3453 - Patterns of Locoregional Recurrence and Prognosis in Early-Stage Natural Killer/T-Cell Lymphoma after Chemotherapy with Sandwiched Radiotherapy: A Post Hoc Analysis of a Randomized Controlled Clinical

S. Wang¹, J. Y. Chen¹, W. L. Zhao², C. Xu¹, W. G. Cao¹, Y. M. Han¹, S. Cheng², P. P. Xu², H. J. Zhong², and G. Cai¹; ¹Department of Radiation Oncology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China, ²Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine at Shanghai, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China

Purpose/Objective(s): To investigate patterns of locoregional recurrence, prognosis, appropriate timing of radiotherapy, and radiation techniques after chemotherapy with sandwiched radiotherapy for patients with early-stage natural killer/T-cell lymphoma (NKTCL). Materials/

Methods: Post hoc analysis of 87 early-stage NKTCL patients who received 4 cycles of chemotherapy with sandwiched radiotherapy from a prospective, multicenter, randomized, phase III trial (NCT02631239) were performed. We used the Kaplan Meier method to estimate survival, and the log-rank test to compare results. Patterns of failure and frequency of locoregional recurrence sites were analyzed. Cox hazards regression were performed to evaluate predictors of survival outcomes.
Results: With a median follow-up of 37.9 months, the over response rate was 85.1% in all patients. The 3-year overall survival (OS), progress-free survival (PFS), and locoregional recurrence-free survival (LRRFS) were 87.1%, 84.6%, and 90.8%, respectively.B symptoms (P=0.086) and tumor originating from Waldeyer’s ring (P=0.083) trends to correlate with inferior OS. Nasal cavity (66.7%) and nasopharynx (66.7%) were the most common site of locoregional recurrence. A very low incidence of cervical lymph node relapse was observed (16.7% in all locoregional recurrence patients). Long chemotherapy-radiotherapy interval (CRI) (31-35 days) was trend to associate with higher LRRFS (100% vs. 86.0%, P = 0.09) than short CRI (21-30 days). Long radiotherapy-chemotherapy interval (RCI) (32-35 days) result in better OS (91.8% vs. 80.3%, P = 0.043), PFS (90.9% vs. 76.6%, P = 0.013), and LRRFS (95.7% vs. 83.9%, P = 0.007) than short RCI (21-31days). Patients received different techniques during radiotherapy resulted in similar survival outcomes. The rate of OS, PFS, and LRRFS did not differ in complete response (CR) and non-CR patients after induction chemotherapy and the entire course of treatment. The most common grade 3 or higher radiation-induced toxicities were mucositis (9.2%) and dysphagia (4.6%).
Conclusion: Results of this study indicated that chemotherapy sandwiched with radiotherapy is an effective and well-tolerated regimen for early-stage NKTCL. Locoregional recurrence of NKTCL has its own pattern. The timing of radiotherapy is crucial for patients with early-stage NKTCL. Finally, similarly high survival was observed among patients with different techniques, and treatment responses in this study.