The concept of oligometastases in colorectal cancer: from the clinical evidences to new therapeutic strategies

Purpose of review The concept of oligometastases, defining cancers with limited metastatic capacity and attaining a limited number of secondary sites, is now widely accepted, particularly in colorectal cancer. Currently, however, accurate predictive markers for oligometastatic tumors are still lacking. For this reason, it remains challenging to translate this concept into clinical recommendations. In the present work, we review recent publications on oligometastases in colorectal cancer, showing the evidences for such presentation and underlying the need for the identification of biomarkers, necessary to further develop new therapeutic strategies. Recent findings This review of recently published series confirms that long-term survival and cure could be obtained in patients undergoing surgical resection for colorectal metastases, particularly in the cases of liver metastases. Similar results are observed in other secondary sites such as in pulmonary metastases. Furthermore, in patients with unresectable metastases, significant survival benefit could be still obtained using nonresectional targeted approaches, as thermal ablation or stereotactic radiotherapy. Although these clinical evidences could now serve as proof-of-concept for the existence of an oligometastatic phenotype in colorectal cancer, neither clinical characteristics nor biological biomarkers have been established to be able to prospectively define the patients that will benefit from such therapeutic approaches targeting the metastatic sites. This emphasizes the need for further studies aiming at better defining early clinical and biological characteristics of these patients. As, currently, the reliable identification of the oligometastatic patients could only rely on the demonstration of favorable long-term outcomes after metastases-directed therapies, we propose that retrospective studies will be pivotal to analyze this question. Summary Extensive research is undergoing to define biologically the oligometastatic phenotype in colorectal cancer. Currently, the selection of the patients for potentially curative metastasectomy remains mostly empirical.