Reacción a "Reactions: some progesterone analogues increase risk of developing a type of brain tumour, study finds"

This paper reports on a carefully conducted study using records from the French National health Data System to study the association of progestogen medications and risk of meningioma.  An association of high doses of certain types of progestogens with meningioma has previously been reported, but these are rarely used in clinical practice.  The aim of this study was to investigate more commonly used progestogens.

The press release is a good summary of the findings.  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.  In particular, the size of the effect is quite large, there are no obvious confounders or biases, and the effect was seen for some medications and not others (any confounding and bias would be expected to affect all medications similarly).

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.  Use of medroxyprogesterone acetate for more than one year was associated with a five-fold increase in risk of meningioma.  While this sounds like a very large risk it is important to realise that meningioma is rare and a five-fold increase in a rare disease is still a rare disease.  To put some numbers on this, based on UK cancer registration data, approximately 40 out of 10,000 30-year old women 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. This small increase in risk needs to be considered in relation to the benefits of using an injectable form of contraception.