Prospective Study of 3′-Deoxy-3′-¹⁸F-Fluorothymidine PET for Early Interim Response Assessment in Advanced-Stage B-Cell Lymphoma

Abstract

Purpose Current clinical and imaging tools remain suboptimal for early assessment of prognosis and treatment response in aggressive lymphomas. Positron emission tomography (PET) with 18F-fluorothymidine (FLT) can be used to measure tumor cell proliferation and treatment response. In a prospective study in patients with advanced stage B-cell lymphoma we investigated the prognostic and predictive value of FLT PET in comparison to standard imaging with FDG PET and clinical outcome. Patients and Methods 65 patients were treated with an induction/consolidation regimen consisting of four cycles of R-CHOP-14 followed by 3 cycles of ICE. FLT PET was performed at baseline and at interim (iPET) after 1–2 cycles of therapy. FDG PET was performed at baseline, after cycle 4, and at the end of therapy. The relationship between PET findings, progression free survival (PFS) and overall survival (OS) was investigated. Results With a median follow-up of 51 months, PFS and OS were 71% and 86% respectively. FLT iPET, analyzed visually, using a 5-point score, or semi-quantitatively, using SUV and ΔSUV, predicted both PFS and OS (p<0.01 for all parameters). Residual FLT SUVmax on iPET was associated with an inferior PFS (HR: 1.26, p=0.001) and OS (HR: 1.27, p=0.002). Using FDG PET, findings in the end of treatment scan were better predictors of PFS and OS than findings on interim scan. Baseline PET imaging parameters, including SUV, proliferative or metabolic tumor volume, did not correlate with outcome. Conclusion FLT PET after 1–2 cycles of chemotherapy predicts PFS and OS, and a negative FLT iPET may potentially help design risk-adapted therapies in patients with aggressive lymphomas. In contrast, the positive predictive value of FLT iPET remains too low to justify changes in patient management.

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