Prospective comparison between magnetic resonance imaging and computed tomography in colorectal cancer staging.

BACKGROUND: Diffusion-weighted (DW) imaging is a functional magnetic resonance imaging (MRI) technique that detects lesions with high cellularity, such as malignant tumours. This prospective study was performed to compare the accuracy of DW-MRI with multidetector computed tomography (MDCT) in staging of colorectal cancer.

METHODS: Thirty patients with histologically proven colorectal cancer were prospectively recruited. Each patient underwent both MDCT and DW-MRI of the abdomen-pelvis for primary staging. Images were evaluated for nodal and distant metastases. The reference standard was histopathological findings for nodal involvement and surveillance imaging for suspected hepatic metastases.

RESULTS: The primary cancers were located in the rectum (n = 16, 53.3%), sigmoid colon (n = 9, 30%) and right colon (n = 5, 16.6%). For nodal metastases, the sensitivity and specificity of DW-MRI were 84.6% (95% confidence interval (CI): 54.6-98.1%) and 20.0% (95% CI: 2.5-55.6%) compared with 84.6% (95% CI: 54.6-98.1%) and 40.0% (95% CI: 12.2-73.8%) for MDCT. For liver metastases, the sensitivity and specificity for DW-MRI were 100.0% (95% CI: 63.1-100.0%) and 100% (95% CI: 84.6-100%) compared with 87.5% (95% CI: 47.4-99.7%) and 95.5% (95% CI: 77.2-99.9%) for MDCT. DW imaging altered the clinical management in three (10.0%) patients by detecting missed hepatic metastases in two patients and accurately diagnosing another patient with a hepatic cyst, mistaken for metastasis on MDCT.

CONCLUSION: DW-MRI is more accurate for detecting hepatic metastases in colorectal cancer compared with MDCT.