Every form of hormonal contraceptive increases the risk of breast cancer, a study suggests.
Previous research has shown that the combined contraceptive pill – which contains oestrogen and progestogen – could increase the risk of breast cancer by about 20 per cent.
But a new study has shown newer pills containing progestogen alone, increasingly popular in recent years, carry the same risk as older alternatives.
The findings were also applicable to both types of hormonal contraceptive taken in any form – whether injection or implant.
A team from the University of Oxford analysed data from more than 9,000 women who developed invasive breast cancer between the ages of 20 to 49, and 18,000 closely-matched women who did not develop the disease.
Historically, most women favoured a ‘combined’ contraceptive pill that contains two hormones, oestrogen and progestogen. But now prescription for the progestogen only pill are on par
Analysis revealed those who were taking, or had recently stopped taking, the newer progestogen-only pill also had a 20 to 30 per cent increased risk of breast cancer.
However this effect appeared to wear off once women had ceased use, with no excess risk 10 years after they stopped taking the contraceptives.
The team said their research, published in the journal Plos Medicine, helps ‘fill a gap’ in the knowledge about associated risks with taking hormonal contraceptives.
But they said these risks must be weighed against the well-known benefits of taking them.
WHAT METHODS OF CONTRACEPTION ARE CURRENTLY AVAILABLE?
Contraception aims to prevent pregnancy. A woman can get pregnant if a man’s sperm reaches one of her eggs.
Contraception tries to stop this happening by keeping the egg and sperm apart, by stopping egg production or by stopping the combined sperm and egg attaching to the lining of the womb.
Contraception is free for most people in the UK. The options available include:
- caps or diaphragms
- combined pill
- contraceptive implant
- contraceptive injection
- contraceptive patch
- female condoms
- IUD (intrauterine device or coil)
- IUS (intrauterine system or hormonal coil)
- natural family planning (fertility awareness)
- progestogen-only pill
- vaginal ring
Gillian Reeves, Professor of statistical epidemiology and director of the Cancer Epidemiology Unit at the University of Oxford, said: ‘I don’t really see that there’s any indication here to say that women need to necessarily change what they’re doing.
‘Yes, there is an increase here, and yes, nobody wants to hear that something that they’re taking is going to increase their risk for breast cancer by 25%.
‘The main purpose of doing this research was really to fill a gap in our knowledge.
‘We’ve known for many years that combined oral contraceptives, which women have been using for decades, also have an effect on breast cancer risk, a small increase in risk which is transient.
‘We weren’t absolutely sure what the corresponding effect of these progestogen-only contraceptives would be.
‘What we’ve shown is that they’re just the same in terms of breast cancer risk, they seem to have a very similar effect to the other contraceptives, and the effect that we’ve known about for many years.’
Kirstin Pirie, statistical programmer at Oxford Population Health, and one of the lead authors, said: ‘The findings suggest that current or recent use of all types of progestogen-only contraceptives is associated with a slight increase in breast cancer risk, similar to that associated with use of combined oral contraceptives.
‘Given that a person’s underlying risk of developing breast cancer increases with advancing age, the absolute excess risk of breast cancer associated with either type of oral contraceptive will be smaller in women who use it at younger ages.
‘These excess risks must, however, be viewed in the context of the well-established benefits of contraceptive use in women’s reproductive years.’
Commenting on the study Dr Kotryna Temcinaite, head of research communications at Breast Cancer Now, said: ‘This research suggests there is a small increased risk of developing breast cancer for women while they are using, or soon after stopping, a newer progestogen-only contraceptive.
‘The level of risk is around the same as for the older combined pill containing oestrogen and progestogen, which we’ve known about for some time. For both types of contraceptives, if you stop using them, this added risk of breast cancer reduces over time.
A team from the University of Oxford analysed data from more than 9,000 women who developed invasive breast cancer between the ages of 20 to 49, and 18,000 closely-matched women who did not develop the disease. Analysis revealed those who were taking, or had recently stopped taking, the newer progestogen-only pill also had a 20 to 30 per cent increased risk of breast cancer
‘The study didn’t look at what hormonal contraceptives the women may have used in the past or consider how long they may have been on the progestogen-only contraception.
‘It also didn’t factor in whether a family history of the disease contributed to their level of risk. So further work is needed to help us fully understand the impact of using this type of contraception.
‘Breast cancer is rare in young women. A slight increase in risk during the time a woman uses hormonal contraceptive means only a small number of extra cases of the disease are diagnosed.’
Professor Stephen Duffy, from the Centre for Prevention, Detection and Diagnosis at Queen Mary University of London, added that the results are ‘reassuring in that the effect is modest’.
NHS figures revealed back in 2008 there were just under six million prescriptions for combined hormonal contraceptives in England, compared to under two million of the progestogen-only pill.
However by 2020 the gap had closed and prescriptions for both stood at around 3.2 million.