Limited role of interim PET/CT in patients with diffuse large B-cell lymphoma treated with R-CHOP

Abstract

Positron emission tomography (PET) has been found useful in monitoring response to treatment of malignant lymphoma. We investigated the ability of interim PET to monitor response to standard dose R-CHOP chemotherapy in chemotherapy-naïve patients with diffuse large B-cell lymphoma (DLBCL). Between March 2004 and April 2009, 155 DLBCL patients treated with R-CHOP and available for interim and post-treatment PET/CT were identified and included in this analysis. Response, progression-free survival (PFS), and overall survival (OS) were compared between interim PET/CT-negative and positive group, and among three patient groups which were categorized based on their interim and post-treatment PET/CT: those with early metabolic complete response (mCR), delayed mCR, and never mCR. Interim PET/CT-negative patients (n=100) showed superior CR rates to interim PET/CT-positive patients (n=55; 93% vs 62%, P<0.001). However, there was no difference in PFS (P=0.07) and OS (P=0.24) between interim PET/CT-negative and positive group. We categorized patients into three groups, with 100 (64%) in the early mCR group, 35 (23%) in the delayed mCR group, and 20 (13%) in the never mCR group. Early mCR and delayed mCR group did not differ significantly in PFS (P=0.84) or OS (P=0.20). However, the survival outcome in the never mCR group was significantly inferior to the combined early and delayed mCR group. The result from this study suggests that interim PET/CT might be an inappropriate tool for designing risk-adaptive therapy in chemotherapy-naïve DLBCL patients treated with R-CHOP. Prospective trials should be performed to clearly determine the role of interim PET/CT.

Prospective International Cohort Study Demonstrates Inability of Interim PET to Predict Treatment Failure in Diffuse Large B-Cell Lymphoma

“…(63%) achieved remission after a positive I-PET (24). These smaller studies provide reassurance that our findings are not a unique phenomenon.…”

“…Similarly, 2-y EFS and OS, stratified by I-PET response after 2-3 cycles chemotherapy, were comparable to recent studies from high-income countries, likewise using visual PET reporting and early I-PET scanning after 2-3 cycles (Table 3) (22)(23)(24)(25)(26).…”

Role of Imaging in the Staging and Response Assessment of Lymphoma: Consensus of the International Conference on Malignant Lymphomas Imaging Working Group

“…In DLBCL, early indication of poor response is especially important because salvage treatment of progressive or relapsed disease is less effective in the rituximab era. 134 However, although early data favored iPET, 55,57,59 more recent data have suggested iPET is less predictive for response with immunochemotherapy 30-32,58, 135,136 (Appendix Table A2, online only), and end-of-treatment PET is a better predictor.…”

“…28-32,93, [135][136][137] The drop in PPV may be related to improved outcomes with rituximab or better supportive care 126,138 or may possibly occur because so-called false-positive metabolic activity is more frequent with immunotherapy. 30 A different cutoff or combination of factors may be required for modern management of DLBCL.…”

Early Determination of Prognosis by Interim 3′-Deoxy-3′-18F-Fluorothymidine PET in Patients with Non-Hodgkin Lymphoma

“…These studies showed that patients with significant residual 18 F-FDG uptake after 2-3 cycles of chemotherapy had 2-y PFS rates of only 0%-30%. However, the widespread use of rituximab in NHL patients is associated with false-positive 18 F-FDG PET findings (13,26), suggesting a need for validation of the utility of interim 18 F-FDG PET response analysis in the rituximab era. Recently, 2 studies on interim 18 F-FDG PET in DLBL patients treated with rituximab-containing regimens were published (12,27).…”