Our cells are miraculous little engines, but imperfect replicators. During the transcription phase of cell division, mistakes are made as it copies its DNA. Most of the time, the transcription errors affect relatively unimportant bits of DNA, but occasionally what the researchers term "cancer driver genes" are mutated, and when you get several such mutations in those genetic sequences, bad things are likely to happen.
Cancer can be caused by tobacco smoke or by an inherited trait, but new research finds that most of the mutations that lead to cancer crop up naturally. Lung cancer is largely the result of environmental causes, while the vast majority of childhood cancer is a result of these bad-luck mutations, they found.
As such, they're largely unpreventable at present, and in many cases, untreatable. Complicating the situation are the effects of various hormones in relation to cancer cells. Clearly, there's much more to be learned, but the science is improving; when my sarcoma developed - the cause of which remains unclear for that type - I found that not only was it an unusual form, but that as recently as the late 1980s, the only available treatment for the thing in my arm involved amputation at the shoulder. Even then, survival rate was extremely poor. As newer, less extreme approaches to treatment were developed, survival rates for patients with such sarcomas improved to, on average, two years following diagnosis. At nearly five years following diagnosis - lucky me - I am, according to the lead specialist on the cancer team, their "success story". I'll never play the piano; on the other hand, I never could in the first place.