Use of liver magnetic resonance imaging after standard staging abdominopelvic computed tomography to evaluate newly diagnosed colorectal cancer patients.

Abstract

To investigate the impact of liver magnetic resonance imaging (MRI) in staging evaluation of newly diagnosed colorectal cancer patients. No clear guidelines regarding how to use liver MRI in evaluating newly diagnosed colorectal cancer. We included 863 adults who had newly diagnosed colorectal cancer without concomitant malignancies and received portal-phase contrast-enhanced abdominopelvic computed tomography (CT). Patients who had diminutive indeterminate hypoattenuating ["too-small-to-characterize" (TSTC)] hepatic lesions without other suspicious/indeterminate findings (TSTC-liver-on-CT), metastasis-negative hepatic findings (negative-liver-on-CT), and hepatic lesions suspicious or indeterminate for metastasis excluding TSTC lesions as seen on CT were identified. Per-patient rate of hepatic metastasis unsuspected by CT and the diagnostic yield of liver MRI for such lesions were assessed. There were 261 TSTC-liver-on-CT patients, 464 negative-liver-on-CT patients, and 138 patients with suspicious hepatic findings on CT. Among TSTC-liver-on-CT patients, the rate of hepatic metastasis was 2.2% (5/230, excluding patients without follow-up) and the yield of liver MRI was 3% (3/96). Negative-liver-on-CT patients gave the MRI yield of 0% (0/94). Among negative-liver-on-CT patients, the rate of hepatic metastasis discovered within 6 months of curative surgery was 1.1% (4/350, excluding patients without follow-up) when the liver was cleared by negative CT alone and 2% (2/88, excluding patients without follow-up) when cleared also by negative MRI (P = 0.347). Among the patients who had suspicious hepatic findings on CT, the MRI yield was 25% (19/77). The diagnostic yield of liver MRI for hepatic metastasis was very low in newly diagnosed colorectal cancer patients who showed TSTC hepatic lesions or metastasis-negative hepatic findings on CT. Staging liver MRI is likely unnecessary for them.