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[Value of PET/CT in the prognosis of extranodal NK/T cell lymphoma].

Objective: To explore the value of Positron-Emission Tomography/Computed Tomography (PET/CT) in the prognosis of extranodal NK/T cell lymphoma. Methods: The patients of NK/T cell lymphoma diagnosed from January 2007 to July 2016 in Department of Pathology of Beijing Tongren Hospital were enrolled in this study. Seventy-two in-hospital patients were examined on the invasion of adjecent tissue or organ by PET/CT. The PET/CT results were analyzed retrospectively. Kaplan-Meier method was used to analyze the prognostic value of the positive results by PET/CT on overall survival (OS). Results: There were 54 males and 18 females with median age of 44.5 years (13-75 years). According to Ann Arbor staging system, there were 16 cases (22.2%) in stage Ⅰ, 29 cases (40.3%) in stage Ⅱ, 6 cases (8.3%) in stage Ⅲ and 21 cases (29.2%) in stage Ⅳ. According to the IPI scoring system, there were 34 cases (47.2%) in the low risk group (0-1 point), 21 cases (29.2%) in the low-middle risk group (2 points), 16 cases (22.2%) in the middle-high risk group (3 points), and 1 case (1.4%) in the high risk group (4-5 points) . The median follow-up time was 29.2 months (1-118 months). The disease occured in unilateral nasal cavity in 26 cases (36.1%), bilateral nasal cavities in 36 cases (50.0%), nasopharynx, oropharynx and pharynx in 10 cases (13.9%). The tumors of 51 cases involved the surrounding tissue, including nasal wings in 29 cases (40.3%), nasal sinus in 29 cases (40.3%), maxillofacial soft tissue in 18 cases (25.0%), orbital in 12 cases (16.7%), maxilla and skull base in 8 cases (11.1%), eyelid in 6 cases (8.3%), brain tissue in 3 cases (4.2%), eyeball in 2 cases (2.8%). In addition, cervical and inguinal lymphadenopathy were found in 54 cases (75.0%) . Splenomegaly and hepatomegaly were found in 10 cases (13.9%) and 2 cases (2.8%), respectively. Survival analysis showed that the clinical stage and IPI were significantly associated the clinical prognosis (P=0.000, 0.001, respectively). Involvement of the maxillofacial soft tissue, eyelid, orbital, maxilla and skull base and brain tissue were significantly related to reduced the overall survival time (P=0.006, 0.000, 0.024, 0.001 and 0.015, respectively). Involvement of palate or tonsil, the nosewingand nasal sinus did not show significant shorter overall survival (P=0.091, 0.063, and 0.139, respectively). Cox regression multivariate analysis showed maxilla and skull base involvement was independent adverse prognostic factor (P=0.047). Conclusions: The PET/CT examination can accurately detect the extent of adjacent and distant tissues of tumor involvement of NK/T cell lymphoma by showing the tumor structure and metabolic status, thus has important value in the clinical staging and prognosis predication.