That was the attention-grabbing headline of George Johnson’s article in the New York Times January 5, 2014. The article notes the decline in deaths from heart disease (down 68%), cancer (down 10%) and stroke (down 79%). With the advances in treatments and prevention efforts, deaths from heart disease and stroke are likely to continue, at least in the developed world. However, Johnson notes, “For the oldest among us, the two killers are fighting to a draw. But there are reasons to believe that cancer will remain the most resistant. It is not so much a disease as a phenomenon, the result of a basic evolutionary compromise. As a body lives and grows, its cells are constantly dividing, copying their DNA – this vast genetic library – and bequeathing it to the daughter cells. They in turn pass it to their own progeny: copies of copies of copies. Along the way, errors inevitably occur. Some are caused by carcinogens but most are random misprints. Over the eons, cells have developed complex mechanisms that identify and correct many of the glitches. But the process is not perfect, nor can it ever be. Mutations are the engine of evolution. Without them we never would have evolved. The trade-off is that every so often a certain combination will give an individual cell too much power. It begins to evolve independently of the rest of the body. Like a new species thriving in an ecosystem, it grows into a cancerous tumor. For that there can be no easy fix. These microscopic rebellions have been happening for at least half a billion years since the advent of complex multicellular life- collectives of cells that must work together, holding back, as best each can, the natural tendency to proliferate. Those that do not – the cancer cells – are doing, in a Darwinian sense, what they are supposed to do: mutating, evolving and increasing in fitness compared with their neighbors, the better behaved cells of the body.”
Johnson goes on to aver that more progress in preventing cancer deaths can be made “by reducing the incidence of obesity, a metabolic imbalance that, along with diabetes, gives cancer an edge.”
Two brief observations. First, for many years policy-makers’ attention to obesity has been based on its impact on cardiovascular disease. With improvements in treatments for other cardiovascular risks, such as hypertension or high cholesterol, we are seeing a reduction in cardiovascular disease, already affecting clinical trials, such as Look Ahead and SCOUT. What happens when, as Johnson predicts, heart disease is not the major killer but cancer is? And this leads to the second point. The relationship of obesity to various cancers is mixed, a sign of research-neglect. Much more work needs to be done to understand why obesity is associated with some cancers but not others, what is the effect of weight loss on cancer progression and recovery, etc. The Institute of Medicine report is an excellent starting place to begin to focus on the obesity-cancer connection.