8521 Background: Combination chemotherapy of IMEP was active as a first-line as well as a second-line treatment for NTCL in a retrospective analysis. Thus, we conducted a prospective, multicenter, phase II study of IMEP chemotherapy in previously, untreated stage I/II NTCL. Methods: Patients with chemo-naïve stage I/II NTCL were enrolled between December 2004 and February 2009 and they received 6 cycles of IMEP (ifosfamide 1.5 g/m 2 on days 1 to 3; methotrextate 30mg/m 2 on days 3 and 10; etoposide 100mg/m 2 on days 1 to 3; and prednisolone 60mg/m 2 /day on days 1 to 5) followed by involved field radiotherapy (IFRT). Response was evaluated every 2 cycles of chemotherapy and 4 to 8 weeks after completion of IFRT using modified Response Evaluation Criteria in Solid Tumors. Results: Overall, 44 patients including 29 males were analyzed by the intent-to-treat principle. Overall response rates were 73% (complete remission [CR], 11 [27%] of 41 evaluable patients) after IMEP chemotherapy and 78% (CR, 18 [67%] of 27) after IMEP followed by IFRT. Grade 3 to 4 neutropenia and thrombocytopenia were documented in 33 (75%) and 7 (16%) patients, respectively. Only 8 (18%) patients experienced grade 3 febrile neutropenia. 2-year progression-free survival (PFS) and overall survival (OS) were 56% and 66%, respectively. High Ki-67 (≥ 70%) and Ann Arbor stage II independently reduced PFS (hazard ration [HR]=5.6, 95% confidence interval [CI] 1.8-17.6; P=.004) and OS (HR=4.8, 95% CI 1.9-12.2; P=.001), respectively. Conclusions: IMEP followed by IFRT is active and safe against patients with previously untreated stage I/II NTCL.

Patients with newly diagnosed, stages IE to IIE, nasal ENKTL are best treated with frontline CCRT.