PUBLISHED ON: 29 November 2018

Health claims surrounding cannabis products frequently hit the news. But is there any evidence that they could reduce the risk of breast cancer coming back?   

Cannabis oil

Breast Cancer Care’s Helpline often gets calls from people who are worried about their breast cancer returning after treatment, and who want to know if they can do anything to help. 

Medical cannabis and cannabis oils have been in the news a lot recently. While these stories haven’t been about cancer, it’s clear some people believe cannabis could have anti-cancer properties. 

However, despite ongoing research in this area, there’s no reliable evidence that any type of cannabis is an effective treatment for cancer. 

What are cannabinoids? 

Cannabis contains ingredients called cannabinoids. Two of these are THC (tetrahydrocannabinol) and CBD (cannabidiol).  

THC is the chemical responsible for most of the effects that cannabis has on the mind or behaviour. CBD doesn’t cause these effects.  

Some people think that cannabinoids like CBD may have health benefits.  

Can cannabinoids be used to treat cancer? 

According to Cancer Research UK: ‘Many hundreds of scientific papers looking at cannabinoids and cancer have been published, but these studies simply haven’t found enough robust scientific evidence to prove that these can safely and effectively treat cancer.’  

The problem is that almost all these studies have been carried out either on cancer cells in the laboratory or on animals. And what works in the laboratory or in animals doesn’t necessarily have the same effect in the human body. 

The chemicals used in these studies are also very different to the cannabis oils and products available to buy. 

While a quick Google search will uncover examples of people who claim to have treated their cancer using cannabis oil, it’s not possible to draw conclusions from individual stories like these. 

In order to properly assess the effects of cannabinoids on cancer, large clinical trials are necessary.  

Is cannabis oil illegal?  

According to the NHS website: ‘Many cannabis-based products are available to buy online, but their quality and content is not known. They may be illegal and potentially dangerous.’  

Some cannabis-based products, such as hemp oil, can be bought legally as supplements from health food stores. However, there’s no guarantee that these products have any health benefits. 

As the NHS website states: ‘Health stores sell certain types of ‘pure CBD’. However, there's no guarantee these products will be of good quality. And they tend to only contain very small amounts of CBD, so it's not clear what effect they would have.’  

A very small number of people may get medical cannabis on prescription, for example if they have a severe form of epilepsy, or vomiting or nausea caused by chemotherapy. However, this likely to be the case only if other treatments have been tried first. 

Dealing with worries about recurrence 

Most people worry about breast cancer coming back (recurrence). These worries are normal, and the fear and anxiety usually lessens with time. 

Knowing how to continue to be breast and body aware after treatment and the symptoms you should report can help manage your feelings of uncertainty. 

The treatment you received will have been given to reduce the risk of the breast cancer coming back at its original site or elsewhere in the body. 

Everyone copes with worries about recurrence in their own way, and there are no easy answers. But keeping quiet about them is probably not the best approach.  

Breast Cancer Care’s Forum lets you share your worries with other people in a similar situation to you. 

You can also read our tips on coping with anxiety and find suggestions in BECCA, our free app that helps you move forward after breast cancer treatment. 

Worries about recurrence