Neoplasm risk in individuals with neurofibromatosis 1 – a Danish nationwide cohort study with long-term follow-up

Background: As larger population-based studies assessing neoplasm risk in neurofibromatosis 1 (NF1) are limited, we aimed to evaluate overall neoplasm risk, specific cancer types, and second primary cancers. Methods: Using Danish registries and clinical databases, we identified 2053 individuals with NF1 and 20,530 population comparisons. We calculated cumulative incidences for first and second primary neoplasms for the study population born 1971–2020 and for adult-onset cancers in the study population born 1951–2020. We used multistate models to estimate the probabilities of being neoplasm-free, having one neoplasm, having ≥two neoplasms or being dead at a certain age. Results: The 50-year cumulative incidence of any first neoplasm was 27.2% (95% confidence interval [CI] 23.1–31.4%) for NF1 individuals and 5.0% (4.0–6.0%) for comparisons. Moreover, the cumulative incidence of second primary neoplasm was 21.1% (14.4–27.8%) for NF1 individuals and 6.4% (0.0–15.0%) for comparisons 20 years after the first neoplasm. A person born with NF1 had a 69.8% (65.6–74.2%) probability of being alive and without neoplasm history at age 50 compared to 93.5% (92.4–94.6%) for a person without NF1. Conclusion: The highly increased risks for primary and secondary neoplasms and mortality warrant close clinical surveillance of individuals with NF1.