Role Of 18F-FDG PET/CT In Patients With Nasal-type Natural Killer T-cell Lymphoma

Objective:We assessed the potential of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography （PET/CT） imaging in the diagnosis, staging and prognosis monitoring of patients with nasal-type natural killer T-cell lymphoma （NKTCL）.Methods:32 consecutive patients （2010.5-2014.12） with newly diagnosed nasal-type NKTCL, who underwent pretreatment and/or posttreatment ¹⁸F-FDG PET/CT, were analyzed in this retrospective study.Results:The cohort consisted of 32 patients. Among them, there were 21 males and 11 females, the mean age was 47 years. The primary site of tumor was in the nasal cavity in 19 patients, in the nasopharynx in 8 patients, and other sites include paranasal sinus, tonsil, soft palate and gingiva. In the 32 cases, nasal obstruction was the most commom symptom, followed by fever, pharyngalgia, rhinorrhea, epistaxis and mass in nasal cavity.13 patients had B symptoms,8 patients showed involvement of cervical lymph nodes and an elevated serum LDH level was observed in 12 patients. In the 32 cases,15 patients were in Ann Arbor stage I,11 patients were in Ann Arbor stage II, one patient was in Ann Arbor stage III and 5 patients were in Ann Arbor stage IV.16 patients had International Prognostic Index （IPI） score 0 or 1 （mild risk）, while 13 patients had IPI score 2 or 3 （moderate risk） and there were no patients in severe risk （data were not available for 3 patients）. In the 32 cases,16 patients received combined chemotherapy available for 3 patients). In the 32 cases,16 patients received combined chemotherapy and radiotherapy,13 patients received chemotherapy alone and 3 patients received radiotherapy alone.Among 32 patients, there were 14 patients received whole-body ¹⁸F-FDG PET/CT before initial treatment,10 patients received PET/CT after initial treatment and other 8 patients received PET/CT both before and after initial treatment. Among the 22 patients who underwent whole-body ¹⁸F-FDG PET/CT before initial treatment, all primary lesions were found by PET/CT （sensitivity 100%）. PET/CT found primary lesions in two patients, and compared with CT/MRI results, PET/CT found other additional lesions and changed the Ann Arbor stage in five patients. During subsequent treatment, ¹⁸ patients underwent posttreatment ¹⁸F-FDG PET/CT, and PET/CT found disease progression in 13 patients, disease control in two, progression-free disease in two, and in the last patient, PET/CT found disease control and disease relapse, successively. Until the final follow-up （2015.9）,17 patients survived,10 patients died of tumor related diseases and 5 patients loss to follow-up. The average overall survival （OS） is ¹⁸ months, and the average progression-free survival （PFS） is 13 months. Among the 22 patients who underwent whole-body ¹⁸F-FDG PET/CT before initial treatment, univariate survival analysis showed that B symptoms （P<0.05）, LDH level （P<0.01）, and treatment （P<0.05） were significant predictors of OS and PFS.Conclusions:¹⁸F-FDG PET/CT may be an effective diagnostic work-up, staging and prognosis monitoring tool in nasal-type NKTCL. A ¹⁸F-FDG PET/CT scan after treatment could not only predict therapeutic response but also find disease relapse or progression.