It has been known for a while that oral contraceptives can help reduce a woman's risk of developing endometrial cancer. But now a report that combined data from several studies has found that the protection lasts for several years after she stops taking the birth control pills.
The new study is what is called a meta-analysis, which is a statistical analysis of data from many studies on the same subject. The researchers pooled data from 36 prospective and retrospective epidemiological studies that included 27,276 women with endometrial cancer and 115,743 women who did not have it. The average age of the women with endometrial cancer was 63.
Thirty-five percent of the women who had endometrial cancer and 39% of the women who did not have it had used oral contraceptives at some point in their lives, for an average of 3 years and 4.4 years, respectively.
The analysis showed that the longer women had used oral contraceptives, the greater the protection they received. Each 5 years of using birth control pills was associated with a 24% lower risk compared with those who had never used them. For 10 to 15 years of use, the risk was cut nearly in half, and the protection persisted for more than 30 years after they stopped taking the pills.
The study concluded that the use of oral contraceptives in developed countries has prevented about 400,000 cases of endometrial cancer over the past 50 years. This includes cases in 200,000 women in the last 10 years alone.
Young women should be told that birth control pills are an excellent form of contraception and that they reduce the risk of developing endometrial cancer, the report concluded.
The study was published in the journal The Lancet Oncology.