Risk in the context of cancer family history
The concept of risk is complex and poorly understood by the general public and health professionals (Gigerenzer and Edwards, 2003). In the context of cancer family history, risk refers to the probability that an individual might carry a specific cancer-predisposing gene mutation or be affected with a specific genetic cancer disorder. Assessment of cancer risk is based on the information that is available at a particular point in time and should be regarded as an ‘ongoing process of analysis of estimates’ (Baptista, 2005).
Cancer risk factors
Cancer risk factors may be inherited or acquired. All individuals have an inherited level of cancer risk associated with their individual baseline set of genetic variants, ranging from highly penetrant mutations to low-penetrance variants. Individuals at increased risk because of inherited mutations with high penetrance can sometimes, but not always, be identified because they have a strong family history of cancer.
Risk of cancer is not, however, fixed at birth and is affected by acquired, and often modifiable, lifestyle choices and events such as diet, weight, smoking, alcohol consumption and reproductive choices. Cancer risk is also altered by broader influences, such as social, economic, occupational and environmental factors. Modifiable risk factors ultimately influence risk by causing acquired (somatic) genetic changes or alterations in gene expression, which either increase or decrease cancer risk. Ageing is of course a non-modifiable risk factor because it increases exposure to life and environmental events, which in turn increase the likelihood of acquired genetic changes, thus increasing cancer risk.