Changes and developments in cancer prevention

During the last 125 years, there has been a massive decrease in mortality from infectious disease, as a result of improved public health and later as a result of antibiotic use. This has led to a consequent increase in life span from less than 50 (when cancer is rare) to more than 70 (when cancer is common). As a result of these changes, cancer has moved from being a very minor cause of mortality in 1876 to one of the two major causes by 2000. During the last century theories of the causation of cancer have changed progressively. In the early phase the main cause was thought to be environmental contamination with carcinogenic chemicals. Later, it was thought that all cancers were caused by cancers, then that cancer was caused by a breakdown in immune-surveillance. For 40 years we have known that tobacco smoke is a major cause of respiratory and other cancers, and preventive measures are currently having a dramatic effect on male lung cancer mortality. During the last 25 years it has become apparent that diet is the other major cause of cancer, but theories have moved steadily from a search for causal agents (e.g., too much fat) to protective agents (e.g., too little fruit and vegetable). Currently it is accepted that all of the above theories contribute to the total cancer risk.