Collection of metabolic response data in a standardized fashion will greatly aid future pooling of study data and meta-analyses to allow the best determination of the predictive and prognostic value of the PET Response Criteria in Solid Tumors (PERCIST 1.0) in a variety of clinical settings and with a variety of treatments. Positron Emission Tomography (PET) Response Criteria in Solid Tumors (PERCIST 1.0) describes in detail methods for controlling the quality of fluorine 18 fluorodeoxyglucose PET imaging conditions to ensure the comparability of PET images from different time points to allow quantitative expression of the changes in PET measurements and assessment of overall treatment response in PET studies. The steps for actual application of PERCIST are summarized. Several issues from PERCIST 1.0 that appear to require clarification, such as measurement of size and definition of unequivocal progression, also are addressed.© RSNA, 2016

Purpose This study is an integrated efficacy analysis of the five clinical trials of tositumomab and iodine-131 tositumomab in patients with relapsed or refractory low-grade, follicular, or transformed low-grade non-Hodgkin’s lymphoma (NHL) that resulted in the regulatory approval of the iodine-131 tositumomab by the US Food and Drug Administration. Patients and Methods This integrated analysis included 250 patients. Patients received a single course of iodine-131 tositumomab. Responses were assessed by an independent panel of radiologists and oncologists. Results Response rates in the five trials ranged from 47% to 68%; complete response rates ranged from 20% to 38%. With a median follow-up of 5.3 years, the 5-year progression-free survival was 17%. Eighty-one (32%) of 250 patients had a time to progression of ≥ 1 year (termed durable response population). For the durable response population, 44% had not progressed at ≥ 2.5 to ≥ 9.5 years and had a median duration of response of 45.8 months. The median duration of complete response was not reached. The durable response population had many poor prognostic characteristics, including bone marrow involvement (41%), bulky disease ≥ 5 cm (49%), and transformed histology (23%). Forty-three percent of the patients had been treated with more than four prior therapies and 36% had not responded to their most recent therapy. Conclusion The tositumomab and iodine-131 tositumomab therapeutic regimen produces high response rates in patients with relapsed or refractory low-grade, follicular, and transformed low-grade NHL, with a sizable subgroup of patients achieving long-term durable responses.

This article provides a summary of the claims of precision of standardized uptake value measurements and the context of the technically confirmed fluorodeoxyglucose PET/CT Profile by the Quantitati... The Quantitative Imaging Biomarkers Alliance (QIBA) Profile for fluorodeoxyglucose (FDG) PET/CT imaging was created by QIBA to both characterize and reduce the variability of standardized uptake va...

Objectives: ¹⁸F-FDG-PET/CT has shown increased accuracy compared to morphologic imaging in differentiating malignant peripheral nerve sheath tumors (MPNST) from benign neurofibromas (BNF) in patients with neurofibromatosis type-1 (NF1). Delayed ¹⁸F-PET imaging typically enhances malignant tumor to background. Our goal was to compare the effectiveness of (1) early (1-hour) and delayed (4-hour) ¹⁸F-FDG-PET/CT imaging in differentiating MPNSTs from BNFs in patients with NF1, (2) with and without liver activity normalization. Methods: NF1 patients presenting new symptoms or enlarging lesions were clinically evaluated with early and delayed ¹⁸F-FDG PET/CT imaging. SULmax (maximum standardized uptake value derived for lean body) as well as SULmax/liver (lesion uptake adjusted to mean liver activity) were obtained for all sites identified with abnormal metabolic activity. Qualitative and quantitative evaluations, including ROC comparison of early and delayed imaging sessions, were carried out. Histopathology and clinical follow-up (1-9 years) were considered as gold standard. Results: 41 NF1 patients with early and delayed ¹⁸F-FDG-PET/CT scans were identified and 93 lesions were retrospectively analyzed, representing 24 MPNSTs (all histologically confirmed) and 69 BNFs (26 histologically confirmed). Qualitative evaluation on early imaging showed sensitivity, specificity, PPV and NPV for separating MPNSTs from BNFs of 91%, 84%, 67% and 96% versus 91%, 81%, 63% and 96% on 4-hr delayed imaging. The mean SULmax was significantly higher for MPNSTs compared to BNFs on both early scans (6.5 versus 2.0,P < 0.01) and delayed imaging (8.3 versus 2.3, P < 0.02). However, SULmax overlap between benign and malignant lesions persisted even after normalization to mean liver activity. ROC-derived best SULmax cut-offs were 3.2 on early (AUC 0.973) and 4.1 on delayed scans (AUC 0.978). ROC analysis for SULmax/liver improved test specificity (94% vs 87%,P < 0.05) on early and (93% vs 88%,P < 0.05) on delayed imaging. Conclusion: Qualitative interpretation of ¹⁸F-FDG-PET/CT discriminates MPNSTs from BNFs in NF1 patients with similar accuracy on both early and delayed imaging. Quantitative data showed better sensitivity on delayed acquisition and best test specificity with lesion-SULmax normalization to liver activity, more so than with delayed imaging at 4 hours.

Response is the logical outcome measure of a treatment in a clinical or research setting. Objective response assessment involves the use of a test to segregate patients who are likely to experience improved survival from those who are not. Early and accurate response assessment is critical for determining therapy effectiveness in clinical settings, for effective trial designs comparing two or more therapies, and for modulating treatment on the basis of response (ie, response-adapted therapy). 2-[fluorine 18]fluoro-2-deoxy-d-glucose (FDG) PET/CT can provide both functional and structural information about a disease process. It has been used at several stages of patient management, including imaging-based tumor response assessment, for various malignancies. FDG PET/CT can be used to differentiate patients with lymphoma who have a residual mass but no residual disease after treatment (ie, complete responders) from those who have a residual mass and residual disease after treatment. Similarly, in solid malignancies, the functional changes in glucose uptake and metabolism precede the structural changes (commonly seen as tumor shrinkage) and necrosis. Response assessment criteria have been developed on the basis of findings on FDG PET/CT images and are continuously being revised to ensure standardization and improve their predictive performance. Published under a CC BY 4.0 license. Quiz questions for this article are available through the Online Learning Center.