Phase 2 Clinical Trial of Simultaneous Boost Intensity Modulated Radiation Therapy With 3 Dose Gradients in Patients With Stage I-II Nasal Type Natural Killer/T-Cell Lymphoma: Long-Term Outcomes of Survival and Quality of Life.

PURPOSE:The aim of this study was to investigate the treatment results and long-term quality of life in patients with early-stage extranodal natural killer/T-cell lymphoma who were prospectively treated with simultaneous boost intensity modulated radiation therapy (SIB-IMRT) with 3 dose gradients. METHODS AND MATERIALS:Sixty patients with stage I-II nasal cavity natural killer/T-cell lymphoma (NKTCL) and Waldeyer's ring NKTCL were enrolled in a single-arm, prospective, phase 2 clinical trial from August 2011 to April 2015. All patients were treated with definitive radiation therapy combined with short-course induction chemotherapy. A newly designed SIB-IMRT scheme was uniformly adopted, with 54.6 Gy for the gross tumor volume (GTV) of the primary tumor and GTV of the positive lymph nodes, 50.7 Gy for the high-risk clinical target volume (CTV), and 45.5 Gy for the low-risk CTV, all delivered in 26 daily fractions. Before SIB-IMRT, L-asparaginase-based induction chemotherapy was used in 95.0% (57/60) of patients. RESULTS:With a median follow-up time of 95.8 months, the 5-year locoregional recurrence-free survival, progression-free survival, and overall survival rates were 83.3%, 81.7%, and 88.3%, respectively. Dosimetric analysis in the first 21 patients showed satisfying conformality for planning target volume of GTV, high-risk CTV, and low-risk CTV, while the organs at risk were well protected. The results of long-term quality-of-life investigations in patients without progression were favorable, and nasal discomfort was the most common symptom. No grade 3 or 4 acute or late toxicities were observed. CONCLUSIONS:The scheme of target volume delineation and dose setting that we designed has favorable clinical effects with mild side effects in treating patients with stage I-II nasal cavity NKTCL and Waldeyer's ring NKTCL.