Identification of Patients With Localized Ewing Sarcoma at Higher Risk for Local Failure: A Report From the Children's Oncology Group

Abstract

To identify clinical and treatment variables associated with a higher risk of local failure in Ewing sarcoma patients treated on recent Children's Oncology Group protocols. Data for 956 patients treated with ifosfamide and etoposide-based chemotherapy on INT-0091, INT-0154, and AEWS0031 were analyzed. Local treatment modalities were defined as surgery, definitive radiation therapy (RT), or surgery plus radiation (S+RT). Five-year cumulative incidence of local failure was determined. The local failure rate for the entire cohort was 7.3%, with a 3.9% rate for surgery, 15.3% for RT (P<.01), and 6.6% for S+RT (P=.12). The local failure incidence was 5.4% for extremity tumors, 13.2% for pelvis tumors (P<.01), 5.3% for axial non-spine tumors (P=.90), 9.1% for extraskeletal tumors (P=.08), and 3.6% for spine tumors (P=.49). The incidence of local failure was 14.8% for extremity tumors and 22.4% for pelvis tumors treated with RT, compared with 3.7% for extremity tumors and 3.9% for pelvis tumors treated with surgery (P≤.01). There was no difference in local failure incidence by local treatment modality for axial non-spine, spine, and extraskeletal tumors. The local failure incidence was 11.9% in patients aged ≥18years versus 6.7% in patients aged <18years (P=.02). Age ≥18years (hazard ratio 1.9, P=.04) and treatment with RT (hazard ratio 2.40, P<.01) remained independent prognostic factors for higher local failure incidence on multivariate analysis. Tumor size (</≥ 8cm) was available in 40% of patients and did not correlate with local failure incidence. Local tumor control is excellent and similar between surgery and RT for axial non-spine, spine, and extraskeletal tumors. Age ≥18years and use of RT, primarily for pelvis and extremity tumors, are associated with the highest risk of local failure.Further efforts should focus on improving outcomes for these patients.