Brain Tumor Research: A Type Of Commonly Used Birth Control Doubles Glioma Risks, Study Says

Could taking certain kinds of birth control increase your risk of developing glioma, a rare type of brain tumor?

In a study published Thursday in the British Journal of Clinical Pharmacology, a Danish neurologist reports that using hormonal birth control (including estrogen or combination hormones) can increase the risk of gliomas, and that using progestin-only birth control for longer than five years more than doubles the risk of developing gliomas. Progestin-only birth control includes the mini-pill, implants, and the Depo-Provera shot.

Neurologist Dr. David Gaist, from Odense University Hospital and the University of Southern Denmark, used information from the national registries of health records. The study examined cancer cases and prescriptions. The study focused on women in Denmark ages 15- to 49-years-old who had been diagnosed with gliomas. He then took a look at what forms of birth control they used, if any, and how long they were on the birth control.

Oncology Nurse Advisor reported on the glioma-risk study. According to that report, discovering that progestin-only birth control increased glioma risks in the study by 2.4 times came as a surprise, because “previous studies have found that estrogen and progestin may decrease the risk of gliomas, but particularly in post-menopausal women.”

The Natural College of Natural Medicine remarked earlier on the the use of progestin and the increased risks of another type of cancer with its use.

“While synthetic progestins may mimic some of progesterone’s effects, progestins may react differently with progesterone receptors in the body. A significant consequence of the side effects seen with synthetic progestins has been an increase in the risk of developing breast cancer.”

Gaist remarked that there is no imperative reason for women to stop using progestin-only birth control measures at this point, because gliomas are exceedingly rare.

“If you look at women in Denmark aged 15 to 49, about five in 100,000 experience that terrible diagnosis in a year, and that figure includes women on hormonal contraceptives, so it’s a very rare event.”

“It is important to keep this apparent increase in risk in context,” Dr. Gaist explained to the Daily Telegraph about the risk of gliomas with progestin-only birth control types.

Gaist commented that earlier studies relied on self-reporting, but his data came directly from medical records and national registries, which are significantly more accurate.

Suzi Gage, from the Guardian, said that the birth control link is still inconclusive, and that “obesity is thought to impact on glioma rates, but data on this was not available for the women included in this study.”

In Denmark, government regulations require that physicians avoid prescribing birth control that features estrogen to women who are considered obese. Consequently, women who are obese in Denmark would be more likely to use progestin-only birth control measures, and if Gage is right, perhaps more likely to develop glioma.

[Photo by Mschocke]