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Prostate Cancer and Cannabis: State of the Research

Since its establishment almost two decades ago, Movember has become a global phenomenon. Alongside testicular cancer and mental health, prostate cancer awareness is one of the core focus areas of the month-long event.

 

By 2030, the movement aims to reduce the number of men dying prematurely by a quarter. When it comes to prostate and testicular cancer, this means halving the number of men suffering the side effects of treatment and the number of men dying from these conditions.


Over a remarkably similar timeline, cannabis has received a lot of attention for its anti-tumoral properties as well as its ability to reduce the challenging side effects of chemotherapy.

 

With the growth of medical cannabis, more patients than ever are now relying on the pain relieving and antiemetic properties of the plant during conventional cancer treatments. The use of cannabis by patients with cancer is by no means a new development.


Prostate cancer remains the leading non-skin cancer diagnosis for men in the US and elsewhere. There is a growing interest in the plant by patients with prostate cancer. According to a recent survey, many patients with prostate cancer are already relying on it for the treatment of cancer-related symptoms.


Where does the research stand on cannabis use for the treatment of prostate cancer? How many men already rely on the plant during cancer treatment, with or without the support of their oncology team?


Cannabinoid Receptor As a New Target for the Treatment of Prostate Cancer


In 2005, researchers working out of the Department of Dermatology at the University of Wisconsin published a new theory for the treatment of prostate cancer in the pages of Cancer Research. In their model, they discovered significantly higher levels of both CB1 and CB2 cannabinoid receptors in cultured human prostate cancer cell lines when compared to healthy prostate cell lines. 


The team applied WIN-55,212-2, which is a potent cannabinoid receptor agonist, to prostate cancer cells to find it had powerful results for reducing cell viability. WIN-55,212-2 also promoted cell-apoptosis and reduced cancer cell proliferation. WIN-55,212-2 is an often used cannabinoid receptor agonist, which is different in molecular structure but very similar in effects to THC.


Since 2005, a growing body of research has supported cannabinoids and endocannabinoids as proapoptotic options. Prostate cancer cells, as well as many other cancer cell lines, consistently measure significantly higher levels of both endocannabinoid receptors than normal cells.


A higher number of cannabinoid receptors has opened up both phyto- and endocannabinoids as possible treatment options. As a 2015 publication in Oncology Reports highlighted, “Recent evidence shows that derivatives of Cannabis sativa and its analogs may exert a protective effect against different types of oncologic pathologies.”


The natural evolution of this theory led researchers at the University of British Columbia to publish “In Vitro Anticancer Activity of Plant-Derived Cannabidiol on Prostate Cancer Cell Lines” in 2014. This preliminary study sought to explore the anti-inflammatory and reported anti-tumor properties of the non-intoxicating cannabinoid, cannabidiol (CBD). 


The authors reported, “Results obtained in a panel of prostate cancer cell lines clearly indicate that cannabidiol is a potent inhibitor of cancer cell growth, with significantly lower potency in non-cancer cells.” Their results also demonstrated how CBD extracts down-regulated pro-inflammatory proteins and both CB1 and CB2 receptors, which proliferate within prostate cancer cells.


In 2015, a team of scientists out of the University of Chile explored endocannabinoid impact on prostate cancer. Like other previous studies, they measured elevated levels of both CB1 and CB2 receptors in prostate cancer cell lines, then applied treatments using naturally occurring cannabinoids like anandamide (plus two analogs). 


As with THC analogs (WIN-55,212-2) and cannabis extracts, these treatments inhibited cancer cell growth, on several different prostate cancer cultures. 


The Use of Medical Cannabis in Prostate Cancer Treatment Today


These are still early days in the research on the topic of cannabis for prostate cancer treatment. Cannabinoid receptors and, in turn, cannabinoids seem like excellent targets for cancer treatment, but it is far too soon to discuss clinical trials. Laboratory work on cell lines is a far cry from well-controlled human trials.


However distant the prospect of therapeutic cannabis for use in the treatment of cancer, there is a growing interest among cancer patients for the imagined or theorized therapeutic benefits. Among prostate cancer patients specifically, there is already substantial use of medical cannabis. 


The Canadian Urological Association Journal published details of a recent survey about the “Prevalence and predictors of cannabis use among men receiving androgen-deprivation therapy for advanced prostate cancer.”

 This 2019 survey found 23 percent of survey respondents had recently used cannabis. They also uncovered that “[t]he majority of men experiencing common [androgen-deprivation therapy] side effects reported some degree of relief following cannabis use.”


In 2018, a more extensive patient survey confirmed that a significant number of patients were relying on the plant for cancer-related symptoms. The results, published in Current Oncology, assessed four cancer-care centers in Canada (where it is legal to possess medical cannabis provided registration). This survey covered cancer as a general diagnosis and did not specify a type of cancer. 


Of the patients who reported cannabis use in the preceding six month period, 70 percent of respondents confirmed it was for a cancer-related reason. Of the patients who confirmed cannabis use within the preceding week, 71 percent reported it was for cancer-related reasons. The most common symptoms patients treated with cannabis were cancer-related pain as well as nausea and vomiting. 


A Challenge for Both Patients and Physicians


With the chasm between hard clinical science and patient interest, oncologists are between a rock and a hard place. How can oncologists follow medical best-practices, yet at the same time respond to the tsunami of patient interest in (if not outright use of) cannabis


Most patients are interested in the properties of the plant, which reduces pain and nausea associated with chemotherapy, but some patients have taken it a step further. In some reports, patients have controversially forgone conventional cancer treatment in favor of cannabis. Many reports are circulating online about patients who have cured their cancer with cannabis alone. These reports are all unproven but commonly shared and are receiving more attention than ever before.


The current research doesn’t conclusively support cannabis for the treatment of prostate cancer, but at the very least, there is a well-established body of work confirming its usefulness when combined with chemotherapy, radiation, and other treatments. 


An approved pharmaceutical cannabinoid, Dronabinol, has been used for the treatment of chemotherapy-induced nausea and vomiting for three decades. Dronabinol is a synthetic cannabinoid, but as Donald I. Abrams, MD stated in an opinion piece for Oncology Journal, “It would stand to reason that the parent compound might also have activity for this indication.” 


In some capacity, cannabis will likely play a role in the future treatment of prostate cancer. At the very least, it is already an established means to combat the side effects of current cancer treatments. At the most, future clinical trials may prove that the anti-tumor properties detailed in Petri dishes with prostate cancer cell lines also apply to real patients. With the growing patient demand for medical cannabis, everyone could benefit from a cautious review of the current body of research.

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