Objective: To assess 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) images in primary thyroid lymphoma (PTL) patients before and after treatment.
Methods: We conducted a retrospective review of data for ten patients (four men, six women) of mean age 65 (range 48-88) years, with histopathologically confirmed malignant thyroid lymphoma who underwent pre-treatment and post-treatment 18F-FDG PET between January 2005 and December 2014. Thyroid uptake was assessed by the 5-point scale score based on maximum intensity projection images.
Results: Four of the ten patients were judged to have a complete metabolic response (scores 1-3) and four to have a partial metabolic response (PMR; scores 4-5). Three of the four PMR patients had a good outcome with a treatment-free interval and overall survival of at least 53.0 months, although two of these three patients showed residual FDG uptake in the thyroid for more than 2 years after completion of treatment. Two of the ten patients were considered to have progressive metabolic disease.
Conclusions: In patients with PTL, residual FDG uptake in the thyroid after treatment that corresponds to a PMR may not always indicate a poor outcome.
Keywords: 5-Point scale; FDG PET/CT; Lugano classification; Primary thyroid lymphoma; Treatment response.