General Information About Osteosarcoma and Malignant Fibrous Histiocytoma (MFH) of Bone
Osteosarcoma occurs predominantly in adolescents and young adults. Review of data from the Surveillance, Epidemiology and End Results program of the NCI resulted in an estimate of 4.4 per million new cases of osteosarcoma each year in people aged 0 to 24 years. The U.S. Census Bureau estimates that there will be 110 million people in this age range in 2010, resulting in an incidence of roughly 450 cases per year in children and young adults younger than 25 years. Osteosarcoma accounts for approximately 5% of childhood tumors. In children and adolescents, more than 50% of these tumors arise from the long bones around the knee. Osteosarcoma can rarely be observed in soft tissue or visceral organs. There appears to be no difference in presenting symptoms, tumor location, and outcome for younger patients (<12 years) compared with adolescents.[4,5] Two trials conducted in the 1980s were designed to determine if chemotherapy altered the natural history of osteosarcoma following surgical removal of the primary tumor. The outcome of patients in these trials who were treated with surgical removal of the primary tumor recapitulated the historical experience before 1970; more than half of these patients developed metastases within 6 months of diagnosis, and overall, approximately 90% developed recurrent disease within 2 years of diagnosis. Overall survival for patients treated with surgery alone was statistically inferior. The natural history of osteosarcoma has not changed over time, and fewer than 20% of patients with localized resectable primary tumors treated with surgery alone can be expected to survive free of relapse.[6,8,9]
Pretreatment factors that influence outcome include site and size of the primary tumor and presence or absence of clinically detectable metastatic disease. After administration of preoperative chemotherapy, surgical resectability and the degree of tumor necrosis influence outcome. In general, prognostic factors in osteosarcoma have not been helpful in identifying patients who might benefit from treatment intensification or who might require less therapy while maintaining an excellent outcome.
The site of the primary tumor is a significant prognostic factor for patients with localized disease. Among extremity tumors, distal sites have a more favorable prognosis than proximal sites. Axial skeleton primary tumors are associated with the greatest risk of progression and death, primarily related to the inability to achieve a complete surgical resection.
- Pelvis: Pelvic osteosarcomas make up 7% to 9% of all osteosarcomas; survival rates for patients with pelvic primary tumors are 20% to 47%.[11,12,13] Complete surgical resection is associated with positive outcome for osteosarcoma of the pelvis.[11,14]
- Craniofacial/head and neck: Within the craniofacial osteosarcoma group, patients with mandibular tumors have a significantly better prognosis than patients with extragnathic tumors. For patients with osteosarcoma of craniofacial bones, complete resection of the primary tumor with negative margins is essential for cure.[16,17,18] There is a better prognosis for patients who have osteosarcoma of the head and neck than for those who have appendicular lesions when treated with surgery alone.
Despite a relatively high rate of inferior necrosis following neoadjuvant chemotherapy, fewer patients with craniofacial primaries develop systemic metastases than do patients with osteosarcoma originating in the extremities.[19,20,21] This low rate of metastasis may be related to the relatively smaller size and higher incidence of lower grade tumors in osteosarcoma of the head and neck.
While small series have not shown a benefit from adjuvant chemotherapy for patients with osteosarcoma of the head and neck, one meta-analysis concluded that systemic chemotherapy improves the prognosis for these patients. Another large meta-analysis detected no benefit from chemotherapy for patients with osteosarcoma of the head and neck, but suggested that the incorporation of chemotherapy into treatment of patients with high-grade tumors may improve survival. A retrospective analysis identified a trend toward better survival in patients with high-grade osteosarcoma of the mandible and maxilla who received adjuvant chemotherapy.[18,22]
Radiation therapy was found to improve local control, disease-specific survival, and overall survival in a retrospective study of osteosarcoma of the craniofacial bones, which had positive or uncertain margins after surgical resection.[Level of evidence: 3iiA] Radiation-associated craniofacial osteosarcomas are generally high-grade lesions, usually fibroblastic, that tend to recur locally with a high rate of metastasis.
In the German series, approximately 25% of patients with craniofacial osteosarcoma had osteosarcoma as a second tumor, and in 8 of these 13 patients, osteosarcoma arose following treatment for retinoblastoma. In this series, there was no difference in outcome for primary or secondary craniofacial osteosarcoma.
- Extraskeletal: Osteosarcoma in extraskeletal sites is rare in children and young adults. With current combined-modality therapy, the outcome for patients with extraskeletal osteosarcoma appears to be similar to that for patients with primary tumors of bone.