Clinical value of metabolic tumor volume by PET/CT in extranodal natural killer/T cell lymphoma

This study investigated whether metabolic tumor volume (MTV) by PET/CT as indicator of extent of lymphoma burden would be a prognostic factor in stage IE/IIE extranodal natural killer/T cell lymphoma (ENKTCL). Eighty patients with stage IE/IIE ENKTCL in the upper aerodigestive tract underwent PET/CT at diagnosis were enrolled and 32 patients received upfront radiotherapy (RTx). MTV was measured on PET/CT images by the extranodal region above SUV, 2.5. Receiver operating curve analyses indicated that an MTV of 35.2 cm3 was the ideal cut-off to distinguish between low and high MTV groups. Clinical outcomes were compared according to several prognostic factors (age, stage, high performance status [PS], high International Prognostic Index, elevated lactate dehydrogenase [LDH], local tumor invasiveness [LTI], high MTV and up-front RT). High PS, elevated LDH, LTI, high MTV and upfront RT were associated with survivals. In multivariate analysis, high MTV (PFS, HR = 4.170, 95% CI = 1.714-10.147, p = 0.002; OS, HR = 4.102, 95% CI = 1.617-10.408, p = 0.003) and up-front RT (PFS, HR = 0.410, 95%CI = 0.178-0.946, p = 0.037; OS, HR = 0.365, 95% CI = 0.152-0.872, p = 0.023) were significant independent prognostic factors. Upfront RTx and extent of tumor burden, as measured by the MTV, had significant prognostic value in patients with ENKTCL.