FDG-PET May Be Helpful in the Determination of Transformation to an Aggressive Subtype in Low-Grade Lymphoma.

The therapeutic management of the patient with transformed low-grade lymphoma is quite different from those with pure indolent disease. In cases of transformation FDG uptake characteristics may help identify an area of transformation in indolent disease and thereby impact management. Our objective was to evaluate the potential of FDG-PET imaging in the determination of transformation

Methods: A total of 60 patients with low-grade lymphoma (48 patients) and those with known transformation to DLCL (12 patients) underwent FDG-PET imaging prior to therapy. In the indolent group, 27 patients were diagnosed with a follicular histology and 11 with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and 10 were with marginal zone lymphoma. A total of 370 lesions were evaluated and SUV’s were obtained for all visualized lesions. Mean values were calculated on a patient and total site basis. Additionally, mean SUV values were calculated for lesions with the highest SUV’s, in groups with indolent and transformation histology.

Results: Results are summarized in the Table. There was a significant difference in the mean SUV’s between the group with transformation and that with indolent lymphoma (7.6 ± 4.6 vs. 4.5 ±2.5). More importantly, the mean values for SUV in the lesions with the highest FDG uptake were significantly different between the two groups (13.8 ±5.3 vs 5.8±2.9). Among the patients who had a biopsy taken from the lesions with the highest SUV’s the range was 8 to 27 and the mean value was 14.9±8.0.

Conclusions: In patients with indolent lymphoma, areas of significant increase in FDG (particularly SUV’s >12) should be considered targets for biopsy.