Menopausal hormone therapy and risk of ovarian cancer: systematic review and meta-analysis

Knowledge about the impact of menopausal hormone therapy (MHT) on the risk of ovarian cancer (OvC) is insufficient, and studies are inconsistent. Mortality from OvC ranks highest among cancer sites in female reproductive organs. We performed meta-analyses to assess the impact of specified types of MHT on the risk of OvC in cohort studies (CS), case-control studies (CCS), randomized controlled trials (RCT) and cancer registry studies (CRS). We used data published 1966-2006 on estrogen therapy (ET), estrogen/progestin therapy (EPT) or MHT (unspecified regimen) identified by a structured, computerized and manual literature search. We identified 42 studies (30CCS, 7CS, 1 RCT and 4 CRS) with 12 238 cases. The risk of OvC (ever-use, annual risk) is increased 1.28-fold by ET [confidence interval (CI) 1.18-1.40] and 1.11-fold by EPT (CI 1.02-1.21) with a suggestion of greater risks with ET. There appears to be no differential impact of any therapy on histological subtypes. Risks were greater in European than North American studies for both ET and EPT. In conclusion, ET as well as EPT, are risk factors for OvC. Given the widespread use of MHT, known benefits should be weighed against the increased risk of OvC, and more studies are warranted, particularly on factors with the greatest apparent risks.