3694 - Patterns of Failure of Early Stage Extranodal NK T-Cell Lymphoma Nasal-Type and Implications for Future Treatment Strategies
Presenter(s)
J. R. B. Oo1, A. M. Conteh1, S. M. Hiniker2, M. S. Binkley2, and R. T. Hoppe2; 1Department of Radiation Oncology, Stanford University, Stanford, CA, 2Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA
Purpose/Objective(s): Extranodal NK T-cell lymphoma (ENKTL), nasal type is a rare and aggressive malignancy most commonly seen in South-East Asia and Central America. Combined modality therapy has been shown to have good outcomes for Stage I-II disease, with median overall survival of 70% (range: 52-85%) at 5 years 1. Conventional radiotherapy fields include the gross tumor volume (GTV) without elective nodal radiation. This study aims to identify patterns of failure in early stage ENKTL.
Materials/Methods: Electronic medical databases were queried to identify patients with early stage (stage I-II) ENKTL, nasal type from 2007 – 2024. Patient demographics, tumor and treatment characteristics, details of recurrence, and patient follow-up data were recorded from the medical record. Time to failure is defined as date from last treatment to identification of first failure and was classified as local/in-field, regional, or distant failure. All failures were biopsy confirmed to be ENKTL.
Results: There were 26 patients identified. Median follow-up time is 63 months (range: 36-128). All patients received radiotherapy, with median dose 50 Gy (range: 45-54Gy). Majority (n=17, 71%) of patients received concurrent chemoradiotherapy with DeVIC, while 29% of patients received chemotherapy first prior to radiation. Only one patient was treated with definitive radiotherapy alone. Radiation therapy fields included GTV (pre-chemo GTV if received prior chemotherapy. The neck was included in the clinical treatment volume (CTV) only if there was gross or suspicious LN involvement. Half of the patients (n=13, 50%) developed relapse. Median time to relapse is 15 months (range: 10-44 months). Most common site of failure is distant metastases (n=5, 42%), followed by local/in-field (n=4, 33%), and rarely regional nodal (n=2, 16%). While the patients with recurrence tended to be older (59.1 ± 11.7 vs. 49.4 ± 14.6 years, p=0.072) and had larger PTV volumes (292.0 vs. 143.9 cc, p=0.050), these trends did not reach significance (p<0.05). Overall survival (80.4 ± 53.9 months) did not differ significantly between relapse groups (p=0.688). Gender (p=0.228), stage (p>0.9), EBV levels prior to treatment (p=0.7), PINK (p=0.11), PINK-E (p=0.58), extension to an adjacent sinus (p>0.9), and chemotherapy (0.531) prior to radiation were not predictive for relapse on multivariate Cox regression.
Conclusion: Following definitive therapy for early-stage ENKTL, nasal type, the most common site of failure is distant failure, followed by local/in-field, and only occasionally to the cervical lymph nodes. This study is limited by its small sample size. Continuing efforts are being made to identify specific tumor characteristics that predict for recurrence. Future treatment strategies should focus on better systemic therapy to prevent distant relapse as well as local and regional recurrence.