Differences in Incidence and Distribution of Colorectal Cancer among Races and Ethnic Societies: Lifestyle, Genes or Both?

dence of CRC in central Israel is signifi cantly lower in the Arab population compared with the Jewish citizens, for both males and females, and that this diversity has not changed during the last two decades. They also found that, in the Arab population, CRC tends to be right sided. Similar fi ndings have been reported by other investigators [11] . The genetic background of Jews and Arabs is almost identical: the two groups share common prehistoric ancestors and have a common geographic and ecological milieu. Israel is therefore an ideal testing ground for these concepts because of a well-defi ned population of subgroups that have retained their ethnicity. The intra-population variations in incidence, morbidity and mortality suggest that at least some genetic differences partially account for these obvious differences in the degree of susceptibility to CRC. Furthermore, there is a genetic susceptibility for germ line predominant mutations among the Jewish population for developing breast ( BRCA 1,2 mutations) and colon (APC) cancers, which are known in the literature as the Ashkenazi Jewish mutations. It is also possible that lifestyle differences, and in particular differences in diet, may be a protecting factor among Palestinians (as in the economically under-developed world), and a risk factor among the Ashkenazi Jews (as in the economically developed world). Our group [12] conducted a molecular epidemiology study in order to compare molecular genetic differences The onset of colorectal cancer (CRC) is less an ‘event’ than the result of successive ‘stages’ in the protracted process of colorectal carcinogenesis. CRC is the fourth most common incident cancer and the second leading cause of cancer death in Western societies [1] . Incidence rates vary approximately 20-fold around the world, with the highest rates seen in the developed world and the lowest rate in India [2, 3] . The international differences, migrant data, and recent rapid changes in incidence rates in several countries show that CRC in particular is highly sensitive to environmental changes. Among immigrants and their descendants, incidence rates rapidly reach those of the host country, often even with the fi rst generation of immigrants [5, 6] . Among Jews in Israel, CRC is the leading cause of death from cancer, while the Palestinian population appears to be protected from it [7] . It has long been noted that Israelis of European origin are more susceptible to CRC than Asian-African born Jews (42/100,000 vs. 25/100,000, respectively, mean age standardized rates for 1989–1993) [7] . Studies from the US and Australia have also corroborated the fi ndings that Jewish populations, particularly those of European origin, are at high risk for CRC [8] . The incidence of the disease among Palestinians is estimated to be 7/100,000, approximately one-fi fth that of Jews in Israel [7] . The study of Fireman et al. [9] in this issue of Digestion confi rmed their previous observation [10] : the inciPublished online: November 23, 2005