Numerous studies have suggested that oral contraceptives can increase the risk of developing breast cancer. However, a recent paper has noted that 'more recent formulations have received relatively little scrutiny'. Unfortunately, the study confirmed that contemporary oral contraceptives are still associated with an increased breast cancer risk, but the risk seemed to depend on the formulation.
The authors examined 1102 women aged 20 to 49 years with invasive breast cancer and 21,952 matched controls. Overall, women who used oral contraceptives within the previous year were 50% more likely to develop breast cancer than never or former users. Using oral contraceptives in the last year that included high-dose oestrogen (odds ratio [OR] 2.7), ethynodiol diacetate (OR 2.6) or triphasic dosing with an average of 0.75mg of norethindrone (OR 3.1) were associated with 'particularly elevated' breast cancer risks. However, triphasic dosing with an average of 0.75mg of norethindrone was the only oral contraceptive that showed a significantly different risk to the other formulations. On the other hand, some formulations - such as low-dose oestrogen and norethindrone 0.50mg - did not significantly increase breast cancer risk compared to never or former use.