within individual tumours.
According to the National Cancer Institute, there are currently no ongoing clinical trials targeting cannabis as a treatment for cancer (4). The only trial to publish results was conducted in 2006 in Spain. The results were inconclusive.
The only clinical evidence currently available comes from individual case studies, but as no two persons’ cancers are identical, such evidence is of very limited scientific value.
What is worrying is the negative effect that cannabinoids may have on cancer immunotherapy. The use of immunotherapy-based treatments in cancer care (i.e. stimulating the cancer-fighting ability of the immune system) has increased dramatically over the last decade. These treatments are generally easier to tolerate as they target only the cancer cells, leaving healthy cells alone and sparing patients from some of the debilitating side effects of chemotherapy.
In a study of 140 patients receiving the immunotherapy drug Nivolumab, the response rate for patients who used cannabis was less than half the response rate of those who didn’t (15.9% vs 37.5%) (5). Although this was a fairly small study, it is an important reminder that non-licensed drugs have the potential to significantly affect the efficacy of standard treatment protocols.
The pre-clinical studies have certainly demonstrated that particular agents found in cannabis have the potential to exert anti-tumour effects. However, the lack of clinical research coupled with the potential of these agents to increase rather than suppress the growth of cancer and the impact they may have on licensed immunotherapy treatments worries me greatly. Until there is a lot more clinical research in this highly controversial area, I will not be using it and I would strongly advise others to refrain from doing so.