PURPOSE

To report the detection rate of colorectal tumors with computed tomography (CT) performed within 1 year before diagnosis for indications other than colon abnormalities. Strategies to improve cancer detection are reported.

METHODS

Two board-certified, subspecialty-trained abdominal radiologists retrospectively reviewed patient health records and CT images with knowledge of tumor location/size. Patients were classified into 3 groups: prospective (colon abnormality suggesting neoplasm documented in radiologic report), retrospective (not documented in radiologic report but detected in our retrospective review of CT images), and undetected (neither prospectively nor retrospectively detected). Retrospective detection confidence and morphologic characteristics of each tumor were also recorded.

RESULTS

Of 209 included patients, 106 (50.7%) had prospectively detected tumors, 66 (31.6%) had retrospectively detected tumors, and 37 (17.7%) had undetected tumors. Asymmetric bowel wall thickening and polypoid masses were present more often in the retrospective group than in the prospective group (27% vs. 10.5% and 26% vs. 17.1%, respectively). Tumors in the ascending colon were more likely to be detected retrospectively than prospectively (odds ratio, 2.75; 95% CI 1.07-7.08; P = 0.04). Undetected tumors were smaller on average (2.9 cm) than prospective (6.0 cm) and retrospective (4.9 cm) tumors (P = 0.03). Detection confidence was lower for retrospectively detected tumors than for prospectively detected tumors (P = 0.03). Indications other than abdominal pain were most common for retrospectively detected tumors (P = 0.03). Use of intravenous contrast material was lowest in the undetected group (P = 0.003). The prospective group had more pericolonic abnormalities, regional/retroperitoneal lymph node involvement (P < 0.001), and distant metastases than did the retrospective group (P = 0.01).

CONCLUSION

Half of all colorectal tumors were not detected prospectively. Radiologists should perform meticulous colon tracking regardless of the indication for CT. The right colon merits additional examination. Polypoid and asymmetric morphologic characteristics were most often overlooked, but these characteristics can be learned to improve detection.