Cancer Research UK has funded research into cannabinoids, notably the work of Professor Chris Paraskeva in Bristol investigating the properties of cannabinoids as part of his research into the prevention and treatment of bowel cancer. He has published a number of papers detailing lab experiments looking at endocannabinoids as well as THC, and written a review looking at the potential of cannabinoids for treating bowel cancer.
We also support the only two UK clinical trials of cannabinoids for treating cancer, mentioned above, through our national network of Experimental Cancer Medicine Centres.
Our funding committees have previously received other applications from researchers who want to investigate cannabinoids but these failed to reach our high standards for funding. If we receive future proposals that meet these stringent requirements, then there is no reason that they wouldn’t be funded, assuming we have the money available.
To robustly test the potential benefits of cannabinoids in cancer, clinical trials in large numbers of people with control groups of patients – who aren’t given the treatment in question – would be needed.
Results have been published from only one small clinical trial testing whether cannabinoids can treat cancer in patients, led by Dr Manuel Guzman and his team in Spain. Nine people with advanced, incurable glioblastoma multiforme – the most aggressive brain tumour – were given highly purified THC through a tube directly into their brain.
This study showed that THC given in this way is safe and doesn’t seem to cause significant side effects, which suggests that cannabinoids could be worth pursuing in further clinical trials. But because this was an early stage trial without a control group, it couldn’t show whether THC helped to extend patients’ lives.
A handful of other clinical trials of cannabinoids for cancer are being set up. We’re helping to support the only two UK trials of cannabinoids for treating cancer, through our Experimental Cancer Medicine Centre (ECMC) Network. Both are at very early stages. One is testing a man-made cannabinoid called dexanabinol in patients with different types of advanced cancer. The second is testing whether Sativex (nabiximols), a highly purified pharmaceutical-grade extract of cannabis containing THC and CBD, can treat people with glioblastoma multiforme brain tumours that have come back after treatment.
Results from the second trial have now been released. These showed that combining Sativex with the chemotherapy temozolomide increased the number of patients who were alive one year after their brain tumour came back from 53% to 83%. This was a small trial with 21 patients taking part, so larger clinical trials are needed to confirm what the benefits of Sativex might be, and which patients are most likely to respond to this combination of treatments.
“But it worked for this patient…”
Doctors sometimes publish case reports about extraordinary or important observations they have seen in their clinic. For example, there is a published case report of a 14-year old girl from Canada who was treated with cannabis extracts (also referred to as “hemp oil”). But very little reliable information can be taken from a single patient treated with what’s an unknown mix of cannabinoids outside of a controlled clinical setting.
Dr Wai Liu at St George’s University is researching cannabis and cannabinoids for treating cancer (not funded by Cancer Research UK) to build up the evidence. He is happy to collect individual stories from UK patients and can be contacted by email. In the US, the Office of Cancer Complementary and Alternative Medicine gathers similar stories for their Best Case Series.
Unanswered questions
There are still many unanswered questions around the potential for using cannabinoids to treat cancer. It’s not clear:
which type of cannabinoid – either natural or synthetic – might be most effective
what kind of doses might be needed
which types of cancer might respond best to cannabinoids
how to avoid the psychoactive effects of THC
how best to get cannabinoids, which don’t dissolve easily in water, into cancer cells
whether cannabinoids will help to boost or counteract the effects of chemotherapy
These questions must be answered for cannabinoids to be used as safe and effective treatments for cancer patients. It’s the same situation for the many hundreds of other potential cancer drugs being developed and tested in university, charity and industry labs all over the world. Without doing rigorous scientific research, we will never sift the ‘hits’ from the ‘misses’. If cannabinoids are to get into the clinic, these hurdles first need to be overcome and their benefits proven over existing cancer treatments.
Can cannabis prevent or cause cancer?
There is no reliable evidence that cannabis can prevent cancer. There has been some research suggesting that endocannabinoids (mentioned earlier) can suppress tumour growth, and in experiments where mice were given very high doses of purified THC, they seemed to have a lower risk of developing cancer. But this is not enough solid scientific evidence to suggest that cannabinoids or cannabis can cut people’s cancer risk.
The evidence is a lot less clear when it comes to whether cannabis can cause cancer. This is because most people who use cannabis smoke it mixed with tobacco, a substance that we know causes cancer.
This complex issue hit the headlines in 2012 when the British Lung Foundation released a study suggesting that the cancer risks of cannabis had been underestimated, although this has been questioned by some experts, including Professor David Nutt.
What about controlling cancer symptoms such as pain or sickness?
There is good evidence that cannabinoids may be beneficial in managing cancer pain and side effects from treatment.
As far back as the 1980s, cannabinoid-based drugs including dronabinol (synthetic THC) and nabilone were used to help reduce nausea and vomiting caused by chemotherapy. But there are now safer and more effective alternatives and cannabinoids tend to only be used where other approaches fail.
In some parts of the world, medical marijuana has been legalised for relieving pain and symptoms (palliative use), including cancer pain. But one of the problems with using herbal cannabis is managing the dose. Smoking cannabis or taking it in the form of tea often provides an inconsistent dose, which may make it difficult for patients to monitor their intake. So, researchers are turning to alternative dosing methods, such as mouth sprays, which deliver a reliable and regulated dose.
Large-scale clinical trials in the UK have been testing whether a mouth spray formulation of Sativex (nabiximols; mentioned earlier) can help to control severe cancer pain that doesn’t respond to other drugs. Results from these didn’t find any difference in self-reported pain scores between the treatment and the placebo.
Cannabinoids may also have potential in combating the loss of appetite and wasting (cachexia) experienced by some people with cancer, although so far clinical evidence is lacking. One clinical trial comparing appetite in groups of cancer patients given cannabis extract, THC and a placebo didn’t find a difference between the treatments, while another didn’t show any benefit and was closed early.
Is Cancer Research UK investigating cannabinoids?
Cancer Research UK has funded research into cannabinoids, notably the work of Professor Chris Paraskeva in Bristol investigating the properties of cannabinoids as part of his research into the prevention and treatment of bowel cancer. He has published a number of papers detailing lab experiments looking at endocannabinoids as well as THC, and written a review looking at the potential of cannabinoids for treating bowel cancer.
We also support the only two UK clinical trials of cannabinoids for treating cancer, mentioned above, through our national network of Experimental Cancer Medicine Centres.
Our funding committees have previously received other applications from researchers who want to investigate cannabinoids but these failed to reach our high standards for funding. If we receive future proposals that meet these stringent requirements, then there is no reason that they wouldn’t be funded, assuming we have the money available.
Unfortunately, some scammers are using the email address
[email protected] and claiming to be based at our head office, tricking cancer patients and their families into handing over money for “cannabis oil”, after which they receive nothing in return. This is a scam and has nothing to do with Cancer Research UK or our employees. If you believe you have been a victim of this fraud, please contact the police.
“It’s natural so it must be better, right?”
There’s no doubt that the natural world is a treasure trove of biologically useful compounds, and there are countless examples where these have been harnessed as effective treatments.
Numerous potent cancer drugs have also been developed in this way – purifying a natural compound, improving it and testing it to create a beneficial drug – including taxol, vincristine, vinblastine, camptothecin, colchicine, and etoposide. But although these purified drugs in controlled high doses can treat cancer, it doesn’t mean that the original plant (or a simple extract) will have the same effect. So, although cannabis contains certain cannabinoids, it doesn’t automatically follow that cannabis itself can treat cancer.
“Have you seen this video? This guy says cannabis cures cancer!”
There are many videos and anecdotes online claiming that people have been completely cured of cancer with cannabis, hemp/cannabis oil or other cannabis derivatives.
Despite what these sources may claim, it’s impossible to tell whether these patients have been ‘cured’ by cannabis or not. There is usually no information about their medical diagnosis, stage of disease, what other cancer treatments they had, or the chemical make-up of their treatment. These sources also only publish the “success stories”, and don’t share how many people who used cannabis or its derivatives had no benefit, or worse, were potentially harmed.
Robust scientific studies describe the detail of experiments and share the results – positive or negative. This is vital for working out whether a potential cancer treatment is truly safe and effective, or not. And publishing this data allows doctors around the world to judge the information for themselves and use it for the benefit and safety of their patients.
This is the standard to which all cancer treatments are held, and it’s one that cannabinoids should be held to, too.