Age factors

As a general rule, with increasing age there is an increase in the incidence of cancer. This has been attributed to a longer duration for genes to mutate by chance or to be acted upon by carcinogens - a cumulative effect. Examples of cancers which follow this trend are those of the gastrointestinal and urinary tracts.

However, there are some notable exceptions:

• an early peak in incidence with a rapid decline to minimal levels afterwards:
  • the second most common cause of mortality in the infant and childhood group is cancer, e.g. neuroblastoma and Wilms' tumour, and for these there is usually a strong inherited component
  • seminomas and teratomas peak in incidence before 30 years of age and then fall to minimal incidence
• osteosarcoma has a bimodal distribution; it is common in adolescence when bone growth is rapid and also after 45 years of age as a consequence of Paget's disease
• uterine cervical carcinoma arises with increasing frequency in adolescence and then increases relatively slowly in incidence until the menopause when it again declines