Low risk of solid tumors in persons with Down syndrome

Purpose: The aim of this study was to investigate cancer incidence in a large cohort of persons with Down syndrome. Methods: Down syndrome was identified from the Danish Cytogenetic Register. Cancer occurrence was identified by linkage to the Danish Cancer Registry. Standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) were calculated based on observed and expected numbers from rates for all Danish residents. The cohort consisted of 3,530 persons with Down syndrome contributing 89,570 person-years at risk. Results: Acute leukemia risk was highest from 1-4 years of age and remained elevated until age 30. The overall risk of solid tumors was decreased (SIR 0.45; 95% CI 0.34-0.59), especially in persons 50 years or older (SIR 0.27; 95% CI 0.16-0.43). We found a significantly lower risk of lung cancer (SIR 0.10; 95% CI 0.00-0.56), breast cancer (SIR 0.16; 95% CI 0.03-0.47), and cervical cancer (SIR 0.0; 95% CI 0.00-0.77). Testicular cancer was the only solid tumor with an increased SIR (2.9; 95% CI 1.6-4.8). Conclusions: The risk of all major groups of solid tumors was decreased, except testicular cancer. Altered screening strategies should be considered for persons with Down syndrome. This unusual pattern of cancer occurrence may help understanding carcinogenesis in the general population.