Osteosarcoma in patients younger than 12 years old without metastases have similar prognosis as adolescent and young adults.

Background: Childhood cancer is relatively rare and tends to present specific age distribution, as a prognostic factor for some of these diseases. Information on how young age affects prognosis, response to chemotherapy, and local control options in children versus AYA with osteosarcoma (OST) is minimal.

Methods: In order to identify the main differences in clinical pathologic features, surgical approaches and survival rates of primary high grade OST of the extremity between children (n = 156; <12 years old) and AYA (n = 397; 12-30 years old), the institutional database with 553 patients treated by BOTG studies over 15 years were reviewed.

Results: There were no differences in metastases at diagnosis, tumor size, and grade of necrosis between the two age groups. The rate of amputation was 30% higher in the children group (P = 0.018). The rate of limb salvage surgery using reconstruction with allograft or autograft was 70% higher in the children group (P = 0.018) while endoprosthesis rate was 40% higher in the AYA group (P = 0.018). The log rank test revealed that survival is similar between the two age groups for non-metastatic patients (P = 0.424 for OS and P = 0.393 for EFS). Metastatic patients of both ages group had higher risk of dying compared to non-metastatic (HR 3.283 95% CI 2.581-4.177; P < 0.001). Children with metastases at diagnosis had less OS time (P = 0.049) and EFS time (P = 0.032) than adolescents.

Conclusion: Non-metastatic OST in preadolescent patients does not appear to be significantly different from those seen in AYA patients, but has local control challenges. Children presenting with metastases should be considered an ultra-high-risk group.