Effects of gross tumor volume and radiation dose on survival and locoregional recurrence in early-stage extranodal NK/T-cell lymphoma treated with intensity-modulated radiation therapy.

ABSTRACT

PURPOSE: To investigate the prognostic value of gross tumor volume (GTV) in early-stage extranodal NK/T-cell lymphoma (ENKTCL) treated with intensity-modulated radiation therapy (IMRT) and explore the interactive effect of GTV and radiotherapy (RT) dose on locoregional recurrence (LRR). METHODS: The data of 319 early-stage ENKTCL patients who underwent IMRT were reviewed retrospectively. Overall survival (OS), progression-free survival (PFS), and locoregional control (LRC) were estimated using Kaplan-Meier method and compared using the log-rank test. Cox proportional hazards regression was performed to identify independent risk factors for survival outcomes. Penalized spline regression was used to flexibly model the association of continuous predictors (GTV and RT dose) with mortality, progression, and relapse. RESULTS: The 5-year OS, PFS, and LRC for the entire cohort were 72.9, 64.4, and 89.9%, respectively. The risks of disease mortality, progression, and recurrence increased steadily with increasing GTV. Patients with GTV < 35 mL had significantly higher 5-year OS (83.0% vs. 59.4%; P < 0.001), PFS (76.7% vs. 48.4%; P < 0.001), and lower 5-year cumulative LRR rate (4.9% vs. 14.5%; P = 0.004), than patients with GTV ≥ 35 mL. The risk of LRR was low with RT doses of 50-56 Gy, independent of GTV. For patients with GTV ≥ 35 mL, dose ≥ 56 Gy was not associated with decreased LRR. CONCLUSION: Larger GTV is associated with worse survival and higher LRR in early-stage ENKTCL patients treated with IMRT. A dose of 50-56 Gy may be appropriate to achieve lower risk of LRR, regardless of GTV.