Colorectal cancer (CRC) is one of the most common malignancies in Western countries. Over the last 20 years, and the last decade in particular, the clinical outcome for patients with metastatic CRC (mCRC) has improved greatly due not only to an increase in the number of patients being referred for and undergoing surgical resection of their localised metastatic disease but also to a more strategic approach to the delivery of systemic therapy and an expansion in the use of ablative techniques. This reflects the increase in the number of patients that are being managed within a multidisciplinary team environment and specialist cancer centres, and the emergence over the same time period not only of improved imaging techniques but also prognostic and predictive molecular markers. Treatment decisions for patients with mCRC must be evidence-based. Thus, these ESMO consensus guidelines have been developed based on the current available evidence to provide a series of evidence-based recommendations to assist in the treatment and management of patients with mCRC in this rapidly evolving treatment setting.

Introduction: The RAS/RAF/MAP kinase–ERK kinase (MEK)/extracellular-signal-regulated kinase (ERK) (MAPK) and the PI3K/AKT/mammalian target of rapamycin (mTOR) (PI3K) pathways are frequently deregulated in human cancer as a result of genetic alterations in their components or upstream activation of cell-surface receptors. These signalling cascades are regulated by complex feedback and cross-talk mechanisms. Areas covered: In this review the key components of the MAPK and AKT pathways and their molecular alterations are described. The complex interactions between these signalling cascades are also analysed. Expert opinion: The observation that the MAPK and the PI3K pathways are often deregulated in human cancer makes the components of these signalling cascades interesting targets for therapeutic intervention. Recently, the presence of compensatory loops that activate one pathway following the blockade of the other signalling cascade has been demonstrated. Therefore, the blockade of both pathways with combinations of signalling inhibitors might result in a more efficient anti-tumor effect as compared with a single agent. In addition, the MAPK and PI3K pathways are activated by mutations that coexist or can be mutually exclusive. In this regard, a large-scale characterization of the cancer genome might offer personalized cancer genomic information, which may improve the anti-tumor efficacy of signalling inhibitors.