[Long-term effect of risk-adaptive therapy for early stage extranodal NK/T cell lymphoma]

Objective: This study aimed to evaluate the role of extended involved-field intensity modulated radiation therapy (IMRT) for patients with early stage extranodal nasal-type NK/T-cell lymphoma (NKTCL) in a single center, and to explore the long-term effect of risk-adaptive therapy. Methods: Among 238 patients with early stage NKTCL, there were 191 in high-risk group [any risk factor of age > 60, elevated serum lactate dehydrogenase (LDH), Eastern Cooperative Oncology Group (ECOG) score≥2, primary tumor invasion, or Ann Arbor stage Ⅱ] and 47 in low-risk group (no risk factor). A total of 204 patients received radiotherapy combined with chemotherapy, 15 received radiotherapy alone and 19 received chemotherapy alone. One-hundred and eighty-six patients had radiotherapy at a dose ≥50 Gy and 159 patients received chemotherapy with asparaginase-based regimen. Results: The 5-year overall survival (OS) rate and progression- free survival (PFS)rate of all patients were 66.2% and 57.5%. Five-year OS and PFS rates in low-risk group were 91.8% and 88.0%, while 59.3% and 49.3% in high-risk group. The survival of patients in low-risk group were better than those in high-risk group (both P<0.001). The five-year OS rate in combined therapy group, radiotherapy group and chemotherapy group were 71.7%, 52.3% and 20.7%, respectively (P<0.001). The five-year PFS rate were 63.5%, 23.3% and 24.1%, respectively (P<0.001). Among 219 patients receiving radiotherapy, the 5-year OS and PFS rate of patients with primary site radiotherapy dose ≥ 50 Gy were 72.6% and 66.1%, higher than those of patients with a dose <50 Gy (57.3% and 30.9%, respectively; P=0.031, P<0.001). In the high-risk group, the 5-year OS and PFS rate of the patients who received radiotherapy combined with more than 4 cycles of chemotherapy were 66.5% and 62.6%, higher than those of patients received less than 4 cycles of chemotherapy (56.7% and 46.4%, P=0.045 and 0.020, respectively). Cox multivariate analysis showed that ECOG score (HR=2.208, P=0.001), primary site (HR=4.887, P<0.001), primary tumor invasion (HR=3.265, P=0.001) and radiation dose (HR=1.895, P=0.011) were independent factors of OS in early NKTCL patients. Conclusion: Extended-involved field IMRT with radiation dose more than 50 Gy was the main treatment for patients with early stage NKTCL. Radiotherapy combined with adequate cycle chemotherapy significantly improved prognosis of high-risk patients.