The role of 18F-FDG-PET in detecting Richter's transformation of chronic lymphocytic leukemia in patients receiving therapy with a B-cell receptor inhibitor

The role of 18 F-FDG-PET in detecting Richter transformation of chronic lymphocytic leukemia in patients receiving therapy with a B-cell receptor inhibitorChronic lymphocytic leukemia (CLL) is a low grade B-cell malignancy.Approximately 2-10% of CLL can undergo Richter transformation (RT) to an aggressive lymphoma, most commonly diffuse large B-cell lymphoma (DLBCL). 1-3Management of RT is extremely challenging and the clinical outcome is dismal. 4In CLL patients with suspected disease progression, distinguishing between progressive CLL and RT is critically important, as the management and prognosis are different.While tissue biopsy is the gold standard for diagnosing progressive CLL versus RT, 18 F-fluorodeoxyglucose (FDG) positron emission tomography (PET) may play an important role in the diagnostic workup.In the chemoimmunotherapy (CIT) era, several studies showed that a maximum standardized uptake value (SUV max ) ≥5 had high sensitivity (88-91%) and varied specificity (47-80%) in detecting RT, [5][6][7] and a French study 8 reported high sen-