Neurologic disorders in long-term survivors of neuroblastoma - a population-based cohort study within the Adult Life after Childhood Cancer in Scandinavia (ALiCCS) research program.

Neuroblastoma is the commonest extracranial solid tumor of childhood, yet rare, and with poor survival before 1990, especially for high-risk disease; thus, information on late effects is sparse. With great advances in cancer treatment, survival has reached 80% in the Nordic countries. The aim of the study was to investigate the risk of developing neurologic disorders after neuroblastoma. Through population-based cancer registries of four Nordic countries we identified 654 5-year survivors of neuroblastoma (diagnosed 1959-2008) and 133,668 matched population comparisons. We grouped neurologic diagnoses from national hospital registries into 11 main diagnostic categories and 56 disease-specific sub-categories and calculated relative risks (RRs), absolute excess risks (AERs), cumulative incidence and mean cumulative count (MCC). Information on cancer treatment was available for 49% of survivors. A hospital contact for a neurologic disorder was observed in 181 survivors 5 years or more from cancer diagnosis with 59 expected, yielding a RR of 3.1 (95% CI 2.7-3.6) and an AER of 16 per 1,000 person-years (95% CI 12-19). The most frequent disorders included epilepsy, paralytic syndromes, diseases of the eyes and ears and hearing loss. The cumulative incidence of any neurologic disorder was 31% in survivors 20 years after cancer diagnosis with a MCC of 0.5 unique diagnoses. All risks were highest in survivors of high-risk neuroblastoma. Neuroblastoma survivors represent a population with a high risk of developing neurologic disorders. Our results should contribute to improving health care planning and underscores the need for systematic follow-up care of this vulnerable group of survivors.