Diagnostic role of 18F-fluorodeoxyglucose positron emission tomography for follicular lymphoma with gastrointestinal involvement.

aimTo investigate the capacity for 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) to evaluate patients with gastrointestinal lesions of follicular lymphoma.

methodsThis retrospective case series consisted of 41 patients with follicular lymphoma and gastrointestinal involvement who underwent 18F-FDG-PET and endoscopic evaluations at ten different institutions between November 1996 and October 2011. Data for endoscopic, radiological, and biological examinations performed were retrospectively reviewed from clinical records. A semi-quantitative analysis of 18F-FDG uptake was performed for each involved area by calculating the maximum standardized uptake value (SUVmax). Based on the positivity of 18F-FDG uptake in the gastrointestinal lesions analyzed, patients were subdivided into two groups. To identify potential predictive factors for 18F-FDG positivity, these two groups were compared with respect to gender, age at diagnosis of lymphoma, histopathological grade, pattern of follicular dendritic cells, mitotic rate, clinical stage, soluble interleukin-2 receptor levels detected by 18F-FDG-PET, lactate dehydrogenase (LDH) levels, hemoglobin levels, bone marrow involvement, detectability of gastrointestinal lesions by computed tomography (CT) scanning, and follicular lymphoma international prognostic index (FLIPI) risk.

resultsInvolvement of follicular lymphoma in the stomach, duodenum, jejunum, ileum, cecum, colon, and rectum was identified in 1, 34, 6, 3, 2, 3, and 6 patients, respectively. No patient had esophageal involvement. In total, 19/41 (46.3%) patients exhibited true-positive 18F-FDG uptake in the lesions present in their gastrointestinal tract. In contrast, false-negative 18F-FDG uptake was detected in 24 patients (58.5%), while false-positive 18F-FDG uptake was detected in 5 patients (12.2%). In the former case, 2/19 patients had both 18F-FDG-positive lesions and 18F-FDG-negative lesions in the gastrointestinal tract. In patients with 18F-FDG avidity, the SUVmax value of the involved gastrointestinal tract ranged from 2.6 to 17.4 (median: 4.7). For the 18F-FDG-negative (n = 22) and -positive (n = 19) groups, there were no differences in the male to female ratios (10/12 vs 4/15, P = 0.186), patient age (63.6 ± 2.4 years vs 60.1 ± 2.6 years, P = 0.323), presence of histopathological grade 1 vs 2 (20/2 and 17/2, P = 1.000), follicular dendritic cell pattern (duodenal/nodal: 13/5 vs 10/3, P = 1.000), mitotic rate (low/partly high, 14/1 vs 10/3, P = 0.311), clinical stage according to the Ann Arbor system (stages IE and IIE/other, 15/7 vs 15/4, P = 0.499), clinical stage according to the Lugano system (stages I and II-1/other, 14/8 vs 14/5, P = 0.489), soluble interleukin-2 receptor levels (495 ± 78 vs 402 ± 83, P = 0.884), LDH levels (188 ± 7 vs 183 ± 8, P = 0.749), hemoglobin levels (13.5 ± 0.3 vs 12.8 ± 0.4, P = 0.197), bone marrow involvement (positive/negative, 1/8 vs 1/10, P = 1.000), detectability by CT scanning (positive/negative, 1/16 vs 4/13, P = 0.335), and FLIPI risk (low risk/other, 16/6 vs 13/6, P = 0.763), respectively in each case.

conclusionThese findings indicate that it is not feasible to predict 18F-FDG-avidity. Therefore, 18F-FDG-PET scans represent a complementary modality for the detection of gastrointestinal involvements in follicular lymphoma patients, and surveillance of the entire gastrointestinal tract by endoscopic examinations is required.