Personal Health Navigator

Don’t count on medical marijuana curing prostate cancer

Medical Marijuana sign

flickr photo by Chuck Coker

QUESTION: I have been battling prostate cancer for 11 years. My prostate was removed in 2003 and I also received radiation treatment. The cancer seemed under control. In the past year, however, the count from my PSA test has gone from 4.1 to 8.4. Now my doctor is recommending that I do hormone-deprivation therapy that will eliminate testosterone from my body. My doctor says testosterone can fuel prostate cancer. But the therapy has lots of side effects including the loss of sexual desire. The other point is that I have not taken drugs for most of my life and I don’t want to start now.  I really hope I can avoid this treatment if there is an alternative. On the Internet, I noticed a study that said marijuana could fight prostate cancer.  There are also numerous web sites dealing with curing cancer with cannabis oil. I am not sure if my doctor will approve of the treatment. I would appreciate knowing how to approach my doctor, or what steps to take to obtain cannabis oil. I believe that this natural remedy is going to be a breakthrough in cancer research.

ANSWER:  I think you’re going to have a hard time finding a doctor who is willing to treat your cancer with some type of marijuana – whether it be smoking pot or consuming it in oil form.

As you are likely aware, the federal government recently changed the rules that regulate access to medical marijuana. You now have to obtain permission from a physician before being able to order it from a licensed supplier.  In the past, Health Canada controlled who could legally use cannabis.

The major medical associations have objected to this responsibility being placed on doctors – many of them feel uneasy about being made the gatekeepers for a product that’s outside their customary treatments.

There have been a few notable exceptions to this generally negative reaction from the medical community. For instance, Dr. David Juurlink, a drug safety expert and head of Clinical Pharmacology and Toxicology at Sunnybrook Health Sciences Centre, has gone on the record saying he believes there is a legitimate role for medical marijuana in selected patients.

In a commentary published in June in the Canadian Medical Association Journal, Dr. Juurlink wrote “a case can be made for the judicious prescribing of cannabis, particular for patients who have previously experienced meaningful symptomatic improvement with its use, and for those who have not benefited from or are intolerant of conventional medications.”

Furthermore, he wrote, “the strongest argument in favour of medicinal cannabis rests in one of the most fundamental objectives of medicine: the relief of suffering, which is always best done in a patient-specific context and with due consideration of the drugs we might other-wise prescribe.”

So you might think that he would be sympathetic to your point of view. However, even Dr. Juurlink says the existing scientific evidence doesn’t justify using medical marijuana to halt the advance of cancer.

“The idea that cannabis would influence prostate cancer in a meaningful way sounds more than a little far-fetched to me,” Dr. Juurlink said in a telephone interview.

The study that you saw online involved experiments conducted on animals and tissue samples in a lab.  The research is not yet at the stage where it has moved into human clinical trials.

“If the available evidence consists of animal studies, the idea that cannabis favourably influences the clinical course of prostate cancer should be taken with a very large grain of salt,” says Dr. Juurlink. “Rarely can we extrapolate animal research to what happens in people.”

It’s also important to keep in mind that marijuana is composed of many different chemical compounds, which may have contradictory effects. (Some of these compounds may actually promote rather than curb the growth of cancer cells.)

Although marijuana has been studied for years, there is a dearth of high-quality research exploring its potential medicinal uses. What can be said is that cannabis may have a role in the control of certain symptoms. Some patients may find it helps relieve pain or improves appetite while they are undergoing chemotherapy. Control of symptoms is one thing, but stopping or slowing the advance of a disease is something else entirely.

Still, it’s not surprising that you – or any member of the public – might think marijuana is a proven disease fighter. After all, more than 20 U.S. states have recently approved the use of marijuana for the treatment of a wide range of medical conditions – including cancer.

The state legislators, unfortunately, did not base their endorsement of medicinal pot on a careful review of the medical literature, according to a New York Times article that ran under the headline Politicians’ Prescriptions For Marijuana Defy Doctors and Data. 

“There is no rigorous scientific evidence that marijuana effectively treats the symptoms of many of the illnesses for which states have authorized its use,” writes Catherine Saint Louis in the June 26, 2014 edition of the newspaper.

“Instead, experts say, lawmakers and the authors of public referendums have acted largely on the basis of animal studies and heart-wrenching anecdotes. The results have sometimes confounded doctors and researchers,” she adds.

For now at least, hormone therapy – also known as androgen deprivation therapy (ADT) – is still the most reliable treatment option for patients with advanced prostate cancer.

“It has a response rate of more than 90 per cent which is unusually high in the cancer field,” says Dr. Urban Emmenegger, a medical oncologist at the Odette Cancer Centre of Sunnybrook.

That means ADT will have some effect on the vast majority of patients, though the degree of response varies from one individual to the next, says Dr. Emmenegger, who specializes in treating men with metastatic prostate cancer.

As your doctor correctly explained, prostate cancer is partly fuelled by male hormones, or androgens, which include testosterone. Take those hormones out of the equation and prostate cancer tends to shrink or grow more slowly for a while. Eventually, though, the cancer finds a way around the hormone shortage and resumes its growth. ADT basically buys patients more time. (For the record, women also produce some testosterone, but men make a lot more of it.)

The testicles are the main source of testosterone in a man’s body. So ADT seeks to “silence” the testicles and reduce hormone levels. This end result can be achieved by surgically removing the testicles or by taking certain medications that lower androgen production. Essentially, the patient is castrated – either physically or chemically – which results in a wide range of unpleasant side effects.

In addition to the loss of libido and problems maintaining an erection, a man may also suffer from hot flashes, fatigue, depression, muscle loss, weight gain, thinning bones and even breast enlargement. In some respects, men on ADT experience many of the same adverse effects faced by women during menopause.

There is no denying that ADT can have a huge negative impact on a patient’s quality of life.  However, in most cases, it also has an almost immediate effect in slowing the advance of the cancer.

“Obviously, the patients have to decide whether they want to go through the side effects or not,” says Dr. Emmenegger. “But this is such a good treatment, I usually advise them to go ahead with it and closely monitor the side effects.”

Dr. Emmenegger says there are ways to lessen some of the side effects. For example, certain medications may help to treat erectile dysfunction. Other drugs can minimize bone loss. And if depression is an issue, it may be worthwhile seeing a psychologist or psychiatrist with expertise in treating cancer patients.

Not so long ago, most men on ADT suffered in silence. But there is now greater recognition that the treatment’s side effects need to be addressed.

In fact, a new book, entitled Androgen Deprivation Therapy:  An Essential Guide for Prostate Cancer Patients and Their Loved Ones, offers lots of advice and coping strategies.

“The book is all about managing the side effects of these drugs,” says the lead author, Richard Wassersug, an adjunct professor in the Department of Urologic Sciences at the University of British Columbia.

The book – which can be purchased through online book dealers – includes contributions from 10 Canadians experts. (More details are available at the website www.lifeonadt.com )

“A huge part of the book promotes physical exercise because the patients on these drugs gain weight, lose muscle mass, get weaker bones – and all of those symptoms can be fought by taking exercise really seriously,” says Prof. Wassersug who is the Co-Lead for Vancouver’s new Prostate Cancer Supportive Care Program.

“If a man has to go on these drugs, then a real lifestyle intervention is in order. But it takes a huge commitment,” he adds.

Prof. Wassersug knows first hand of what he speaks.  He was diagnosed with prostate cancer in 1998 at the age of 52.  When the surgical removal of his prostate gland and radiation therapy failed to stop the cancer, Prof. Wassersug decided to go on ADT. Since then, he has become an outspoken advocate for prostate cancer patients, urging men to be as informed as possible about their condition.

With this background in mind, let’s now return to your question. I admit that, up to now, I have skirted around your main query about how to get your doctor’s approval for using medical marijuana. That’s because I expect your physician will simply reiterate that androgen deprivation therapy is your best option.  And if that’s what happens, then ask what can be done to lessen the side effects. You may find that discussion extremely helpful in making an informed decision about the next stage of your cancer treatment.

About the author

Paul Taylor

Paul Taylor, Sunnybrook’s Patient Navigation Advisor, provides advice and answers questions from patients and their families, relying heavily on medical and health experts. Email your questions to AskPaul@sunnybrook.ca
and follow me on Twitter @epaultaylor

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