Doobie-ous conclusions

I contribute quite a lot to the Herald & Guardian Comments sections.  And I’ve noticed something.  Whenever there is a story on cancer, eventually someone will post a message along the lines of “Cannabis Cures Cancer!!  Fact!!!!”  The Guardian in particular is rife with this sort of thing.  Every comments section for every cancer story has at least one of these.

Where has this idea come from?  Why have so many people latched onto this notion that Cannabis is A Secret Cure For Cancer?  And is it true?  Can it be true?

Well…….no, it can’t.  Sorry folks, but this is nonsense.  I think that a lot of people just love to think that there is a secret magic cure out there somewhere.  And if that secret magic cure is a recreational drug, then even better.  This is certainly the case for the “wine prevents cancer” stories that I mentioned in Just One Cornetto, and it is especially true in the case of an illegal drug like cannabis.  But I’m afraid that the facts just don’t stack up.

There has been plenty of research carried out into the potential clinical uses of cannabis.  Most of the research carried out so far has been in cancer cells cultured (ie. grown) in plastic dishes.  The researchers dosed the cancer cells with cannabinoid extracts to see what effect they had.  And hey presto!  Some of the cancer cells stopped growing!  Now this in itself is not that impressive.  It is relatively easy to kill cancer cells grown in culture dishes.  Loads of things do this.  Hydrochloric acid….Alcohol….even pure water can kill cancer cells in dishes.  This doesn’t mean that any of these things will have the slightest effect in human cancer patients.  Well…the water would be good for hydration, I suppose….. and the alcohol would get them tipsy.  But hydrochloric acid…?  Let’s just say, I wouldn’t recommend it!

Some researchers have also reported that cannabinoid extracts exhibited promising results in other preclinical models (ie. some animal models as well as cells in culture).  Now this is a bit better.  It’s still not conclusive proof that there is anything to this, but it certainly warrants further investigation.

Now spot that in the last few paragraphs, I didn’t say that cannabis has shown promise in preclinical models.  I said cannabinoid extracts.  And that’s the point.  Before commencing these studies, the researchers took the cannabis leaves and mushed them up in chemical solvents to break them down.  Then, they poured the resulting gloop into a special types of filter called a HPLC that separates out the constituent parts.  They could then collect a large number of fractions, each containing a large hotch-potch of different molecules.  It is the various fractions extracted from cannabis that have been under investigation. Not cannabis itself.

Even if there is a protein or enzyme in cannabis that has some efficacy, it is only one among hundreds, if not thousands.  What concentration is the active agent likely to be at in the plant itself?  It’s highly unlikely that there will be enough in the natural product to show efficacy.  Also, what are the thousands of OTHER components doing?  Are they beneficial?  Poisonous?  In fact, some research has shown that there are cannabinoid extracts that actually make the cancer cells grow faster.  So, whether cannabis has pro-cancer effects or anti-cancer ones will depend on the overall amounts of the good and bad components found in the leaves themselves.  The good stuff might be there at a higher level than the bad stuff, but it could just as easily be the other way round.

Still, it is certainly possible that an active anti-cancer compound could be purified from cannabis.  Does this mean that it would inevitably become a new treatment?  No.  I’m afraid not.  The sad fact is that there are numerous instances of new drugs that look very promising in these preclinical models, but fail when they enter clinical trials.  Therefore, you cannot just extrapolate preclinical effects to human cancer patients. If you could, then there would be absolutely no point in carrying out clinical trials.

Take a look at the figure below.  This is an estimate of the attrition rate for new compounds during drug development (ie. the rate at which compounds fail).  Now, the take home message is that for every 5-10,000 compounds that show early promise, only one will make it through the clinical trials process to become a new drug.  Just let me repeat that.  The most optimistic chance is 1 in 5,000.

Drug Discovery Attrition rates

Let me put it this way: What this statistic means is that all that the current research can tell us is that cannabinoid extracts have only a 0.02% chance of being effective in human cancer patients.  But let’s try to be positive here!  In fact, let’s be overly optimistic!  Let’s say that the cannabinoid extracts make it through the initial screening.  Let’s say that a compound is isolated, which can be chemically modified to improve its performance, and turn it into a potential new drug, and enough of it can be produced to undergoes full preclinical assessment.  This would mean that it would still only have a 1 in 250 chance, or 0.4% chance of being an effective anti-cancer treatment.

So, sorry folks, but the idea that cannabis is a secret Cure For Cancer, but that this knowledge is being repressed by The Man is just nonsense.

But, I’m a magnanimous guy. It’s Friday night as I write this, and I’ve had a few beers. So, if any of you still want to believe that cannabis is an effective cancer treatment, based on the premise that it contains tiny, no miniscule traces of a compound that has, at best, a 99.6% chance of being Completely Bloody Useless, then go ahead, knock yourself out.  Puff away, to your heart’s content. The result will be, quite literally, Your Funeral.

Further info on this can be found on the CRUK homepage.

ResearchBlogging.org

AG McCluskey (2015). Doobie-ous conclusions Zongo’s Cancer Diaries

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5 thoughts on “Doobie-ous conclusions

  1. Pingback: Evidence, Shmevidence | zongo's cancer diaries

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