Evaluation of efficacy and clinical impact of 18F-FDG-PET in the diagnosis of recurrent medullary thyroid cancer with increased calcitonin and negative imaging test

Abstract

AimTo evaluate the efficacy and clinical impact of the FDG-PET in the diagnosis of suspicion of recurrence of medullary thyroid cancer (MTC) in patients with elevated serum calcitonin and negative imaging test. Material and methodsWe performed a retrospective study of 31 consecutive cases from February 2001 to October 2007 of 17 women and 14 men, mean age 56.2 years (range: 26–88), with anatomical-pathology diagnosis of MTC and suspicion of recurrence due to abnormal elevation of calcitonin and negative imaging tests. All the patients underwent whole body FDG-PET scan with a dedicated PET or PET-CT 60min after intravenous injection of 333–434 MBq of 18F-FDG. Results were confirmed by pathology study in 45.2% of the patients and by clinical follow-up with a mean of 4 years (range: 16 months–8 years). ResultsSensitivity was 88%, specificity 84.6%, positive predictive value (PPV) 88%, negative predictive value (NPV) 84.6% and diagnostic accuracy 87%. The results of the FDG PET modified the therapeutic strategy in 14 cases (45.2%). A comparison was made of the mean values of calcitonin using the Student's t-test between positive PET studies for the disease and negative ones. No significant differences were found (p=0.3). ConclusionsIn patients with MTC and suspected recurrence with elevated calcitonin and negative imaging test, the FDG is the best test for the diagnosis of occult recurrence in MTC with elevated calcitonin and negative imaging techniques with elevated clinical impact. It facilitates the therapeutic management of the patients with MTC recurrence, and should be included in the diagnosis algorithm in these patients.