A Proposal For A New Staging System For Extranodal Natural Killer T-Cell Lymphoma, Nasal Type, To Predict The Treatment Strategy: A Multicentre Study From The Chinese Southwest Oncology Group And Asia Lymphoma Study Group.

7552 Background: The survival of patients with extranodal natural killer T-cell lymphoma (ENKTL), a rare and highly aggressive malignancy, is not accurately predicted by the routine lymphoma Ann Arbor staging system (AASS). Therefore, an optimal staging system for ENKTL is warranted. Methods: A training cohort of patients with newly diagnosed ENKTL from 19 Chinese centres was assessed to develop a new staging system for ENKTL. The results were validated in an independent cohort including patients from Korea, Singapore and China. The new staging system was named the Chinese Southwest Oncology Group and Asia Lymphoma Study Group staging (CA) system. Results: Based on analyses of the 1168-patient training cohort, the CA system used the following classification scheme: stage Ⅰ, lesions confined to the nasal cavity or nasopharynx without local invasiveness; stage Ⅱ, non-nasal-type disease or lesions confined to the nasal cavity or nasopharynx with local invasiveness and without lymph node involvement; stage Ⅲ, lesions with regional lymph node involvement; and stage Ⅳ, involvement of lymph nodes on both sides of the diaphragm or disseminated disease. The 5-year OS rates for stages Ⅰ through Ⅳ were 60.7%, 42.9%, 17.5%, and 32.1% for the AASS and 70.8%, 53.1%, 38.6%, and 29.9% for the CA (P < 0.001). Patient distribution was more balanced with CA than with the AASS. The 985-patient validation cohort produced similar survival and distribution results to those of the training cohort. CA exhibited better prognostic value than the AASS for all 2153 patients (ROC, 0.69; 95% CI, 0.64-0.74 vs 0.62; 95% CI, 0.68-0.56; P = 0·01) and predicted that the best treatment choice based on non- anthracycline treatment was radiotherapy alone for stage Ⅰ; chemotherapy combined with radiotherapy, regardless of the treatment sequence, for stage Ⅱ; induction chemotherapy followed by radiotherapy for stage Ⅲ; and intensive chemotherapy for stage Ⅳ patients. Conclusions: The CA system outperformed the AASS in staging ENKTL patients and could be useful for treatment strategy prediction and future clinical trial design.