Osteosarcoma in children

Osteosarcoma is a highly malignant primary bone tumor composed of spindle cells and characterized by the formation of osteoid or immature bone tissue.

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Epidemiology of osteosarcoma

The incidence of osteosarcoma is 2.1 per 1,000,000 population per year. The age peak of incidence is 10-19 years. At an older age, osteosarcoma usually occurs against a premorbid background (Paget's disease, previous bone irradiation, multiple exostoses, fibrous dysplasia of bone).

The most common localization of osteosarcoma (up to 90% of cases) is the long tubular bones. The bones that form the knee joint are affected in 50% of cases, the proximal end of the humerus - in 25%.

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Diagnosis of osteosarcoma

In half of the cases of osteosarcoma, an increase in alkaline phosphatase activity in the blood plasma is noted, but this sign is nonspecific, since it is found in many bone diseases.

Locally, a dense tumor associated with bone is detected. Pain is the most common complaint of patients with osteosarcoma. As a rule, no effusion is found in adjacent joints, and movements are preserved. Pathological fractures occur in less than 1% of cases. Systemic symptoms are also rare.

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X-ray

The most common radiographic signs of bone tumors are foci of osteolysis or pathological (tumor) osteogenesis. Often a mixed picture is observed with a predominance of one or another component. The osteolytic type of bone changes is the most difficult to diagnose. In this case, osteosarcoma must be differentiated from fibrosarcoma, bone cysts, and giant cell tumor. Tumor osteogenesis is one of the reliable signs of osteosarcoma.

Radiographic evaluation of bone tumors is carried out according to the following parameters.

• Localization of osteosarcoma. According to the "field" theory, spindle cell tumors (including osteosarcoma) are localized predominantly in the metaphyseal region of long tubular bones, while small round cell tumors (Ewing's sarcoma, non-Hodgkin's lymphomas) are localized in the diaphyseal region.
• Osteosarcoma borders. Reflect the growth rate and reaction of surrounding tissues. Malignant and aggressive benign tumors are characterized by unclear borders or their absence.
• Bone destruction. This sign is a reliable symptom of a bone tumor. The most pronounced bone destruction is detected in highly malignant neoplasms. It serves as a marker of tumor activity.
• Condition of the bone matrix (pathological osteogenesis). Areas of increased density may be due to the presence of calcifications, foci of sclerosis or newly formed bone tissue.
• Periosteal reaction. Benign tumors, as a rule, do not cause periosteal destruction. Malignant bone tumors, on the contrary, are characterized by the presence of a pronounced periosteal reaction with a wide transition zone and involvement of soft tissues in the process.

Bone scintigraphy plays an important role in assessing the spread of the tumor. The relationship of the tumor to surrounding tissues is assessed using angiography and MRI.

Treatment of osteosarcoma in children

Until the early 1980s, the generally accepted treatment tactic for localized osteosarcoma was amputation of the limb to the joint located above the affected bone. Organ-preserving surgeries became possible due to the introduction of chemotherapy and improvements in orthopedic technology. Currently, such surgeries are performed on most patients with osteosarcoma, and the treatment results do not deteriorate. A necessary condition for organ-preserving surgeries is the possibility of tumor resection within healthy tissues with subsequent restoration of limb function. The patient's wishes regarding the type of surgery are always taken into account.

The volume of the operation is determined by the location and size of the tumor. Clear visualization of the lesion is extremely important for high-quality surgical treatment. The volume of removal and long-term consequences of the operation largely depend on the involvement of neurovascular bundles in the tumor process. For their accurate visualization, preoperative angiography is advisable. Tumor involvement of the main vessels and nerves, as well as extensive involvement of surrounding tissues or their contamination with tumor cells, determined by biopsy, are contraindications to organ-preserving operations.

Chemotherapy has made a significant contribution to improving the treatment outcomes for osteosarcoma. The most effective drugs are doxorubicin, cisplatin, ifosfamide, and high-dose methotrexate. The main goal of postoperative chemotherapy is to achieve local tumor control.

Osteosarcoma is a tumor that is insensitive to radioactive radiation. The antitumor effect is achieved only with doses that lead to severe and irreversible side effects. Currently, radiation is used for palliative purposes in the case of inoperable tumors (osteosarcoma of the axial skeleton, facial bones) and in the presence of bone metastases.