Summary.-The results of the first 3 years of cancer registration on the Caspian Littoral are described. The main finding, confirming previous reports, is a very large variation within the region of the incidence of oesophageal cancer. Possible sources of bias are considered and shown to contribute little to the pattern of incidence. Among women there is a thirty-fold variation in the incidence across the regions; among men a ten-fold variation. In the north-east of the region the tumour is at least as common in women as in men, and is more common than almost any tumour anywhere in the world. Among other tumours, stomach cancer has a strikingly uniform incidence by comparison; breast cancer shows an incidence gradient of opposite slope.

A peculiar distribution of esophageal cancer was observed in the Caspian littoral of Iran, where an ad hoc cancer registry has been in operation since 1968. A very high incidence, among the hghest recorded in the world, with a higher incidence in women than in men (male: 108.8 cases per 100,000 population; female: 174.1 per 100,000), was recorded in the northeastern corner of the region; this sparsely populated, semidesert area of the central Asian type, with predominantly saline soils, was settled by Turkomans. A lower incidence with a change in the male-to-female ratio was observed in the southeastern and central parts of the region, which are located in the piedmont area of the Elburz Mountains; these areas have more abundant rainfall and nonsaline soils, and are densely populated by Iranians. A steady decline in the incidence with an increase in the preponderance of male cases was observed toward the west, reaching the lowest figures (male: 17.2 cases per 100,000 population; female: 5.5 per 100,000) in the Caspian rain belt, with its heavily leached soils and somewhat subtropical characteristcs. Changes in the natural vegetation and in the agricultural practices parallel the changing features of the climate. A multidisciplinary, multidisease, and multifactorial study is in preparation. By plotting the detailed physical, biotic, and cultural characteristics of the selected ecological regions on the intrinsic characteristics of the population groups experiencing different esophageal cancer risk, new and profitable working hypotheses as to the etiology of esophageal cancer might be produced.

No abstract

Data for the distribution of alleles controlling two blood group systems and secretor status, for hemoglobin types, five serum protein groups and 15 red cell enzyme systems has been obtained. Eleven of the systems showed polymorphic variation and these systems have been used to calculate genetic distances using Morton's Kinship measure. No systematic relationship between genetic distance and geographic location of linguistic affiliation is apparent. There is, however, an apparent cline of decreasing frequency of PGDc from east to west and also significant differences in the frequency of G6PD deficiency corresponding to variation in the ecology of the region. Genetic distance comparisons with other selected populations reveal that the Turkic and Turkoman speaking peoples in the Caspian area cluster with the Kurds, Greeks and Iranis. The Persian speakers are genetically remote from these populations; they are, however, close to the Parsis who migrated from Iran to India at the end of the Seventh Century A.D. Several unusual genetic variants were detected, including a novel MDH phenotype, a superoxide dismutase phenotype identical with the Scandinavian type, and rare forms of LDH, PGM locus 2, ceruloplasmin, diaphorase, peptidases and PHI.