18F-Fluorodeoxyglucose (FDG) PET for Measurement of Response and Prediction of Outcome to Relapsed/Refractory Mantle Cell Lymphoma (MCL) Therapy with Bendamustine-Rituximab(BR)

In a single-arm, phase 2 clinical trial, bendamustine-rituximab (BR) demonstrated an overall response rate of 82% among 45 patients with relapsed or refractory mantle cell lymphoma (MCL), with manageable tolerability. A prespecified 18F-FDG PET analysis was conducted to assess the predictive value of the metabolic response to BR compared with the response by International Working Group (IWG) criteria.Adult patients with relapsed or refractory MCL underwent 18F-FDG PET at screening and after 6 cycles of BR therapy. Scans were reviewed by a central facility and scored using the 5-point Deauville scale, comparing uptake to the liver and mediastinum in up to 6 lesions, to determine metabolic response rates, indicated by negative posttreatment scans. Metabolic responses were compared with study outcomes assessed by IWG criteria.Complete 18F-FDG PET data were available for 32 of 45 patients. All patients had positive baseline scans, with baseline scores ranging from 4 to 5. Complete metabolic responses (CMR) were observed in 24 (75%) patients after 6 cycles of BR. Patients attaining a CMR had a 96% overall response rate by IWG criteria, with 62.5% achieving a complete response. Of the 8 patients not attaining a CMR, 6 responded to BR but none achieved a complete response. CMR was associated with a greater 1-y progression-free survival of 91.5%, compared with 12.5% without CMR; a longer median duration of response of 20.6 mo, compared with 7.8 mo; and improved overall survival at 1 y. 18F-FDG PET data from patients with refractory or advanced disease demonstrated CMR in more than half.Compared with positive end-of-treatment 18F-FDG PET, negative scans, indicating a CMR, were predictive of improved 1-y survival, duration of response, and overall survival for patients with relapsed or refractory MCL receiving BR.