Discussion Author: Eric M Alcaraz
Ewingâ€™s sarcoma is a malignant tumor found in bone or soft tissue. It belongs to a spectrum of neoplastic processes known collectively as the Ewingâ€™s sarcoma family of tumors (EFT). This group also includes Askinâ€™s tumor (malignant small-tumor of the thoracopulmonary region) and peripheral neuroectodermal tumor. Both goups originate from the neuroectodemal line. EFT comprise the second most common primary bone malignancy affecting children and adolescents, making up 3.5% of cancers in 10 to 14 year olds and 2.3 percent of cancers in 15 to 19 year olds. The peak incidence of EFT is 10 to 15 years old, and there is a slight male predominance . Further epidemiological studies show that these tumors mainly affect Caucasians, with very rare instances in blacks and Asians.
In general, the EFT can develop in any bone or soft tissue; however, the most common sites of origin are flat and long bones. Clinically, patients present with localized pain and swelling ongoing for a few weeks or months. The pain is initially considered mild but progresses rapidly in intensity. It is usually aggravated by exercise and worse at nighttime. A distinct soft tissue mass can sometimes be palpable and tender to touch.
Approximately 80% of patients with EFT present with localized disease; however, subclinical metastatic disease is presumed to be present in almost all patients, as is evidenced with the 80-90% relapse rate in patients undergoing local therapy alone. For this reason systemic chemotherapy is the standard of treatment. Overt metastases is seen in nearly 25% of patients with EFT. Sites of metastatic disease are usually the lung and bone, which is the same for recurrent disease. Lung metastases accounts for nearly 70 to 80% of disease, leading to the highest rate of mortality in patients with EFT. Metastases to the bone is found mostly in the spine.
Diagnosis of EFT usually begins with a plain film of the affected area. EFT involving bone appears as a poorly marginated destructive lesion. Their appearance has been previously described as a â€śmoth eatenâ€ť or â€śpermeativeâ€ť lesion, representing a series of finely destructive lesions. A CT scan of the site in question better delineates the degree of cortical disruption. In addition, CT scanning is preferred for detection of small pulmonary metastases. MRI can further define the tumor size, intra- or extraosseous extent, specifically with regards to invasion of the chest wall, and the relationship of the tumor to surrounding nerves, vessels, organs, and fascial planes. With both CT and MRI, the tumors appear as heterogeneous masses, owing to areas of hemorrhage and necrosis.
Evaluation of metastases begins with CT chest, followed by bone scan of the entire skeleton. PET scan can be helpful in the later stages, when determining the response to chemotherapy and radiation therapy. With regards to labs, standard cell blood count and chemistries should be evaluated. LDH, meanwhile, is a known prognostic factor for patients with EFT. Definitive diagnosis is based on CT guided core needle biopsy. With known predisposition for metastases to bone, a bone marrow biopsy is also recommended to rule out widespread disease.
Overall prognosis is dependent on a number of factors, to include tumor size, location, response to location, and most important, the presence or absence of metastases. The 20 to 25% of those with overt metastases have the worst outcome. One study showed a five year relapse free survival rate of those with localized disease to be 55% compared to 21% in those with overt metastases.
Treatment of EFT has advanced significantly over the past 30 years, as amputation is no longer considered absolute and limb sparing surgery is a more viable option. In almost all instances, definitive local therapy along with systemic combination therapy is required. Chemotherapy is followed by localized therapy - either surgery, radiation, or both, depending on tumor size, location, and potential consequences of the therapy. Following local treatment, chemotherapy is continued for up to a year. For patients with overt metastatic disease, as well as those with recurrence following initial therapy, multiple modalities are also recommended. There is a lower success rate in patientswith metastatic or recurrent disease. The primary goal in these patients is pain relief and prolonging the progession free interval.
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