Positron emission tomography for preoperative staging in patients with locally advanced or metastatic colorectal adenocarcinoma in lymph node metastasis.

Background/aims: The impact of positron emission tomography was prospectively evaluated using 18 (F)-fluoro-deoxyglucose (FDG-PET) for the detection of lymph node (LN) metastasis in preoperative locally advanced colorectal adenocarcinoma, compared with computed tomography (CT) and pathologic findings.

Methodology: Fifty-three patients who were suspected of LN involvement by CT were staged preoperatively for LN metastasis using FDG-PET and CT. Regional LNs were classified into 3 groups, N1, N2-3, and N4, according to the Japanese General Rules for Clinical and Pathological Studies on Cancer of the Colon, Rectum and Anus (6th Edition). A comparison of pathologic findings with CT and FDG-PET findings was used to calculate sensitivity, specificity, and accuracy.

Results: The sensitivity, specificity and accuracy of CT/FDG-PET were 91.3%/52.2%, 91.7%/75.0% and 65.9%/72.3%, respectively, for N1, 91.7%/75.0%, 72.2%/94.4% and 77.1%/89.6%, respectively, for N2-3, and 100%/100%, 17.6%/100% and 41.7%/100%, respectively, for N4. The detection rate of the num ber of metastatic N1 LNs by CT was significantly higher than by FDG-PET, and not significantly in the N2-4 area. LNs hidden by strong halation of the primary tumor were not detected by FDG-PET.

Conclusions: While FDG-PET is markedly more sensitive than CT for detection of N4 LN involve. ment, the number of metastatic LNs is difficult to determine.