Preoperative imaging for hepatic resection of colorectal cancer metastasis

Abstract

Despite recent advances in chemotherapeutic agents, the prognosis for metastatic colon cancer remains poor. Over the past two decades, hepatic metastasectomy has emerged as a promising technique for improving survival in patients with metastatic colon cancer and in some cases providing long-term cure. To maximize safety and efficacy of metastasectomy, appropriate pre-operative imaging is needed. Advancements in computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) have led to improved detection of occult lesions and better definition of surgical anatomy. While CT, PET and MRI have a comparable sensitivity for detection of large liver metastases, MRI excels at detection of subcentimeter liver metastases compared to CT and FDG-PET, especially with the combination of diffusion weighted imaging (DWI) and hepatocyte-specific contrast agents. CT may be useful as a screening modality or in preoperative planning such as volumetric estimation of the remnant liver size or in defining preoperative arterial anatomy for hepatic artery infusion pump placement. While technologic advancements have led to unprecedented image quality and clarity, this does not replace the need for a dedicated, competent radiologist with experience in hepatic imaging.

Keywords: Colorectal metastases; hepatic artery infusion pump; hepatic resection; preoperative imaging; volumetrics.

Figure 1

Aberrant hepatic arterial anatomy. Cross-sectional imaging can help identify anomalous arterial anatomy prior to placement of hepatic artery infusion pumps. (A) depicts a normal hepatic artery originating from the celiac trunk, white arrows in (B) and (C) show replaced right and left hepatic arteries, respectively.

Figure 2

Colorectal liver metastases on CT, PET, and MRI. A 48-year-old woman with multiple liver metastases in the right hepatic lobe imaged on contrast-enhanced CT (A), 18FDG-PET (B), and MRI (C-F), within a five-week period. On MRI, T1 weighted pre-contrast (C), T1 weighted post-contrast (D), T2 weighted (E) and diffusion weighted imaging (F) sequences are obtained routinely.

Figure 3

Small colorectal liver metastases on MRI using delayed hepatobiliary phase imaging and diffusion weighted imaging. A 52-year-old woman who underwent percutaneous radiofrequency ablation in the right hepatic lobe (large arrow), developed a 3-mm recurrence within two months (small arrow), visible on (A) diffusion weighted imaging (DWI) and (B) delayed hepatobiliary phase imaging with Gd-EOB-DTPA. Two months later, this recurrence grew to 7 mm and innumerable additional metastases appeared, as seen on (C) DWI and (D) delayed hepatobiliary phase imaging.

Figure 4

Volumetric analysis of the liver to estimate remnant liver volume. Three-dimensional reconstructions can be created from cross-sectional imaging using specialized computer software. Here, a program from Pathfinder Therapeutics, Nashville, TN, is used to plan a left hepatectomy. The lesion is depicted in green and a resection plane can be drawn to avoid major vessels while maintaining an adequate margin. Preoperative liver volume (PLV) and remnant liver volume (RLV) can be calculated and displayed.