Epidemiology of endometrial cancer

Endometrial cancer is the commonest gynaecological cancer mostly affecting women in the postmenopausal age group. Rates vary around the world but are highest in white women in Western populations. Some risk factors are related to reproduction such as early age at menarche, late age at menopause and nulliparity. Others are more directly oestrogen-related, such as use of unopposed oestrogen replacement therapy which is associated with an increased risk, and use of the combined oral contraceptive pill, associated with a decreased risk. Obesity, diabetes and hypertension increase the risk of endometrial cancer while smoking, low-fat diets and physical exercise appear to decrease the risk, and all of these possibly exert their effects by various indirect influences on oestrogen levels, thus influencing the level of stimulation of the target endometrial epithelium. From a histological and molecular pathology perspective, at least two major types of endometrial tumours can be distinguished. The proportion of type II tumours is reported to range from 20 to 50%. Few epidemiological studies have distinguished between these two tumour types, and these studies have included relatively small numbers of type II tumours. There is evidence that endocrine and nutritional lifestyle factors affect the risk of type I but not type II tumours, with age being the only identified risk factor for type II cancer.