Oral contraceptives were associated with a reduced risk of endometrial and ovarian cancer, which continued for up to three decades after patients stopped using them.
However, data from the observational study published in Cancer Research showed that there was no similar association in terms of decreased breast cancer risk.
“It was clear that women who took oral contraceptive pills were at a much lower risk of developing both ovarian and endometrial cancer. Fifteen years after stopping oral contraceptives, the risk was about 50% lower, ”said study author Asa Johansson from Uppsala University in Sweden in a press release. “However, up to 30 to 35 years after discontinuation, the risk was still found to be lower.”
The study’s authors conducted an observational study between 2006 and 2010 of 256,661 women enrolled in the UK biobank (a separate study aimed at improving the prevention, diagnosis and treatment of various diseases in the UK). The women included in this observational study were born between 1939 and 1970 and reported on lifestyle, medical history, previous exposures, and physical measurements themselves.
According to the authors, the aim of the study was to identify long-term associations between the risk of breast, endometrial and ovarian cancer and the use of oral contraceptives and to determine whether the risks differed in women who never used oral contraceptives.
Of the women included in the observational study, 82% (210,433 people) were considered users, which means that they had used or were still using oral contraceptives. The remaining 18% (46,218 people) never used oral contraceptives and were never considered to be users.
The authors identified 17,739 cases of breast cancer, 1,966 cases of ovarian cancer, and 2,462 cases of endometrial cancer among study participants. The number of cancer cases was significantly higher in those who never used oral contraceptives, which was due to a higher mean age compared to those who used contraceptives.
The study results showed that the risk of developing ovarian or uterine lining cancer was lower for each user than for any user. Although the authors did not see the same significant association between the use of oral contraceptives and the reduced risk of breast cancer.
“Surprisingly, we found only a slightly increased risk of breast cancer with oral contraceptives, and the increased risk disappeared within a few years of discontinuation,” stated Johansson in the press release. “Our results suggest that the lifelong breast cancer risk may not differ between users and never-users, even if there is an increased risk for land appointments.”
The authors also found that the longer a patient used an oral contraceptive, the lower the risk, which was specifically observed with endometrial cancer. Compared to previous studies, the lengthy follow-up, according to the authors, shows that oral use of contraceptives reduces the risk of endometrial and ovarian cancer for up to 30 to 35 years after discontinuation.
According to the authors, the results underscore the importance of a better understanding of the short- and long-term effects of exposure to these hormone drugs.
“In addition to protecting against pregnancy, our results have shown that oral contraceptive pills also have other beneficial effects,” study author Therese Johansson, a postdoctoral fellow at Uppsala University, said in the press release. “Our results can enable women and doctors to make more informed decisions about which women to use oral contraceptive pills.”
However, the authors noted that it is important to take into account that oral contraceptives have changed over the years. Most oral contraceptives today contain lower doses of estrogen and progestin compared to those used by the women in this study.
“Our results may therefore not be directly applicable to oral contraceptives in use today, but should be important for future drug development for cancer prevention and for new types of cancer,” the authors concluded.
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