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Scientific Session 26 — SS26: Nuclear Medicine

Friday, May 10, 2019

Abstracts 1274-3132



3132. Concordance of PET/CT and Clinical Evaluation in CAR T-cell Therapy Response

Rupasov A*,  Reagan P,  Puri S. University of Rochester, Rochester, NY

Address correspondence to A. Rupasov (andrey_rupasov@urmc.rochester.edu)

Objective: To evaluate the concordance of PET/CT imaging findings and clinical parameters in patients receiving novel chimeric antigen receptor (CAR) T-cell therapy for relapsed and refractory lymphoma as part of a study or clinical trial at the University of Rochester Medical Center Wilmot Cancer Institute. Significant emphasis is given to delineating imaging findings to suggest pseudoprogression as opposed to true progression of disease.

Materials and Methods: Retrospective analysis that included a chart and imaging review was performed on all patients that have received the CAR T-cell therapy at our institution. Parameters used to evaluate clinical progression were selected and included report of B symptoms, physical examination findings, and presence of cytopenias. All posttreatment imaging was performed within our network of university imaging centers, and at minimum consisted of 18F-FDG PET/CT at 28 and 100 days, extending from skull base to thighs. The Deauville five-point scale was used to evaluate treatment response.

Results: Of the 13 patients evaluated, 10 were treated for diffuse large B-cell lymphoma (DLBCL), 2 were treated for follicular lymphoma, and 1 was treated for mantle cell lymphoma. One patient in the DLBCL group was excluded because imaging findings were equivocal on 28-day and 100-day scans. Progression of disease was demonstrated in 1 patient; partial response was demonstrated in 3 of 12 patients; complete response was demonstrated in 8 of 12 patients. The absence of B symptoms and a benign physical examination did not correlate with imaging findings in the single patient with biopsy-proven progression. The presence of cytopenias correlated poorly with imaging findings and other clinical parameters of well-being. Pseudoprogression was observed in two patients, characterized by an initial increase in lesional size with an accompanying decrease in lesional 18F-FDG uptake on day 28, with metabolic and morphologic response on day 100. One patient with pseudoprogression also demonstrated significant decrease in nodal attenuation on CT, reflective of necrosis.

Conclusion: The preliminary results demonstrate good concordance of PET/CT imaging features and clinical parameters in evaluation of response to CAR T-cell therapy; however, the study is low-powered and ongoing. An estimated 20-30 additional patients are expected to be treated by March 2019. The cases of pseudoprogression feature lesional growth with a concurrent decrease in metabolic activity on early follow-up, followed by concordant decrease in size and activity on subsequent examinations.