Intraoperative detection of disappearing colorectal liver metastases as a predictor of residual disease.

Purpose: The aim of this study was to evaluate the intraoperative detection rate of residual liver metastases after chemotherapy and to assess the correlation between disappeared liver metastases (DLMs) upon preoperative imaging and complete pathological response.

Methods: Between February 2004 and December 2008 clinicopathological data of 292 consecutive patients who underwent liver resection for colorectal liver metastases were prospectively collected and analyzed in a "per lesion" study. Thirty-three patients with 67 DLMs were included.

Results: During laparotomy, we identified 45 out of 67 DLMs (67%). Six DLMs were detected by macroscopic liver examination (9%) and 39 (58%) by intraoperative ultrasound (IOUS). Overall, persistent microscopic residual disease at pathological examination of the resected specimen or recurrence in situ identified during the follow-up were observed in 41 (61.2%) of 67 LMs that had shown a complete response by imaging. At multivariate analysis moderate or severe hepatic steatosis (p = 0.016), subglissonian localization of nodules (p = 0.019) and residual microscopic disease (p = 0.0006) were associated with IOUS detection of residual metastases. Preoperative chemotherapy with more than six cycles (p = 0.022) and intraoperative detection of nodules by IOUS (p = 0.001) were independent predictors of residual disease.

Conclusions: Systematic US exploration of the liver leads to increase the intraoperative detection rate of DLMs. Furthermore, the majority of DLMs identified by IOUS presents residual disease at pathological examination and should be treated.