Evaluation of prognostic factors in a tumor volume-adapted treatment strategy for localized Ewing sarcoma of bone: The CESS 86 experience

Background. The Cooperative Ewing Sarcoma Study (CESS 86), conducted by the German Society of Pediatric Oncology and Hematology (GPOH), was planned on the basis of the results of the preceding CESS 81 study. The prognostic significance of tumor volume in localized Ewing sarcoma of bone was well documented in the CESS 81 trial. As a consequence, the treatment intensity was adapted to volume in the follow-up CESS 86 trial: the four-drug combination used in CESS 81 was amended for patients with large tumor volume (≥ 100 ml), where ifosfamide was substituted for cyclophosphamide. Procedure. From January 1986 to June 1991, 177 protocol patients with localized Ewing sarcoma of bone were registered in CESS 86. The prognostic implication of tumor volume and several covariates was evaluated using Kaplan-Meier life table analysis and Cox's proportional hazard model. Results. The estimated 5- and 8-year event-free survival (EFS) rates were both 59%. Age, gender, tumor site, and a tumor volume of 100 ml did not distinguish groups of patients with different prognosis. However, the prognosis of patients with tumors >200 ml (8-year EFS rate: 42%) was significantly inferior compared to patients with tumors both of 100 to 200 ml (70%) and of <100 ml (63%). In contrast to CESS 81, the histological response to chemotherapy was no longer a significant prognostic factor (EFS: 64% for good and 50% for poor responders, respectively). Conclusions. Despite risk-adapted treatment intensity, tumor volume retained its prognostic significance; the cut point, however, was shifted toward larger volumes.