Oral Contraceptive Use and Survival in Women with Invasive Breast Cancer

Abstract

Background Oral contraceptives (OCs) are widely used in the U.S. Although the relation between OC use and breast cancer incidence has been widely studied, the few studies examining associations between OC use prior to breast cancer diagnosis and survival are inconsistent. Methods Women with invasive breast cancer participating in the Women's Contraceptive and Reproductive Experiences (CARE) Study, a population-based case-control study (4565 women ages 35–64 years), and the California Teachers Study (CTS) cohort (3929 women ages 28–91 years) were followed for vital status. 1064 women died in the CARE Study (median follow-up, 8.6 years) and 523 died in the CTS (median follow-up, 6.1 years). Cox proportional hazards regression provided hazard rate ratio estimates (RRs) with 95% confidence intervals (CIs) for risk of death from any cause and from breast cancer. Results No association was observed for any OC use prior to diagnosis and all-cause mortality (CARE Study: RR=1.01 (95% CI=0.86–1.19); CTS: RR=0.84 (95% CI=0.67–1.05)). A decreased risk of all-cause mortality was observed in the CTS among women with more than 10 years of OC use (RR=0.67, 95% CI=0.47–0.96); however, no trend of decreasing risk with increasing OC duration was observed (P-trend=0.22), and no association was observed in the CARE study. No associations were observed for breast cancer-specific mortality. Conclusions OC use is not associated with all-cause or breast cancer-specific mortality among women with invasive breast cancer. Impact These two independent studies demonstrated no overall association between OC use and survival among women with breast cancer.

Meta‐analysis of oral contraceptive use and risks of all‐cause and cause‐specific death

“…Whether the present findings are applicable to current users of OCs is not clear. It was not possible to perform meta‐analyses regarding the current use of OCs to examine this question because of the limited number of included studies reporting relevant risk estimates [3,11]. However, the results of the present random‐effects meta‐regression in relation to time since last OC use alleviate this concern, at least in part.…”

“…The pooled HRs for all‐cause mortality ranged from 0.89 (95% CI 0.85–0.94) [10] to 0.96 (95% CI 0.89–1.04) [16] when different studies were omitted. The exclusion of three cohorts [10–12] in which a questionnaire had been used to assess exposure produced an inverse association (HR 0.89, 95% CI 0.85–0.94) between ever use of OCs and all‐cause mortality, with no evidence of heterogeneity ( I 2 = 0.0%). The exclusion of three cohorts [10,15,16] with a mean follow‐up duration of more than 10 years resulted in an HR of 0.96 (95% CI 0.87–1.06) for all‐cause mortality, with no evidence of heterogeneity ( I 2 = 0.0%).…”

“…The mean duration of follow‐up ranged from 5.0 years [14] to 35.4 years [15]. Five cohorts [11–13,23] were comprised of women with breast cancer. The quality of the included cohorts was generally good, with eight cohorts being of high quality.…”

“…The quality of the included cohorts was generally good, with eight cohorts being of high quality. As for the method of exposure assessment, interviews and questionnaires were adopted for six [11,13–16,23] and four [3,10–12] cohorts, respectively. For five cohorts [11,13–15,23], the investigators relied on death certificates for ascertainment of the cause of death, and for four cohorts [3,11,12,16], the investigators relied on death registries; in the remaining cohort study [10], the cause of death was confirmed through family reports, death certificates, or medical records.…”

“…There is also a concern that OC use might be associated with an increased risk of mortality, although findings have not been conclusive. Most prospective studies [10–14] have identified a null association between OC use and all‐cause mortality, whereas some studies [15,16] have found that ever‐users of OCs have slight benefits in terms of all‐cause mortality.…”