We would like to draw the attention of the hematology and nuclear medicine communities to the importance of standardized uptake value (SUV) harmonization in response evaluation in non-Hodgkin lymphoma (NHL) patients.In NHL patients, the response evaluation during treatment (interim positron emission tomography (PET)) is currently assessed by comparing the residual metabolic activity in the most active tumor lesion to the liver uptake. These PET-based response criteria are described in the Deauville 5-point scale, in which the tumor-to-liver ratio is the discriminator between positive and negative test results. 2 This situation could be encountered in PET centers running several PET systems or during a system upgrade.Therefore, visual and quantitative analysis of PET data in the setting of multicenter trials can only be performed reliably if the PET procedure is standardized. Currently, initiatives such as the European Association of Nuclear Medicine (EANM) Research Ltd. (EARL) accreditation for PET/CT systems (http://earl.eanm.org/cms/website.php) and the North American Quantitative Imaging Biomarker Alliance (QIBA) (http://qibawiki.rsna.org/index.php?title=Main_Page) aim to ensure comparable performance of PET/CT systems, in addition to the procedure guidelines for tumor PET imaging published by the EANM and the Society of Nuclear Medicine (SNM). 3-5New generation PET systems generally outperform older PET systems in terms of spatial resolution and activity recovery, thereby increasing SUVs substantially.6-8 We studied the impact of SUV reconstruction dependency on the tumor-to-liver ratio in 23 NHL patients (13 diffuse large Bcell lymphoma (DLBCL), 6 follicular lymphoma and 4 other subtypes) with a total of 388 lesions. The local Ethics Committee (ref. A12-D24-VOL13, Comité de protection des personnes Nord Ouest III) waived signed informed consent for this type of study.To mimic a situation in which a patient would undergo a PET exam on different generation PET systems, we reconstructed the PET raw data of these patients with a former generation ordered subset expectation maximization (OSEM) algorithm known to meet the EANM guidelines, the recently commercially available point-spread function (PSF) reconstruction without filter for optimal tumor detection (PSFallpass) and a PSF reconstruction with a Gaussian filter optimized to fulfill EANM requirements (PSFEANM). A detailed description of the PSFEANM strategy is provided elsewhere. 9The PET procedure was performed according to the EANM guidelines. All PET studies were performed on a Biograph TrueV (Siemens Medical Solutions) PET/CT system equipped with PSF reconstruction. Regions of interest (ROIs) were drawn on the axial slice on which lesions displayed the highest FDG uptake by means of a 50% isocontour method and the SUVmax for each lesion was measured. A fixed size ROI of 3 cm diameter was used to measure the SUVmax of the physiological liver uptake in the middle of the right liver lobe. For each lesion and reconstruction type, the tumor-to-liver ratio wa...

The prognostic value of fluorodeoxyglucose positron emission tomography (FDG-PET) and gallium-67 scan (GS) performed early after chemotherapy was assessed in 40 patients with newly diagnosed aggressive lymphoma. FDG-PET and GS were performed before and after three cycles of CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone) or two cycles of ACVBP (doxorubicin, cyclophosphamide, vindesine, bleomycin, prednisone), with or without rituximab. Thirty-five patients had diffuse large B-cell lymphoma (DLBCL), two had mantle-cell lymphoma and three had T-cell lymphoma. Four patients relapsed despite early negative FDG-PET and GS including all three patients with T-cell lymphoma. Nine patients stayed in remission despite positive FDG-PET and/or GS of whom five showed moderate intensity residual bone uptake. Seven of these nine early false positives had a negative exam at the end of treatment. In patients with DLBCL, the 2-year event-free survival was 85% for negative versus 30% for positive FDG-PET patients (P = 0.003) whereas it was 78% for negative versus 33% for positive GS patients (P = 0.018). Sensitivity, specificity and diagnostic accuracy of FDG-PET and GS were not significantly different: 90% versus 70%, 76 versus 80% and 80 versus 77%, respectively. We conclude that both FDG-PET and GS are valuable tools to early predict outcome in patients with DLBCL.

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