KRAS and colorectal cancer: The late implementation of PGx can in fact lead to discard potential useful drugs, or to the approval for unselected patients of drugs which are beneficial only in a subset of them: one clear example is the approval of cetuximab in 2004 for the treatment of unselected colorectal cancer patients, and the following discovery in 2006 of no-benefit, possibly detrimental, from the therapy in KRAS mutated patients[31].