Use of oral contraceptives confers long-term protection against endometrial cancer, a new study published online ahead of print in the journal The Lancet Oncology has shown.
Although previous research has demonstrated that oral contraceptives reduce the incidence of endometrial cancer, researchers from the Collaborative Group on Epidemiological Studies on Endometrial Cancer sought to investigate the long-term impact of oral contraceptive use after use ceases.
For the study, researchers analyzed data from 27,276 women with endometrial cancer and 115,743 women without endometrial cancer who participated in 36 epidemiological studies. Of those, 35% and 39% had used oral contraceptives for median durations of 3.0 years and 4.4 years, respectively.
Results showed that every 5 years of oral contraceptive use was associated with a 24% reduction in endometrial cancer risk (RR = 0.76; 95% CI: 0.73, 0.78; P<0.001).
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Researchers found that the risk reduction lasted for more than 30 years after patients stopped taking oral contraceptives. However, reduction in risk differed by tumor type, with a stronger risk reduction for carcinomas than sarcomas.
Moreover, researchers estimate that about 400,000 cases of endometrial cancer prior to age 75 have been prevented since 1965 by oral contraceptives and 200,000 cases prevented since 2005.
- Collaborative Group on Epidemiological Studies on Endometrial Cancer. Endometrial cancer and oral contraceptives: an individual participant meta-analysis of 27,276 women with endometrial cancer from 36 epidemiological studies. Lancet Oncol. 2015. [epub ahead of print]. doi: 10.1016/S1470-2045(15)00212-0.