18F-FDG-PET/CT in the surveillance of patients with lymphoma

Objectives To assess the utility of 18F-FDG-PET/CT in detecting recurrence in patients with lymphoma free of disease during follow up. To define accurate patterns of recurrence.

Methods Patients with lymphoma were retrospectively and longitudinally included. Inclusion criteria: clinical complete remission and negative PET/CT study. The conventional surveillance was performed with PET/CT. Studies with at least one lesion with pathologic metabolism not explained by physiologic or inflammatory processes or doubtful lesions were interpreted as positive. Pathologic locations and their distribution (unique or multiple and supra and/or infradiafragmatic) were analyzed. The pathologic lesions were histologically or clinically evaluated with a minimal follow up of 8 months. Cases without diagnostic confirmation were excluded.

Results 186 PET/CT scans of 102 patients were included. 57 had a Hodgkin’s lymphoma and 45 a non Hodgkin’s lymphoma. 27 PET-CT scans were positive and suspicious of relapse. 13 were true positive (8 patients) and 14 false positive (10 patients). The rate of asymptomatic recurrences was of 7,8%. 16/27 studies showed pathologic lesions affecting multiple locations, 13 corresponding to demonstrated recurrence belonging to 8 patients (4 with supra and infradiafragmatic and 4 with infradiafragmatic involvement. The pattern more frequently related to recurrence was infradiafragmatic adenopatical involvement. The sensitivity, specificity, PPV, NPV and accuracy of PET-CT in detecting recurrence was 100%, 92%, 48%, 100% and 92 % respectively per study and 100%, 89%, 44%, 100% and 90 % respectively per patient.

Conclusions 18F-FDG-PET/CT is a sensitive technique in the detection of recurrence in asymptomatic patients. Nevertheless in positive studies, especially in cases of solitary locations, histological confirmation should be obtained