The median age of patients with ESFT is 15 years, and more than 50% of patients are adolescents. Well-characterized cases of ESFT in neonates and infants have been described.[11,12] Based on data from 1,426 patients entered on European Intergroup Cooperative Ewing Sarcoma Studies (EI-CESS), 59% of patients are male and 41% are female. Primary sites of bone disease include the following:
- Lower extremity (41%).
- Pelvis (26%).
- Chest wall (16%).
- Upper extremity (9%).
- Spine (6%).
- Skull (2%).
For EOE, the most common primary sites of disease are the following:
- Trunk (32%).
- Extremity (26%).
- Head and neck (18%).
- Retroperitoneum (16%).
- Other sites (9%).
Approximately 25% of patients will have metastatic disease at diagnosis.
Prognostic Factors for Ewing Sarcoma
There are two major types of prognostic factors for patients with Ewing sarcoma: pretreatment factors and treatment response factors.
- Site: Patients with Ewing sarcoma in the distal extremities have the best prognosis. Patients with Ewing sarcoma in the proximal extremities have an intermediate prognosis, followed by patients with central or pelvic sites.[14,15,16] Patients with tumors of the sacrum have a very poor prognosis.
- Size: Tumor volume has been shown to be an important prognostic factor in most studies. Cutoffs of either 100 mL or 200 mL are used to define larger tumors. Larger tumors tend to occur in unfavorable sites.[16,18]
- Age: Infants and younger patients (<15 years) have a better prognosis than adolescents aged 15 years or older, young adults, or adults.[12,14,15,16]
- Gender: Girls with Ewing sarcoma have a better prognosis than boys.[10,15]
- Serum lactate dehydrogenase: Increased serum lactate dehydrogenase (LDH) levels prior to treatment are associated with inferior prognosis. Increased LDH levels are also correlated with large primary tumors and metastatic disease.
- Metastases: Any metastatic disease defined by standard imaging techniques or bone marrow aspirate/biopsy by morphology is an adverse prognostic factor. The presence or absence of metastatic disease is the single most powerful predictor of outcome. Patients with metastatic disease confined to lung have a better prognosis than patients with extrapulmonary metastatic sites.[14,16,19] The number of pulmonary lesions does not seem to correlate with outcome, but patients with unilateral lung involvement do better than patients with bilateral lung involvement. Patients with metastasis to bone only seem to have a better outcome than patients with metastases to both bone and lung. Positron emission tomography (PET) scans using fluorine-18-fluorodeoxyglucose (FDG) are under investigation as a staging tool that may provide additional information and alter therapy planning. Whole body MRI may provide additional information which could potentially alter therapy planning.
- Standard cytogenetics: Complex karyotype (defined as the presence of 5 or more independent chromosome abnormalities at diagnosis) and modal chromosome numbers lower than 50 appear to have adverse prognostic significance.
- Detectable fusion transcripts in morphologically normal marrow: Reverse transcription polymerase chain reaction can be used to detect fusion transcripts in bone marrow. In a single retrospective study utilizing patients with normal marrow morphology and no other metastatic site, fusion transcript detection in marrow was associated with an increased risk of relapse.
- Other biological factors: Overexpression of the p53 protein, Ki67 expression, and loss of 16q may be adverse prognostic factors.[26,27,28] High expression of microsomal glutathione S-transferase, an enzyme associated with resistance to doxorubicin, is associated with inferior outcome for Ewing sarcoma.