[27], [28], [29], [30]. In addition, it has been shown that the emergence of KRAS mutant clones can be detected months before radiographic progression [27], [29]. In colorectal cancer, it has been suggested that early initiation of a MEK inhibitor may be a rational strategy for delaying or reversing drug resistance [27], [29]. The gene discussed is KRAS; the disease is colorectal cancer.