Esophageal cancer in kashmir (India): an enigma for researchers

About 90% of esophageal cancers worldwide are Squamous Cell Carcinomas (SCC), mostly occurring in defined high-incidence areas of low and middle-resource countries. Historically, the highest incidences are reported in regions of Central Asia. One such region is Kashmir Valley in Northern India. In this review, we summarize a large body of epidemiological, toxicological and observational information on occurrence, dietary patterns and lifestyles to discuss factors that may be involved in the etiology of SCC in Kashmir Valley. To date, no single factor can be identified as the main cause of the excess incidence of SCC as compared to other regions of India. Three main components emerge as important factors: a societal component with poor, rural lifestyle and general deprivation, status in particular in vitamins and oligoelements; a lifestyle component with the use of copper utensil in cooking, the consumption of spicy, deep fried foodstuffs, and the drinking of hot salty tea; and an environmental component with exposure to high levels of dietary nitrosamines from diverse sources. Overall, these three components are similar to the general pattern of factors that have been involved in causing SCC in other high-incidence area in the so-called "esophageal cancer belt", namely in central China (Cixian, Lixian) and in Northern Iran (Golestan). Further comparative studies between these regions are needed to identify the contributions of these various components.