Staging of primary colorectal carcinomas with fluorine-18 fluorodeoxyglucose whole-body PET: correlation with histopathologic and CT findings.

PURPOSE: To evaluate the diagnostic usefulness of positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) in patients with primary colorectal carcinomas. MATERIALS AND METHODS: Forty-eight patients with biopsy-proved (n = 44) or high clinical suspicion for (n = 4) colorectal cancer underwent whole-body PET after intravenous administration of 10 mCi (370 MBq) of FDG. FDG PET results were correlated with computed tomographic (CT), surgical, and histopathologic findings. RESULTS: PET depicted all known intraluminal carcinomas in 37 patients (including two in situ carcinomas) (sensitivity, 100%), but findings were false-positive in four of seven patients without cancer (three with inflammatory bowel conditions, one who had undergone polypectomy). Specificity was 43% (three of seven patients); positive predictive value, 90% (37 of 41 patients); and negative predictive value, 100% (three of three patients). No FDG accumulation was noted in 35 hyperplastic polyps. FDG PET depicted lymph node metastases in four of 14 patients (sensitivity, 29%). Results were similar to those obtained with CT (true-positive, two of seven patients [sensitivity, 29%]; true-negative, 22 of 26 patients [specificity, 85%]). FDG PET depicted liver metastases in seven of eight patients and was superior to CT, which depicted liver metastases in three patients (sensitivity of 88% and 38%, respectively). FDG PET and CT, respectively, correctly depicted the absence of liver metastases in 35 and 32 patients (specificity, 100% and 97%; negative predictive value, 97% and 86%). CONCLUSION: FDG PET has a high sensitivity and specificity for detection of colorectal carcinomas (primary and liver metastases) and appears to be superior to CT in the staging of primary colorectal carcinoma.

Superiority of SPET to planar imaging in the detection of colorectal carcinomas with 111In monoclonal antibodies.

The aim of this study was to assess the contribution of single photon emission tomography (SPET) to planar imaging of colorectal carcinoma in patients being evaluated with 111In-labelled monoclonal antibodies CYT-103 (OncoScint CR/OV) or IVP ZCE 025. Planar and SPET scans from 110 colorectal carcinoma patients were scored individually as follows: 1=negative, 2=equivocal, 3=positive. The planar and SPET images identified 67 and 93 of 113 documented lesions, respectively. The planar and SPET findings were concordant in 55 patients. SPET converted planar findings from 1 to 3 in 11 patients and from 2 to 3 in 21 patients. SPET provided a better definition of the extent of the tumour in 21 patients. Both imaging tests were true-negative in five patients, and failed to detect tumours in six patients. We strongly recommended SPET in all patients undergoing immunoscintigraphy, since it identified tumours missed on planar scans in 35% of patients and provided additional information regarding tumour burden in 23% of patients.