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Hormone replacement therapy and incidence of central nervous system tumours in the Million Women Study

Benson VS, Pirie K, Green J, Bull D, Casabonne D, Reeves GK, Beral V, for the Million Women Study Collaborators

International Journal of Cancer 2010;127 :1692-8.


We examined the relation between use of HRT and 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 three 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 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 (1.02-2.45), respectively, and in past users of HRT were 1.07 (95% CI 0.93-1.24), 1.02 (95% CI 0.82-1.27), 1.29 (95% CI 0.96-1.72), and 1.71 (95% CI 1.07-2.73), respectively. Among current users of HRT there was significant heterogeneity by type of HRT with users of oestrogen-only HRT at higher risk of all CNS tumours (RR = 1.42, 95% CI 1.21-1.67) than users of oestrogen-progestagen HRT (RR = 0.97, 95% CI 0.82-1.16]) (heterogeneity p <0.001), when compared to never users. 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.