Marginal Gains

Marginal GainsThere are some common misconceptions about cancer. The first is one that I’ve spoken about before, namely the idea that cancer is a single disease. It isn’t. As I described back in No Cure For Cancer…?, the word “cancer” is an umbrella term used to describe a huge number of different diseases (over 200) that produce similar symptoms, namely uncontrolled cell growth.

But another big misconception is the one that I want to talk about here. It is the same one I mentioned back in Just One Cornetto, the one that the media continually try and punt – the idea that research into cancer is all about finding the “major breakthrough”, the “magic bullet”, the “wonder drug”….. This is nonsense. It isn’t how research works. And it isn’t how improvements in cancer treatment come about.  There have been no “major breakthroughs”. I doubt there ever will be. It’s the wrong way to think about it. Survival rates for cancer are improving, but not because of one huge change, but from numerous small improvements.

So, a better way to think of cancer research is to think of it as being a bit like the recent successes of UK cyclists in eg. the Olympics, Commonwealth games & Tour de France. UK cycling has gone through a real renaissance in recent years and UK cyclists have gone from being barely known about to household names: people such as Chris Hoy, Bradley Wiggins, Victoria Pendleton, Chris Froome… And when Dave Brailsford, the former performance director of British Cycling, was asked to explain the improved performances, he described the theory of Marginal Gains:

“The whole principle came from the idea that if you broke down everything you could think of that goes into riding a bike, and then improved …. [each thing] … by 1%, you will get a significant increase when you put them all together”.

For a cyclist, what this means is making little changes.  Lots of little changes.  They’ll change what they eat, they’ll change how they sit on a bike, they’ll change how they train….. But that is not all.  The cyclist won’t just change his or her fitness and training regime or diet, they’ll change everything.  They will also change they way they sit in a chair, or lie in bed to try and conserve energy and ensure they are properly rested.  They will even take the same pillows, mattresses and quilts when they travel.   They will change what they wear.  They will even change how they wash their hands, to reduce the chances of infection.  And when all of these changes are put together, it results in a huge improvement in overall performance.

cs_surv_trendsAnd the same is true for cancer statistics.  Take a look at the figure on the left.  This shows how the survival rates for common cancers have improved over the last 40 years***.  Now, some survival rates are a lot better than others, obviously, but that is to be expected given that we are talking about a huge variety of different diseases.  But the main thing is that the arrows all point to the right.  Across the board, survival is improving.

Now, the point is, these improvements have not been caused by giant leaps forward – by major breakthroughs – but by lots of smaller things added together.  In some cases it is improvements in diagnosis, meaning that the cancers are being caught earlier.  Also, as I mentioned in Bullseye!, improvements in scanning technology has improved the targeting of radiotherapy, leading to more precise treatments and improved outcomes.

And, obviously, new chemotherapy drugs have been developed.  But the changes in outcome from the new drugs that have come through in the last 40 years have not come from huge, major changes.  Instead, they have made relatively small improvements.  Now, when I say that, it is a bit simplistic.  So, rather than saying specific changes make small improvements, it would be better to say that specific changes improve the outcome for a small number of patients.

Imagine that a new chemotherapy drug is being developed. Now different drugs will have different ways of working, but let’s say that this particular drug targets a growth signal.  Now, before the drug enters the clinic, the research team, who think that this new drug may be effective in Lung Cancer, take a look at a range of patient tumour biopsy material, to see if the specific growth signal – the target  of the new drug – is there.  And they discover that the signal is only present in 10% of Lung Cancer patients.

Now, in one sense, this could be considered a huge disappointment.  After all, it means that 90% of patients will not benefit from the new drug.  But the research team won’t focus on who won’t benefit, they focus on who will – ie the 10%.  So, in Science-speak, they will say that there is a specific Patient Cohort, representing 10% of total Lung Cancer patients, where the new treatment could be very effective.  And when the research team check through biopsies of patients with other types of cancer, they find that their drug’s target is also found in 8% of Breast Cancers, 2% of Prostate Cancers, 4% of Colorectal Cancer…..

So, we have small numbers of patients, with different diseases, who could potentially benefit from the new treatment.  Now, if you look at the individual numbers, you might think, “Only effective in 2% of Prostate Cancer?  That’s rubbish!”, but the point is, all of these little numbers add up…..

And THAT is what causes improvements in cancer treatment.  Ignore what the Media says – it’s not about the “major breakthrough”, it is about Marginal Gains – lots and lots of little changes, that add up to overall increases in survival rates.

*** You can find more information on Survival trends over time for common cancers on the CRUK website, HERE, or in the article listed below:

Quaresma, M., Coleman, M., & Rachet, B. (2015). 40-year trends in an index of survival for all cancers combined and survival adjusted for age and sex for each cancer in England and Wales, 1971–2011: a population-based study The Lancet, 385 (9974), 1206-1218 DOI: 10.1016/S0140-6736(14)61396-9

AG McCluskey (2015). Marginal Gains Zongo’s Cancer Diaries


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