Cancer in persons with down syndrome in Israel

In this chapter we assess the incidence rates of leukemia and other malignancies in persons with Down syndrome in Israel. The target population consisted of all persons with Down syndrome in the period of 1948-1995 and the study population was divided into two subgroups: 1) Persons born in Israel between 1979-95 (registry group) and 2) Persons currently or past-institutionalised, born before 1979 (institution group). The study population was linked to the Cancer Registry and cases diagnosed through December 1995 were subsequently identified. The observed incidence rates were compared to expected rates in the general population. Standardised Incidence Ratios (SIR) and 95% confidence intervals were computed for each disease category. Analyses of results were performed separately for each subgroup of our study population. In the registry group seven cancer cases were observed as compared to 1.5 expected (SIR=4.67 95% CI 1.9-9.6), all of which were leukemia cases. For the institution group a total of 17 cancer cases were observed compared to 12.8 expected. These included four cases of leukemia (SIR=6.90 95% CI 1.9-17.7). An excess of gastric cancer in males, based on two cases (SIR=11.9 95% CI 1.3-42.9) was also observed. The significant excess of leukemia in the Down syndrome population in Israel is in accordance with other international studies. The excess of gastric cancer in males with Down syndrome, which has not been reported before, should be further explored.