Cohort Profile: The Golestan Cohort Study--a prospective study of oesophageal cancer in northern Iran.

The earliest reports of high incidence of oesophageal cancer (OC) in the northern parts of Iran date back to the early 1970s. A population-based cancer registry was established in 1969 as a joint effort between Tehran University and the International Agency for Research on Cancer (IARC). This registry confirmed the high incidence of OC in the eastern portion of the Caspian Sea littoral, in the area that is now known as Golestan Province. The highest incidence rates were reported from the semi-desert plain settled mainly by people of Turkmen ethnicity in Gonbad and Kalaleh counties, with estimated incidence rates of 109/10 among men and 174/10 among women (adjusted to the 1970 World Standard Population). The registry also showed low incidence of OC in the nearby Gilan province, 300 km to the west of Golestan, with incidence rates of 15/10 and 5.5/10 among men and women, respectively. A series of studies were conducted in the region in the 1970s, but they were not conclusive in explaining the