Majority of Transformed Lymphomas Have High SUVs on PET Scanning Similar to Diffuse Large B Cell Lymphoma (DLBCL).

Background: In our previous work, we correlated non-Hodgkins (NHL) histology with intensity of FDG uptake (SUVmax) on positron emission tomography in untreated patients: an SUVmax greater than 10 predicted an aggressive lymphoma with >80% certainty and an SUVmax greater than 13 predicted an aggressive lymphoma with >90% certainty. We sought to evaluate SUVmax in a series of patients with transformed lymphoma.

Methods: All PET scans for lymphoma indications at our institution 1999-5/2007 were evaluated. Patients were included if they had biopsy proven transformation. FDG-PET scans were included if they were no more than sixty days prior to or 90 days after biopsy proven transformation. Patients had no therapy for sixty days prior to PET scan unless there was documented progression of disease after the last treatment.

Results: Among the indolent diagnoses (n= 44), the following specific histologies were identified: 9 follicular lymphoma grade 1 (FL I), 9 FL grade 2 (FL 2), 7 small lymphocytic lymphoma / chronic lymphocytic leukemia (SLL/CLL), 11 marginal zone lymphoma (MZL) including one of mucosa associated lymphoid tumor (MALT) type, one mycoses fungoides, and one indolent lymphoma otherwise not specified. 5 FL 3 (FL 3), including one specified as grade 3a (FL 3a) were considered indolent if they preceded a diagnosis of DLBCL. Among the aggressive diagnoses (n= 28), the following specific histologies were identified: 37 DLBCL, one follicular lymphoma grade IIIa included as it was preceded by FLI, one large peripheral T-cell lymphoma, and 5 Large cell lymphoma(LCL), not otherwise characterized on account of biopsy size. Standard uptake values (SUV) were measured at the biopsy site when possible (n=38). In 6 patients the biopsy site was completely excised before the PET scan. The SUV of biopsy site ranged from 3-38, with a median of 10 and mean of 15. Among evaluable patients, 17/36 (47%) biopsies had an SUV above 10; and 12/36 (33%), above 13. The SUVmax for a transformed aggressive lymphoma ranged from 3.2–40, with a median of 12 and mean of 15. 27/44 (61%) patients had an SUVmax above 10; and 21/44 (48%), above 13.

Conclusions: Similar to patients with de-novo aggressive lymphoma, the majority of patients with transformed lymphomas have high SUVmax for a given pre-treatment staging study. Therefore, transformation to aggressive lymphoma should be suspected in patients with indolent lymphoma found to have high SUVs on FDG PET, and biopsies should be directed to the site of greatest PET avidity whenever feasible.