The level of breast cancer risk increased the longer a woman had been taking hormonal contraceptives, with the average risk increase being 20% among all current and recent users of these forms of contraceptives.
The researchers saw a 9% increased breast cancer risk among women taking hormonal contraceptives for under a year, rising to 38% if more than 10 years.
Among women who had been using hormonal contraceptives for more than five years, a slight risk persisted for at least five years after they stopped, according to the study published Wednesday in the
New England Journal of Medicine.
The results suggested a “rapid disappearance of excess risk of breast cancer after discontinuation of use among women who have used hormonal contraceptives for short periods,” the authors write in the paper. The authors noted that other studies have found no evidence of a persistent risk.
In an accompanying editorial, David Hunter, professor of epidemiology and medicine at the Nuffield Department of Population Health in the UK, said that the link between oral contraceptives and breast cancer is already well-established. However, this new study is important because it looked at newer preparations of contraceptives, he told CNN.