Heterogeneity of CD20 antigen expression and glucose metabolism in correlation with therapeutic response in radioimmunotherapy for B-cell lymphoma

180 Objectives To evaluate tumor accumulations and heterogeneity of 111In-Zevalin (In-Zevalin) and 18F-FDG (FDG) as compared to therapeutic response in patients receiving Zevalin therapy. Methods Sixteen patients with B-cell non-Hodgkin’s lymphoma who underwent Zevalin therapy along with In-Zevalin SPECT/CT and FDG PET/CT were enrolled. Patients received In-Zevalin, followed by SPECT/CT scanning at 48 hrs after administration. SUVmax of FDG of lesions was measured on PET/CT while lesion accumulation of In-Zevalin as %ID/g and SUVmax of In-Zevalin (In-Zevalin SUVmax) was measured on SPECT/CT, and skewness and kurtosis of voxel distribution were calculated to evaluate heterogeneity of CD20 antigen expression. As another intratumoral heterogeneity index, cumulative SUVmax-volume histograms describing percentage of total tumor volume above thresholds of In-Zevalin SUVmax (AUC-CSH) were calculated. All lesions (n=42) were classified into responders and non-responders lesion-by-lesion on pre- and post-therapeutic CT images. Results A positive correlation was observed between FDG SUVmax and accumulation of In-Zevalin. Accumulation of In-Zevalin was 0.0022±0.0009 and 0.0024±0.0008%ID/g (n.s.), and 2.74±1.43 and 3.29±1.47 SUVmax (n.s.) for responders and non-responders, respectively. In contrast, voxel distribution of In-Zevalin demonstrated skewness of 0.58±0.16 and 0.73±0.24 (p Conclusions Pretherapeutic glucose metabolism was predictive of tumor response. There was a positive correlation between glucose metabolism and CD20 expression, and the heterogeneity rather than absolute levels of CD20 expression correlated well with tumor response.