PURPOSE: To identify potential clinical prognostic factors associated with a higher risk of local recurrence in patients with localized pelvic Ewing sarcoma treated with radiation therapy. METHODS AND MATERIALS: Data for 101 patients treated with definitive radiation therapy (RT) or both surgery and radiation (S + RT) to primary pelvic tumors on INT-0091, INT-0154, and AEWS0031 were analyzed. Imaging data for patients who did not receive radiation were not available for central review; therefore, patients with surgery alone were not included. Cumulative incidence rates for local failure at 5 years from time of local control were calculated accounting for competing risks. RESULTS: The most common pelvic subsite was sacrum (44.6%). RT was used in 68% of patients and S + RT in 32%. The local failure rate was 25.0% for RT and 6.3% for S + RT (P = .046). There was no statistically significant difference in local control modality by tumor characteristics. Tumors originating in the ischiopubic-acetabulum region were associated with the highest local failure incidence, 37.5% (P = .02, vs sacrum and iliac/buttock tumors), particularly those treated with RT (50.0%, P = .06). A higher incidence of local failure was seen with each additional 100 mL of tumor at diagnosis (P = .04). Multivariable analysis demonstrated RT alone (hazard ratio [HR], 5.1; P = .04), tumor subsite (particularly ischiopubic-acetabulum tumors; HR 4.6; P = .02), and increasing volume per 100 mL (HR, 1.2; P = .01) were associated with a higher incidence of local recurrence. CONCLUSIONS: Combination surgery and RT is associated with improved local control in patients with pelvic Ewing sarcoma compared with definitive RT. Tumors involving the ischiopubic-acetabulum region and increasing tumor volume at diagnosis are associated with inferior local control. Tumor characteristics did not correlate with choice of local therapy modality suggesting an opportunity to develop best local therapy practices guidelines for future studies based on tumor features.

Purpose

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.

Methods and materials

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.

Results

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 ≥18 years versus 6.7% in patients aged <18 years (P=.02). Age ≥18 years (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 (ConclusionsLocal tumor control is excellent and similar between surgery and RT for axial non-spine, spine, and extraskeletal tumors. Age ≥18 years 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.

ARST1321, a trial of patients with advanced soft tissue sarcoma, was the first National Clinical Trials Network study codeveloped by pediatric and adult consortia with two treatment cohorts. We report on the findings of a survey to identify barriers to enrolling adolescent and young adult patients (15-39 years) onto the nonchemotherapy arm. The survey response rate was 31% with a 70% completion rate. Common identified reasons for low accrual in order of decreasing frequency included insufficient funding, lack of study awareness or interest, competing trials, toxicity concerns, philosophical differences in the therapy backbone, and regulatory and infrastructure barriers. Clinical Trials.gov ID: NCT02180867.