Diagnostic Performance of Non-Colonographic Routine CT for Detecting Advanced Colorectal Cancer

Advanced-stage colorectal cancers (CRCs) are occasionally detected on routine abdominal CT scans performed in daily clinical practice. This study aimed to evaluate the diagnostic performance of routine CT scans for detecting advanced CRCs.

We studied patients who underwent routine CT examinations for gastrointestinal symptoms or abnormalities between March 2015 and April 2025, and who subsequently underwent colonoscopy within six months. CT images were interpreted by two radiologists as part of routine clinical practice. Colonoscopic and pathological findings were used as reference standards for advanced CRC (p-T2 or deeper). Diagnostic performance was expressed as percentages with 95% confidence intervals.

A total of 350 patients were reviewed (female 44.6%; mean age 64.6 ± 17.2 years; intravenous contrast administration 44.6%). Colonoscopy identified 46 advanced CRCs (median size 56 mm; range 16-105 mm; T2 n=1, T3 n=16, T4 n=18, unknown n=11; proximal colon n=13, distal colon n=16, rectum n=17). Except for one CRC obscured by a large gastric gastrointestinal stromal tumor, all remaining 45 CRCs were suspected on CT (sensitivity 97.8% [88.5-99.9]). Among 304 patients without advanced CRC, 292 were correctly classified as negative (specificity 96.1% [93.2-97.9]). The positive predictive value, negative predictive value, and overall accuracy were 78.9% [66.1-88.6], 99.7% [98.1-100], and 96.3% [93.7-98.0], respectively. In subgroup analysis stratified by contrast enhancement, diagnostic accuracy was 96.8% [92.7-99.0] with contrast and 95.9% [92.0-98.2] without contrast (p=0.65).

Routine abdominal CT without colonographic technique demonstrated excellent diagnostic performance for detecting advanced CRC.