As a child of the 1960s, when I settled down to write a blog about cannabis and breast cancer, I thought, “This will be easy.” That was weeks ago! It turns out that there is now a lot of research to consider on the benefits and risks of cannabis use, and I have a lot of catching up to do.

This is the first of a three-part blog series on cannabis. It will provide a general overview about why cannabis might be considered useful to treat or ameliorate the collateral damage of breast cancer and its treatments. The next two will explain how cannabis interacts with the immune system through the endocannabinoid system, and how this may affect cancer cells.

First, we have to get our definitions straight. The cannabis plant (Cannabis sativa) produces at least 545 chemical compounds of different biogenetic classes. Many of these phytochemicals have been shown to have medicinal and physiological activity. The most prominent and most studied metabolites are tetrahydrocannabinol (THC) and cannabidiol (CBD). THC is the metabolite that causes the high you get from smoking marijuana. CBD is more likely to provide relief from short-term side effects or the long-term collateral damage of cancer treatments. Some products contain THC and CBD, while some contain only THC or CBD. The proportion of THC to CBD in a product that contains both will determine the effect of these cannabinoids. There are also non-cannabinoid metabolites that have therapeutic potential.

The most surprising thing I learned while researching these blogs: our bodies have cannabidiol receptors that are similar to the estrogen receptors that are the targets of the hormonal therapies we use to treat hormone-sensitive breast cancer.

So, to begin: Is cannabis safe? One review of 25 English-language pooled studies found that marijuana use was indeed basically safe, though some research suggests it may increase the risk of testicular cancer.

In 2020, a study published in the Journal of Cannabis Research (yes, this journal exists!) showed that people are using medical cannabis for a wide range of health issues, highlighting the need for more research on its clinical benefits. Some of the most common uses include improving mental health and sleep, and reducing pain, neurological problems, and cancer-related side effects.

A 2020 study published in the journal Pharmaceuticals assessed the short-term outcomes of medical cannabis treatment prescribed by oncologists to treat cancer-related side effects. The study found THC was better for sleep than CBD. However, CBD oils appeared to help more with the collateral damage of cancer treatments. The American Pain Society guidelines on cannabis use for pain recommend cannabis oils that have low levels of THC and high levels of CBD.

Have questions about cannabis use? Put them in the comments and I will try to address them in my next two blogs on cannabis and cancer.



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