A meta-analysis from 54 epidemiological studies reported that there is a slightly increased relative risk (RR = ) of having breast cancer diagnosed in women who are currently using COCs. The excess risk gradually disappears during the course of the 10 years after cessation of COC use. Because breast cancer is rare in women under 40 years of age, the excess number of breast cancer diagnoses in current and recent COC users is small in relation to the overall risk of breast cancer. These studies do not provide evidence for causation. The observed pattern of increased risk may be due to an earlier diagnosis of breast cancer in COC users, the biological effects of COCs or a combination of both. The breast cancers diagnosed in ever-users tend to be less advanced clinically than the cancers diagnosed in never-users.
Drugs such as Nolvedex bind to the oestrogen receptors , therefore reducing the effects of the heightened oestrogen in the body. Such drugs do nothing to reduce the amount of oestrogen in the body; they merely reduce its effects via competition for the receptors . If the user wishes to reduce the amount of oestrogen they should look to drugs such as proviron and anastrozole , which are known as anti-aromatases - . they lower the conversion of the steroid to oestrogen and therefore reduces the overall amount of oestrogen present.