Dietary consumption of processed meat increases risk of lung cancer

Background: Processed meat, commonly consumed in Italy and other western countries, contains high levels of nitrates and nitrites (added for preservation or improvement of color and taste). These nitrogen species are transformed into carcinogenic N-nitroso compounds. High consumption of processed meat has been found associated with increased risk of colorectal, breast, and bladder cancers. However, the epidemiologic evidence for an association between dietary intake of processed meat and lung cancer risk is sparse. Objective: To investigate the relationship between dietary consumption of processed meat and lung cancer risk in the Environment And Genetics in Lung cancer Etiology (EAGLE), a population-based case-control study of lung cancer. Methods: Between 2002 and 2005, 2101 primary lung cases were enrolled from 13 hospitals of a defined catchment area including 216 municipalities of the Lombardy Region of Italy. Healthy controls (2120) were randomly selected and recruited from the same residential area, matched on gender, residence, and age (±5 years) to the cases. Comprehensive epidemiological data were collected through an interview-based computer-assisted questionnaire and dietary intakes via a short self-administered questionnaire. Processed meats consumed by the EAGLE participants included cooked ham, smoked ham, “raw” ham (prosciutto), salami, baloney, salted beef, coppa (Italian sausages), and bacon. Logistic regression analysis was used to compute odds ratios (ORs) and 95% confidence intervals (CIs). All analyses were adjusted for the matching variables, body mass index, education, alcohol consumption, and smoking history (cigarette intensity, duration of cigarette smoking, and years since last cigarette smoked for former smokers). Results did not change after further adjustment for consumption of total fruits and vegetables or previous lung diseases. Results: Compared to the lowest tertile of intake frequency, statistically significant positive associations were found for the middle (OR: 1.23; 95% CI: 1.03-1.49) and highest (OR: 1.63; 95% CI: 1.34-1.97) tertiles of processed meat intake and lung cancer risk (p-trend: <<0.001). The significant positive associations persisted after stratification by smoking status, and was stronger in never smokers (OR: 2.1; 95% CI: 1.24-3.56; p-trend: 0.006). Analyses by lung cancer histology, showed elevated associations for adenocarcinoma (OR=1.83; 95% CI: 1.43-2.34) and squamous cell carcinoma (OR=1.83; 95% CI: 1.34-2.5), but not for small cell carcinoma (OR=1.1; 95% CI: 0.72-1.69). Conclusions: Consumption of processed meat was significantly associated with higher risk of lung cancer in this population-based case-control study independent of smoking status. Further investigation into the mechanisms by which processed meat might contribute to the etiology of lung cancer is warranted.