Diffuse Large B-Cell Lymphoma: Prospective Multicenter Comparison of Early Interim FLT PET/CT versus FDG PET/CT with IHP, EORTC, Deauville, and PERCIST Criteria for Early Therapeutic Monitoring

Purpose: To compare the performance characteristics of interim fluorine 18 ( F-18) fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) (after two cycles of chemotherapy) by using the most prominent standardized interpretive criteria (including International Harmonization Project [IHP] criteria, European Organization for Research and Treatment of Cancer [EORTC] criteria, and PET Response Criteria in Solid Tumors (PERCIST) versus those of interim 18F fluorothymidine (FLT) PET/CT and simple visual interpretation. Materials and Methods: This HIPAA-compliant prospective study was approved by the institutional review boards, and written informed consent was obtained. Patients with newly diagnosed diffuse large B-cell lymphoma (DLBCL) underwent both FLT and FDG PET/CT 18-24 days after two cycles of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone or rituximab, etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin. For FDG PET/CT interpretation, IHP criteria, EORTC criteria, PERCIST, Deauville criteria, standardized uptake value, total lesion glycolysis, and metabolic tumor volume were used. FLT PET/CT images were interpreted with visual assessment by two reviewers in consensus. The interim (after cycle 2) FDG and FLT PET/CT studies were then compared with the end-of-treatment FDG PET/CT studies to determine which interim examination and/or criteria best predicted the result after six cycles of chemotherapy. Results: From November 2011 to May 2014, there were 60 potential patients for inclusion, of whom 46 patients (24 men [mean age, 60.9 years +/- 13.7; range, 28- 78 years] and 22 women [mean age, 57.2 years +/- 13.4; range, 25- 76 years]) fulfilled the criteria. Thirty-four patients had complete response, and 12 had residual disease at the end of treatment. FLT PET/ CT had a significantly higher positive predictive value (PPV) (91%) in predicting residual disease than did any FDG PET/ CT interpretation method (42%- 46%). No difference in negative predictive value (NPV) was found between FLT PET/ CT (94%) and FDG PET/ CT (82%- 95%), regardless of the interpretive criteria used. FLT PET/ CT showed statistically higher (P < .001-.008) or similar NPVs than did FDG PET/ CT. Conclusion: Early interim FLT PET/ CT had a significantly higher PPV than standardized FDG PET/ CT- based interpretation for therapeutic response assessment in DLBCL. (C) RSNA, 2016