Hormone replacement therapy and ovarian cancer risk: A meta-analysis

Objectives. Epidemiologic findings are inconsistent concerning the risk for ovarian cancer associated with hormone replacement therapy (HRT). We conducted a meta-analysis to summarize the available evidence from observational studies to examine this relation. Methods. We searched PUBMED and MEDLINE for relevant studies that were published from January 1, 1966, through May 1, 2007. Study-specific risk estimates were pooled by the use of a random-effects model. Results. Eight cohort (including 4715 cases and 1,555,374 participants) and 19 case-control studies (involving 8240 cases and 20,996 controls) were included. We found a summary relative risk (RR) of 1.24 (95% confidence interval [CI] 1.15-1.34) from cohort studies and a summary odds ratio [OR] of 1.19 (95%CI 1.02-1.40) from case-control studies for ever HRT use. However, the risk estimates of case-control studies might be upwardly biased. Summary risk estimates of four cohort and six case-control studies that distinguished estrogen replacement treatment (ERT) and estrogen-progestin replacement treatment (EPRT) from HRT both indicated that association was stronger among ERT user than EPRT user. Based on data abstracted from six case-control studies, duration of HRT use was not significant. The summary risk estimates for less than 5 years, 6-10, and more than 10 years use were 1.02, 1.13, and 1.21, respectively and 95%CI for each estimate crossed 1.0. Conclusion. HRT use was associated with increased risk of ovarian cancer. These findings may expand the range of possible risks associated with HRT use. However, this positive association should also be considered in the context of HRT's other favorable effects on health. (C) 2007 Elsevier Inc. All rights reserved.