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https://www.cancer.gov/types/bone/patient/osteosarcoma-treat…

Osteosarcoma

Osteosarcoma is a malignant primary bone tumor in which cancer cells produce osteoid, the immature matrix of bone. It is the most common primary malignant bone tumor in children and adolescents, excluding blood-cell tumors. - Robbins & Kumar Basic Pathology, p. 782

Who is affected?

It has two age peaks:
  • Adolescents, especially during the growth spurt
  • Older adults, usually when there is an underlying risk factor such as Paget disease of bone, previous radiotherapy, or a bone infarct
It occurs slightly more often in males. In younger patients, it usually develops in the metaphysis of long bones, most often near the knee: the distal femur or proximal tibia. - Robbins & Kumar Basic Pathology, p. 782

Symptoms

Typical features are:
  • Progressive, persistent bone pain, sometimes worse at night
  • Local swelling or a growing mass
  • Reduced movement of a nearby joint
  • Limping, when the leg is involved
  • Occasionally, a pathological fracture through weakened bone

Imaging features

An initial plain X-ray may show an aggressive, mixed bone-destroying (lytic) and bone-forming (sclerotic) lesion, often extending through the cortex into soft tissues.
A classic but non-specific sign is the Codman triangle: triangular reactive bone formed when the growing tumor elevates the periosteum. MRI is used to define local extent and surgical planning; chest CT is important because the lungs are the commonest site of spread.
Distal femur osteosarcoma with soft-tissue bone formation and a Codman triangle
Distal femoral osteosarcoma with periosteal elevation producing a Codman triangle. - Robbins & Kumar Basic Pathology, p. 782

Diagnosis and staging

Diagnosis requires a carefully planned core-needle or open biopsy, ideally performed by the specialist sarcoma team that will provide definitive surgery. Poorly placed biopsies can complicate limb-sparing surgery.
Staging generally includes:
  • X-ray and MRI of the affected bone
  • CT of the chest for lung metastases
  • Assessment for skeletal metastases, often with bone scan or PET/CT depending on local protocol
  • Histology confirming malignant cells making osteoid

Types

The usual type is conventional high-grade intramedullary osteosarcoma, accounting for about three-quarters of cases. Other variants include telangiectatic, low-grade central, small-cell, parosteal, periosteal, and high-grade surface osteosarcoma. - Grainger & Allison’s Diagnostic Radiology, p. 1048

Causes and risk factors

Most cases are sporadic, but recognized associations include:
  • Rapid bone growth during adolescence
  • RB1 mutations, including hereditary retinoblastoma
  • TP53 mutations, including Li-Fraumeni syndrome
  • Prior radiation treatment
  • Paget disease of bone
  • Bone infarction
Osteosarcoma commonly has complex genetic changes, with alterations in RB and TP53 among the important abnormalities. - Robbins & Kumar Basic Pathology, p. 782

Treatment

Treatment should be delivered by a multidisciplinary sarcoma team. For most high-grade conventional tumors, it combines:
  1. Chemotherapy before surgery to treat microscopic systemic disease and assess tumor response.
  2. Wide surgical removal of the tumor, preferably with limb-sparing reconstruction when safe. Amputation is used when adequate cancer clearance and a functional limb cannot be achieved.
  3. Postoperative chemotherapy.
In children and adolescents, a common backbone is MAP chemotherapy: high-dose methotrexate, doxorubicin, and cisplatin, although regimens vary by age, country, tumor site, and clinical circumstances. Osteosarcoma is relatively resistant to radiotherapy; radiation is mainly considered when surgery cannot fully control local disease.
If pulmonary metastases can be completely removed, surgery for lung nodules may be part of curative-intent treatment. The NCI treatment summary notes that spread is most often to the lungs and outlines multimodal treatment for localized and metastatic disease.

Prognosis

Outcome depends mainly on:
  • Whether metastases are present at diagnosis
  • Ability to completely remove the primary tumor and all visible metastases
  • Tumor location and size
  • Histologic response to preoperative chemotherapy
  • Development of recurrence, especially early recurrence
Localized, completely resectable disease has a substantially better outlook than metastatic or recurrent osteosarcoma. Lung-only metastases generally have a better outlook than spread to bone or multiple organ sites.
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