Why a Cure For Cancer Is So Elusive

George Johnson writes in the NYT that cancer is on the verge of overtaking heart disease as the No. 1 cause of death and although cancer mortality has actually been decreasing bit by bit in recent decades, the decline has been modest compared with other threats. The diseases that once killed earlier in life — bubonic plague, smallpox, influenza, tuberculosis — were easier obstacles. For each there was a single infectious agent, a precise cause that could be confronted. But there are reasons to believe that cancer will remain much more resistant because 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. 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 and like a new species thriving in an ecosystem, it grows into a cancerous tumor. 'Given a long enough life, cancer will eventually kill you — unless you die first of something else (PDF). That would be true even in a world free from carcinogens and equipped with the most powerful medical technology,' concludes Johnson. 'Maybe someday some of us will live to be 200. But barring an elixir for immortality, a body will come to a point where it has outwitted every peril life has thrown at it. And for each added year, more mutations will have accumulated. If the heart holds out, then waiting at the end will be cancer.'"