Analysis of discordant PET and CT findings in 18F-FDG PET-CT scans in the management of oncology patients.

BACKGROUND: Discordant findings are often noted between PET-CT and CT images of 18F-FDG PET-CT scans and cause ambiguity in image interpretation. This study aimed at determining the significance of these findings in the management of oncology patients. CONTEXT: Discordant findings are often noted between PET-CT and CT images of 18F-FDG PET-CT scans and cause ambiguity in image interpretation. AIM: This study aimed at determining the significance of these findings in the management of oncology patients. METHODS: This was an observational, descriptive study. Hence, retrospective analysis of all discordant findings in oncology patients undergoing a PETCT imaging between Jan 2013 and Jan 2016 was done. Those patients who had a follow-up period of minimum 1 year in either of the following forms - repeat PETCT imaging, other radiological imaging, clinical, or histopathological evidence were included. From all the discordant lesions, the sensitivity, specificity, positive predictive, negative predictive value, and accuracy of both PET-CT and CT modalities were determined. RESULTS: Of 348 discordant lesions, 16.7% was noted in soft tissues, 25% in viscera, 28.7% in lungs, 14.1% in lymph nodes, and 15.5% in bones. At the end of follow-up, 15.2% lesions were PET true positive, 57.5% PET true negative, 10.1% CT true positive lesions, 13.8% CT true negative, and 3.4% were inconclusive. CONCLUSION: 18F-FDG PET-CT is superior to CT imaging and should be considered as the first-line imaging modality in oncology patients.