Value of 18F-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 18 referred for fluorine-18-uorodeoxyglucose positron emission tomography/computed tomography (F-18-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) F-18-FDG PET/CT and TOF F-18-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 18 less than 90 days between obtaining biopsy and F-18-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 150 mg/dL. Two hundred forty six (246) selected patients were scanned with non-TOF PET/CT, and 82 18 18 patients were scanned with TOF F-18-FDG PET/CT. Results: The SUVmax of NHL tends to be higher in TOF F-18-FDG PET/CT than non-TOF F-18-FDG PET/CT. New aggressive NHL had significantly higher SUVmax than new 18 18 indolent NHL in both, non-TOF F-18-FDG PET/CT (13.6 +/- 7.7g/mL vs. 5.3 +/- 3.4g/mL, P<0.0001) and TOF F-18-FDG PET/CT (20.5 +/- 9.8g/mL vs. 6.6 +/- 4.7g/mL, P<0.0001). A receiver operating characteristic curve analysis for 18 new cases in non-TOF F-18-FDG PET/CT (n=204), demonstrated SUVmax of 10g/mL as the most balanced cutoff between aggressive and indolent NHL, with the area under the curve (AUC) of 86%, specificity of 94%, 18 and sensitivity of 71%. While SUVmax of 13g/mL was the most balanced cut-off for new cases in TOF F-18-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 F-18-FDG PET/CT and > 13g/mL in TOF F-18-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 SUV max levels.