Increasing survival disparity between children, adolescents, and young adults with osteosarcoma or Ewing sarcoma of bone from 1990 to 2024: a population-based cohort study

BACKGROUND AND PURPOSE: Bone sarcomas are important contributors to early-life cancer mortality and morbidity. Optimisation of treatment regimens has improved survival, but the survival disparity between children, adolescents and young adults has widened. Population-based studies are needed to understand and address these disparities. This is the first comprehensive study of early-life bone sarcomas in Denmark. Patient/material and methods: We combined population-wide data from national registers from 1990 to 2024 with clinical data from patient records. We calculated age-standardised incidence rates, 5-year relative survival rates stratified by several clinical factors, and Aalen-Johansen estimators for relapse/progression and death within 5 years. RESULTS: A total of 578 patients under 40 years of age were diagnosed with either osteosarcoma (n = 336) or Ewing sarcoma of bone (n = 242) in Denmark between 1990 and 2024. Five-year relative survival improved for patients aged 0-24 years but stagnated for those aged 25-39 years. We observed age-dependent differences in the distribution of tumours and in relative survival across anatomical sites, tumour sizes, and treatment regimens. Metastatic disease or a tumour diameter of > 8 cm reduced relative survival by 19 to 45 percentage points. INTERPRETATION: Survival disparities between children, adolescents, and young adults with bone sarcomas are likely multifactorial. Age-dependent differences in the distribution of tumours across anatomical sites and in tumour size appear to play a role. The incidence of and survival from relapse/progression also appear to favour younger patients. Including patients in international, joint paediatric-adult treatment protocols remains a high priority.