About a month ago, I finally wrote the post I had been promising to write for months before about medical marijuana. At the time, I also promised that there would be follow-up posts. Like Dug the Dog seeing a squirrel, I kept running into other topics that kept me from revisiting the topic. However, over the past couple of weeks, the New York Times gave me just the little nudge I needed to come back and revisit the topic, first by openly advocating the legalization of marijuana, then by vastly overstating the potential medical benefits of pot (compare the NYT coverage with my post from a month ago), and finally this weekend by running a story lamenting the federal law that makes research into medical marijuana difficult in this country.
I stated my position on marijuana last time, which is that marijuana should be at least decriminalized or, preferably, legalized, taxed, and regulated, just like tobacco and alcohol. I also likened the cult of medical marijuana to the “new herbalism,” because it (1) vastly inflates the potential of medicinal uses of marijuana and (2) ascribes near-mystical powers to smoking or making extracts out of marijuana, rather than identifying and isolating constituents of the plant that might have medicinal value. All of this is very much like herbalism in alternative medicine. Indeed, promoting laws legalizing medicinal marijuana is such an obvious ploy to open the door to full legalization that some advocates don’t even bother to disingenuously deny it any more. Given that I tend to support legalization, as a physician this sort of deception irritates me. It also has consequences, particularly when overblown claims are made for what cannabis can do. Perhaps the best example of this is the claim that cannabis cures cancer, which pops up all over the Internet in memes such as the one in the image above.
A while ago, I wrote about how the Cleveland Clinic had recently opened a clinic that dispensed herbal medicine according to traditional Chinese medicine (TCM) practice. As regular readers of the SBM blog might expect, I was not particularly impressed or approving of this particular bit of infiltration of quackademic medicine into a major academic medical center, particularly given some of the amazingly pseudoscientific treatments espoused by the naturopath who was running the clinic. I also pointed out that, although herbalism is the most plausible (or perhaps I should say the least implausible) of modalities commonly associated with “complementary and alternative medicine” (CAM) or “integrative medicine”, it still exhibits a number of problems, the biggest of which is what I like to call either the delivery problem or the bioavailability problem. In brief, herbs, when they work, are adulterated drugs. The active ingredient is usually a minor constituent, embedded in thousands of other constituents that make up herbs, and it’s almost impossible to control lot-to-lot consistency with respect to content or active ingredients given how location, weather, soil conditions, rainfall, and many other factors can affect how the plants from which the medicines are extracted grow and therefore their chemical composition. To demonstrate the concept, I pointed out that it’s much safer and more predictable to administer digoxin to a patient who needs its activity on the heart than it would be for the patient to chew on some foxglove leaves, given that the therapeutic window (the difference between the doses needed to produce therapeutic effects and the lowest dose that will cause significant toxicity) is narrow.
Which brings me to medical marijuana, a.k.a. medical cannabis.
A friend asked me to look at the evidence for hash oil as a treatment for glioma. His teenage daughter was recently diagnosed with brain cancer: a grade 3 anaplastic ependymoma. It recurred very rapidly after surgery and radiotherapy and the latest tissue diagnosis shows an aggressive grade IV glioma. Her prognosis is not good. No further attempts at curative therapy are indicated; the oncologist prescribed only palliative therapy with temozolomide. Her father, who had recently lost his wife to cancer (breast cancer metastatic to lungs and brain), was understandably devastated. As he puts it, he remains “focused on the belief that just maybe a cure can be found.” He stumbled on what he calls “earth-shattering news” regarding hash oil. He and his friends established a private wiki website which they are constantly updating with information about THC (tetrahydrocannabinol, the active ingredient in marijuana and hash) and other possible cancer cures: everything from curcumin to diet. He asked me to look at the information he has accumulated. He said
I hope to convince you in the same way I have done with my daughter’s GPs and her neuro-oncologist at BC Children’s Hospital.
The oncologist was not exactly convinced. He didn’t say he thought hash oil was likely to work; he only said it would be reasonable to try it as a complementary therapy. He said
the data published so far appears very preliminary, most of its potential effectiveness in vivo so far appears in colonic disease, having said that there doesn’t appear to be any obvious down side as a complementary therapy and may have synergistic effect, so may be reasonable as add on to temodal if she tolerates it
I wasn’t convinced either.
I will discuss two issues here:
- What does the evidence say about gliomas and hash oil?
- When is it reasonable to try an unproven treatment as a last resort?