Abstract and Introduction
Abstract
The authors conducted a nationwide cohort study to evaluate the association between postmenopausal hormone therapy and meningioma incidence in Finland. All women who had used hormone therapy at least for 6 months at the age of 50 years or older during 1994–2009 were included. Women who had used postmenopausal hormone therapy were identified from the medical reimbursement register of the Social Insurance Institution (131,480 estradiol users and 131,248 estradiol-progestin users), and meningioma cases were identified from the Finnish Cancer Registry. During the average 9 years of follow-up, 289 estradiol users and 196 estradiol-progestin users were diagnosed with meningioma. Ever use of estradiol-only therapy was associated with an increased risk of meningioma (standardized incidence ratio = 1.29, 95% confidence interval: 1.15, 1.44). Among women who had been using estradiol-only therapy for at least 3 years, the incidence of meningioma was 1.40-fold higher (95% confidence interval: 1.18, 1.64; P < 0.001) than in the background population. In contrast, this risk was not increased in users of combination therapy (standardized incidence ratio = 0.93, 95% confidence interval: 0.80, 1.06). There was no difference in risk between continuous and sequential use of hormone therapy. Estradiol-only therapy was accompanied with a slightly increased risk of meningioma.
Introduction
Meningioma is at least twice as common in women as in men. The difference is even more pronounced with spinal meningiomas, which have a female:male ratio of 4:1. The majority of meningiomas are intracranial; spinal meningiomas represent about 10% of all meningiomas. Less than 10% of meningiomas are atypical or malignant. An increased incidence of breast cancer has been detected among meningioma patients and vice versa. This suggests that meningiomas and breast cancer share common risk factors. Because postmenopausal hormone therapy (HT) is associated with breast cancer risk, it might also be a determinant for meningioma incidence. Moreover, both of these tumor types express estrogen and progesterone receptors, and in both diseases the amounts of estrogen and progesterone receptors have effects on prognosis. The association between menopausal HT and meningioma risk has been assessed only in few studies. Thus far, the results have been inconclusive: Cohort studies have shown uniformly positive associations between HT and meningioma risk, but results from case-control studies have been inconsistent.
In Finland, the use of postmenopausal HT can be traced reliably using the medical reimbursement register. Therefore, we evaluated the impact of different components and routes of administration of postmenopausal HT on the risk of intracranial and intraspinal meningiomas in a cohort of women who represented the entire postmenopausal Finnish female population.