Incidence of leukemia and other cancers in Down syndrome subjects in Israel

Epidemiologic data have confirmed the high susceptibility of persons with Down syndrome (DS) to leukemia. The question of proneness to other kinds of cancer is still open. In this study we reassessed the incidence rates of leukemia and other malignancies in Israeli DS subjects, based on the total population. The target population consisted of all DS subjects in Israel in the period of 1948--1995. Due to incompleteness of data, the target population was not fully achieved, thus the study population was divided into 2 subgroups: subjects born in Israel between 1979 and 1995 (registry group) and currently or past-institutionalized subjects born before 1979 (institution group). The cohort was linked with the Cancer Registry, and cancer cases that had been diagnosed through December 1995 were subsequently identified. Observed incidence rates were compared with expected rates in the general population. Standardized incidence ratios (SIR) and 95% confidence intervals (CI) were computed for each disease category. Analyses were performed separately for each subgroup of the study population. In the registry group, 7 cancer cases were observed, compared with 1.5 expected (SIR = 4.67, 95% CI 1.9--9.6), all leukemia cases. For the institution group a total of 17 cancer cases were observed, compared with 12.8 expected. These included 4 cases of leukemia (SIR = 6.90, 95% CI 1.90--17.70). An excess of gastric cancer in male subjects (SIR = 11.9, 95% CI 1.3--42.9) was also observed. Significant excess of leukemia in DS population in Israel is in accordance with previously published data. An excess of gastric cancer in DS male subjects born before 1979, which has not been reported before, should be further explored.