Genes that work perfectly well may become involved when other genes that control them cease to work correctly. Somewhat more than half a million Americans die from cancer as a primary cause each year. While this is still only slightly less than two-thirds as many as die from heart disease, the trend is that heart disease deaths are declining steadily and cancer deaths continue a slight rise. Nearly all of the increase in cancer fatalities in the United States, however, is accounted for by increasing age of the population. The greatest rise in the number of cancer deaths is from lung cancer.
Lung cancer accounts for almost a quarter of all cancer deaths in the United States.
However, lung cancer is not the only form of cancer for which death rates are rising. Rises in death rates have occurred in a number of cancer types, including melanomas liver cancer, multiple myeloma , prostate cancer, non-Hodgkin's lymphoma , and cancers of the esophagus , kidneys , breast, and brain . Another significant increase in incidence is for the skin cancer melanoma . Since the 1930s the increase has been from 1 in 1,500 persons to 1 in 1,200 persons. This increase is thought to be connected to exposure to sunlight, although that is difficult to prove for a large population - the relationship seems clearer in individual cases.