a Proposal for a New Staging System of Extranodal Natural Killer T-cell Lymphoma, Nasal-Type: a Multicenter Study of Chinese Southwest Oncology Group (CSWOG)
Authors: Hong Huangming , Du Xin , Zhang Mingzhi , Wang Jinghua , Zhu Jun , Huang He , Liu Ting , Meng Fanyi , Wu Gang , Guo Ye , Zhao Weili , Jin Jie , Li Juan , Deng Yanming , Gu Kangsheng , Wu Xiangyuan , Ke Xiaoyan , Xie Derong , Lin Daren , Lin Tongyu 
Published: October 2019

Abstract
Purpose: Extranodal NK/T-cell lymphoma, nasal type (ENKTL), is a rare and highly aggressive disease. The Ann Arbor staging system had been unsuitable to proper staging of ENKTL. This study was conducted to establish a new staging system specified for ENKTL, which can identify poor prognostic patients.
Patients and Methods: Patients with untreated, centrally reviewed diagnosis of ENKTL were included in our study. The new staging system was established based on the study of single center consecutive patients treated with CHOP-like regimens with or without involved field radiotherapy (IFRT), then we initinated a multicenter confirmation study and conducted a multicenter prospective study to validate the new staging system.
Results: From Jan 1997 to June 2006, 134 consecutive patients treated in the cancer center of Sun Yat-sen University were analyzed. The following was a summary of the classification system developed: stage I: lesions confined within nasal cavity or nasopharynx without local invasiveness (paranasal sinuses or bony or skin invasion); stage II: localized disease with local invasiveness; stage III: localized disease with regional lymph node involvement (cervical lymph nodes); and stage IV: disseminated disease (lymph nodes on both sides of diaphragm, multiple extranodal site). The distribution of stage I to IV using the new system and Ann Arbor system were 39.6%, 23.9%, 23.1%, 13.4% and 63.4%, 23.1%, 5.2%, 8.2%, respectively. The 5-year OS rate of stage I to IV using the new system were 29.5%, 23.4%, 21.3% and 0.07% compared with 23.8%, 21.3%, 0.0% and 0.0% using the Ann Arbor system. In the multicenter confirmation study conducted in 18 centers in China, 722 patients were analyzed. The results showed that the distribution of the new system compared with Ann Arbor system from stage I to IV were 24.1%, 34.9%, 18.3%, 22.7% vs 59.1%, 19.0%, 6.9%, 15.0%, respectively, and the 5-year OS rate of stage I to IV were 56.0%, 48.3%, 33.8%, 26.1% vs 50.7%, 39.1%, 10.8%, 28.0%, respectively. For the multicenter prospective study, 233 newly diagnosed ENKTL patients treated with non-CHOP-like regimens were enrolled and showed a balanced distribution of 17.2%, 39.9%, 19.3%, 23.6% vs 53.6%, 25.3%, 6.9%, 14.2% from stage I to IV and superior 5-year OS rate: 82%, 73%, 67%, 54% vs 75.2%, 65.6%, 46.9%, 73.8% from stage I to IV using the new system in compared with the Ann Arbor system.
Conclusions: The new staging system with a more balanced distribution and a superior prognostic discrimination as compared with Ann Arbor staging system no matter for CHOP-like or non-CHOP-like regimens, is more suitable for ENKTL and can be recommended used in the future.

Disclosures
No relevant conflicts of interest to declare.