Dosimetric And Clinical Outcome Of Intensity-modulated Radiotherapy For Patients With Early-stage Nk/T-cell Lymphoma Of Waldeyer Ring

Purpose:To assess the target coverage, normal tissue sparing, toxicity, and treatment outcome of high-dose extended-field intensity-modulated radiotherapy (IMRT) in patients with early-stage NK/T-cell lymphoma (NKTCL) of Waldeyer ring.Methods and Materials:Between March2005and August2012,30patients with early-stage NKTCL of Waldeyer ring received curative IMRT with or without chemotherapy. All patients had Ann Arbor stage Ⅰ (16,53%) or Ⅱ (14,47%) disease.53%of patients had nasal invasion and70%presented with B symptoms. Target volume was contoured following the extended-field approach. The curative dose was50Gy, and the prophylactic dose was40Gy for the cervical and supraclavicular lymph nodes. The dose-volume histograms of the target volume and critical normal structures were evaluated in all patients. The overall survival (OS), progression-free survival (PFS), and locoregional control (LRC) were calculated using the Kaplan-Meier method.Results:The median average dose to the PTV50and PTV40were53.2Gy and43.0Gy, respectively. The percentage of PTV50and PTV40receiving less than95%of the prescribed dose were1.4%and0.9%, respectively. The median conformity index of PTV50was0.85. The2-year OS, PFS and LRC in the whole group were71.2%,57.4%, and87.8%, respectively. The2-year OS and PFS were54%and44%for patients with nasal invasion, and93%and75%for patients without (P=0.017for OS; P=0.023for PFS). Distant nodal and/or extranodal metastasis was the primary pattern of failure (11of13patients,84.6%). Fourteen (46.7%) patients had grade1-2acute toxicities and16patients (53.3%) had grade3-4acute toxicities.23.3%and33.3%of patients had grade>3acute dysphagia and grade3acute mucositis, respectively. Grade1and grade2late xerostomia were the most common late toxicities, observed in15(68%) and6(27%) patients, respectively. The mean dose to the parotid glands was significantly higher in patients with grade2late xerostomia than in patients with grade0-1late xerostomia (31.4Gy vs.25.7Gy,P=0.018).Conclusions:In patients with early-stage NK/T-cell lymphoma of Waldeyer ring, IMRT achieved excellent target coverage and conformity, as well as favorable overall survival and local control. Treatment-related toxicities were acceptable. The severity of late xerostomia was associated with the mean dose to the parotid glands.