Cancer Health Center

The Enneking staging system for musculoskeletal neoplasms is based on grade, site, and presence of metastases.[1] All conventional osteosarcomas are high grade; site is graded as intracompartmental or extracompartmental. To be intracompartmental, an osteosarcoma must be confined within the periosteum; such lesions are IIA in the Enneking system. The great majority of osteosarcomas extend beyond the periosteum, which makes them IIB. The presence of clinically detectable metastases is graded as stage III in this system. For practical purposes, there are essentially two classes of patients: those who present without clinically detectable metastatic disease (localized osteosarcoma) and those who present with clinically detectable metastatic disease (metastatic osteosarcoma).

For patients with confirmed osteosarcoma, in addition to plain x-rays of the primary site, pre-treatment staging studies should include MRI and/or computed tomography (CT) scan of the primary site. Additional pre-treatment staging studies should include bone scan, postero-anterior and lateral chest x-ray, and CT scan of the chest. PET using fluorine-18-fluorodeoxyglucose is an optional staging modality.[2]

Localized Osteosarcoma

Localized tumors are limited to the bone of origin. Patients with skip lesions confined to the bone which includes the primary tumor should be considered to have localized disease if the skip lesions can be included in the planned surgical resection.[3] Approximately one-half of the tumors arise in the femur; of these, 80% are in the distal femur. Other primary sites in descending order of frequency are the proximal tibia, proximal humerus, pelvis, jaw, fibula, and ribs.[4] Compared with osteosarcoma of the appendicular skeleton, osteosarcoma of the head and neck is more likely to be low grade [5] and to arise in older patients. A retrospective analysis identified a trend toward better survival in patients with osteosarcoma of the mandible and maxilla who received adjuvant chemotherapy.[6] The German-Austrian-Swiss osteosarcoma cooperative group performed a retrospective review of patients with craniofacial osteosarcoma. Primary sites other than the maxilla and mandible and incomplete surgical resection were associated with inferior survival probability.[7][Level of evidence: 3iiB]

Metastatic Osteosarcoma

Radiologic evidence of metastatic tumor deposits in the lungs, other bones, or other distant sites is found in approximately 20% of patients at diagnosis, with 85% to 90% of metastatic disease presenting in the lungs. The second most common site of metastasis is another bone.[8] Metastasis to other bones may be solitary or multiple. The syndrome of multifocal osteosarcoma refers to a presentation with multiple foci of osteosarcoma without a clear primary tumor, often with symmetrical metaphyseal involvement. Multifocal osteosarcoma has an extremely grave prognosis.[4]

References:

1. Enneking WF: A system of staging musculoskeletal neoplasms. Clin Orthop Relat Res (204): 9-24, 1986.
2. Meyer JS, Nadel HR, Marina N, et al.: Imaging guidelines for children with Ewing sarcoma and osteosarcoma: a report from the Children's Oncology Group Bone Tumor Committee. Pediatr Blood Cancer 51 (2): 163-70, 2008.
3. Kager L, Zoubek A, Kastner U, et al.: Skip metastases in osteosarcoma: experience of the Cooperative Osteosarcoma Study Group. J Clin Oncol 24 (10): 1535-41, 2006.
4. Longhi A, Fabbri N, Donati D, et al.: Neoadjuvant chemotherapy for patients with synchronous multifocal osteosarcoma: results in eleven cases. J Chemother 13 (3): 324-30, 2001.
5. Patel SG, Meyers P, Huvos AG, et al.: Improved outcomes in patients with osteogenic sarcoma of the head and neck. Cancer 95 (7): 1495-503, 2002.
6. Canadian Society of Otolaryngology-Head and Neck Surgery Oncology Study Group.: Osteogenic sarcoma of the mandible and maxilla: a Canadian review (1980-2000). J Otolaryngol 33 (3): 139-44, 2004.
7. Jasnau S, Meyer U, Potratz J, et al.: Craniofacial osteosarcoma Experience of the cooperative German-Austrian-Swiss osteosarcoma study group. Oral Oncol 44 (3): 286-94, 2008.
8. Harris MB, Gieser P, Goorin AM, et al.: Treatment of metastatic osteosarcoma at diagnosis: a Pediatric Oncology Group Study. J Clin Oncol 16 (11): 3641-8, 1998.