Occupational benzene exposure and the risk of chronic myeloid leukemia: a meta-analysis of cohort studies incorporating study quality dimensions.

Objective: We documented previously that if study quality is accounted for, evidence from occupational cohort studies on benzene supports a possible association with some lymphoma subtypes, in particular multiple myeloma, and acute and chronic lymphocytic leukemia. Here, we extend these analyses to chronic myeloid leukemia (CML).
Methods: Three strategies to assess study quality (stratification by the year-of-start of follow-up, stratification by the strength of the reported acute myeloid leukemia (AML) association, and stratification by the quality of benzene exposure assessment) were employed in a meta-analysis of occupational benzene exposure and CML. We hypothesized that stratification by these study quality dimensions would identify a subgroup of occupational cohort studies that is most informative for the evaluation of the possible association between benzene and CML.
Results: The overall meta-relative risk (mRR) was non-significantly elevated (1.23; 95% confidence interval (CI): 0.93-1.63). The mRRs increased with increasing study quality for all dimensions with a significant elevation for studies with start of follow-up after 1970 (1.67; 95% CI: 1.02-2.74). The highest study quality stratum for AML significance and exposure quality showed an elevated but non-significant increased mRR (1.40; 95% CI: 0.86-2.27, and 1.68; 95% CI: 0.74-3.84, respectively).
Conclusions: Although limited by low statistical power, the current meta-analysis provides support for a possible association of occupational exposure to benzene and the risk of CML.
(Copyright © 2012 Wiley Periodicals, Inc.)