Increased risk for non-Kodgkin's lymphoma (NHL) may be associated with exposures to pesticides and certain chronic viral infections, including hepatitis C virus (HCV). To study the possible association of agricultural pesticides with NHL in a region with high rates of chronic HCV, we conducted a case-control study in Egypt to assess viral and environmental risk factors for this malignancy.
Cases (N = 227) and controls (N = 227) were recruited during 1999–2002 at two major referral hospitals in Cairo: the National Cancer Institute and the Kasr El-Aini Faculty of Medicine Hospital System, Cairo University. Cases were adults with B-cell NHL diagnosed within 6 months of recruitment and confirmed by pathology and/or immunohistochemistry. T-cell lymphomas were excluded. Since NHL is more common in males than females, and since rural males are more likely than others in Egypt to apply pesticides, we stratified the study by gender and region (urban vs. rural). From the orthopedic wards we selected an age-matched group of cancer-free controls in each stratum: there were 61 cases: 61 controls who were urban males, 76:76 rural males, 43:43 urban females, and 47:47 rural females. Participants were interviewed concerning their medical history, social factors, and a wide range of environmental exposures. For those who reported work in farming, an exposure matrix of year, crop, and pest yielded putative pesticide chemicals based on Ministry of Agriculture records. Subjects provided a blood sample for serological testing of HCV antibody (by ELISA) and viral RNA (by PCR). Case-control comparisons were made using logistic regression stratified by gender and region. Adjusted odds ratios (OR) and their 95% confidence intervals (CI) are reported below.
In all 4 strata, cases were more likely than controls to be positive for HCV RNA, a marker of current (presumed chronic) infection: OR = 4.1 (1.5–11.2) for urban males, OR = 3.2 (1.1–9.4) for urban females, OR = 1.8 (0.9–3.6) for rural males, and OR = 2.6 (1.1–6.3) for rural females. Among rural males, significantly more cases (21%) than controls (9.2%) were exposed to organophosphate insecticides: the adjusted OR was 2.5 (1.0–6.5). Duration of organophosphate use was also significantly associated with NHL in a linear model. Ongoing recruitment is aimed towards an optimal sample size for testing the synergistic effects of HCV and pesticides.
In Egypt, chronic HCV infection is associated with an increased risk for B-cell NHL in both men and women. Pesticide exposures in rural men are also associated with increased risk for this malignancy. We speculate that there may be additive or synergistic increased risks for NHL imposed by the burden of viral and environmental risk factors.
(1) Georgetown University, USA
(2) Menoufiya University, Egypt
(3) Centers for Disease Control & Prevention, USA
(4) Desert Research Institute, Egypt
(5) University of Maryland, Baltimore. USA
(6) National Cancer Institute of Cairo University, Egypt