In September of 2011, confirmed what had been long expected – asbestos exposure is one of the causes of ovarian cancer. While lung cancer and mesothelioma were long known to be caused by asbestos exposure, the Monographs Working Group of the International Agency for Research on Cancer (IARC) earlier this year concluded that there is now sufficient evidence for a causal association between asbestos and ovarian cancer. The IARC’s conclusion prompted Leslie Sayner of the University of Illinois at Chicago, School of Public Health to conduct a study “[t]o more fully evaluate and characterize this association.”
Sayner and her colleagues performed a meta-analysis of 18 studies of women who had been exposed to asbestos through their work. Sayner, et al., explained that one concern in interpreting the findings was because “until recently it has been very difficult to distinguish pathologically between peritoneal mesothelioma and ovarian cancer (Kannerstein et al. 1977).” Despite this, “we also did not observe a large attenuation of the association when we assumed that 20% of the ovarian cancer cases in each study were misclassified. Given our findings from this sensitivity analysis, it would seem unlikely that the association between occupational asbestos exposure and ovarian cancer could be fully explained by tumor misdiagnosis.”
Moreover, the analysis found no uniform conclusion on how asbestos increases susceptibility to ovarian cancer, though several theories have been proposed based on chronic inflammation caused by fibers persisting in ovarian tissue and thereby causing damage. The analysis also found that, while the fibers can be found in the ovaries during biopsy, it is still unknown how the fibers get into the ovaries – whether they are transported directly through the reproductive tract or carried through the bloodstream or the lymph system, whereby they are transported through the reproductive tract, or by the fibers penetrating the ovary through the mesothelium. Moreover, the analysis noted the difficulty in controlling for age, and the possible latency of time between exposure and development of disease, a range more fully understood with regard to mesothelioma.
Even with the acknowledged difficulties and stated limitations of the studies, the meta-analysis found that across all the studies, women exposed to asbestos were approximately one-and-three-quarter times more likely to develop ovarian cancer as those who were not exposed. For the full analysis, see Occupational Exposure to Asbestos and Ovarian Cancer, A Meta-Analysis (M. Constanza Camargo; Leslie T. Stayner; Kurt Straif; Margarita Reina; Umaima Al Alem; Paul A. Demers; Philip J. Landrigan) published in Environmental Health Perspectives. 2011; 119(9):12111217.