This study was performed to assess the prognostic value of the proposed histopathologic method to evaluate the response of the primary tumor to preoperative chemotherapy in Ewing's sarcoma.

The response to chemotherapy was evaluated from the specimens of 118 Ewing's sarcoma patients, who were preoperatively treated by chemotherapy alone. Responses were graded I to III (macroscopic viable tumor, microscopic viable tumor, and no viable tumor cells, respectively). Follow-up data were available for all patients, with a mean follow-up duration of 86 months (range, 30 to 158).

A statistically highly significant difference was observed in outcome among the three groups of patients. For patients with total necrosis (grade III response), the estimated 5-year disease-free survival rate was 95%, in contrast to 68% for grade II responders and 34% for grade III responders (P < .0001). This difference was also confirmed when any single group was compared with the other groups. Among the parameters tested, patient age and the size of tumor had some prognostic value.

The proposed histopathologic grading, to evaluate the effect of chemotherapy on the primary tumor, had the strongest correlation to clinical outcome. This method could therefore be used to identify patients with a high risk of recurrent disease. These patients could be randomized to receive alternative postoperative treatments to investigate whether more aggressive therapies will improve outcome.