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Tumours are the wages of age, not the wages of sin

My Times column on cancer, luck and good deaths:


If we could prevent or cure all cancer, what would we die of? The new year has begun with a war of words over whether cancer is mostly bad luck, as suggested by a new study from Johns Hopkins School of Medicine, and over whether it’s a good way to die, compared with the alternatives, as suggested by Dr Richard Smith, a former editor of the BMJ.

It is certainly bad luck to be British and get cancer, relatively speaking. As The Sunday Times reported yesterday, survival rates after cancer diagnosis are lower here than in most developed and some developing countries, reflecting the National Health Service’s chronic problems with rationing treatment by delay. In Japan, survival rates for lung and liver cancer are three times higher than here.

Cancer is now the leading cause of death in Britain even though it is ever more survivable, with roughly half of people who contract it living long enough to die of something else. But what else? Often another cancer.

In the western world we’ve conquered most of the causes of premature death that used to kill our ancestors. War, smallpox, homicide, measles, scurvy, pneumonia, gangrene, tuberculosis, stroke, typhoid, heart disease and cholera are all much rarer, strike much later in life or are more survivable than they were fifty or a hundred years ago.

The mortality rate in men from coronary heart disease, for instance, has fallen by an amazing 80 per cent since 1968 — for all age groups. Mortality rates from stroke in both sexes have halved in 20 years. Cancer’s growing dominance of the mortality tables is not because it’s getting worse but because we are avoiding other causes of death and living longer.

It is worth remembering that some scientists and anti-pesticide campaigners in the 1960s were convinced that by now lifespans would be much shorter because of cancer caused by pesticides and other chemicals in the environment.

In the 1950s Wilhelm Hueper — a director of the US National Cancer Institute and mentor to Rachel Carson, the environmentalist author of Silent Spring — was so concerned that pesticides were causing cancer that he thought the theory that lung cancer was caused by smoking was a plot by the chemical industry to divert attention from its own culpability: “Cigarette smoking is not a major factor in the causation of lung cancer,” he insisted.

In fact it turns out that pollution causes very little cancer and cigarettes cause a lot. But aside from smoking, most cancers are indeed bad luck. The Johns Hopkins researchers found that tissues that replicate their stem cells most run the highest risk of cancer: basal skin cells do ten trillion cell divisions in a lifetime and have a million times more cancer risk than pelvic bone cells which do about a million cell divisions. Random DNA copying mistakes during cell division are “the major contributors to cancer overall, often more important than either hereditary or external environmental factors”, say the US researchers.

The study does not exonerate lifestyle altogether: lung, skin and colorectal cancers are ones with risks higher than their stem-cell replication rate would imply. So diet and sunburn do matter, as well as smoking. But it does imply that even if everybody lived in the healthiest possible way, we would still get a lot of cancer.

Jonathan Haidt, author of a book called The Righteous Mind, points out that the political left tends to agonise about the morality of food these days in the same way that the right agonises about the morality of sex: railing against fast food, junk food, genetically modified food, cheap food, food waste. But there’s no diet with anything like the cancer risk that smoking brings.

To the noticeable disappointment of the bossier end of the public health lobby, cancers are mostly not the wages of sin, just the wages of age. Short of genetically engineering us with the DNA repair genes of bowhead whales, which live for centuries, there is little we can do to prevent it.

Just because cancer is mostly accidental does not make it incurable. But in battling to prevent and cure cancer we are up against a formidable foe: Charles Darwin. Inside a tumour, the cells with cancerous mistakes that make them thrive, grow, divide and spread are the ones that survive at the expense of those that do as they are told and commit suicide.

In becoming more aggressive, cancer literally evolves. Cancer cells massively rearrange their genomes all the time, increasing their “evolvability”. This genetic trial and error eventually enables the tumour to come up with countermeasures to most drugs. Hence the tendency for cancer patients to relapse after remission.

If genetic accidents accumulate in tissues with dividing stem cells, then the longer we live, the more likely we are to get cancer, however careful we are about lifestyle and diet.

Richard Smith has come in for a lot of stick for suggesting that it is a better way to go than the alternative of dementia or organ failure, but he has a point. Many of the burdens that afflict us in our ninth and tenth decades, if we escape cancer, are mental, or require hospital. At home with “love, morphine and whisky”, says Dr Smith, may be better.

And even if we do make progress against Alzheimer’s and Parkinson’s and other mental afflictions, we won’t reach some sunlit upland of ease and comfort.

I have harped on before in these columns about the strange paradox that, despite rapidly increasing average lifespan and a rapidly increasing population of elderly people, the number of people over the age of 115 is actually lower than it was 20 years ago. Once you reach 110 your chance of dying rockets to 50 per cent a year.

Cancer will dominate end-of-life medicine for many, whatever we do. Surely the right approach is to go hell for leather to prevent and cure cancer when we can, especially in the young, but also be prepared rather more than we are — and much more than the American medical profession is — to admit defeat when necessary. I knew people who bravely refused brutal treatment that had little chance of success and asked for palliative care instead. In each case it was harder than it should have been to get what Dr Smith calls “overambitious oncologists” to admit that this was the better course of action.

By Matt Ridley | Tagged:  rational-optimist  the-times