18F-FDG PET for Measurement of Response and Prediction of Outcome to Relapsed or Refractory Mantle Cell Lymphoma Therapy with Bendamustine-Rituximab.

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 (18)F-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.

METHODS: Adult patients with relapsed or refractory MCL underwent (18)F-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.

RESULTS: Complete (18)F-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. (18)F-FDG PET data from patients with refractory or advanced disease demonstrated CMR in more than half.

CONCLUSION: Compared with positive end-of-treatment (18)F-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.