KRAS and colorectal cancer: For example, kras-mutant colorectal cancer is resistant to treatment with the EGFR antibody cetuximab, but kras-wild-type tumor tissue responds rather well to the treatment with this antibody.9 The restriction of phase 1 trials to subpopulations makes these studies more costly, since the requirement for highly specific patient populations triggers a longer recruitment period and a higher number of participating study sites.