Etiologic clues from the similarity of histology-specific trends in esophageal and lung cancers

Objective: We tested whether descriptive evidence exists for differing roles of specific tobacco constituents on different histologic subtypes of esophageal cancer. Esophageal adenocarcinoma incidence rates are increasing while squamous cell esophageal cancer rates are declining in Westernized countries as are the histology-specific lung counterparts. Squamous cell lung cancers, while caused by smoking, are believed to be caused by different constituents of tobacco smoke than lung adenocarcinomas. Smoking is also a risk factor for esophageal cancers. Methods: We compared patterns of incidence of squamous cell cancers of the lung with those of squamous cell esophageal cancers, and incidence trends in lung adenocarcinomas with those of esophageal adenocarcinomas during the time period from 1976 to 2000 using data from the population-based Los Angeles Cancer Surveillance Program. Results: Rates of squamous cell esophageal cancer declined in a similar fashion to those of squamous cell lung cancer, while esophageal adenocarcinoma incidence increased at a rate similar to that of lung adenocarcinoma, in both men and women, and blacks and whites. Histology-specific socio-economic gradients in lung and esophageal cancers were also strikingly similar. Increases in esophageal adenocarcinoma were confined to the lower third of the esophagus. Conclusions: While increases in obesity over time might explain these trends, they are also consistent with a specific effect of some constituent of tobacco smoke working through reflux disease to cause esophageal adenocarcinoma.