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:

  1. What does the evidence say about gliomas and hash oil?
  2. When is it reasonable to try an unproven treatment as a last resort?

What Does the Evidence Show?

Several plausible mechanisms have been demonstrated, suggesting that it might work; but the evidence consists almost entirely of in vitro (test tube) and animal studies, with only a couple of small pilot studies in humans and a lot of speculation.

The Guzman study was a pilot study of 9 patients who got THC injected directly into their tumors.

The Salazar study concluded

we identify what we believe is a new route that links the ER stress response to the activation of autophagy and promotes the apoptotic death of tumor cells. The identification of this pathway will help to understand the molecular events that lead to activation of autophagy-mediated cell death by anticancer drugs and may contribute to the design of new therapeutic strategies for inhibiting tumor growth.

The Kogan study elucidates cellular anti-cancer mechanisms of THC but warns “sometimes they can act also as pro-cancer agents, especially in low concentrations, acting mostly through growth factors and their receptors activation/induction.” It concludes

In summary, cannabinoids possess some anticancer activity. Possibly they may represent a new class of anticancer drugs that retard cancer growth, inhibit angiogenesis and the metastatic spreading of cancer cells.

None of these studies concluded that we should be treating glioma patients with any form of THC.

A study by Foroughi reports spontaneous regression in 2 glioma patients. One happened to have smoked pot almost every day, the other used it twice a week. They speculate that the THC might have had something to do with the regression. But it might just as well have been coincidental. Spontaneous regression is known to occur in gliomas. A 2004 German study showed spontaneous regression in a mouse model. A study in the Archives of Ophthalmology documented 13 cases of spontaneous regression in humans with large optic gliomas.

The literature is confusing because it addresses different doses, different compounds, and different routes of administration: THC, smoking pot, hash oil, injecting it directly into tumors, applying it topically to skin tumors, inhaling, taking it by mouth, etc. Positive pilot studies are an encouragement to further studies; they are not proof that the treatment works.

The information on the Internet includes glowing testimonials but is contaminated with obvious bias. Advocates come mostly from the ranks of notorious “legalize marijuana” activists. Emotions run high. Many arguments in favor are full of the kind of fallacies we often discuss here, including “they didn’t listen to Semmelweis.” Protestations that THC research is being unfairly suppressed are not credible. Cancer researchers want to find cures, and even Big Pharma stands to reap huge benefits if active molecules can be separated out, modified, and turned into prescription drugs.

I didn’t find anything I would call “earth-shattering” or even anything that could be considered credible evidence that hash oil can cure advanced gliomas. The most I can conclude from my research is that hash oil has promise and is worth studying.

Last Resort?

When a patient is out of options, it is natural to grasp at any straw. Even though the evidence for hash oil is inadequate, there are some preliminary indications that it might help, and some plausible mechanisms have been elucidated. Isn’t it better to try something that possibly might work than to just give up?

How do you know what to try? The private website addresses all kinds of other possible cancer treatments, including curcumin, garlic, diet, etc. Incidentally, it cites a lot of very untrustworthy sources, such as a book by a doctor who repeats the old myth about cancer and sugar and a company that is selling curcumin pills. Should you try all of these treatments at once? If you try hash oil, how do you decide how much and how often?

We read articles in the popular press, for instance in Reader’s Digest, about the child with the rare disease whose heroic parents refused to give up and kept searching until they found the one doctor in the world who was able to cure their child with a new treatment. We hear about these success stories because they are unusual.

We don’t hear about the vast majority of cases where parents wasted time and money in a futile search.

It disturbed me to read through the private wiki, because it was “déjà vu all over again.” I’ve seen this so many times. Someone desperately wants to find a cure, latches onto something that he thinks might work, locates a mass of evidence to confirm his bias, but fails to appreciate the limitations of that evidence and fails to seek out information that argues against his bias (like the possibility that cannabinoids might have pro-cancer effects, mentioned above). In the course of my long career I’ve seen so many promising treatments bite the dust that I have become not only skeptical but probably cynical about it.

Yes, hash oil might be an effective treatment for gliomas and for other cancers. But we can’t possibly know until we test it properly. A patient with glioma today can’t wait for the results of future tests. Forgoing the treatment might mean dying sooner than necessary, but it is far more likely that using the treatment will be useless. It’s a gamble. Where is that crystal ball when we need it?

When you try a treatment on your own, you are essentially acting as a guinea pig in an uncontrolled experiment. Ideally, you could enroll in a randomized controlled trial that would result in some useful knowledge for future patients. But such trials are not always available, and you might not get the treatment; you run the risk of being assigned to the placebo group.

Is aggressively pursuing a cure really the best goal? Success is possible but very unlikely; and the search can become obsessive; dominate the searcher’s life; and consume time, funds, and energy that might be best employed otherwise. How about pursuing other goals that have a much higher chance of success: spending quality time with the loved one, trying to make the most of whatever time she has left, helping her cope, trying to make her remaining life as worthwhile as possible, saying goodbye, creating good memories for the survivors?

I’m going to be mean and ask some difficult questions. Is this father really doing this for his child or for himself? He wants to be able to say he did everything possible and left no stone unturned, so he will have no guilt feelings afterwards. Is the daughter really on board with all this, or is she cooperating mainly to please her father, knowing that it gives him comfort? Is she giving up the foods she loves to follow a restricted diet that has no proven benefit? Would it be better for all concerned to accept the terrible prognosis and confront its reality in more constructive ways? Do false hopes do more harm than good? There are always real hopes: that palliative therapy might extend life, that a spontaneous regression might occur, that life might still be rich with meaningful experiences?


Hash oil has enough promise to warrant further research but not enough evidence to warrant prescribing it as a cancer cure. Is it worth trying anyway? I don’t know. I am asking questions, not condemning. I can’t imagine what it is like to learn that your beloved child has a fatal illness. I don’t know how I would react, or whether I would want to try something like hash oil. It’s possible that I might feel desperate enough that all my judgment, skepticism, and common sense would fly out the window and I might be persuaded to try even the most wildly irrational things. I do know that refusing to accept reality often has unfortunate consequences. It distresses me when families aggressively pursue a will-o’-the-wisp that ends in failure and uses up precious time they might have spent otherwise to make the patient’s last days more meaningful and to create lasting memories.

What would you do? I welcome readers’ input in the comments.

Posted by Harriet Hall

Harriet Hall, MD also known as The SkepDoc, is a retired family physician who writes about pseudoscience and questionable medical practices. She received her BA and MD from the University of Washington, did her internship in the Air Force (the second female ever to do so),  and was the first female graduate of the Air Force family practice residency at Eglin Air Force Base. During a long career as an Air Force physician, she held various positions from flight surgeon to DBMS (Director of Base Medical Services) and did everything from delivering babies to taking the controls of a B-52. She retired with the rank of Colonel.  In 2008 she published her memoirs, Women Aren't Supposed to Fly.