Taking oral contraceptives does protect against ovarian and endometrial cancer ‘for several decades’, a new study claims.
Sweden-based researchers studied data from 256,661 UK women, comparing those who had never used oral contraceptives and those who had.
They found those with a history of taking the pills had a reduced risk of ovarian cancer and endometrial cancer – cancer of the womb.
The protective effect of contraceptive pills remain for several decades after women stop using them, the experts claim.
However, they found taking oral contraceptives led to a slightly increased risk of breast cancer.
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The study involving more than 250,000 women, shows that oral contraceptive use protects against ovarian and endometrial cancer
The findings align with the official stance of Cancer Research UK – that the contraceptive pill slightly increases the risk of breast cancer but decreases the risk of ovarian and womb cancers.
‘It was clear that women who had used oral contraceptive pills had a much lower risk of developing both ovarian and endometrial cancer,’ said study author Åsa Johansson at Uppsala University in Sweden.
‘Fifteen years after discontinuing with oral contraceptives, the risk was about 50 per cent lower.
‘However, a decreased risk was still detected up to 30-35 years after discontinuation.’
Oral contraceptives, known as ‘the pill’, are a popular form of birth control in the UK, although research continues into their ability to increase the risk of cancers.
80 per cent of all women in Western Europe have used oral contraceptives at some point in their life.
WHAT IS THE COMBINED PILL?
The combined oral contraceptive pill is usually just called ‘the pill’.
It contains the female sex hormones oestrogen and progesterone and works by preventing the ovaries from releasing eggs each month – meaning sperm cannot fertilise them.
The pill is usually taken every day for three weeks then stopped for a week to allow the woman’s period to happen because the womb lining still thickens even if an egg is not released.
The pill is over 99 per cent effective if used properly, meaning fewer than one in 100 women using it will get pregnant.
There is no evidence that the pill makes women gain weight, but it carries a very low risk of causing blood clots or cervical cancer.
The pill does not protect against sexually transmitted infections.
There are two main types – the most common is the ‘combined’ pill, which has two female sex hormones, oestrogen and progestogen.
The oestrogen and progestin in oral contraceptives prevent ovulation and thereby protect against pregnancy.
The other type, the mini-pill, contains progestogen, and is also known as the progestogen-only pill, or POP.
It’s already known oestrogen can stimulate breast cancer cells to grow, meaning extra oestrogen from the combined pill has the potential to increase breast cancer risk.
Ovarian cancer and endometrial cancer are among the most common gynaecological cancers, with a lifetime risk of just over 2 per cent.
Endometrial cancer is slightly more common but as it has clearer symptoms and is therefore often detected at an early stage, the mortality rate is low.
However, ovarian cancer is among the deadliest cancers, since it is often not detected until it has already spread to other parts of the body.
For this new study, researchers compared the incidence of breast, ovarian and endometrial cancers between women that had used oral contraceptive pills and those who had never used them.
They used data from the UK Biobank, which contains genetic and health information from half a million UK participants.
Using UK Biobank, they considered 256,661 UK women born between 1939 and 1970, who had or hadn’t been pill users.
Taking the combined pill increases the risk of breast and cervical cancer, Cancer Research UK says on its website
Information on cancer diagnoses were collected from self-reported data and from national registers until March 2019.
‘Surprisingly, we only found a small increased risk of breast cancer among oral contraceptive users, and the increased risk disappeared within a few years after discontinuation,’ said Johansson.
‘Our results suggest that the lifetime risk of breast cancer might not differ between ever and never users, even if there is an increased short-term risk.’
The results are important because oral contraceptive use has commonly been associated with side effects such as deep vein thrombosis, as well as breast cancer.
‘In addition to protecting against pregnancy, we have shown that oral contraceptive pills also have other positive effects,’ said study author Therese Johansson, also at Uppsala University.
‘Our results can enable women and physicians to make more informed decisions about which women should use oral contraceptive pills.’
The study is published in the journal Cancer Research.
Women taking newer versions of the combined pill have up to a 42% lower risk of getting ovarian cancer: 2018 study
Women taking modern versions of the combined pill to avoid pregnancy are up to 42 per cent less likely to get ovarian cancer, according to a 2018 study in the British Medical Journal.
Newer combined versions of oral contraceptives reduce the cancer risk more than older ones with higher levels of hormones.
The cancer-preventing effect increased with periods of longer use and continued for several years after users stopped taking the drug, researchers said.
Cancer rates were compared among women who take hormonal contraceptives now, those who have done in the past, and those who never had.
Women currently taking any kind of hormonal contraception have a 42 per cent lower cancer risk, the study said, but the effect of pills used in the past was weaker.
The preventative effect on ovarian cancer has been known in oral contraceptive pills with high levels of the sex hormones for some time – but it was not known whether the newer versions of the pill had the same benefit.
The first oral contraceptive pill was approved already in the 1960s, and 80 per cent of all women in Western Europe have used oral contraceptives at some point in their life.
Levels of the hormones oestrogen and progestogen have been getting steadily lower in contraceptive pills since the 1960s and 1970s.
Newer versions of the pill contain other drugs such as desogestrel, gestodene and drospirenone alongside the hormones.
And these pills – commonly sold under brand names Microgynon, Rigevidon, Yasmin, Cerazette and Loestrin 20 – have a stronger cancer-preventing effect.
Researchers at the University of Aberdeen and the University of Copenhagen in Denmark analysed data for nearly 1.9 million Danish women aged 15-49 years between 1995 and 2014.
Women were categorised as never having used hormonal contraceptive drugs, current users, or former users who had stopped taking the drug for more than one year.
Some 86 per cent of women who the hormonal contraceptives used oral products.
Those who had used them at some point in the past had a 34 per cent lower risk of ovarian cancer.
The study authors said: ‘Based on our results, contemporary combined hormonal contraceptives are still associated with a reduced risk of ovarian cancer in women of reproductive age, with patterns similar to those seen with older combined oral contraceptives.’
The researchers took account of several factors, including age and the number of children each women had.
They found the number of cases of ovarian cancer were highest in women who had never used hormonal contraception and lowest among those who were on the pill.
The reduced risk for combined products was seen with nearly all types of ovarian cancer.
And there was little evidence of important differences between pills containing different types of progestogens.
Based on these figures, the researchers said hormonal contraception prevented an estimated 21 per cent of ovarian cancers in this group of women.
The researchers pointed out that one weakness of the research is they did not study older women, among whom most cases of ovarian cancer occur.