 The first Part: Patients in IPGDP regimen chemotherapy followed by radiotherapy arm receive 3 cycles of IPGDP ifosfamide 1.2gm2 iv on days 3-5; pegaspargase 2000Um2 im on day 1; gemcitabine 800mgm2 iv on days 3,8; cisplatin 25 mgm2 iv on days 3-5; dexamethasone 20mgm2 iv on days 3-6 chemotherapy. Then patients undergo radiotherapy. If the disease is considered to progress or as stable during chemotherapy, the patient will directly receive radiotherapy. Patients in another arm receive radiotherapy followed by IPGDP regimen chemotherapy. IPGDP regimen for both arms are 3 cycles, which is repeated every 3 weeks. 