Who Gets Cancer and Why? What Are the Consequences for Human Life and Longevity? How Can We Intervene? How Can We Track Progress?

Abstract

Cancer is initiated by and undergoes further progression from mutation. It is further abetted by factors that may not cause mutation but promote the expansion of mutated clones through cell division. Factors that cause mutation or promote proliferation may come either from innate biological events or exposure to external agents in the environment. Since the process of cancer development is stochastic and probabilistic, reducing exposure to agents that mutate cells or promote excessive cell division will reduce the chances of getting cancer during the span of a human lifetime. Only by knowing what agents and factors contribute to the causation of cancer can exposures be avoided, however. Identifying carcinogenic agents and factors is, therefore, of paramount importance to altering cancer risk. Increasing exposure to proven carcinogenic agents should increase the risk, and decreased exposure should reduce the risk of getting cancer. Unfortunately, proving that a given agent or factor is carcinogenic in humans is extremely challenging. It is unethical to intentionally expose humans to putative carcinogens through direct experimentation, so all information about carcinogenic factors comes from empirical evidence and epidemiological studies. In this chapter, known risk factors for cancer are discussed and classified by alterability. Risk factors that can be altered by behavior are emphasized as the key to cancer prevention. More than half of all cancer in the world could be prevented by altering the behaviors that most strongly increase cancer risk.