Chromosome aberrations in lymphocytes and cancer risk in benzene-exposed workers

The increasing use of biomarkers in the study of groups considered at potential risk of cancer from occupational/environmental exposure to genotoxins has raised the problem of the capacity of such indicators to predict disease risk. Structural chromosome aberrations (CA) in lymphocytes, an indicator of early biological effect of genotoxin exposure, is being applied since three decades. Recently two multicentric cohort studies, one from the Northern European countries (Hagmar et al., Cancer Res. 54, 2919, 1994), one from Italy (Bonassi et al., Cancer Genet. Cytogenet. 79, 133, 1995) have shown an association of increased cancer incidence and mortality, respectively, with the highest fertile of CA frequency. In order to better define the potential predictivity of CA for cancer risk on a more homogenous group, a subcohort of 67 benzene-exposed workers cytogenetically studied from 1965 to 1988, when free of cancer, by one of us (AF), has been extracted from the Italian cohort and followed-up to April 1996. The cohort was subdivided into subjects with "low", "medium", "high" CA levels by tertiles. Standardized mortality ratios (SMR) for all causes, all cancers and specific types of cancers, compared to the Italian population, were calculated. Increased SMRs were found for all causes, all cancers and for respiratory tract and lymphohaemopoietic tissue cancers, with higher risks among the subgroup with medium-high CA levels, and the trend was significant for all cancers. The association was more strong and with a significant trend for the subgroup of 19 subjects who had suffered from severe benzene haemopathy prior to cytogenetic testing, and for the 25 workers with estimated "high" benzene exposure compared to those who had not experienced important signs of benzene toxicity or whose exposure was estimated as "low-medium".