Treatment of Ewing sarcoma family of tumors with a modified P6 protocol in children and adolescents: Analysis of growth signaling pathways expression and clinical outcome.

9560 Background: Overall survival (OS) rates of patients with localized Ewing sarcoma family of tumors (ESFT) are >80% when treated with the MSKCC P6 protocol. However, it has been associated with a 5.8% incidence of secondary leukemias. A modified P6 (mP6) protocol with reduced exposure to chemotherapy is presented. The correlation between clinical outcome and the expression of proteins involved in active growth signaling pathways was explored. Methods: Thirty-one newly diagnosed ESFT patients were enrolled onto this phase II, single-arm, non-randomized protocol. A paraffin-embedded tissue array of 45 specimens was stained with the antibodies against c-KIT, AKT, p- AKT, p-mTOR, IGF-1R, IGFBP-3, MAPK, p27KIP1, and p70S6 kinase. Immunohistochemical staining was correlated with patient OS. Results: Twenty-four patients had loco-regional disease and 7 had metastases. The 4-year event-free survival (EFS) rate for patients with localized tumours is 83% and OS is 92%. The 3-year EFS rate for patients with dista...