Diet and lifestyle factors and risk of subtypes of esophageal and gastric cancer: Classification tree analysis

While a number of risk factors for squamous cell carcinoma of the esophagus (SCC) and adenocarcinomas of the esophagus (EA), gastric cardia (GC) and other (non-cardia) gastric sites (OG) have been identified, little is known about how these factors interact. Our objective is to examine the interaction of diet, other lifestyle, and medical factors and risk of subtypes of esophageal and gastric cancer. We used classification tree analysis to analyze data from a multi-center, population-based case-control study (including 1095 cases and 687 controls) conducted in Connecticut, New Jersey, and western Washington state. We found that frequency of gastroesophageal reflux (GERD) symptoms was the most important risk factor for EA, associated with an increased risk, and that several dietary factors (red meat, non-citrus fruits, dark green vegetables, and raw vegetables) appeared to modify that risk. GERD also emerged as a key risk factor for both GC and OG; several dietary factors further impacted risk of OG. Cigarette smoking, low income, and African American race were important risk factors for SCC, with an additional contribution of diet (non-citrus fruit intake). Our results suggest that different combinations of risk factors interact to determine risk of each of these cancers, with diet playing at least some role in all 4 cancer sites. The findings suggest that classification tree analysis may be useful in partitioning risk and that mapping the complex interactions between risk variables therefore can be important both in future research and in targeted prevention interventions.