Although oral contraceptives are protective for ovarian cancer, it is unclear how long this protection persists. The authors prospectively assessed this question as well as associations of other, less studied contraceptive methods (tubal ligation, rhythm method, diaphragm, condoms, intrauterine device, foam, spousal vasectomy) and infertility with ovarian cancer risk among 107,900 participants in the US Nurses' Health Study. During 28 years of follow-up (1976-2004), 612 cases of invasive epithelial ovarian cancer were confirmed. Duration of oral contraceptive use was inversely associated with risk (p-trend = 0.02), but no clear trend was observed for years since last use. However, for women using oral contraceptives for >5 years, the rate ratio for ovarian cancer for ≤20 years since last use was 0.58 (95% confidence interval (CI): 0.39, 0.87), with no association found for >20 years since last use (rate ratio (RR) = 0.92, 95% CI: 0.61, 1.39). Tubal ligation (RR = 0.66, 95% CI: 0.50, 0.87) was associated with decreased ovarian cancer risk, whereas intrauterine device use (RR = 1.76, 95% CI: 1.08, 2.85) and infertility (RR = 1.36, 95% CI: 1.07, 1.75) were associated with an increased risk. Results suggest that the beneficial effect of oral contraceptives on ovarian cancer risk attenuates after 20 years since last use. Furthermore, tubal ligation, intrauterine device use, and infertility were associated with ovarian cancer risk.
- Contraceptives, oral
- Ovarian neoplasms