Pediatric osteosarcoma

Synonyms

2

Overview

Osteosarcoma is the most common type of bone cancer. The average age at diagnosis is 15. Boys and girls have a similar incidence of this tumor until late adolescence, at which time boys are more commonly affected. In rare cases, osteosarcoma occurs in adults. Although osteosarcoma tends to occur in the larger bones, such as the shin (near the knee), thigh (near the knee) and upper arm (near the shoulder), it can occur in any bone. A number of variants of osteosarcoma exist, including conventional types (osteoblastic, chondroblastic, and fibroblastic), telangiectatic, multifocal, parosteal, and periosteal.  The cause of osteosarcoma is not known. In some cases, it runs in families, and at least one gene has been linked to increased risk. Treatment varies from person to person and may include surgery, chemotherapy, radiation therapy, and samarium.

Symptoms

 

  • Abnormality of metabolism/homeostasis
  • Osteosarcoma
  • Retinoblastoma

Causes

The cause of osteosarcoma is not known. In some cases, it runs in families, and at least one gene has been linked to increased risk.

Prevention

Genetical counselling is recommended for couples willing to have children.

Diagnosis

Family physicians and orthopedists rarely see a malignant bone tumor (most bone tumors are benign). The route to osteosarcoma diagnosis usually begins with an X-ray, continues with a combination of scans (CT scan, PET scan, bone scan, MRI) and ends with a surgical biopsy. A characteristic often seen in an X-ray is Codman's triangle, which is basically a subperiosteal lesion formed when the periosteum is raised due to the tumor. Films are suggestive, but bone biopsy is the only definitive method to determine whether a tumor is malignant or benign.

The biopsy of suspected osteosarcoma should be performed by a qualified orthopedic oncologist. The American Cancer Society states: "Probably in no other cancer is it as important to perform this procedure properly. An improperly performed biopsy may make it difficult to save the affected limb from amputation." It may also metastasise to the lungs, mainly appearing on the chest X-ray as solitary or multiple round nodules most common at the lower regions.

Variants

  • Conventional: osteoblastic, chondroblastic, fibroblastic OS
  • Telangiectatic OS
  • Small cell OS
  • Low-grade central OS
  • Periosteal OS
  • Paraosteal OS
  • Secondary OS
  • High-grade surface OS
  • Extraskeletal OS

Prognosis

Prognosis is separated into three groups.

  • Stage I osteosarcoma is rare and includes parosteal osteosarcoma or low-grade central osteosarcoma. It has an excellent prognosis (>90%) with wide resection.
  • Stage II prognosis depends on the site of the tumor (proximal tibia, femur, pelvis, etc.), size of the tumor mass, and the degree of necrosis from neoadjuvant chemotherapy. Other pathological factors such as the degree of p-glycoprotein, whether the tumor is cxcr4-positive, or Her2-positive are also important, as these are associated with distant metastases to the lung. The prognosis for patients with metastatic osteosarcoma improves with longer times to metastases, (more than 12 months-24 months), a smaller number of metastases, and their resectability. It is better to have fewer metastases than longer time to metastases. Those with a longer length of time (>24months) and few nodules (two or fewer) have the best prognosis, with a two-year survival after the metastases of 50%, five-year of 40%, and 10-year of 20%. If metastases are both local and regional, the prognosis is worse.
  • Stage III osteosarcoma, with lung metastases depends on the resectability of the primary tumor and lung nodules, degree of necrosis of the primary tumor, and maybe the number of metastases. Overall survival prognosis is about 30%.

Deaths due to malignant neoplasms of the bones and joints account for an unknown number of childhood cancer deaths. Mortality rates due to osteosarcoma have been declining at about 1.3% per year. Long-term survival probabilities for osteosarcoma have improved dramatically.

Treatment

A complete radical, surgical, en bloc resection of the cancer, is the treatment of choice in pediatric osteosarcoma. Although about 90% of patients are able to have limb-salvage surgery, complications, particularly infection, prosthetic loosening and non-union, or local tumor recurrence may cause the need for further surgery or amputation.

Patients with osteosarcoma are best managed by a medical oncologist and an orthopedic oncologist experienced in managing sarcomas. Current standard treatment is to use neoadjuvant chemotherapy (chemotherapy given before surgery) followed by surgical resection. The percentage of tumor cell necrosis (cell death) seen in the tumor after surgery gives an idea of the prognosis and also lets the oncologist know if the chemotherapy regimen should be altered after surgery.

Standard therapy is a combination of limb-salvage orthopedic surgery when possible (or amputation in some cases) and a combination of high-dose methotrexate with leucovorin rescue, intra-arterial cisplatin, adriamycin, ifosfamide with mesna, BCD (bleomycin, cyclophosphamide, dactinomycin), etoposide, and muramyl tripeptide. Rotationplasty may be used. Ifosfamide can be used as an adjuvant treatment if the necrosis rate is low.

Despite the success of chemotherapy for osteosarcoma, it has one of the lowest survival rates for pediatric cancer. The best reported 10-year survival rate is 92%; the protocol used is an aggressive intra-arterial regimen that individualizes therapy based on arteriographic response.[20] Three-year event-free survival ranges from 50% to 75%, and five-year survival ranges from 60% to 85+% in some studies. Overall, 65–70% patients treated five years ago will be alive today. These survival rates are overall averages and vary greatly depending on the individual necrosis rate.

Fluids are given for hydration, while antiemetic drugs (such as the 5-HT3 receptor antagonists e.g. granisetron and ondansetron) help with nausea and vomiting. Filgrastim or pegfilgrastim help with white blood cell counts and neutrophil counts. Blood transfusions and epoetin alfa help with anemia.

Resources

Refer to Research Publications.