Epidemiology of esophageal cancer in the high-risk population of iran.

The Iranian population includes several ethnic groups scattered throughout Iran, which differ with regard to their rates for cancer. An infamous 'Asian esophageal cancer belt'stretches to the east from the Caspian littoral in Iran via Turkmenistan to the Northern provinces of China. Apart from the eastern part of the Caspian littoral area of Iran which has the highest incidence of esophageal cancer in the world, other parts of the country have variable rates, ranging from 3 to more than 15 cases per 100,000 population, but rates have decreased sharply in the high incidence areas. Studies of the etiology of esophageal cancer in Iran and especially among the Turkmen ethnic population have indicated that several factors are behind the striking high incidence. Certain risk factors such as a family history of esophageal cancer, low socioeconomic status and poor nutritional diet are well studied and plausible evidence for their etiologic contributions exist. While thermal irritation and coarse food (physical damage to the mucosal lining of the esophagus) have attracted attention in correlational studies, conclusions about their etiologic contribution are inconclusive.