Abstract: Background and purpose: The clinical course and prognosis of extranodal NK/T cell lymphoma are highly variable. The majority of early-stage patients are treated primarily with radiotherapy. The primary tumor invasion (PTI) is a common clinical feature for the patients with extranodal NK/T cell lymphoma. The aim of this study was to analyze the clinical characteristics, treatment, survival and prognostic factors in patients with extranodal NK/T cell lymphoma. Methods: The study included a total of 99 patients with pathologically confirmed extranodal NK/T cell lymphoma in the Fourth Hospital of Hebei Medical University from Jan. 2010 to Dec. 2015. Mean age was 45.5 years (6-76 years); male to female ratio was 2.1 to 1. Of all patients, 56 (56.6%) had B symptoms, 7 received radiotherapy alone, 29 received chemotherapy alone, and 63 received concurrent chemoradiotherapy. Median radiation dose was 52 (34-60) Gy. There were 73 patients receiving chemotherapy with L-asparaginase or pegaspargase and 19 without. Median chemotherapy had 6 (1-12) cycles. Results: The median overall survival (OS) was 59.9 months for all patients. The median progression-free survival (PFS) was 73.5 months. The 1-, 2- and 5-year OS rates were 76.8%, 68.8% and 61.4%, respectively. The 1-, 2- and 5-year PFS rates were 84.5%, 81.6% and 78.3%, respectively. The 1-, 2- and 5-year distant failure-free survival (DFFS) rates were 83.4%, 83.4% and 76.8%, respectively. The patients who received radiotherapy alone and concurrent chemoradiotherapy had significantly longer survival time than those who received chemotherapy alone. The 5-year OS rates were 66.0% and 47.3% (χ²=4.782, P=0.029), respectively. The 5-year PFS rates were 85.8% and 58.7% (χ²=5.949, P=0.015), respectively. The 5-year OS rates of the patients with and without PTI were 71.5% and 55.5% (χ²=4.950, P=0.026), respectively. The 5-year PFS rates were 81.5% and 72.0% (χ²=0.983, P=0.321), respectively. The complete response (CR) was observed in 62.6% patients. The 5-year OS was 84.1% in patients with CR and 27.6% in no-CR (χ²=31.566, P=0.000), the 5-year PFS rates were 92.2% and 52.4% (χ²=18.417, P=0.000), respectively. Conclusion: Most patients with early-stage extranodal NK/T cell lymphoma who received radiotherapy alone and chemoradiotherapy had significantly longer survival time than those who received chemotherapy alone. Multivariate Cox regression analysis for OS showed that Ann Arbor stage and lactate dehydrogenase (LDH) were independent prognostic factors. LDH was the only independent prognostic factor for PFS.

Key words: Lymphoma, Extranodal natural killer/T-cell, Radiotherapy, Chemotherapy, Prognosis