The use of oral contraceptives has long been associated with increased risk of breast cancer. However, the research used to prove this association involved women exposed to older formulations of oral contraceptives that are now less commonly used.
US researchers have conducted a nested case-control study to investigate the effect of contemporary oral contraceptive use on breast cancer risk and to determine if risk varies with formulation type, and publish their findings in
Cancer Research (2014;74:4078–4089)
Oral contraceptive use within the previous year was associated with a 50% increased risk of breast cancer compared with no use or former use (95% confidence interval 1.6–1.9). Researchers also found risk varied according to formulation type.
The researchers conclude that if these findings are confirmed, formulation type could influence discussions on the benefits and harms of contraceptive use.