(RxWiki News) You're taking the pill, or maybe you've tried one of the injectable contraceptives. Now you hear something about an association between birth control and cancer and you start to freak. No need to.
A recent study involving black women in South Africa finds that oral contraceptive pills (OCP) and injectable contraceptives actually lower risks of both ovarian and uterine cancer.
However, these birth control methods also increase the chance of breast and cervical cancer while the medicines are being taken.
"Talk to your OB/GYN about the best contraception for you."
Researchers at the National Health Laboratory Services in Johannesburg, South Africa analyzed the data from a case-control study of black women between the ages of 18-79.
Margaret Urban and colleagues compared the methods of contraception cancer patients reported they used. The study involved 1,664 women with breast cancer, 2,182 women with cervical cancer, 182 women with ovarian cancer and with uterine cancer.
This information was compared to the contraceptive use of 1,492 women with diagnosed cancers but who had no history of hormonal contraceptive use.
It has been established through previous studies that the pill is associated with an increased risk of reproductive cancers. However, little is known about the risks associated with injectable contraceptives, which are more commonly used among women in South African than among women in the United States.
For this study, researchers adjusted for potential confounding factors, including age, year of diagnosis, education, smoking, alcohol, age at first birth and number of sexual partners.
The study found that use of oral and injectable contraceptives was associated with what scientists call a "transiently increased risk of breast and cervical cancer." This means that the risks are elevated as long as a woman is using the contraceptive. Once she stops using the birth control method, her risk is no longer increased.
The study also found that long-term use of these forms of contraceptives reduced the risk of ovarian and uterine cancer.
There was no difference in risks between oral and injectable contraceptives.
dailyRx asked Iris Romero, M.D., assistant professor of obstetrics/gynecology at the University of Chicago, to explain what this all means.
She began by explaining, "The relationship between injectable contraception and cancer has been difficult to investigate in the United States because very few women use this form of contraception, the most common of which is Depo-provera.
"Pharmacologically the OCPs and injectable contraception are very different. Specifically OCPs usually contain an estrogen and a progestin hormone and injectable contraception usually only has a progestin hormone."
The findings that there were no differences in risks among the two methods offers new understanding, Dr. Romero says. "Clinically, this important new information because it has been hypothesized that the detrimental effect of OCPs in some cancers is driven by the estrogen component, and the therefore a progestin only approach would be safer. The findings reported here would not support that assumption," she explained.
Dr. Romero continued by saying that "like several other studies, these authors report that current users of OCPs have an increased risk of breast cancer but that risk decreases to baseline 10 years after the method is stopped."
"When thinking about breast cancer it is important to keep in mind that the incidence of breast cancer in the age group that uses contraception is low.
"Most women get breast cancer long after they have stopped using contraception and all studies indicate that there is not long-term effect of having been on contraception when you are younger," Dr. Romero adds.
In terms of increased cervical cancer risks, Dr. Romero points out the differences between incidence rates of this cancer in women in the United States and in other parts of the world, including South Africa.
"While cervical cancer is a leading cause of cancer-related deaths worldwide, it is relatively rare in the United States with approximately 12,000 new cases per year. The progress we have made with cervical cancer in the US is a direct result of wide-spread screening using the Pap smear," Dr. Romero told dailyRx.
"Cervical cancer in the United States will likely only continue to decrease as more young people are vaccinated against human papilloma virus (HPV), the virus that causes cervical cancer," she notes.
So despite what appears to be a frightening association between the pill and cancer, Dr. Romero offers women reassurance. She says that "nothing reported in this paper would be grounds for not using OCPs or injectable contraception. Whether in South Africa or in the United States the concern for unplanned pregnancy should far outweigh the concern for a small increase in the risk of breast or cervical cancer from using contraception."
Dr. Romero adds that "for any women with lingering concerns regarding the risk of cancer and OCPs or injectable contraception… intra-uterine contraception like Mirena or Paragard provides highly effective, reversible contraception and is not associated with an increased risk of breast or cervical cancer."
The South African study was published in March, 2012 issue of PLoS Medicine.
This research was funded in part by the South African Medical Research Council and the (South African) National Health Laboratory Service.
The authors reported no conflicts of interest.