Survival Benefit of Adjuvant Radiation Therapy Following Asparaginase-Based Chemotherapy in Patients With Chemoresponsive Advanced-Stage Extranodal NK/T Cell Lymphoma: A Multicenter Study Using the China Lymphoma Collaborative Group Database.

Purpose: Radiation therapy (RT) is an essential component in the first-line treatment of early-stage extranodal NK/T cell lymphoma (ENKTCL) who have received asparaginase (ASP)-based chemotherapy (CT), but its effects on advanced-stage disease are unclear. This study is to evaluate the potential role of adjuvant RT following ASP-based CT for advanced-stage ENKTCL.

Methods and materials: Data for 170 patients with advanced-stage ENKTCL who received ASP-based CT from the China Lymphoma Collaborative Group database were prospectively reviewed. Initial response after CT was classified as complete response (CR), partial response (PR), stable disease (SD), and progressive disease (PD). CR and PR after CT were defined as "chemoresponsive" disease. One hundred and five patients received ASP-based CT alone (CT alone), whereas 65 patients received CT followed by RT (CT + RT). Of the 112 chemoresponsive patients achieving CR and PR after CT, 58 patients received additional RT, whereas 54 patients did not. Overall survival (OS) and progression-free survival (PFS) were estimated by the Kaplan-Meier method, and compared using the log-rank test. Univariable Cox regression analysis was initially performed to identify potential factors associated with OS and PFS. Factors with a Pvalue <.2 in univariable analysis were then included in the multivariable analysis to determine the independent prognostic factors for OS and PFS.

Results: CR, PR, SD, and PD following CT were 32.9%, 32.9%, 4.1%, and 30.0%, respectively. Patients who achieved CR (OS: hazard ratio [HR], 0.14, 95% CI, 0.07-0.27, P < .001; PFS: HR, 0.11, 95% CI, 0.06-0.20, P < .001) and PR (OS: HR, 0.23, 95% CI, 0.13-0.39, P < .001; PFS: HR, 0.18, 95% CI, 0.11-0.30, P < .001) had significantly higher OS and PFS than those who achieved SD and PD. The 5-year OS and PFS rates were 60.6% and 49.0% for CR and PR, with 69.5% and 63.4% for CR, and 54.2% and 39.4% for PR, respectively. The median OS and PFS for SD + PD were 8.1 and 3.6 months, respectively. In 170 patients, CT + RT versus CT alone significantly improved OS and PFS. The OS rates at 2 and 5 years were 68.7% and 60.8% for CT + RT, compared with 44.6% and 26.7% for CT alone (HR, 0.36; 95% CI, 0.21-0.60; P < .001). The corresponding PFS rates were 58.6% and 47.7% for CT + RT, compared with 33.6% and 23.0% for CT alone (HR, 0.41; 95% CI, 0.26-0.65; P < .001). Moreover, in 112 chemoresponsive patients, CT + RT significantly improved OS, with 2- and 5-year OS rates of 77.8% and 69.0% for CT + RT versus 64.5% and 48.0% for CT alone (HR, 0.43; 95% CI, 0.21-0.90; P = .020). Multivariable Cox regression analyses confirmed that radical RT versus no RT was independently associated with improved OS both in all patients (HR, 0.32; 95% CI, 0.15-0.67; P = .002) and chemoresponsive patients (HR, 0.41; 95% CI, 0.17-0.94; P = .044).

Conclusions: Addition of RT to ASP-based CT provided significant survival benefits in all patients and chemoresponsive patients with advanced-stage ENKTCL.