Abstract: Objective To investigate the relationship between abnormal nasal microbiota and prognosis in patients with extranodal NK/T-cell lymphoma（ENKTCL）. Methods The clinical data and bacteria culture results of nasal swab of 244 newly diagnosed ENKTCL patients were retrospectively analyzed. The patients were divided into a normal microbiota group（n=114） and an abnormal microbiota group（n=130） according to the presence of abnormal microbiota ，and the correlation analysis was conducted among clinical characteristics，treatment effects and prognosis. Results A total of 409 dominant strains were cultured in patients with abnormal microbiota，mainly staphylococcus aureus，streptococcus aureus，staphylococcus epidermis and pseudomonas aeruginosa. The proportion of patients with elevated lactate denhydrogenase，and medium risk or high risk with a prognostic score of PINK≥1 in the abnormal microbiota group were significantly higher than those of the normal microbiota group（P=0.044；P=0.003）. In the end of treatment，the complete response rate and 5-year progression-free survival of patients in the abnormal microbiota group were significantly lower than those in the normal microbiota group（45.5% vs 61.4%，P<0.05；48.4% vs 63.9%，P=0.048）. Subgroup analysis suggested that in the early stage and low-risk PINK patients，the imbalance of flora was significantly correlated with PFS（P=0.022，0.011）. Conclusions Abnormal nasal microbiota is closely related to the prognosis of patients with ENKTCL. Strategies aiming at abnormal nasal microbiotas may enhance the therapeutic effects and prognosis of ENKTCL.

Key words: Extranodal NK/T-cell lymphoma, Microecological balance, Abnormal microbiotas, Immunotherapy