A comprehensive study involving more than 250,000 women showed that oral contraceptive use may be protective against the development of ovarian and endometrial cancers, but the effect on lifetime risk of breast cancer is more limited. The protective effect on ovarian and endometrial cancers was seen to remain for several decades after discontinued use. These results were published by Karlsson et al in the journal Cancer Research.
Ovarian and endometrial cancers are among the most common gynecologic cancers, with a lifetime risk of just over 2%. The first oral contraceptive was approved in the 1960s; these agents include estrogen and progestin, which are synthetic forms of the female sex hormones. The estrogen and progestin in oral contraceptives prevent ovulation and thereby protect against pregnancy.
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Study Findings
In the current study, researchers compared the incidence of breast, ovarian, and endometrial cancers between women that had used oral contraceptives and never-users. They performed an observational study using data from 256,661 women from the UK Biobank database, born between 1939 and 1970.
“It was clear that women who had used oral contraceptives had a much lower risk of developing both ovarian and endometrial cancers. Fifteen years after discontinuing oral contraceptives, the risk was about 50% lower. However, a decreased risk was still detected up to 30 to 35 years after discontinuation,” said study coauthor Åsa Johansson, PhD, of the Department of Immunology, Genetics, and Pathology at Uppsala University in Sweden.
However, oral contraceptives have previously been associated with an increased risk of breast cancer.
“Surprisingly, we only found a small increased risk of breast cancer among oral contraceptive users, and the increased risk disappeared within a few years after discontinuation,” said Dr. Johansson. “Our results suggest that the lifetime risk of breast cancer might not differ between ever- and never-users, even if there is an increased short-term risk.”
Increased odds were seen for breast cancer in women when limiting the follow-up to 55 years of age, but not for the full time span.
The study authors concluded, “Given the body of evidence presented in our study, we argue that oral contraceptives can dramatically reduce women's risk of ovarian and endometrial cancer[s], whereas their effect on lifetime risk of breast cancer is limited.”
Disclosure: For full disclosures of the study authors, visit cancerres.aacrjournals.org.
