For about 20 years, science has been testing CBD as an adjunct therapy for cancer treatment. In almost all cases, from colon cancer to breast cancer, CBD has been found to conclusively help shrink tumors and stop or slow metastasis. As a natural, non-toxic form of cancer treatment, CBD has shown promising results and hopefully will be widely accepted into medical and especially oncological practices in the near future.
Cannabidiol was listed as a Schedule I drug until 2018, the vast majority its clinical studies on cancer treatment have been conducted on lab mice or human cells. Now that it is legal, a plethora of cancer studies using CBD treatment are currently underway, and though many are yet unpublished, they are forthcoming soon.
There has been much patient testimony as to the positive results of CBD use to treat some of the side effects of cancer and cancer treatment, such as nausea/vomiting, insomnia, depression and anxiety, general malaise, loss of appetite.
One example of CBD showing promise in cancer treatment is in breast cancer. Breast cancer has a high metastasis rate, and as such, is difficult to treat once cancer has metastasized. Id-1, an inhibitor of basic helix-loop-helix transcription factors, has recently been shown to be a key regulator of the metastatic potential of breast and additional cancers. A study by Sean D. Alexander, et al., published in Molecular Cancer Therapeutics "Report[s] that cannabidiol (CBD), a cannabinoid with a low-toxicity profile, could down-regulate Id-1 expression in aggressive human breast cancer cells."
A separate study published in Anticancer Research in 2018 of 119 cancer patients over a four-year period found that clinical responses were seen in 92% of the 119 cases with solid tumours including a reduction in circulating tumour cells in many cases and in other cases, a reduction in tumour size, as shown by repeat scans. No side-effects were exhibited by any of the patients. The study asserts that pharmaceutical-grade cannabidiol shows promise in the treatment of breast cancer and glaucoma patients.
Cancer of the colon is another focus in which cannabidiol has some hopeful medical prospects. It has already been established that CBD has anti-inflammatory and antioxidant properties. And CBD has shown therapeutic qualities in treating Crohn's Disease and Irritable Bowel Syndrome. But what about colon cancer? A 2012 study published in the Journal of Molecular Medicine examined mice induced with colon cancer. The study conclusively found that "In colorectal carcinoma cell lines, cannabidiol protected DNA from oxidative damage, increased endocannabinoid levels and reduced cell proliferation in a CB1-, TRPV1- and PPARγ-antagonists sensitive manner. It is concluded that cannabidiol exerts chemopreventive effects in vivo and reduces cell proliferation through multiple mechanisms."
For a visual description of how the endocannabinoid system (ECS) and cannabidiol can work to arrest cancer growth, see https://www.mdpi.com/2072-6694/12/11/3203 for a most recent study published in Cancers, 2020.