Jul 28 2015

Anecdotes and Cannabis Oil

An article making the rounds has this claim in the headline: This Man Was Given 18 Months To Live. Here’s How He Illegally Cured His Cancer. The article further explains that he “cured” his cancer with cannabis oil. This is highly misleading for multiple reasons.

This and other articles tell the story of David Hibbit, a 32 year old man who was diagnosed with bowel cancer in 2012. First, let me say that of course I wish nothing but the best for Mr. Hibbit. I hope his cancer is completely gone and he lives a long life with his family. Cancer is a serious and scary disease. It has touched my family, and I am sure statistically it has touched most people reading this.

That, in fact, is why we have to be so careful when relating stories about cancer. Patients have serious and high-stakes decisions to make about how they are going to treat their cancer. Luring them to bad decisions with false promises and misleading but highly emotional stories is irresponsible.

The core of bad reporting about cancer is the anecdote – the heartfelt story of an individual fighting cancer. Such stories are almost universally highly misleading. The public is being given an emotional narrative, not useful information.

Piecing together the details from several articles, you find that headlines and opening paragraphs actually tell a different story than the facts buried deep in the articles. What is reported is that Hibbit was given 18 months to five years to live – that was in 2012, three years ago. That is very different than just 18 months.

Further, you should always take such statements with a huge grain of salt. Doctors never give a specific amount of time that a patient will live, they almost always give a range. That range is based upon statistics. Think of it like a Bell curve, and often the typical range is given at two standard deviations, or the range of time that 95% of patients with the same cancer (type, grade, and stage) will survive with or without specific treatments.

Of course that means that 5% will be outside this range. That’s one in 20 patients, and one in 40 will survive longer than the stated range, just by chance alone. Some cancers have what we call a long tail – if you look at the survival curves, a minority survive for much longer than the typical range.

If you think about it, for every million people every year who are diagnosed with cancer, 1000 patients will survive in the top 0.1%, and 100 in the top 0.01%. That means the world is full of people who have survived much longer than the typical range, by chance alone.

Further, many desperate patients will try unconventional treatments in addition to (or sometimes instead of) standard treatment. You will never hear from the ones who die. You are likely to hear from the hundreds of people in the top 0.01% of survivors, especially if they credit their unconventional treatment with their survival.

This is all a long way of saying that anecdotes are not useful information. They are cherry picked by definition because they are self selective, and the media further selects these headline-worthy stories. You won’t read an article about someone given 1-3 years to live who died after two years, despite using some unconventional therapy along with standard therapy. It’s a non-story.

Another thing to keep in mind is that cancer often has a “honeymoon” phase. After diagnosis, surgery, chemotherapy, and/or radiation therapy, the bulk of the tumor is gone, symptoms are likely improved, and it is easy to feel “cured” of the cancer.  This is typically the phase in which we read that the cancer patient cured themselves with “one weird trick.” The real question, however, is whether or not the cancer will come back. You may have to wait years to find that out, and we rarely get such follow up. When we do such information is buried, not spread virally with shocking headlines.

In the case of Hibbit – from some articles, when you read past the headline, you find he is in year three while the doctors gave his survival range as 18 months to 5 years. This is not as impressive sounding, however. He is in the honeymoon phase. He had bowel cancer and underwent surgery, chemotherapy, and radiation. He had a lymph node recurrence, and underwent further surgery and chemotherapy. He then decided to stop the chemotherapy and use cannabis oil instead. Again, while I wish him the best, it is a little premature at this point to celebrate and declare him cured.

Of course, if he is truly cancer free, we have no way of knowing that the cannabis oil contributed at all to his success. He did have surgery and chemotherapy. He may just be one of the lucky ones.

All of this is why anecdotal evidence is worthless as scientific evidence (other than perhaps to suggest an area of research). Anecdotes, when used this way, are actually worse than worthless, they are actively misleading. They are more likely to lead us to a false and possibly harmful conclusions than to accurate information.

That is exactly why we need science. Scientific study controls for variables, looks at all outcomes systematically, and can tell the difference between a real benefit and just cherry picking the lucky ones. So what does the science say?

David Gorski has already written a thorough review of the published science for cannabis extracts and cancer at Science-based medicine. The bottom line is that there is no clinical evidence showing that cannabis oil improves survival. The basic science studies, mostly looking at human cell lines with cancer, is actually not promising. The concentration of cannabis extracts that inhibit cancer cell growth is actually quite high, which would require taking massive doses to have any effect, much higher than people are actually taking (or can take).

That is another nuance often missed in sensational reports. The fact that a substance inhibits cancer cell growth in a petri dish says nothing. What you really want to know is – at what concentration does it inhibit cancer cell growth? It turns out that cannabis requires a higher concentration than would make it an effective anti-cancer drug. Further research is reasonable, and it would not surprise me if we eventually developed some useful compound from cannabis, but we are years away at best and prospects are modest at best.


Reporting about David Hibbit is extremely sensational and misleading, which graduates from merely annoying to actually dangerous when we are talking about a serious topic like cancer. Just read the comments to any article about Hibbit, it’s full of desperate people with cancer or loved-ones with cancer who will try anything. I wonder how many people will stop their chemotherapy (where at least we know the risks vs benefits) for the false hope of yet another miracle cure.

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