Oncosurgical Strategies for Unresectable Liver Metastases

Abstract

Negative prognostic factors for survival have been previously used to exclude patients from hepatic resection. For patients with colorectal metastases, these factors included high number and large size of metastases, and the presence of extrahepatic disease [4, 5]. The same considerations have been made regarding the width of the resection margin [4, 5]. Empirically, a resection margin of 1 cm or more was used as one of the important selection criteria for hepatic resection of colorectal metastases. Regardless the fact that extensive tumor involvement is associated with unfavorable outcome, long-term survival can be achieved in a large number of patients when complete resection is performed of both intrahepatic and extrahepatic tumor deposits. In addition, it has been shown that a tumor-free resection margin is of more prognostic importance than its width [6]. The improved knowledge of the influence of prognostic factors and of the established impact of complete resection on long-term outcome has resulted in a pragmatic definition of unresectability. In current practice, a liver remnant that is too small in relation to the extent of the resection needed to achieve radicality is the only remaining indicator of unresectability. Patients are considered resectable as long as all liver metastases can be completely resected with tumor-free margins, while leaving at least 25–30% of remnant liver volume to prevent postoperative liver insufficiency [7]. In general, resection margins of >1 cm are recommended, but it should not limit hepatic resection as long as it can be macroscopically complete. Additionally, the presence of resectable extrahepatic disease is no longer considered as a contraindication for surgery. The main causes that are responsible for technical unresectability are therefore multinodularity, large metastases, vascular-ill location of metastases, and extensive extrahepatic disease. In practice, patients with liver metastases can be divided into three categories: 1. Easily resectable. In this group, liver metastases can be completely resected with adequate oncological margins of normal parenchyma. In general, no need exists to improve resectability of the metastases before proceeding to surgery. 2. Marginally resectable. These patients present with more extensive hepatic disease, limiting the possibilities of upfront surgery. Surgery may be limited by difficulties in achieving tumor-free margins due to large tumor involvement. Furthermore, the need for major hepatectomy might endanger a required remnant liver volume of 25–30%. Finally, patients with limited hepatic disease and concomitant resectable extrahepatic disease can also be ascribed to this group. Different methods may be used for these patients to reduce tumor load and to improve “curativity” of resection. 3. Definitely unresectable. This group represents a subset of patients with widespread hepatic disease with extensive concomitant extrahepatic disease, usually disseminated over multiple metastatic sites. In most cases, both upfront chemotherapy treatment and intraoperative strategies are mandatory to control and downsize the metastatic disease and to technically enable curative surgery in these patients. Obviously, the chance of further resectability decreases from group 1 to group 3. However, owing to the increasing efficacy of chemotherapy, some patients will be switched to complex and/or sequential surgery, even when presenting initially as “definitely” unresectable.