Diaphyseal osteosarcomas have distinct clinical features from metaphyseal osteosarcomas

The aim of this study was to clarify the clinical features and outcomes of diaphyseal osteosarcoma.

Patients with newly-diagnosed high-grade osteosarcoma occurring in the long bone were eligible for this retrospective study. Clinicopathological information was collected from our database and compared with 36 diaphyseal, 405 proximal and 519 distal metaphyseal, and 14 whole bone osteosarcoma patients. Additionally, case-control study matching by age, gender, site, and metastatic status at diagnosis with 1:3 ratio of 36 diaphyseal to 108 metaphyseal osteosarcomas patients was also conducted.

Five-year overall survival and metastasis-free survival of the three groups including diaphyseal, metaphyseal, and whole bone osteosarcoma patients showed significant difference (P = .029 and P = .013, respectively), although there is no difference for the survivals between proximal and distal metaphyseal osteosarcoma patients. Case-control study showed that patients with diaphyseal osteosarcomas had a significantly larger tumour (mean 13.5 cm vs 10 cm, P = .026), and demonstrated higher pathologic fracture rate (28% vs 12%, P = .033), superior 5-year metastasis-free survival (74% vs 40%, P = .0068), and slightly better 5-year overall survival (68% vs 46%, P = .074). Prognostic factor analysis showed that a pathologic fracture significantly decreased the survival of the patients with diaphyseal osteosarcoma.

The current study showed that diaphyseal osteosarcoma has distinct clinical features from metaphyseal osteosarcoma having an increased risk of pathologic fractures but with favorable survival outcome.