Interim 18 F-FDG PET (after 1-4 cycles of chemotherapy) may be useful for tailoring a risk-adapted therapeutic strategy in lymphoma. The purpose of this study was to investigate whether semiquantification of standardized uptake values (SUVs) may help to improve the prognostic value of 18 F-FDG PET, compared with visual analysis, after 4 cycles of chemotherapy. Methods: In a previous report, we showed that a 65.7% reduction in maximal SUV (SUVmax) between baseline (PET0) and 2 cycles of chemotherapy (PET2) better predicted event-free survival in 92 prospective patients with diffuse large B-cell lymphoma, by reducing false-positive interpretation of visual analysis. Eighty patients also underwent 18 F-FDG PET after induction had been completed, at 4 cycles of chemotherapy (PET4). Images were interpreted visually (as negative or positive) and by computing the optimal percentage of SUVmax reduction between PET0 and PET4. Survival curves were estimated using Kaplan-Meier analysis and compared using the log-rank test. Median follow-up was 41 mo. Results: With visual analysis, the 2-y estimate for event-free survival was 82% in the PET4-negative group, compared with 25% in the PET4-positive group (P , 0.0001, accuracy of predicting event-free survival, 81.3%). An optimal cutoff of 72.9% SUVmax reduction from PET0 to PET4 yielded a 2-y estimate for event-free survival of 79% in patients with reduction of more than 72.9%, versus 32% in those with reduction of 72.9% or less (P , 0.0001; accuracy of predicting event-free survival, 77.5%). Conclusion: Although SUV semiquantification helps reduce false-positive interim 18 F-FDG PET interpretations at 2 cycles, its performance is equivalent to visual analysis at 4 cycles, when most of the therapeutic effect has occurred upstream. This approach may be useful for objectively tailoring consolidation strategies.

Despite the availability of new tools for the quantitative assessment of disease activity on PET/CT, the SUVmax rather than MTV and TLG remains the only predictor for EFS in DLBCL patients. The magnitude of glycolytic activity rather than the amount of metabolically active burden holds a predominant value for determining the response to chemotherapy in DLBCL.

a significant part of low risk DTC patients, for whom RAI is not recommended, presents an incidental suspicion of lymph-nodal involvement at WBSt confirmed by subsequent SPECT/CT. Such setting would have not been treated by I-131.