Some progestogen medicines used for contraception or to manage conditions like endometriosis have been linked to an increased risk of a type of brain tumour in a large study.
Researchers looked at use of eight progestogen medicines in a group of 18,000 women who had undergone surgery to remove meningiomas and compared it with five times as many matched controls.
They found that prolonged use, for more than a year, of three of the drugs was related to an increased risk of the usually benign tumour.
It included the contraceptive injection medroxyprogesterone acetate which was linked to a 5.6-fold higher risk, they reported in the BMJ.
Two oral pills, medrogestone and promegestone, were also associated with a 4.1 and 2.7-fold greater risk of meningioma respectively.
No excess risk of meningioma requiring surgery was found for progesterone, dydrogesterone, or the widely used hormonal intrauterine systems, regardless of the dose of levonorgestrel they contained, they said.
It follows other studies which had already shown a raised risk of meningioma with some high-dose progestogens but not much had been known about other more commonly used forms of the synthetic hormone they said.
As an observational study no conclusion can be drawn around cause and effect, and there was a lack of clinical detail and medical indications for which progestogens are prescribed in the database looked at, they noted.
But ‘given that medroxyprogesterone acetate is estimated to be used for birth control by 74 million women worldwide, the number of attributable meningiomas may be potentially high,’ they added.
Further studies using other sources of data are ‘urgently needed’ to gain a better understanding of this risk, they concluded.
NHS prescription data suggests there are around 10,000 prescriptions for medroxyprogesterone acetate every month in England.
Paul Pharoah, professor of cancer epidemiology at Cedars-Sinai Medical Centre in the US, said many of the findings in the study did not relate to UK prescriptions but there were risks around medroxyprogesterone acetate.
He added: ‘It is important to note that progestogens are an important component of many types of birth control pill (oral contraceptives) and hormone replacement therapy but there are many different types of progestogens and no association with meningioma was found for the types of progestogens commonly used in the United Kingdom.’
Professor Pharoah said for those taking medroxyprogesterone acetate, the increased risk found in the research was small and would need to be balanced against the benefits.
Dr Karen Noble, director of research, policy and innovation at Brain Tumour Research, said better knowledge of the risk factors of brain tumours could open doors to research on preventative measures, as well as increase understanding of why these tumours arise in the first place.
‘However, the public needs to be cautious when digesting the results from a study such as this before taking action.
‘Although this study has linked certain progestogen treatments to an increased risk of meningioma, it has also demonstrated the safety of other progestogen treatments which were shown to not increase risk.
‘If you are concerned, it is recommended that you speak to your GP before stopping any prescribed treatment.’
Last month, NICE said that GPs should offer a transvaginal ultrasound to all patients with suspected endometriosis.
