Risks of late mortality and morbidity among survivors of childhood acute leukemia with Down syndrome: a population-based cohort study

Background — Children with leukemia and Down syndrome (DS) are at higher risk of acute treatment toxicities than those without DS. Whether late toxicity risks are also elevated is unknown.

Methods — The authors identified all patients diagnosed with leukemia before the age of 18 years in Ontario, Canada between 1987 and 2013 and who survived greater than 5 years since their last pediatric cancer event. Survivors were divided into those with and without DS, matched by birth year, sex, leukemia type, and receipt of radiation. DS survivors were matched to individuals with DS without childhood cancer (DS controls) in a 1:10 ratio. Outcomes were identified through linkage to population-based health services databases.

Results — DS survivors (n = 79) experienced inferior overall survival compared to non-DS survivors (n = 231) (20-year overall survival, 81.7% ± 6.8% vs 98.3% ± 1.2%; hazard ratio [HR], 12.8; P < .0001) and to DS controls (n = 790; 96.3% ± 1.2%; HR, 5.4 P < .0001). Pulmonary and infectious deaths were noted among DS survivors. There was no difference in the incidence of congestive heart failure between DS survivors and either control cohort, nor of hearing loss or dementia between DS survivors and DS controls.

Conclusions — DS survivors were at substantially higher risk of late mortality than non-DS survivors or DS controls. This excess risk was not attributable to cardiac- or subsequent malignant neoplasm-related late effects, historically main causes of premature death among non-DS survivors. Chronic morbidities associated with DS were not increased compared to DS controls. DS-specific surveillance guidelines may be warranted.