Study of Radiotherapy on Extranodal Natural Killer (NK)/T-Cell Lymphoma of Stage IE

Abstract

In this study, we will examine whether prophylactic cervical node irradiation (PCNI) is necessary for stage IE nasal type Extranodal natural killer (NK)/T-cell lymphoma (ENKTCL) and investigate the survival difference between patients with primary tumors originating from nasal cavity and the Waldeyer ring. From January 2009 to December 2015, 152 pathologically confirmed stage IE ENKTCL patients with nasal cavity and Waldeyer ring primary tumors were retrospectively analyzed. Those patients were divided into three groups according to their primary tumor locations: limited to the nasal cavity (NC group), originating from nasal cavity and invading the Waldeyer ring (NCWR group) and originating from the Waldeyer ring (WR group). All cases were treated with extended-field radiotherapy alone and no PCNI was performed. The overall survival (OS), progression-free survival (PFS) and distant recurrence free survival (DRFS) were obtained after long-term follow-up. Pearson’s chi-square test or Fisher’s exact test was used to analyze the distribution difference of clinical features among the three groups. Univariate and multivariate analyses were performed using the Kaplan-Meier method and the Cox proportional hazards regression. There were 140 cases with primary tumor originating from nasal cavity, including 122 cases in NC group and 18 cases in NCWR group. In addition, there are 12 cases in WR group. For NC group, NCWR group and WR group, the failure rates of cervical lymph nodes were 5.74%, 11.11% and 8.33%. The local recurrence rates were 6.56%, 11.11% and 8.33%. The distant metastasis rates were 11.48%, 22.22% and 41.67%, respectively. There was no significant difference in cervical lymph node failure rates and local recurrence rates among the three groups, but the distant metastasis rates were significantly different (P = 0.014).Survival analyses using Kaplan-Meier method and univariate COX model showed that the three groups had significantly different OS (P = 0.010), PFS (P = 0.019) and DRFS (P = 0.015). OS, PFS and DRFS in NC group was significantly better than those in WR group. However, there was no survival difference in OS, PFS and RFS between the NC group and NCWR group, as well as the NCWR group and WR group. Furthermore, multivariate COX survival analyses demonstrated that the primary site group and ECOG score were independent prognostic factors of OS. And the primary site group and B symptom were independent prognostic factors of PFS and DRFS. Stage IE ENKTCL patients with primary tumors originating from nasal cavity and the Waldeyer ring showed a similar low risk of cervical lymph node recurrence without PCNI, thus there is no need of PCNI for stage IE ENKTCL patients. The main cause of treatment failure was distant recurrence. Moreover, the OS, PFS and DRFS of the Waldeyer ring primary patients were inferior to the nasal cavity primary patients independent from other features, which indicated that they may need more systemic chemotherapy.