Absolute risk of breast cancer in women at increased risk: a more useful clinical measure than relative risk?

Clinicians involved in the care of women with breast cancer often have to counsel unaffected women who believe themselves to be at increased risk of breast cancer, usually because of a positive family history. Effective counselling requires both qualitative and quantitative descriptions of risk, with the most appropriate quantitative measure being absolute risk. The commonest quantitative measure of risk in the epidemiological literature is relative risk, and an estimation of absolute risk from relative risk is not straightforward. In order to aid clinicians in risk assessment, we have calculated the absolute risk of developing breast cancer for women at varying relative risks and presented the results in a graphical format which should be easy to use in a clinical setting.