To verify if faster tumor shrinkage may be used as a prognostic factor, a retrospective analysis of 113 irinotecan-refractory patients enrolled in four clinical trials (BOND, EVEREST, SALVAGE and BABEL) not only showed that the decrease in tumor size was greater in KRAS wild-type patients when compared to mutants (mean relative change −13.73% versus +2.27%, p < 0.001), but also that the rapid tumor shrinkage correlated with a better outcome [62]. The gene discussed is KRAS; the disease is neoplasm.