Oral contraceptive use and risk of breast carcinoma in situ (United States)

Objective Our study assesses the impact of oral contraceptive use on breast carcinoma in-situ (BCIS) risk. Methods We conducted a population based case–control study of incident BCIS among black and white women ages 35–64 years residing in Los Angeles County. Case patients (n = 567) were newly diagnosed with BCIS and control participants (n = 614) were identified by random digit dialing between 1 March 1995 and 31 May 1998. All subjects were required to have had a mammogram in the 2 years before case diagnosis or control recruitment. Data were collected during in-person interviews. Multivariable logistic regression analyses provide estimates of odds ratios (ORs) and 95% confidence intervals (95% CIs). Results Oral contraceptive use was not associated with risk of BCIS (OR = 1.04, 95% CI (0.76–1.42)). Risk did not increase with longer periods of use. No associations with BCIS risk were observed for oral contraceptive use before first term pregnancy, age at first oral contraceptive use, or for time since last use. Risk was not modified by estrogen dose, age, race, or parity. Conclusions Our results are consistent with recent results on invasive breast cancer reported for the Women’s Contraceptive and Reproductive Experiences Study and show no association between oral contraceptive use and risk of BCIS.