Oral contraceptives decrease incidence of ovarian cancer.
Researchers estimate that the widespread use of oral contraceptive pills over the past several decades has significantly decreased the incidence of ovarian cancer—preventing 200,000 cases and 100,000 deaths worldwide over the past 50 years. The report, published in January in the Lancet, noted the prevention numbers could substantially increase as the birth control method becomes more available in low-income households and developing countries, ultimately preventing about 30,000 cases globally each year.
While it has been known that birth control pills confer protection against ovarian cancer, it wasn’t known by how much. Researchers found that long-term use (about 15 years) of the pill can cut the risk of ovarian cancer by about half.
More specifically, the group examined 45 epidemiological studies involving ovarian cancer and oral contraceptives in more than 100,000 women with or without ovarian cancer. Women taking the pill for less than five years lowered their risk by 22 percent, while women taking the pill for five to nine years lowered their risk by 36 percent, and 10 to 14 years of use cut the risk by 44 percent.
Women who took the pill for 15 years or more decreased their risk by 58 percent. Researchers note that oral contraception may cause a slight increase in breast and cervical cancer risk, though not to the extent of hormone replacement therapy in postmenopausal women. However, the risk of breast and cervical cancer is small and disappears after stopping birth control use, whereas the ovarian cancer protection benefit continues even after a woman stops taking the pill—up to nearly 30 years.
However, the researchers do not advocate widespread use of the pill as chemoprevention against ovarian cancer, and women should weigh their individual risks with the benefits.
The hormones in oral contraceptives are the key to ovulation suppression, which is believed to be the factor that reduces ovarian cancer risk. And while the dose of hormones in contraceptive pills has been significantly reduced since the 1960s, it appears the varying hormone levels had no effect on the risk reduction since risk was consistent from the ’60s through the ’80s.