Does the primary tumor site in stage I extranodal natural killer/T-cell lymphoma matter?

The purpose of this study was to investigate whether the primary tumor site in stage I extranodal natural killer/T-cell lymphoma (ENKTCL) had a prognostic value. Between January 2009 and December 2015, 152 stage I ENKTCL patients with primary disease in the nasal cavity and Waldeyer's ring were enrolled for this retrospective study. All patients received extended field intensity-modulated radiotherapy alone without prophylactic cervical node irradiation at a total dose of 50 Gy. In this study, there were 122 patients whose primary tumors were localized in the nasal cavity (NC group), and no adjacent structures were involved. A total of 18 patients had a primary disease involving the nasal cavity and Waldeyer's ring (NC-WR group), and the remaining 12 patients had primary tumors confined to Waldeyer's ring (WR group). We found that there was no significant difference in cervical lymph node failure rates among the NC, NC-WR, and WR groups. In terms of the 5-year overall survival (OS) rates, there was a significant difference among the NC, NC-WR, and WR groups (p=0.004), with the WR group having the worst OS. Multivariate analyses showed that the primary site (p=0.011) and ECOG (Eastern Cooperative Oncology Group) score (p=0.013) were independent prognostic factors for OS. In summary, patients with stage I ENKTCL had a good local control rate with radiotherapy alone and without prophylactic cervical node irradiation (PCNI), regardless of the site of the primary tumor. So, we think PCNI for stage I ENKTCL patients is not necessary. Patients with a primary tumor site located in Waldeyer's ring had the worst prognosis. And combined treatment with radiotherapy and chemotherapy should be considered in patients with primary tumors located outside the nasal cavity.