To Örebro University

Background/Objectives: Children and adolescents undergoing treatment for cancer are exposed to multiple factors that impact the development of peak bone mass and bone quality. The aims of this study were to examine the risks and cumulative incidence of osteoporotic fractures in childhood cancer survivors and identify subgroups at higher risk.

Design/Methods: In the national cancer registries of Denmark, Finland, Iceland and Sweden we identified patients diagnosed with cancer before 20 years of age from the start of registration in the 1940s and 1950s through 2008. We compared 26.334 one‐year survivors with a cohort of 162.372 age‐ and sex‐matched population comparison subjects selected from the national population registries. With data derived from national hospital registries we estimated the standardized hospitalization rate ratios (SHRR) and the mean cumulative count (MCC) of hospital admissions for osteoporotic fractures. To identify subgroups at risk we used Cox regression models to generate hazard ratios (HR) for osteoporotic fractures. Death and new cancer were treated as competing risks.

Results: The estimated SHRR for the first osteoporotic fracture was 1.41 (95% CI; 1.27‐1.58) but the MCC for recurrent osteoporotic fractures did not differ between the survivors and the comparison group. The SHRR for isolated hip fractures was 2.90 (2.32‐3.63). The adjusted HR for osteoporotic fracture as the first event was 1.53 (1.09‐2.16) if cancer was diagnosed 15‐19 years and 2.10 (1.48‐2.98) for long‐term survivors of CNS tumors. Survivors 15‐19 years at cancer diagnosis and long‐term survivors of CNS tumors were also at higher risk of experiencing a second fracture, HR 3.29 (1.65‐6.55) and HR 2.71 (1.45‐5.05), respectively.

Conclusions: Childhood cancer survivors are at higher risk of being hospitalized for osteoporotic fractures but the burden of recurrent fractures is not higher. For subgroups at risk, surveillance of bone health and measures to increase bone strength and prevent fractures should be encouraged.