Utility of low dose 18F-FDG PET-CT in patients with suspected colorectal carcinoma recurrence using conventional diagnostic methods

Abstract

ObjectiveTo evaluate the efficacy of 18F-FDG PET-CT in the diagnosis of recurrence of colorectal cancer (CRC) in patients with elevated values of carcinoembryonic antigen (CEA) and/or signs of recurrence in the multidetector computerized tomography (MDCT), and to demonstrate that good results can be obtained applying the as low as reasonably achievable (ALARA) principles. Material and methodsA retrospective study of 54 patients with suspected CRC, who underwent an 18F-FDG PET-CT, administering a mean dose of 222MBq (6mCi) of 18F-FDG, from 07/2007 to 01/2011 was carried out. Seven patients were excluded, thus studying 47 patients (27 males, 20 females, mean age 63 years). Recurrence was confirmed by histopathology study in 14 cases and by clinical evolution in 33.The patients were divided into 4 groups. A: patients with elevation of CEA and suspected recurrence in the MDCT. B: elevation of CEA, without suspicious lesions in the MDCT. C: normal levels of CEA and positive MDCT. D: normal levels of CEA and uncertain MDCT. ResultsWe found sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and overall accuracy of 91%, 69%, 89%, 75% and 85% respectively. For group A, we found 100% sensitivity, in group B, 75% sensitivity with 100% specificity, for C, sensitivity was 89% with 71% specificity. Finally, in group D, sensitivity was 100% and specificity 60%, respectively. ConclusionApplying a low dose, the 18F-FDG PET-CT has high diagnostic performance in patients with suspicion of CRC, approaching in a higher grade the ALARA criteria.