An injectable contraception used by some women in the UK has been linked to an increased risk of a type of brain tumour.
A study, published in the British Medical Journal (BMJ), found people using injectable medroxyprogesterone acetate for more than a year appear to have a higher risk of meningioma – a tumour of the membranes covering the brain and spinal cord.
It is usually benign but can cause serious problems in some patients due to its location in and around the brain and spinal cord.
The new study linked some types of progestogen (similar to the hormone progesterone) to an increased risk of meningioma, though several types are not used in the UK.
However, it found that prolonged use of medroxyprogesterone acetate was “associated with an excess risk of intracranial meningioma”.
The French researchers, including from the French National Agency for Medicines and Health Products Safety, said: “In countries for which the use of medroxyprogesterone acetate for birth control is frequent (74 million users worldwide), the number of attributable meningiomas may be potentially high.”
NHS prescription data suggests there are around 10,000 prescriptions for medroxyprogesterone acetate every month in England.
The new study used data from the French national health system for 18,061 women (average age 58) who underwent meningioma surgery from 2009-18.
Each case was matched to five control women without meningioma (total 90,305) by year of birth and area of residence.
The results showed that prolonged use of medroxyprogesterone acetate injection was associated with a 5.6-fold increased risk of meningioma.
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: “The authors note that causality cannot be determined in an observational study such as this but, given what we know about the risk factors for meningioma, it seems quite likely that the association reported for medroxyprogesterone acetate is causal.
“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.
“This means that women taking the commonly used birth control pills or hormone replacement therapy are not at increased risk of meningioma.
“It is important that women do not stop using their birth control pills without consulting their doctor.
“The notable exception is medroxyprogesterone acetate (also known as Depo-Provera) which is sometimes used as an injectable form of contraception in the UK.”
Prof Pharoah said around 40 out of 10,000 30-year-old women in the UK would be expected to be diagnosed with a meningioma before the age of 80.
“This increases to 200 in those who have used medroxyprogesterone acetate,” he added.
“This small increase in risk needs to be considered in relation to the benefits of using an injectable form of contraception.”
Dr Karen Noble, director of research, policy and innovation at Brain Tumour Research, said: “Any increased understanding of the risk factors of brain tumours is beneficial to the brain tumour community; it may open doors to research on preventative measures, as well as increase our 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.”
