Oral contraceptives prevent womb cancer
Use of oral contraceptives (usually referred to as "the pill"), even for just a few years, gives substantial long-term protection against endometrial (womb) cancer, and the longer the pill is used the greater the reduction in risk, according to a detailed re-analysis of all the available evidence, published in The Lancet Oncology journal.
Researchers from the Collaborative Group on Epidemiological Studies on Endometrial Cancer estimate that in the past 50 years (1965-2014) about 400000 cases of endometrial cancer have been prevented by oral contraceptive use in high-income countries, including about 200000 in the last decade (2005-2014).
"The strong protective effect of oral contraceptives against endometrial cancer -- which persists for decades after stopping the pill -- means that women who use it when they are in their 20s or even younger continue to benefit into their 50s and older, when cancer becomes more common," explains study author Professor Valerie Beral, from the University of Oxford in the UK.
She added "Previous research has shown that the pill also protects against ovarian cancer. People used to worry that the pill might cause cancer, but in the long term the pill reduces the risk of getting cancer."
The researchers pooled data on 27276 women with endometrial cancer in 36 studies from North America, Europe, Asia, Australia, and South Africa -- virtually all the epidemiological evidence ever collected on the effect of oral contraceptives.
The findings reveal that every 5 years of oral contraceptive use reduces the risk of endometrial cancer by about a quarter. In high-income countries, 10 years of oral contraceptive use reduces the risk of developing endometrial cancer before age 75 from 2.3 to 1.3 cases per 100 users.
Although estrogen doses in oral contraceptives have decreased appreciably over the years, with pills in the 1960s typically containing more than double the estrogen dose of pills in the 1980s, the reduction in endometrial cancer risk was at least as great for women who used the pill during the 1980s as for those who used it in earlier decades.