Disappearing liver metastases from colorectal cancer: impact of modern imaging modalities.

BACKGROUND: Chemotherapy is often used before a resection for colorectal liver metastases. After chemotherapy, metastases may disappear on cross-sectional imaging but residual metastatic disease may still exist. The aim of this retrospective study was to investigate the impact of new advancements in imaging technology such as magnetic resonance imaging (MRI) with liver-specific contrast (Gd-EOB-DTPA) and contrast-enhanced intra-operative ultrasound (CE-IOUS) on disappearing liver metastases (DLM).
METHODS: Twenty-nine patients with one or more DLM undergoing surgical exploration were included. Pre-operative imaging consisted of contrast-enhanced multi-detector computed tomography (MDCT) and/or MRI with liver-specific contrast. At surgery, CE-IOUS was used when tumours known from pre-chemotherapy imaging were not found by inspection or intra-operative ultrasound.
RESULTS: Patients presented 66 DLM. At surgical exploration, 42 DLM were identified and treated (64%). CE-IOUS detected one additional DLM not found by intra-operative ultrasound. For metastases ≤10 mm on histological analysis, imaging sensitivities for MRI and MDCT before surgery but after chemotherapy were 26/49 (53%) and 24/66 (36%), respectively.
CONCLUSION: A majority of DLM are identified during surgery using intra-operative ultrasound, with only little additional value of CE-IOUS. The sensitivities of post-chemotherapy imaging modalities for small metastases are low in the setting of DLM. For surgical planning, an optimized pre-chemotherapy imaging is essential.