Role of organochlorine compounds in the etiology of pancreatic cancer: a proposal to develop methodological standards.

Studies on the possible role of organochlorine compounds in the etiology of pancreatic and other cancers face a set of methodologic and logistic issues that stem from the lipophilic nature of most organochlorines, and from the fact that tumor-induced lipid mobilization, weight loss, and metabolic changes can be profound before diagnosis. The question thus arises: do the xenobiotic concentrations in blood and adipose tissue result, in part, from such pathophysiologic changes? To assess and control potential selection and information biases, a flexible framework is warranted. It could be based on indicators such as time elapsed between the first symptom of cancer and blood or fat sample extraction; signs, symptoms and clinical status at the time of extraction; cholesterol and triglycerides levels; other laboratory findings; tumor stage at diagnosis; diagnostic procedures; treatment type and timing; clinical complications; and survival. Before adopting qualitative criteria and quantitative standards, their impact upon causal estimators should be assessed empirically.