Background: The incidence of osteosarcoma varies considerably with age and preschool children are extremely rarely affected. This study was conducted to investigate presentation, treatment, and outcome in very young children with osteosarcoma.

Patients and methods: The authors retrospectively analyzed the data of 2706 consecutive COSS patients with newly diagnosed high-grade osteosacroma of bone and identified 28 patients (1.0%) aged less than five years at diagnosis. Demographic, diagnostic, tumor, and treatment related variables; response and survival data of these 28 were analyzed.

Results: Of the 28 (male, N=16; female, N=12) toddlers, 27 presented with high-grade central osteosarcoma of an extremity (femur, N= 12; humerus, N=10; tibia, N=5) and one with a secondary osteosarcoma of the orbit. The size of primary extremity tumors was large (≥ 1/3 of the involved bone) in 20/27 evaluable patients. Primary metastases were detected in 4 children. All patients received multiagent chemotherapy, and 13/20 analyzed tumors responded well (> 90% necrosis) to neoadjuvant chemotherapy. Limb sparing surgery was performed in 11, ablative procedures were performed in 14, and no local surgery was performed in two patients with extremity tumors. With a median follow-up of 3.8 years (6.2 years for survivors), 13 patients were alive (CR1, N=12; CR3, N=1). Four patients never achieved a complete remission and 12 developed recurrences (local, N=3; metastatic, N=8; site unknown, N=1); and 15 of these 16 patients died. Five-year overall and event free survival probabilities were 50% (SE 10%) and 46% (SE 10%). Better survival was correlated with good response to chemotherapy.

Conclusions: Osteosarcoma is extremely rare in pre-school children. These young patients often have large tumors which may require mutilating resections. Prognosis may be poorer than in older patients.