PDGFRB and gastrointestinal stromal tumor: Regorafenib (BAY 73-4506, Stivarga®) is an oral multi-kinase inhibitor with anti-angiogenic (VEGFR 1-3 and TEK), anti-stromal (PDGFR and FGFR) and anti-tumourigenic (KIT, RET, RAF1 and BRAF) properties with efficacy in pre-clinical [11] phase I/II [12, 13] and phase III clinical studies for GIST [8].