Among current users of combined supplements the risk rises with five or more years' treatment

Breast cancer is a hormonal cancer that is common after the menopause, and hence the effects of hormone supplementation are of enormous concern to women. The epidemiology of breast cancer remains largely unexplained, as known risk factors explain only around 40% of the disease. This is due to its prolonged, complicated, and multifactorial aetiology. Studies suffer from subtle selection processes that lead to unmeasured confounding, from long delays in measuring the effects on early carcinogenic changes, and from imprecision in investigations of modifying effects among important subgroups.

Hormone supplements are clearly effective in relieving menopausal symptoms and preventing osteoporosis if taken for long enough. Do these and the putative protective effect on coronary heart disease1 make them the most important advance in preventive medicine in the past 50 years?2 Endometrial cancer is a serious problem with unopposed oestrogen, and, assuming that the protection from heart disease is real, breast cancer might still be a serious problem with either oestrogen or combined (opposed) preparations. How might these considerations balance out for a woman wanting to understand the benefits and risks? For a 50 year old woman the baseline lifetime risk of coronary heart disease is around 45%, of hip fracture is 15%, and of breast cancer is 8%. Clearly, such aggregate data will weigh differentially with the potential relief of symptoms, prevention …