Prospective Translational Study Investigating Molecular Predictors of Resistance and Response to Regorafenib Monotherapy

This is an exploratory translational research study to obtain research biopsies of RAS mutant metastatic colorectal cancer (mCRC) tumour tissue prior to commencement of regorafenib multi-tyrosine kinase inhibitor (MKI) treatment targeting vascular endothelial growth factor receptor (VEGFR), tumour microenvironment and oncogenic driver alterations, and again at development of resistance. Candidate markers of resistance will be identified in tissue biopsies through genetic and other molecular analysis and parallel collection of serial blood specimens will facilitate the identification of resistance markers and the tracking of resistance evolution in circulating nucleic acids. Early dynamic contrast enhanced MRI (DCE-MRI) along with diffusion weighted (DW)-MRI imaging at the beginning, and on day 15+/-7 post treatment will be performed. Additionally, dual contrast enhanced CT (DECT) will be performed according to routine clinical evaluation time points before drug administration and at 8 weeks after drug administration. Disease will be monitored with serial CT scans of the chest abdomen and pelvis (CT-CAP) every eight weeks, until progression. The aim of the study is to identify novel predictive biomarkers of resistance and response to this targeted therapy in mCRC previously treated with oxaliplatin, fluoropyrimidines and irinotecan, using genetic, epigenetic, transcriptomics, proteomic and live tissue culture methods. These molecular analyses will be performed on metastatic tumour tissue samples taken firstly before commencement of regorafenib, and secondly on progression of disease, and thirdly from archival primary or metastatic tumour tissue. There is an additional biopsy at 8 weeks in patients with response or stable disease, as determined by Response Evaluation Criteria in Solid Tumours (RECIST) 1.1 criteria.