Influence of Clinical Factors and Timing of Blood Extraction on Lipid Concentrations in Pancreatic Cancer

Abstract

ISEE-250 Objective: To analyze potential implications for the design, conduct, analysis, and interpretation of epidemiologic studies of relationships among clinical factors, timing of blood extraction, and serum concentrations of lipids in patients with exocrine pancreatic cancer (EPC). Material and Methods: Subjects were 144 incident cases of EPC prospectively recruited in 5 teaching hospitals in eastern Spain. A structured form was used to collect clinicopathologic information from medical records. Cases were interviewed face-to-face by trained monitors during hospital stay. Total cholesterol and triglycerides concentrations were determined enzymatically using CHOD-PAP and GPO-PAP. Results: Higher concentrations of cholesterol were observed among patients with a shorter interval from first symptom of cancer to blood extraction (IES), and thereafter concentrations decreased with time. The relationship between cholesterol and tumor stage was “n-shaped”: as compared with patients with a tumor in stage I, those with tumors in stages II and III showed increasing cholesterol levels (difference between medians up to 66 mg/dL), and then cholesterol was again lower in patients with stage IV tumors. Jaundice and the other components of the cholestatic syndrome increased cholesterol and triglycerides. Invasive diagnostic tests were associated with lower cholesterol. All these factors were related to changes >50 mg/dL in cholesterol (P < 0.05), even when adjusting by stage. Models including IES, number of invasive tests, jaundice, weight loss, and stage explained over 28% of the variation in lipid concentrations. Conclusions: Results suggest that restriction and adjustment by stage may be insufficient to prevent biases due to disease-induced changes in blood concentrations of lipids. They also emphasize the importance of accounting for clinical symptoms, procedures, and timing of blood extraction in studies on the etiologic significance of lipids and lipophilic compounds, either risk factors (eg, persistent toxic substances) or protective agents (eg, fat-soluble drugs and vitamins).