The search strings include “colorectal cancer AND (crosstalk OR communication) AND (signalling OR pathway) AND therapy resistance”, “colorectal cancer AND (monotherapy OR combinational therapy) AND drug resistance AND MAPK pathway”, “colorectal cancer AND (monotherapy OR combinational therapy) AND drug resistance AND PI3K pathway”, “colorectal cancer AND (monotherapy OR combinational therapy) AND drug resistance AND Wnt pathway”, “colorectal cancer AND drug resistance AND Notch”, and “colorectal cancer AND (MAPK OR PI3K OR Wnt OR Notch) AND drug resistance”. This evidence concerns the gene PIK3CA and colorectal cancer.