Women who used the oral contraceptive known as “the pill” are less likely to develop colorectal, endometrial, or ovarian cancer than women who had never taken it, a long-term data study reports, adding that the pill’s protective effects appear to last up to 30 years.
A higher risk of breast and cervical cancer is seen in current or recent users, the researchers said, but that risk “is lost” within about five years of stopping the pill’s use.
The study, which followed 46,022 women for up to 44 years, is titled “Lifetime cancer risk and combined oral contraceptives: the Royal College of General Practitioners’ Oral Contraception Study,” and published in the American Journal of Obstetrics and Gynaecology.
Lisa Iversen and colleagues at the University of Aberdeen in Scotland investigated the long-term cancer risks or benefits associated with use of combined oral contraceptives, including the estimated overall lifetime balance.
They used data from the Oral Contraception Study, a continuing cohort survey initiated in 1968 by the Royal College of General Practitioners. The women examined entered that study in 1968 and 1969.
“Because the study has been going for such a long time we are able to look at the very long term effects, if there are any, associated with the pill,” Iversen, a research fellow with the Institute of Applied Health Sciences at the University of Aberdeen, said in a news release.
They also looked at the risk of all types of cancer in women who have ever used the pill. Overall, they found that oral contraceptive use was associated with a reduced risk of colorectal, endometrial, ovarian, and lymphatic and hematopoietic cancers.
“What we found from looking at up to 44 years’ worth of data, was that having ever used the pill, women are less likely to get colorectal, endometrial and ovarian cancer,” said Iversen. “So the protective benefits from using the pill during their reproductive years are lasting for at least 30 years after women have stopped using the pill.“
In addition to breast and cervical cancer, an increased risk of lung cancer was also seen, but this was observed only in women who smoked and used oral contraceptives when recruited to the study.
“There was no evidence of new cancer risks appearing later in life among women who had used oral contraceptives,” the researchers wrote. “Thus, the overall balance of cancer risk among past users of oral contraceptives was neutral with the increased risks counterbalanced by the endometrial, ovarian, and colorectal cancer benefits that persist at least 30 years.”
An estimated 100 million to 150 million women worldwide today use oral contraceptives daily.
“These results from the longest-running study in the world into oral contraceptive use are reassuring,” Iversen said.