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Predictive Value of Initial 18F-FLT Uptake in Patients with Aggressive Non-Hodgkin Lymphoma Receiving R-CHOP Treatment

R-CHOP (rituximab, cyclophosphamide, doxorubicine, vincristine, and prednisone)–like chemotherapy is the standard therapy in aggressive B-cell lymphoma. 18F-FDG PET has high prognostic implications at treatment completion but is limited as an early predictor. Here, we present the results of a prospective study correlating the initial uptake of the in vivo proliferation marker 3′-deoxy-3′-18F-fluorothymidine (18F-FLT) with the clinical outcome of patients with aggressive non-Hodgkin lymphoma treated with R-CHOP. Methods: Sixty-six eligible patients were evaluated prospectively with 18F-FLT PET before R-CHOP. PET was performed 45 min after injection of 300–370 MBq of 18F-FLT. Mean and maximum standardized uptake values (SUVs) were calculated on a lesion-by-lesion basis. Response was assessed at the end of therapy. International Prognostic Index (IPI) scores and clinical parameters (Ann Arbor stage, lactate dehydrogenase, performance status, extranodal disease) were determined in all patients. Response was assessed according to revised response criteria after the end of therapy. After treatment, patients were followed in intervals from 4 wk to 6 mo (mean follow-up, 23.1 mo [range, 1–63 mo]), and progression-free and overall survival were determined. Results: All lymphoma lesions identified by a reference method (18F-FDG PET/CT or multislice CT of the trunk) showed increased focal tracer uptake (mean 18F-FLT SUV, 7.3 ± 2.5). Response assessment revealed progressive disease in 4, partial response in 3, and complete response (CR) in the remaining 55 patients. The IPI score was predictive for achieving CR (P = 0.034). Importantly, initial mean SUV was also significantly higher in patients who showed progressive disease and partial response than in patients who achieved CR (P = 0.049). In addition, we found a significant correlation between IPI score and initial 18F-FLT uptake. Conclusion: Taken together, high 18F-FLT uptake is a negative predictor of response to R-CHOP treatment in aggressive B-cell non-Hodgkin lymphoma and correlates with the IPI score. Thus, 18F-FLT PET may represent a useful tool for implementing risk-adapted treatment in these patients.