Occupational Exposure to Asbestos and Ovarian Cancer: A Meta-analysis

OBJECTIVE: A recent Monographs Working Group of the International Agency for Research on Cancer (IARC) concluded that there is sufficient evidence for a causal association between exposure to asbestos and ovarian cancer. We performed a meta-analysis to quantitatively evaluate this association. DATA SOURCES: Searches of PubMed and unpublished data yielded a total of 18 cohort studies of women occupationally exposed to asbestos. DATA EXTRACTION: Two authors independently abstracted data; any disagreement was resolved by consulting a third reviewer. DATA SYNTHESIS: All but one study reported standardized mortality ratios (SMRs) comparing observed numbers of deaths with expected numbers for the general population; the exception was a study that reported standardized incidence ratios. For simplicity, we refer to all effect estimates as SMRs. The overall pooled SMR estimate for ovarian cancer was 1.77 (95% confidence interval, 1.37-2.28), with a moderate degree of heterogeneity among the studies (I-2 = 35.3%, p = 0.061). Effect estimates were stronger for cohorts compensated for asbestosis, cohorts with estimated lung cancer SMRs > 2.0, and studies conducted in Europe compared with other geographic regions. Effect estimates were similar for studies with and without pathologic confirmation, and we found no evidence of publication bias (Egger's test p-value = 0.162). CONCLUSIONS: Our study supports the IARC conclusion that exposure to asbestos is associated with increased risk of ovarian cancer.