Osteosarcoma in children 5 years of age or younger at initial diagnosis

Since osteosarcoma is extremely rare in children < or =5 years of age, we sought to investigate if tumor characteristics, treatment strategies, and outcomes differ compared to older patients.

Patients <20 years of age with high-grade osteosarcoma reported to national SEER database from 1973 to 2006 were separated into two groups based on age at diagnosis: < or =5 years (n = 49) and 6-19 years (n = 1,687). Patient, tumor, and treatment characteristics were compared using Fisher exact tests. Overall survival was estimated by Kaplan-Meier methods and compared using log-rank tests and Cox models.

Patients < or =5 years had higher proportions of osteosarcoma arising from the upper limb compared to older patients (24.5% vs. 11.2%; P = 0.006). These very young patients had a significantly higher proportion of telangiectatic histology (10.2% vs. 2.9%; P = 0.017). Sex, metastatic status, race, or ethnicity did not differ by age. A higher proportion of very young patients was treated with amputation (55.2% vs. 27.3%; P = 0.002). Five-year overall survival was inferior for patients with localized osteosarcoma 5 years of age or younger compared to older children (51.9% vs. 67.3%; P = 0.03). After controlling for metastatic status, year of diagnosis, and tumor site, the hazard ratio for death in very young patients was 1.6 (95% confidence interval 1.02-2.36; P = 0.04) compared to older patients.

Tumor characteristics, treatment, and outcomes differ among children < or =5 years of age compared to older pediatric patients. These differences may reflect differences in tumor biology.