In recent decades, the efficacy of cannabis has become a point of interest for researchers and oncologists who treat various types of cancer. Scientific evidence has mounted, with study after study confirming that the plant has powerful healing ability for multiple forms of cancer.
Cannabis as a treatment for cancer can both alleviate side effects caused by more conventional chemotherapy regimens as well as a proven ability to inhibit the growth of tumors.
A 2016 study in Current Oncology concluded that "cannabinoids induce tumor cell death and inhibit tumor angiogenesis and invasion in animal models of cancer." The mechanism of action is believed to be upregulation of genes responsible for killing cancer cells. Cannabis has been also shown to increase autophagy, the process of removing and "recycling" dysfunctional cells (including cancer cells), in animal studies.
For management of symptoms caused by cancer itself and commonly prescribed treatments like chemotherapy, respondents in one 2018 study by the leading medical journal Cannabis and Cannabinoid Research found that over 95% of patients prescribed cannabis reported moderate or significant improvements in their symptoms. Encouragingly, cannabis treatment also substantially improved quality of life in the cancer patients studied: "only 18.8% of patients reported good/very good quality of life before treatment initiation, whereas 69.5% did so after the 6-month cannabis regime".
The mechanism of action in the treatment of prostate cancer has recently been discovered. Prostate cancer cells were shown in one study to have a higher concentration of CB1 and CB2 receptors than normal cells. Introducing cannabis causes "a dose and time dependent decrease in cell viability, and increased apoptosis along with decrease in androgen receptor protein expression, PSA expression, and secreted PSA, suggesting that cannabinoids should be considered as agents for the management of prostate cancer".
Cannabis as a treatment for lung cancer shows promise as well. Dr. Len Horovitz, a New-York based lung specialist, said that cannabis "seems to have a suppressive effect on certain lines of [lung] cancer cells".
Glioma, a type of brain cancer, has been shown to respond well to cannabis treatment. Studies in labs have shown that when cannabis is introduced induce self-destruction of cancer-causing cells called "glioma-initiating cells" through similar mechanisms of action described for prostate cancer and liver cancer treatments.