Accuracy of PET/CT for the Detection of Synchronous Malignant Lesions in Patients With Endoscopically Obstructive Colorectal Cancer.

BACKGROUND

This study aimed to assess the diagnostic performance of positron emission tomography/computed tomography (PET/CT) in detecting synchronous malignant lesions in the proximal colon in endoscopically obstructive left-sided colorectal cancer.

MATERIALS AND

METHODS

All patients with a biopsy-proven left-sided endoscopically obstructive colorectal cancer who had a preoperative PET/CT scan and a postoperative total colonoscopy within 6 months after the index surgery between January 2015 and July 2024 at a comprehensive cancer center were enrolled into the study. The synchronous malignant lesions on PET/CT were confirmed with the pathologic examination of the subtotal/total colectomy specimen and postoperative total colonoscopy. The primary endpoint was to evaluate the diagnostic performance of PET/CT in detecting synchronous malignant lesions, and the second endpoint was to determine the ability of PET/CT to distinguish malignant lesions from advanced adenomas.

RESULTS

Out of 90 patients, 50 (55.6%) were male with a mean age of 62.46±10.81 years. The obstructing malignant lesions detected on colonoscopy were located in the rectum, n=8 (8.9%), rectosigmoid junction, n=29 (32.2%), sigmoid colon, n=31 (34.4%), descending colon, n=16 (17.8%), and distal part of the transverse colon, n=6 (6.7%). Nine areas of abnormal fluorodeoxyglucose (FDG) uptake on PET/CT in the proximal part of the colon with a mean SUVmax value of 19.23 (range: 6.4-42) were identified in 6 patients. Four patients with synchronous lesions on PET/CT underwent a total colectomy. Two patients with synchronous lesions on PET/CT were treated with segmental resection with subsequent postoperative endoscopic submucosal dissection (ESD) for the synchronous lesion. The detection rate of PET/CT for synchronous malignant lesions was 4.4% (n=4) with a sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of 100%, 94.4%, 44.4%, 100%, and 94.6%, respectively.

CONCLUSIONS

PET/CT demonstrated a high sensitivity and a high negative predictive value in detecting synchronous malignant lesions located in the proximal colon distal to the obstructing left-sided colorectal cancer. As a result, patients underwent a single-stage surgery and were spared from an unnecessary second surgical intervention.