Interim metabolic tumor volume to predict response in diffuse large B-cell lymphoma.

Abstract

7557 Background: DLBCL is a heterogeneous disease with varied clinical outcomes following treatment with rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP). [18F] fluorodeoxyglucose (FDG) – positron emission tomography (PET)/computed tomography (CT) imaging is ubiquitously used in monitoring of DLBCL. PET-derived metrics for analysis of tumor FDG uptake include: tumor maximum standardized uptake value (SUV); metabolically active tumor volume (MTV); and total lesion glycolysis (TLG), calculated from the intensity of FDG uptake in tumor volume. We evaluated the predictive value of interim SUV, MTV and TLG for patients (pts) with DLBCL treated with R-CHOP. Methods: Pts with DLBCL treated at Emory University 2005-2016 were eligible. Cases were included if there was a diagnosis of DLBCL confirmed by record review, available information on date of diagnosis, date of last contact or date of death. Analyses were restricted to patients who received R-CHOP and had PET/CT scans available at baseline, Cycle 2 or 4 and end of treatment. Maximum SUV, MTV, and TLG were calculated using MIM software for tumor with an SUV threshold of > 4. Logistic regression analysis was used to calculate the predictive value of interim PET/CT metrics on end of treatment response. Results: Pre-treatment PET/CT scans for 42 patients were identified, along with 28 interim and 31 post-treatment scans. The mean pre-treatment MTV was 303ml (range 4 – 1,327) and mean TLG was 3188 (range 28 – 16,176). MTV and TLG were undetectable in 79% of interim scans and 74% of the post-treatment scans. A Deauville score of 3 or less was observed in 71% of the interim PET/CT scans and 56% of the post-treatment scans. A positive interim MTV was correlated with a positive post-treatment MTV and post-treatment Deauville score at 0.58 and 0.66, respectively, and a positive interim MTV result was a significant predictor of a positive post-treatment MTV result (p = 0.02). Conclusions: PET-derived metrics of assessing interim tumor response to therapy offer significant predictive value for end of treatment response, and can guide a response-adapted treatment approach for DLBCL pts that builds on the R-CHOP backbone.