Role of FDG-PET/CT in cases of incidentally detected raised serum CEA with no known malignancy: Experience in a tertiary care referral center

Objectives Elevated CEA is found in a number of cancers including colonic, pancreatic, gastric, lung, and breast. But it is nonspecific. The objective was to investigate the role PET in patients with incidentally elevated CEA and -ve conventional work-up.

Methods The study included 15 asymptomatic patients with raised CEA referred for FDG-PET/CT after a negative conventional work-up including OGD, colonoscopy and CT abdomen, during 2003-2008. Patients with a previous history of malignancy were excluded. Final diagnosis was made by Clinical, Biochemical and histopath examinations.

Results 8 patients had +ve PET/CT scans, of which 5 (33.3%) were medullary thyroid cancer (MTC) and 3 (21%) lung cancer. Of the 7 negative PET scans, 4 were shown to be benign (BPH, fibroadenoma, colonic polyps, goiter), while 3 are not yet to be diagnosed. All the patients with medullary thyroid cancer were found to have raised serum calcitonin.

Conclusions 53% of patients had +ve PET/CT, which in the final analyses turned out to be malignant lesions. In cases with negative PET/CT scan, no malignancies were detected during a 12 month follow up period. Majority of patients (62.5%) with a positive FDG-PET/CT scan and raised CEA had MTC. In all such cases hypermetabolic nodules were detected on PET/CT scans, which turned out to be medullary carcinomas at the final diagnosis. It can be inferred that serum calcitonin, which is a recognized marker for medullary thyroid carcinoma should be routinely checked in patients with raised CEA before subjecting such patients to the more expensive procedures like PET/CT.