A patient recently asked if Cannabis oil might be used to cure a small skin cancer.
Never having been asked this before, a thorough review of the available literature was carried out, but sadly there have been absolutely no published clinical trials to date so it is impossible to recommend this treatment.
Cannabinoids do bind to receptors which are present in many cells and there is some evidence in highly controlled laboratory circumstances that cannabinoids may inhibit some cancers. Sadly, there is also evidence that it may actually accelerate growth in others. There have been no useful trials in living humans and animal trials are not conclusive. The link at the end of this article gives more information and is maintained by the Uk Cancer Society so may be seen as a trusted and valid reference.
The proposed mechanisms of action of cannabis oil are plausible but unfortunately that does not make it safe or effective.
A search of the internet lists many sites where people claim to have had skin cancers cured by cannabis oil. This effect may occur for one of the following reasons:
- It is possible that the cannabis oil actually removed the cancer (a small proportion probably do get better as a result of treatment)
- The act of rubbing itself can stimulate immune reactions which can deal with some skin cancers.
- Some skin cancers will naturally go away on their own.
- The skin cancer may actually have been something else entirely (misdiagnosis of these lesions is common)
It is important to note that some of the cancers being illustrated as treated with the oil are of a type that can spread and potentially kill the patient. We feel that using a totally untrialled medication like cannabis oil in such circumstances is very unwise.
Cannabis oil is of course illegal in New Zealand so as a treatment option it is not valid in any case. Hemp oil contains cannabinoids but the concentration is much lower.
The good news is that not all skin cancers need surgery - some may be suitable for treatment with cream, especially in older patients and in many cases, the treatment is fully funded.
If you think you may have a skin cancer, please make an appointment - our doctors are very good at skin diagnoses and can give you proper treatment advice from leaving harmless things alone through creams to surgical removal if required.
We feel that it is important to point out that there is also good evidence that smoking cannabis (as opposed to a topical application) significantly increases the risk of lung and head and neck cancer, whether or not it is used in combination with tobacco. Whilst there may in the future be a place for medicinal use of cannabinoids, at present the evidence very strongly suggests that in almost all cases the side effects outweigh the benefits.
Addendum September 2016:
We have been asked to provide evidence to support the statement that cannabis smoking causes cancer. The spectrum of carcinogens in cannabis smoke is similar to that in tobacco smoke. It is the inhaling of burned leaves that results in tar deposition in the lungs. Cannabis smoke is generally retained in the lungs for longer than tobacco smoke which may also explain how cannabis causes chronic obstructive pulmonary disease. In a New Zealand study in 2008, it was found that cannabis smoking was associated with similar, or higher rate of lung cancer than tobacco smoking. Cannabis has also been associated with testicular cancer. Recent evidence casts doubt on the assertion that head and neck cancers are caused by cannabis smoking though it is important to note that the development of head and neck cancer is very slow and often occurs in association with other risk-factors. Some studies have shown an association and some have not. It remains our advice that the smoking of any substance is profoundly unwise and there is no reason to believe that cannabis is any safer than tobacco.
Cannabis Sativa: Flores Y Plantas