Utility of F-18 FDG PET/CT for the Diagnosis and Therapeutic Management of Extranodal Natural Killer (NK)/T-Cell Lymphoma, Nasal Type

Background: Extranodal natural killer (NK)/T-cell lymphoma, nasal type (ENKTL) is quite rare in Western populations, but relatively common in East Asia (especially China) and Latin America. ENKTL is an aggressive disease with poor prognosis, requiring risk stratification. Similar symptoms, such as nasal obstruction and purulent nasal discharge, are found in patients with nasal NKTL and in patients with chronic rhinosinusitis. The images from contrast-enhanced computed tomography (CT) frequently show no prominent mass. As a result, the diagnosis is often delayed because it is frequently misdiagnosed as sinusitis. F-18 FDG PET/CT is a powerful imaging tool for diagnosis, staging, and evaluation of therapeutic effect in oncology.

Aims: This study was designed to investigate the value of FDG PET/CT in the therapeutic management of extranodal natural killer (NK)/T-cell lymphoma, nasal type.

Methods: A total of 26 patients with NK/T-cell lymphoma, nasal type were diagnosed according to morphologic and immunophenotypic criteria as specified

in the World Health Organization (WHO) classification. All patients underwent FDG PET/CT and clinical information was obtained by review of medical records.

Results: In 26 cases, all nasal/extranasal lesions were FDG-avid evidented to be neoplasm on CT scan and histopathological examinations. FDG-avid lesions in nasal/maxillary areas were uniformly more localized than demonstrated on CT scan, suggesting soft tissue masses on CT were partly due to inflammatory reaction. Among the 26 patients with definite diagnosis, 9 patients were re-staged on the basis of F18 FDG PET/CT with 5 patients down-staged and 4 patients up-staged. Statistical difference of the standardized uptake values (SUV) after 6 courses of chemotherapy and/or radiotherapy between the complete remission (CR) group and the partial remission (PR) group can be found (4.1±2.3 versus 7.8±1.7,P=0.006). The SUV value between pre-reatment and post-treatment were also of statistical significance in 22 patients (11.4±6.2 versus 5.6±2.1,P = 0.000).At a follow up of 18 months, patients got CR had a longer survival time than those got PR, stable disease (SD) or progress disease (PD) in 20 patients out of 26 patients.(median survival:310 days vs 284 days,(95% CI: 0.7156 to 1.365, p<0.05).

Conclusions: Our preliminary study suggests that FDG PET/CT can provide more accurate information on the diagnosis, staged and therapeutic response assessment in extranodal natural killer (NK)/T-cell lymphoma, nasal type. FDG PET/CT can be an invaluable imaging modality in this clinical setting. Further investigation with large patients enrollment is warranted.