There is some evidence that pesticide exposure might be related to prostate cancer. A possible involvement of pesticides in prostate carcinogenesis is suggested by positive findings for farmers in epidemiologic studies of occupation and prostate cancer. Although the overall association reported by recent meta-analyses of farming and prostate cancer reporting a summary relative risk of 1.1 is weak, the majority of studies with relatively large numbers of subjects consistently showed excess relative risks of prostate cancer ranging from 1.06 to 5.0 among farmers, farm laborers, pesticide manufacturers and applicators. This limited evidence from case-control studies may well be inconclusive because of the difficulty in measuring pesticide exposure. What is known is that some pesticides, classified as endocrine-disrupting chemicals (EDCs), can affect normal hormone function. Variations in hormone levels affect prostate cancer risk, since normal growth of the prostate gland is dependent on a critical balance of androgen (sex hormone) levels. Pesticides may affect hormone functioning by mimicking hormones, affecting enzyme systems involved in hormone metabolism, or directly affecting the brain regions involved in hormone functioning.

A large-scale population-based case-control study in California's Central Valley, the nation's leading user of pesticides, simultaneously assessing genetic and environmental risk factors for prostate cancer in an ethnically-diverse population with varying occupational and residential exposures to pesticides would go a long way to addressing NCI's goals for further refining knowledge of prostate cancer etiology. However, the complexities of such a study warrant excellent pilot data and an approach that maximizes the use of existing exposure assessment data, for efficiency's sake. We have been evaluating for some time now the use of Pesticide Use Reporting (PUR) data, refined by additional data on land use, in a Geographical Information System (GIS) to obtain objective historical pesticide exposure estimates.

We propose a pilot study for a large population-based case-control study that will address the following two aims: 1. show that historical residential and PUR/land use data provides substantial reduction in exposure misclassification in both cases and controls compared to current residential and PUR/land use data information alone 2. demonstrate the feasibility of conducting a case-control study of biochemical and environmental risk factors (especially pesticide exposure), susceptibility genes, and their interactions for prostate cancer in the Central Valley. In particular, we will demonstrate the feasibility of our case selection method, and methods of obtaining buccal DNA for genetic hypotheses.

R03CA110846

2004-08-16

2006-07-31