Comparison of population based cancer incidence rates among Circassians, Chechans and Arabs in Jordan (1996-2005).

BACKGROUND: Cancer is a complex disease caused by multiple factors, both genetic and environmental. It is a major health concern worldwide, in the Middle East and in Jordan specifically and the fourth most common killer in the Middle East. HYPOTHESIS: The relative genetic homogeneity of the Circassian and Chechan populations in Jordan results in incidences of cancer that differ from the general Jordanian population, who are mostly Arabs. MATERIALS AND METHODS: National Cancer Registry data were obtained for the years 1996-2005 The Chechen and Circassian cancer cases were identified and cancer registry data were divided into three populations. Crude rates were calculated based on the number of cancer cases and estimated populations. RESULTS: Breast cancer is the most common cancer type constituting about one third of female cancers in all three populations. Higher crude rates are observed in the Circassian and Chechen populations than in the Arab Jordanian population. The rate ratios (95%CI) in Circassians and Chechens with respect to the Arab Jordanian population are 2.1 (1.48, 2.72) and 1.81 (1.16, 2.85), respectively. Lung cancer is the most common cancer in male Arab Jordanians and Chechens with crude rates of 4.2 and 8.0 per 100,000 respectively. The male to female ratio in these two populations in respective order are 5:1 and 7:1. The lung cancer crude rate in Circassians is 6.5 per 100,000 with a male to female ratio of only 1.6:1. The colorectal cancer crude rates in Arab Jordanians and Chechens are similar at 6.2 and 6.0 per 100,000, respectively, while that in Circassians is twice as high. CONCLUSIONS: Considerable ethnic variation exists for cancer incidence rates in Jordan. The included inbred and selected populations offer an ideal situation for investigating genetic factors involved in various cancer types.

Prevalence of MTHFR C677T single nucleotide polymorphism in genetically isolated populations in Jordan.

Methylenetetrahydrofolate reductase (MTHFR) C677T single nucleotide polymorphism is a major inherited risk factor of venous thromboembolism. We sought to determine its prevalence in genetically isolated populations of Chechens and Circassians in Jordan. The MTHFR C677T mutation was analyzed from blood samples taken from 120 random unrelated Chechens and 72 Circassians. The prevalence of the MTHFR mutation in the Chechen population was 27.5% (allele frequency 15%); the prevalence among the Circassians was 50% (allele frequency 29.2%). The prevalence in the Chechen population is similar to that in Jordan and other world populations, but it is higher in the Circassian population. This study will contribute to understanding the interaction between genetic and environmental risk factors underlying thrombosis and will be useful in deciding which genetic variants should be tested in a clinical genetic testing service.