Side Effects of Depo-Provera Birth Control May Increase Risk of Brain Tumors in Women: Study

Millions of women who have taken birth control shots marketed and sold by Pfizer may now be at an increased risk of developing a rare form of brain tumor known as meningioma.

Taking certain forms of birth control and hormone therapy may increase a woman’s risk of developing brain tumors by a factor of five, according to the findings of a new study.

Researchers warn that women who take synthetic progestogen hormone products, including the popular injected contraceptive Depo-Provera, may be more likely to develop meningioma, which can create pressure on the brain and often requires surgical removal. The findings were published on March 27 in the journal The BMJ.

Meningiomas are a type of rare brain tumor that occurs only about 10 times per hundred thousand person-years. They typically are not cancerous and are slow growing, but account for 40% of central nervous system tumors. Even when not cancerous, they can put pressure on the brain, requiring surgical removal or other interventions to decompress the tissue.

Studies have found that this type of brain tumor contains progesterone receptors, which indicates there may be a link between the increased risk of this brain tumor and female sex hormones.

In this latest study, French researchers used data from more than 108,000 women in the French National Health Data System. They examined information from 18,000 women living in France who underwent brain surgery for meningioma between 2009 and 2018. Each woman was matched with five control patients for comparison.

Researchers compared different types of synthetic progestogen hormones and different delivery methods, including oral, vaginal, and injection.

The data indicated taking synthetic progestogens long-term, for more than one year, increases a person’s risk of developing brain tumors. Different types of progestogen hormones increase a woman’s risk of developing the rare brain tumor by different amounts.

The most pronounced brain tumor risk was linked to side effects of Depo-Provera, a commonly used birth control injection, which increased the risk by 5.6 times, the researchers determined. Roughly 74 million women around the world use Depo-Provera for birth control, suggesting that millions of women may face an increased brain tumor risk.

However, other types of progestogen hormones were also linked to an increased risk. Colprone, a hormone replacement therapy (HRT) often used during menopause, was linked to a four times higher risk. Sugestone, an oral pill used for both birth control and hormone replacement during menopause, increased the risk of developing this type of brain tumor by 2.7-fold, according to the data.

Other progestogen-based products, like Mirena and Kyleena intrauterine devices (IUDs) used for birth control, did not increase the risk of brain tumors, and neither did Climaston and Femaston, vaginal hormones widely used to treat infertility, irregular menstrual cycles, polycystic ovarian syndrome (PCOS), and used after miscarriage, the researchers determined.

Progestogen Brain Tumor Risks

Among women not taking hormones, roughly four in every thousand women will develop this type of brain tumor by the age of 80. Using birth control like Depo-Provera increases that risk to 20 in every thousand women, researchers warned.

Other studies have indicated the size of these brain tumors may increase during pregnancy, and then decrease after a woman gives birth. This highlights the potential link between female hormones and tumor growth, and may explain why taking some types of progestogen hormones appears to increase the risk.

“Although the risk of meningioma was already known for three progestogens, this study is the first to assess the risk associated with progestogens that are much more widely used for multiple indications, such as contraception,” the researchers concluded. “Studies from countries with a broader use of (Depo-Provera), which, furthermore, is often administered to vulnerable populations, are urgently needed to gain a better understanding of its dose-response association.”