Early-Stage Extranodal NK/T-Cell Lymphoma, Nasal Type: A Role for Elective Nodal Irradiation?

Purpose: Extranodal NK/T-cell lymphoma (ENKTCL) is rare in the Western Hemisphere and is commonly treated with combined modality therapy (CMT). Methods and Materials: We retrospectively reviewed 35 patients treated with Ann Arbor stage I/II ENKTCL between 1994 and 2015 at a large academic cancer center in the United States. Results: With 11.6 years median follow-up, median overall survival and progression-free survival were 13.5 and 7.5 years, respectively. Eighteen (51%) patients experienced disease relapse, with 5 regional nodal relapses, of which 2 experienced combined regional and distant relapses. All 5 regional nodal relapses occurred exclusively among patients not treated with elective nodal irradiation (ENI). ENI was associated with improved progression-free survival (hazard ratio [HR], 0.21; 95% CI, 0.09-0.52; P = .018) without significant association with OS (HR, 0.33; 95% CI, 0.11-0.94; P = .11). There was a trend toward improved local control with radiation dose to the primary tumor ≥50 Gy (HR, 0.29; 95% CI, 0.08-1.08; P = .098). Conclusions: In this Western Hemisphere cohort of early-stage ENKTCL patients treated with CMT, ENI may have a potential clinical benefit, particularly in patients who are treated with non–asparaginase-containing CMT, such as in patients treated with radiation alone, patients treated with less intensive chemotherapy concurrently, or patients who are unable to tolerate intensive chemotherapy.