HealthDay News — Recent use of oral contraceptives is associated with increased breast cancer risk, which varies by formulation, according to researchers.
“Previous studies of oral contraceptives and breast cancer indicate that recent use slightly increases risk, but most studies relied on self-reported use and did not examine contemporary oral contraceptive formulations,” wrote Elisabeth F. Beaber, PhD, MPH, from the Group Health Cooperative in Seattle, and colleagues in Cancer Research.
To study the association between contraceptive use and breast cancer, the inspectors conducted a nested case-control study among female patients in a large U.S. health care delivery system. Data were examined for 1,102 patients, aged 20 to 49 years diagnosed with invasive breast cancer from 1990 to 2009, and 21,952 matched controls randomly sampled from enrollment records.
The researchers found that, compared with never or former oral contraceptive use, recent use (within the prior year) correlated with increased breast cancer risk (odds ratio [OR], 1.5; 95% CI: 1.3-1.9).
The risks were particularly elevated for recent use of contraceptives involving high-dose estrogen (OR, 2.7; 95% CI, 1.1-6.2), ethynodiol diacetate (OR, 2.6; 95% CI, 1.4- 4.7), or triphasic dosing with an average of 0.75 mg of norethindrone (OR, 3.1; 95% CI: 1.9-5.1), but not for low-dose estrogen oral contraceptives (OR, 1.0; 95% CI, 0.6-1.7).
“If confirmed, consideration of the breast cancer risk associated with different oral contraceptive types could impact discussions weighing recognized health benefits and potential risks,” wrote the researchers.