Predictive Value of Interim and End-of-Therapy 18F-FDG PET/CT in Patients with Follicular Lymphoma

Purpose 18 F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is the standard imaging modality for response evaluation in FDG-avid lymphoma, but the prognostic value is not established in follicular lymphoma (FL). This study investigated the prognostic value of Deauville 5-point scale (D5PS) from paired interim PET/CT (PET Interim ) and end-of-induction therapy PET/CT (PET EOI ) in patients with FL. Methods FL staging and response assessment PET/CT images from 2013 to 2015 were retrospectively reviewed. PET Interim was performed 3 or 4 cycles after chemotherapy and PET EOI after 6 or 8 cycles. D5PS scores of 1, 2, and 3 were considered as negative (−), and scores 4 and 5 were considered as positive (+). Statistical analysis was done using Cox regression analysis, Kaplan–Meier survival analysis, and the log-rank test. Results Thirty-three patients with set of baseline, interim, and end-of-induction therapy PET/CT studies were included. Ten patients (30.3%) had progression. The median progression-free survival (PFS) was 38.8 months (range 3.5–72.7 months). On PET Interim , 23 patients were negative and 10 were positive. On PET EOI scans, 29 patients were negative, and 4 were positive. On multivariate analysis, PET EOI (−) was associated with longer PFS. PET Interim (+) and PET EOI (+) patients had a significantly shorter PFS than PET Interim (−) patients (39.9 months, 95% confidence interval [CI] 23.0–56.9, versus 55.5 months, 95% CI 49.7–61.2, p = 0.005) and PET EOI (−) patients (14.2 months, 95% CI 8.5–19.8, versus 60.5 months, 95% CI 52.1–69.0, p