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.
Division of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
Jelle
J
Vlaanderen
Qing
Q
Lan
Hans
H
Kromhout
Nathaniel
N
Rothman
Roel
R
Vermeulen
D001554:Benzene / Q000009:adverse effects*; D002274:Carcinogens, Environmental / Q000009:adverse effects*; D015331:Cohort Studies; D006801:Humans; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000139:chemically induced*; D009784:Occupational Diseases / Q000139:chemically induced*; D016273:Occupational Exposure / Q000009:adverse effects*; D012307:Risk Factors
D002274:Carcinogens, Environmental; D001554:Benzene