[Development of new treatments for extranodal NK/T-cell lymphoma in Japan]

Extranodal NK/T-cell lymphoma, nasal type (ENKL), accounts for less than 3% of malignant lymphomas in Japan. Based on the results of prospective clinical trials, ENKL treatment has dramatically improved during the last decade in Japan. The Lymphoma Study Group of the Japan Clinical Oncology Group (JCOG) conducted a phase I/II study (JCOG0211) of concurrent chemoradiotherapy for newly-diagnosed, localized ENKL. The trial showed an excellent 5-year overall survival rate (70%) and acceptable toxicity of RT-2/3DeVIC. The NK-cell Tumor Study Group in Japan, together with Asian collaborators, conducted clinical trials (SMILE-PI & PII) of SMILE chemotherapy for patients with newly-diagnosed stage IV, or relapsed/refractory ENKL. The overall response rate for 2 cycles of SMILE in 38 evaluated patients was 79%. The 2013 Japanese Society of Hematology guidelines recommend RT-2/3DeVIC for the treatment of newly-diagnosed ENKL of stage IE and contiguous stage IIE with cervical node involvement. For other ENKL, SMILE or other L-asparaginase-containing chemotherapies are recommended. A large retrospective study evaluating the efficacy and toxicity of these new treatments in clinical practice is currently underway in Japan. Close cooperation between radiation oncologists and international collaboration will be the key factors in developing better first-line treatments for ENKL.