Sarcomas of Bone
Summary of Key Points
Incidence and Epidemiology
• More than 2800 new cases of bone sarcoma are diagnosed annually in the United States.
• No specific etiologic agents are identified in the majority of cases.
• Secondary neoplasms are related to known oncogenic factors. (e.g., ionizing radiation, alkylating chemotherapy agents, combinations of both).
• Hereditary cancer syndromes (tumor suppressor genes) are responsible for some cases.
Diagnosis and Radiographic Staging
• Plain radiographs are recommended.
• Magnetic resonance imaging (MRI) scan of primary tumor is the best radiographic study to obtain.
• Chest computed tomography (CT) is indicated to evaluate for pulmonary metastases.
• Whole-body technetium-99m (99mTc) bone scan is indicated to evaluate for metastases to other bones.
• Positron emission tomography (PET) scanning is controversial and has yet to be generally accepted.
• Needle or open biopsy is necessary for a tissue-specific diagnosis and to determine histologic grade.
• In the pathology review, immunohistochemistry and cytogenetics are important.
Prognostic Factors
• Metastasis at presentation is a worse prognostic finding.
• Histologic grade is the next most significant prognostic indicator.
• Size is less significant, but lesions larger than 10 cm in diameter have a poor prognosis.
• Tumor response to neoadjuvant chemotherapy is important in osteosarcoma and Ewing sarcoma.
• Surgical margins of resection (minimum of a “wide” margin).
Staging System
• The American Joint Committee on Cancer now monitors grade (high and low), and size (8 cm); designates “skip” lesions (T3); and separates metastasis to bone from other sites (Mla, Mlb).
• The Musculoskeletal Tumor Society monitors location. (intracompartmental and extracompartmental), grade (high and low), and metastasis (“skip” lesions, nodal, bone, and lung are all lumped together).
Primary Therapy
• A wide surgical margin is recommended.
• Limb-sparing procedures are appropriate for 70% to 90% of patients.
• Adjuvant irradiation is not routinely used for bone sarcomas.
• Local recurrence rates for limb-sparing procedures approach 5% or less.
• Reconstruction methods can be tailored to patients’ needs.
• New and improved biocompatible implant materials and improved designs are available.
1. Standard treatment for high-grade osteosarcoma includes:
A Chemotherapy and wide surgical excision or radiation
B Wide surgical excision or radiation
C Wide surgical excision and radiation
2. Which of the following associations describes the most common age at presentation:
3. A 14-year-old boy is seen with a large tumor (12 cm) arising from his left distal femur. Magnetic resonance imaging shows the tumor is associated with cortical breakthrough and a soft-tissue mass posteriorly. A bone scan shows activity only in the left distal femur. The needle biopsy demonstrates a high-grade osteosarcoma. What are the Musculoskeletal Tumor Society (MSTS) and American Joint Committee on Cancer (AJCC) stages, respectively?
1. Answer: D. High-grade osteosarcoma is considered to be “micrometastatic” at presentation even without overt metastatic disease. Treatment thus must include systemic chemotherapy and local control. Osteosarcomas are not typically radiosensitive, so surgery is the standard recommendation for local control.
2. Answer: B. Chondrosarcoma is most common in adults. Osteosarcoma is most common in adolescents with a second peak in the fifth to sixth decades of life. Ewing sarcoma is most common in children younger than age 15 years. Malignant fibrous histiocytoma of bone is most common in adults.
3. Answer: E. Both the MSTS and AJCC staging systems highlight the prognostic importance of the presence or absence of metastatic disease. The staging cannot be final until the patient has been assessed for pulmonary metastases with a chest CT.
