title: Hormone replacement therapy and incidence of central nervous system tumours in the Million Women Study.
abstract: We examined the relation between the use of hormone replacement therapy (HRT) and the incidence of central nervous system (CNS) tumours in a large prospective study of 1,147,894 postmenopausal women. Women were aged 56.6 years on average at entry, and HRT use was recorded at recruitment and updated, where possible, about 3 years later. During a mean follow-up of 5.3 years per woman, 1,266 CNS tumours were diagnosed, including 557 gliomas, 311 meningiomas and 117 acoustic neuromas. Compared with never users of HRT, the relative risks (RRs) for all incident CNS tumours, gliomas, meningiomas and acoustic neuromas in current users of HRT were 1.20 (95% CI: 1.05-1.36), 1.09 (95% CI: 0.89-1.32), 1.34 (95% CI: 1.03-1.75) and 1.58 (95% CI: 1.02-2.45), respectively, and there was no significant difference in the relative risks by tumour type (heterogeneity p = 0.2). In past users of HRT the relative risk was 1.07 (95% CI: 0.93-1.24) for all CNS tumours. Among current users of HRT, there was significant heterogeneity by the type of HRT with the users of oestrogen-only HRT at higher risk of all CNS tumours than users of oestrogen-progestagen HRT (RR = 1.42, 95% CI: 1.21-1.67 versus RR = 0.97, 95% CI: 0.82-1.16) (heterogeneity p < 0.001). Among current users of oestrogen-only and oestrogen-progestagen HRT, there was no significant heterogeneity by duration of use, hormonal constituent or mode of administration of HRT.
authors.affiliation: Cancer Epidemiology Unit, University of Oxford, Oxford, United Kingdom. vicky.benson@ceu.ox.ac.uk
authors.forename: Victoria S
authors.initials: VS
authors.lastname: Benson
authors.forename: Kirstin
authors.initials: K
authors.lastname: Pirie
authors.forename: Jane
authors.initials: J
authors.lastname: Green
authors.forename: Diana
authors.initials: D
authors.lastname: Bull
authors.forename: Delphine
authors.initials: D
authors.lastname: Casabonne
authors.forename: Gillian K
authors.initials: GK
authors.lastname: Reeves
authors.forename: Valerie
authors.initials: V
authors.lastname: Beral
mesh_terms: D016543:Central Nervous System Neoplasms / Q000453:epidemiology*; D015914:Estrogen Replacement Therapy / Q000009:adverse effects*; D005260:Female; D005910:Glioma / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D008579:Meningioma / Q000453:epidemiology; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000453:epidemiology; D047648:Perimenopause; D017698:Postmenopause; D011247:Pregnancy; D017697:Premenopause; D012307:Risk Factors; D012727:Sex Characteristics