Quantifying bone marrow uptake of FDG (18fluorodeoxyglucose) improved the diagnostic accuracy of PET/CT for predicting bone marrow involvement in patients with follicular lymphoma, based on the results of a retrospective study.
Visual evidence of focal increased uptake on PET/CT indicates marrow involvement in follicular lymphoma; however, diffuse uptake is a nonspecific finding. Measuring the mean bone marrow standardized uptake value (BM SUV mean) improves PET/CT diagnostic accuracy, Dr. Chava Perry and his colleagues at Tel Aviv Sourasky Medical Center reported in Medicine [(Baltimore). 2016 Mar;95(9):e2910].
The researchers evaluated 68 consecutive patients with follicular lymphoma; 16 had bone marrow involvement – 13 had biopsy-proven involvement and 3 had a negative biopsy with increased medullary uptake that normalized after treatment. BM FDG uptake was diffuse in 8 of them and focal in the other 8.
While focal increased uptake is indicative of bone marrow involvement, diffuse uptake can be associated with false-positive results, as it was in the case of 17 patients (32.7% of those with diffuse uptake). Overall, visual assessment of scan results had a negative predictive value of 100% and a positive predictive value (PPV) of 48.5%.
On a quantitative assessment, however, BM SUV mean was significantly higher in patients with bone marrow involvement (SUV mean of 3.7 [1.7-6] vs. 1.4 [0.4-2.65]; P less than .001). On the receiver operator curve (ROC) analysis, a BM SUV mean exceeding 2.7 had a positive predictive value of 100% for bone marrow involvement (sensitivity of 68%). A BM SUV mean less than 1.7 had an negative predictive value of 100% (specificity of 73%).
A mean standardized uptake value (BM SUV mean) below 1.7 may spare the need for bone marrow biopsy while a BM SUV mean above 2.7 is compatible with bone marrow involvement, although biopsy may still be recommended to exclude large cell transformation, the researchers concluded.
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