From an analysis of more than 46,000 women, researchers from the University of Aberdeen in the United Kingdom found that women who had ever used oral contraceptive pills were at lower risk of colorectal, ovarian, and endometrial cancers, compared with women who had never used the pill.
Furthermore, the study found no link between the use of oral contraceptives during reproductive years and increased risk of new cancers in later life.
The study was led by Dr. Lisa Iversen, of the Institute of Applied Health Sciences at Aberdeen, and the findings were recently published in the American Journal of Obstetrics and Gynaecology.
According to the Centers for Disease Control and Prevention (CDC), around 16 percent of women in the United States aged between 15 and 44 years are currently using oral contraceptive pills as a method of birth control.
Since naturally occurring estrogen and progesterone have been associated with cancer development, numerous studies have investigated whether oral contraceptives might play a role in cancer risk.
Assessing the long-term effects of oral contraceptives
While some studies have uncovered a link between oral contraceptive use and increased risk of breast cancer, others have associated the pill with a reduced risk of certain cancer types, including endometrial and colorectal cancers.
The aim of the new study was to assess the long-term cancer benefits or risks of oral contraceptive use.
To reach their findings, Dr. Iversen and colleagues analyzed the data of 46,022 women who were part of the U.K. Royal College of General Practitioners' Oral Contraception Study from 1968 to 1969.
Participants were monitored for up to 44 years, and the researchers assessed the development of all cancer types during this time.
"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," notes Dr. Iversen.
Findings are 'reassuring'
Compared with women who had never used oral contraceptive pills, those who had used the pills were found to be at lower risk of colorectal, endometrial, and ovarian cancers.
"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," says Dr. Iversen.
The team did identify a greater risk of breast and cervical cancers with oral contraceptive use, but they found that this risk appeared to diminish within 5 years of ceasing use.
Additionally, the researchers found no evidence of increased risk of new cancer development in later life among women who had used oral contraceptives.
The team says that the findings should offer some peace of mind to women who use oral contraceptives.
"These results from the longest-running study in the world into oral contraceptive use are reassuring. Specifically, pill users don't have an overall increased risk of cancer over their lifetime and that the protective effects of some specific cancers last for at least 30 years."
Dr. Lisa Iversen