FDG-PET/CT Is Superior to Enhanced CT in Detecting Recurrent Subcentimeter Lesions in the Abdominopelvic Cavity in Colorectal Cancer

Yoon, Hai Jeon; Lee, Jong Jin; Kim, Yu Kyeong; Kim, Sang Eun

Abstract

PURPOSE
This study aims to compare the performance of contrast-enhanced computed tomography (CeCT) and 18 Ffluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) in detecting small tumor implants and metastatic lymph nodes (LNs) in the abdominopelvic cavity in patients with colorectal cancer.
METHODS
We enrolled 16 patients who were clinically suspected of experiencing a recurrence (6 male, 10 female; mean age 61+/-14 years). All subjects underwent CeCT and PET/CT, and the performance of these methods was compared with regard to detecting recurrences. The final diagnosis of a recurrence was made clinically.
RESULTS
CeCT identified 38 lesions in 12 patients, all of which were detected by PET/CT. PET/CT found 27 additional lesions in 8 patients, comprising 9 seeding nodules (2 in the right upper quadrant of the abdomen and 7 in the pelvic cavity) and 18 LNs (2 celiac, 2 paraaortic, 2 hepatic hilar, 11 common iliac, 1 external iliac). Most additional lesions were located in the pelvic cavity (approximately 78% of seeding nodules and 67% of lymph nodes). The maximum standardized uptake value (SUVmax) of the additional seeding nodules that were detected solely by PET/CT was significantly higher compared with the CeCT- and PET/CT-confirmed nodules (5.5+/-4.2 vs. 2.9+/-2.5, p=0.03). The seeding nodules that were detected only by PET/CT were significantly smaller than the CeCT- and PET/CT-confirmed nodules (long axis: 1.0+/-0.3 cm vs. 2.0+/-1.1 cm, p=0.001; short axis: 0.8+/- 0.3 cm vs. 1.4+/-0.8 cm, p=0.004; mean of both axes: 0.9+/- 0.3 cm vs. 1.7+/-0.9 cm, p=0.001). Similarly, PET/CT-onlydetected LNs were significantly smaller than CeCT- and PET/CT-identified LNs (0.7+/-0.1 cm vs. 2.3+/-1.2 cm, p<0.0001).
CONCLUSION
PET/CT is superior to CeCT in detecting seeding nodules and metastatic LNs in patients with recurrent colorectal cancer. Specifically, PET/CT detects subcentimeter lesions in anatomically deformed pelvic cavities.