Recently published studies demonstrated very high event free survival for patients with a normal interim PET/CT and a high hazard ratio for progression of an interim positive (pathological)study. These findings strongly support the integration of interim PET as a decision point for adjustment of chemotherapy.This study use the minimal therapy considered safe according to the predefined risk factors for patients with interim negative PET. Those with pathologic interim study considered as higher risk patients will have dose escalation of therapy.remission rate ,event free survival and overall survival will be evaluated.