Long-term use of oral contraceptives (commonly referred to as the ‘Pill’) has proved efficient in reducing the risk of endometrial cancer, which affects the lining of the womb, a new study published in The Lancet Oncology Journal reveals.
According to researchers from the Collaborative Group on Epidemiological Studies on Endometrial Cancer, about 400,000 cases of endometrial cancer have been prevented by oral contraceptive use in high-income countries in the past 50 years (1965-2014), including about 200,000 in the last decade (2005-2014).
Researchers assembled data on 27,276 women with endometrial cancer and nearly 116,000 who were cancer-free from 36 studies in North America, Europe, Asia, Australia and South Africa.
They found that every five years on the Pill reduced the chances of developing womb cancer by a quarter in high-income countries. Ten years of oral contraceptive use lowered the incidence of endometrial cancer before the age of 75 from 2.3 to 1.3%.
Professor Valerie Beral, from the University of Oxford, a leading member of the international team, said: “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.
“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 protective element in the Pill that cuts the risk of womb cancer is the hormone estrogen. But even though oral contraceptives in the 1960s contained more than double the estrogen dose used in the 1980s, the level of protection against womb cancer did not differ between the two decades.
This indicated that the hormone content of the modern low-dose Pill was enough to reduce the probability of developing endometrial cancer, said the scientists.
Co-author Dr Naomi Allen, also from the University of Oxford, said: “The existing evidence suggests that medium to long-term use of oral contraceptives (i.e. for five years or longer) results in substantially reduced risk of endometrial cancer.”
According to American Cancer Society, endometrial or uterine cancer is the most common gynecological cancer and affects 1 in 37 women in the United States, with about 55,000 new cases being diagnosed every year. Although the disease is rare in women younger than 35, it increases drastically with age.
According to the study, a woman can reduce her risk by 25-50% by taking hormonal birth control.
While the Pill protects against womb cancer, research suggests it does carry a higher risk for a few other cancers, including an increased risk of cervical and liver cancers, as well as increased blood pressure. It also slightly increases the risk of breast cancer. However the risk diminishes when a woman stops taking oral contraceptives. Cancer Research UK advises women to weigh up the risks, especially those with a family history of these cancers.
This study was funded by the Medical Research Council and Cancer Research UK.
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