Value of 18 F-FDG PET/CT in discrimination between indolent and aggressive non-Hodgkin's lymphoma: A study of 328 patients.

OBJECTIVE: Non-Hodgkin's lymphoma (NHL) cases with inconclusive biopsy findings are not infrequently referred for fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18 F-FDG PET/CT). We searched for maximum standardized uptake value (SUVmax) cut-off values that could discriminate between indolent and aggressive NHL in conventional non-time of flight (non-TOF) 18 F-FDG PET/CT and TOF 18 F-FDG PET/CT.

SUBJECTS AND METHODS: Retrospectively, 328 patients were selected by the following inclusion criteria: biopsy-proven NHL with no more than one histopathological type; new cases with less than 90 days between obtaining biopsy and 18 F-FDG PET/CT scanning; recurrent cases with time interval more than six months since the last therapy with no history of transformation; and blood glucose less than 150mg/dL. Two hundred forty six (246) selected patients were scanned with non-TOF PET/CT, and 82 patients were scanned with TOF 18 F-FDG PET/CT.

RESULTS: The SUVmax of NHL tends to be higher in TOF 18 F-FDG PET/CT than non-TOF 18 F-FDG PET/CT. New aggressive NHL had significantly higher SUVmax than new indolent NHL in both, non-TOF 18 F-FDG PET/CT (13.6±7.7g/mL vs. 5.3±3.4g/mL, P<0.0001) and TOF 18 F-FDG PET/CT (20.5±9.8g/mL vs. 6.6±4.7g/mL, P<0.0001). A receiver operating characteristic curve analysis for new cases in non-TOF 18 F-FDG PET/CT (n=204), demonstrated SUVmax of 10g/mL as the most balanced cut-off between aggressive and indolent NHL, with the area under the curve (AUC) of 86%, specificity of 94%, and sensitivity of 71%. While SUVmax of 13g/mL was the most balanced cut-off for new cases in TOF 18 F-FDG PET/CT (n=57), with AUC of 91%, specificity of 95.5%, and sensitivity of 77%.

CONCLUSION: Both SUVmax>10g/mL in non-TOF 18 F-FDG PET/CT and >13g/mL in TOF 18 F-FDG PET/CT were highly suggestive of an aggressive nature of NHL, while there was an overlap between indolent and aggressive NHL in the lower SUVmax levels.