Academic journal article Environmental Health Perspectives

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

Academic journal article Environmental Health Perspectives

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

Article excerpt

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Data sources: Searches of PubMed and unpublished data yielded a total of 18 cohort studies of women occupationally exposed to asbestos.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 (I2 = 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 Rvalue = 0.162).

Conclusions: Our study supports the IARC conclusion that exposure to asbestos is associated with increased risk of ovarian cancer.

Key words: asbestos, chrysotile, crocidolite, meta-analysis, ovarian cancer, SMR. Environ Health Perspect 119:1211-1217 (2011). http://dx.doi.org/l0.1289/ehp.1003283 [Online 3 June 2011]

In 2008, cancer of the ovary represented the second leading cause of gynecologic cancer death worldwide (Ferlay et al. 2010). The geographical distribution of ovarian cancer is characterized by wide international variation. Highest rates are observed in North America and Northern Europe. In the United States, white women have higher incidence and mortality rates than do other racial and ethnic groups (Horner et al. 2009). Although the etiology of ovarian cancer is not well understood, multiparity, lactation, oral contraceptive use, and tubal ligation or hysterectomy are inversely associated with risk (Permuth-Wey and Sellers 2009; Sueblinvong and Carney 2009), whereas estrogen-only menopausal therapy, tobacco smoking, and other environmental, occupational, and genetic factors are positively associated with ovarian cancer (Antoniou et al. 2000; Grosse et al. 2009; Secretan et al. 2009; Shen et al. 1998).

Approximately 125 million people around the world work in environments in which they are exposed to asbestos, and at least 90,000 people die from asbestos-related lung cancer, mesothelioma, or asbestosis ever)' year (Burki 2009). Asbestos exposure has been identified in some previous reviews as a possible risk factor for ovarian cancer (Hankinson and Danforth 2006; Ness and Cottreau 1999; Shoham 1994). However, this association has not been widely recognized. Perineal use of talc, which may in some formulations contain asbestiform or talc mineral fibers, has also been associated with ovarian cancer in a number of studies (Baan et al. 2006; Langseth etal. 2008).

The association between ovatian cancer risk and asbestos exposure was addressed by a Monographs Working Group that was convened in March 2009 by the International Agency for Research on Cancer (IARC). After considering the potential role of chance, confounding, and other forms of bias, the working group concluded that the evidence is sufficient for a causal association between occupational exposure to asbestos and ovatian cancer (Straif et al. 2009). To more fully evaluate and characterize this association, we performed a meta-analysis.

Materials and Methods

We searched for studies of workers exposed to asbestos published in any language before March 2010 using PubMed software to search Medline (U. …

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