Predictive Potential of FDG-PET/CT for Histological Transformation in Patients with Indolent Lymphoma

Backgrounds and Purpose—In indolent non-Hodgkin lymphoma, histological transformation is a dramatic event which reduces the prognosis significantly. SUVmax values from FDG-PET/CT help differentiate between aggressive and indolent lymphomas, and transformed indolent lymphomas also show an increased FDG uptake. Possibly FDG uptake increases early in the clinical course and could predict histological transformation. Our objective was to predict histological transformation in indolent lymphomas from initial staging FDG-PET/CT. Patients and Methods—A retrospective study was performed. Patients with biopsy-proven indolent lymphoma who had had initial staging FDG-PET/CT were included. Qualitative (foci compared with FDG uptake liver) and semiquantitative (SUVmax-value per focus) analyses were performed of all abnormal foci. Patient characteristics and outcome were evaluated. Results—We included 88 patients, 5 of whom developed a histological transformation. Semiquantitative analysis showed a relation between maximum standardized uptake value and histological transformation (odds ratio 1.25, 95% CI 1.024 1.513). Qualitative analysis showed a negative predictive relation of FDG uptake less than or equal to liver in the occurrence of histological transformation. Transformation-free survival was 100% over 30 months in those with FDG uptake lower than or equal to liver. More FDG uptake than liver showed transformation-free survival of 88% over 30 months. Conclusion—Qualitative analysis of staging FDG-PET/CT in indolent lymphomas could be useful to rule out transformation in the next 30 months. In our study, semiquantitative analysis was statistically significantly associated with histological transformation and maximum standardized uptake value. However, because of the small number of patients, cautious interpretation of the results is warranted. More studies are needed to investigate the role of staging PET/CT in patient with indolent non-Hodkin lymphoma in the prediction of transformation.