Efficacy of 18F-FDG PET/CT in investigation of elevated CEA without known primary malignancy

• Published in: The Indian journal of radiology & imaging 2016-07, Vol.26 (3), p.405-410
• Main Authors: Wong, Simon Sin-man, Yu, Wong L, Wang, Ki, Ahuja, Anil T
• Format: Article
• Language: English
• Subjects: biological; Carcinoembryonic antigen; Histology; Influence; Investigations; neoplasms; Nuclear Med; Positron emission tomography; tomography; tumor markers; unknown primary; x-ray computed
• ISSN: 0971-3026; 0970-2016; 1998-3808; 0971-3026
• DOI: 10.4103/0971-3026.190412

Abstract Aim: To evaluate the efficacy of 18flurodeoxyglucose positron emission tomography/computer tomography (18F-FDG PET/CT) in investigating patients with elevated carcinoembryonic antigen (CEA) and without known primary malignancy, and the impact of PET/CT findings on patient management. Setting and Design: PET/CT scans done in a tertiary hospital between December 2007 and February 2012 for elevated CEA in patients without known primary malignancy were retrospectively reviewed. Materials and Methods: The PET/CT findings, patients' clinical information, level of CEA, histological diagnosis, and subsequent management were retrieved by the electronic patient record for analysis. Statistical Analysis : Data were analyzed using SPSS version 19. Results: One hundred and one PET/CT scans were performed for patients with elevated CEA. Fifty-eight of these were performed for patients with known primary malignancy and were excluded; 43 PET/CT scans were performed for patients without known primary malignancy and were included. Thirty-three (77%) had a positive PET/CT. Among the 32 patients with malignancy, 15 (47%) suffered from lung cancer and 8 (25%) suffered from colorectal cancer. The sensitivity (97%), specificity (82%), positive predictive value (94%), negative predictive value (90%), and accuracy (93%) were calculated. Thirty (91%) patients had resultant change in management. The mean CEA level for patients with malignancy (46.1 ng/ml) was significantly higher than those without malignancy (3.82 ng/ml) ( P < 0.05). In predicting the presence of malignancy, a CEA cutoff at 7.55 ng/ml will achieve a sensitivity of 91% and a specificity of 73%. Conclusion: PET/CT, in our study population, appears to be sensitive, specific, and accurate in investigating patients with elevated CEA and without known primary malignancy. In addition to diagnosis of underlying primary malignancy, PET/CT also reveals occult metastases which would affect patient treatment options.Its role in investigating patients with elevated CEA and without known primary, compared with other investigation modalities, remains to be studied.