Abstract
1608
Objectives 18-Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is an accurate tool for staging, treatment monitoring and response evaluation in lymphoma. The aim of this study is to examine the prognostic role of 18F-FDG PET parameters at baseline in DLBCL patients. Metabolic activity of whole-body tumors was defined by the maximum standardized uptake value (SUV max), mean standardized uptake value (SUV mean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG). All parameters were correlated to early response to treatment, occurrence of relapse and overall survival (OS).
Methods We retrospectively evaluated 51 patients (mean age: 55 ± 17 years, range 23-84) with DLBCL, stage I-IV (26 stage I-II, 25 stage III-IV). All patients had a 18F-FDG PET/CT scan before starting therapy (baseline PET), and after 2-4 cycles of chemotherapy (interim-PET). Forty-six patients had also PET/CT at the end of treatment (EOT PET). All scans were interpreted by two Nuclear Medicine physicians and any dis-agreements were resolved by consensus. At the baseline PET the MTV and TLG, as well as the SUV max and SUV mean, of whole-body tumors were measured using the PETedge tool of the MIMvista software with manual adjustment. Mann-Whitney test and Pearson’s correlation test were used to correlate parameters to early response to treatment, occurrence of relapse and OS. ROC curves were analyzed to find the best MTV sum and TLG sum thresholds predictive for OS and occurrence of relapse.
Results The median follow-up for the OS was 57.6 months. According to Lugano criteria, the early response to treatment (after 2-4 cycles of chemotherapy), was a complete metabolic response (CMR) in 36 patients (70.6%) and a non complete metabolic response (partial, stable or progressive disease) in 15 patients (29.4%). All evaluated parameters had a significant correlation with early response to treatment (p<0,001), occurrence of relapse (p<0.001) and OS (p<0.001). MTV sum > 314.12 was correlated with OS (p<0.05). No significant thresholds were found between the MTV sum and occurrence of relapse, or TLG sum and OS/occurrence of relapse.
Conclusions Information derived from PET/CT performed at baseline (metabolic disease burden) can strongly help to select high-risk patients. In our study MTV sum at baseline is a good predictor of prognosis. A larger study is still going on and more suitable thresholds can be determined with a bigger cohort of patients.