Age-related factors in cancers of the breast, ovary, and endometrium.

The most central epidemiological feature of cancers of the breast, ovary and endometrium is the enormous protective effect of menopause. Simple mathematical "models" of the age-incidence of these tumours suggests that their incidence by age 70 would be between 4 and 8-fold increased if women continued to menstruate into old age. Using the notion of "effective cell-cycle time" to explain this phenomenon, different "models" are constructed for each of these three tumour sites and shown to provide an excellent description of most of the known epidemiology of each of the cancers, and to provide a basis for predicting the long-term effects of various factors on the risk of these diseases. In particular, the model suggests that 5 years of combination-type oral contraceptive use will approximately halve the lifelong risk of both ovarian cancer and endometrial cancer.