Cannabis and cancer: everything you need to know

From palliative pain management to the side-effects of chemotherapy, cannabis can support cancer patients in significant ways. Some studies even suggest that cannabis could help treat, and possibly prevent, certain types of the disease.

Here’s what the science says.

The statistics sound scary: one in two people living in the UK will get cancer in their lifetime. But fortunately, scientists are developing treatments that can truly kick cancer to the curb, with survival rates steadily increasing for decades. 

So, where does cannabis fit into the cancer conversation? While high-quality research still remains scarce, cannabis in its many forms has been shown to benefit people battling cancer in three key ways: pain management, helping ease the side effects of chemotherapy, and potentially even treating (and preventing) some types of cancer. 

How cannabis interacts with the human body

Cannabis has a rich chemical profile made up of around 550 compounds and more than 100 phytocannabinoids. These phytocannabinoids — the most well known being delta-9 tetrahydrocannabinol (THC) and cannabidiol (CBD) — ‘cling’ to cannabinoid receptors present in the human body. 

Scientists have discovered two main cannabinoid receptors (although there is speculation that more exist): CB1 is mainly present in the nervous system, connective tissues, gonads, glands, and organs, and CB2 is mostly found in the immune system. Many tissues, however, contain both CB1 and CB2. 

Cannabinoid receptors are an integral part of the endocannabinoid system (ECS), a complex network of cell receptors and chemical signals in the body that is essential for human health. Cannabis’ phytocannabinoids function similarly to the endocannabinoids that are naturally found in a human’s ECS.

Speaking to Cannabis Health last year, Dr Wai Liu, a senior research fellow at St George’s, University of London who has dedicated much of his career to the study of cannabinoids and cancer, shared his optimism around cannabis and its potential in cancer care and treatment. 

“As chemicals, THC and CBD are fantastic,” Dr Liu said. “They have so many properties and depending on what dosage you use, you can actually have different effects.”

Due to the symbiotic nature of cannabis’ phytocannabinoids and cannabinoid receptors in the body, it only makes sense that cannabis may play an important role in cancer care, treatment and (possibly) prevention.  

Cannabis and cancer: pain management

A number of studies have shown that cannabis can support pain management and reduce opioid use in both cancer and non-cancer situations.

Early last year a comprehensive assessment of the benefits of medical cannabis for cancer-related pain found that most patients surveyed experienced significantly less discomfort while using medical cannabis as well as a decrease in other cancer-related symptoms, leading to a general reduction in use of opioid-based painkillers. 

One area where cannabis has reportedly had significant benefits is in palliative care pain management. A 2022 study from the University Hospital in Syracuse, New York found that the majority of oncology patients (85%) surveyed who used medical cannabis reported symptom improvements, nearly half reported reductions in pain, and just under half reported a decrease in their use of opioid pain medications. A 2021 study in Thailand found similar results.

One recent study, however, which looked at the impact of CBD only on palliative care, found “no detectable effect of CBD on change in physical or emotional functioning, overall quality of life, fatigue, nausea and vomiting, pain, dyspnoea or appetite loss.”

Yet even the authors concede that the cannabis plant is complex, and that their next study will look at a combination of CBD and THC. It’s also important to note that even CBD — depending on whether it’s full-spectrum or CBD isolate, how it’s produced, and a number of other factors — ranges in its effects, and future research on CBD and palliative care should capture this complexity. 

Questions also exist around whether a cannabis ‘placebo’ could have similar effects to the plant itself on pain management. A recent meta-analysis of a number of clinical trials testing both CBD and THC-based treatments against placebos resulted in comparable amounts of pain relief. 

Ted J. Kaptchuk, director of the Program in Placebo Studies and The Therapeutic Encounter at Harvard-affiliated Beth Israel Deaconess Medical Center, said in a statement: “By the strict orthodoxy of modern medicine, a doctor would say cannabis products don’t work—they’re no better than a placebo.” 

But he went on to acknowledge how cannabis can be used to supplement habit-forming opioids which are known to have dangerous side effects.

“If something helps relieve your pain and doesn’t cause any significant harm, I would say go ahead and use it,” said Kaptchuk.

Cannabis and cancer: chemotherapy

Cannabis as a treatment for chemotherapy-induced nausea and vomiting (CNV) has been around since the 1980s, and is perhaps the most well-known form of medical cannabis treatment related to cancer. 

In a review of 28 trials looking at cannabis and CNV (most from before 2000), cannabis-based medicines were favoured amongst patients over other anti-nausea medications available. A 2020 clinical trial looking at the impacts of cannabis on CNV that tested both cannabis and a placebo amongst patients found similar results, with the vast majority (83%) of people surveyed preferring cannabis to the placebo. Less than one-third experienced negative side-effects including sedation, dizziness, or disorientation. 

Cannabis can also help with chemotherapy-induced peripheral neuropathy (CIPN) — essentially nerve damage and associated pain that can come with chemo. One analysis found a significant difference in CIPN between cannabis-exposed patients and controls (15.3% and 27.9%, respectively).

Researchers also found a difference in CIPN depending on whether cannabis was administered before oxaliplatin (a common chemotherapy drug) or after, with 75%  improvement in the cannabis-first scenario. This suggests cannabis has a neuropathy ‘protective effect’ when administered before traditional chemo drugs. 

Cannabis and cancer: treatment and prevention

The potential for cannabis to treat and prevent certain types of cancers is an exciting and evolving field of research, with recent scientific and anecdotal evidence showing promising signs. As Dr Liu emphasised to Cannabis Health, the compounds found in both THC and CBD “definitely have anti-cancer properties”. 

Cannabis has been found to help produce more proteins that stimulate apoptosis, or programmed cell-death, which are overly-regulated in the presence of cancer cells. According to Dr Liu CBD specifically has been found to ‘trick’ cancer cells into producing more of these proteins which can then help a patient regain sensitivity to other treatments.

Dr Liu and his team carried out research several years ago which found that CBD and THC could increase sensitivity to radiotherapy treatments in mice with brain tumours. When given CBD and THC with just minor radiotherapy, the tumours remained unchanged and ceased to grow. When the two therapies were combined, the tumours virtually disappeared.

A promising new study also suggests that the right mixture of cannabinoids could help treat ovarian cancer.

Professor Hinanit Koltai at the Volcani Institue in Isreal asked: ‘What compounds in cannabis are the active ones? And what combination of molecules is optimal?’

After testing different combinations, they found that a purified formulation of THC, CBC and CBG molecules together led to cell apoptosis – or programmed cell death – and was 50 times more effective on cancer cells than on healthy ones. Professor Koltai concluded that cannabis could be a ‘complementary and effective anti-cancer treatment’ for ovarian cancer, with more extensive clinical trials ‘desperately needed’. 

READ MORE: Cannabis and ovarian cancer: continuing Michelle Kendall’s legacy

Another major 2022 study on cannabis and cancer prevention suggests that cannabis use could have a ‘protective factor’ for renal cell carcinoma (one of the 10 most common cancers in the United States, accounting for 90% of all kidney cancers) and prostate cancer.

The study’s authors said: “Previous use of cannabis was associated with a lower risk of bladder cancer, renal cell carcinoma, and prostate cancer.”

The need for more research into cannabis and cancer

Hundreds of studies exist that look at the relationship between cannabis and cancer.

In 2022, Cancer Research UK updated its guidance on cannabis and cancer treatment, a move welcomed by experts in the cannabis and medical communities. The charity even concedes that lab tests have delivered “intriguing results from lab experiments looking at a number of different cancers, including glioblastoma brain tumours, prostate, breast, lung, and pancreatic cancers.”

But as the charity also points out (as do many research reviews related to cancer and cannabis), there is simply not enough definitive, robust evidence to promote cannabis as a means to prevent or treat cancer.

While this consensus is likely frustrating for many cancer patients and for families dealing with the disease, it should also be seen as a clarion call for science to step up when it comes to researching the (seemingly many) benefits that cannabis can have in the fight against cancer.  

As Dr Lui expressed: “I for one, support the call for [more clinical trials], not only because I think it will be useful, but because it is only after a fully-powered clinical trial that we will know once and for all whether cannabinoids have a therapeutic role to play in patients with cancer.

“As I see it, whatever the outcome, the result will be positive – that is, if the results show cannabinoids have no effect, it can then be put to bed, and people can then focus on other drugs that can help in the disease management. However, if the results are positive, patients will then have another drug that may help their case.”

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