Environmental and occupational factors associated with chronic myeloid leukemia: a case-control study

Background

The relationship between chronic myeloid leukemia (CML) and a broad range of exposures to occupational and environmental factors known to cause leukemia in general is limited. CML is by and large incurable and treatment is just palliative and life prolonging, with high case fatality rate, even in the best centers. Furthermore treatment is very expensive. Identification of leukemogenic factors is therefore important if this can lead to simple public health interventions.

Objective

The objective was to determine key environmental and occupational exposure factors that may be associated with CML.

Methods

This was a case-control study involving CML cases enrolled in Glivec International Patient Assistance Program (GIPAP) clinics at the Nairobi Hospital and Aga Khan University Hospital and two control groups for each case, matched for age and sex: a family- and hospital-based control, was carried out. One hundred and eight cases with ageand-gender-matched family- and hospital-based controls were recruited and a standard questionnaire was administered. Individual data on demographics, occupation, environment, and exposures to benzene and farm organochemical products were obtained. Clinical examination was carried out in control subjects. Statistical analysis was done using bivariate and multivariate analysis to look for associations between exposure factors and CML.

Results

The median age at diagnosis of CML cases was 41.32 years with an age range of 8–81 years and a male to female ratio of 1.7:1. Most of our cases were concentrated in or around Nairobi. There was no significant correlation found for exposure to benzene or pesticides. Long duration of exposure to pesticides in the family control group was significantly associated (t-test, P = 0.017) with risk of CML.

Conclusions

Associations between exposures to organic solvents like pesticides and CML were indicated but were not entirely consistent, although no associations with benzene products were found. Nevertheless, for almost all cases of Ph chromosome-positive CML, other explanations must be sought for.