The assessment of tumor status with regard to KRAS showed that 49% of the patients had wild-type tumors and 51% had mutant tumors. Benefit from treatment with TAS-102 was observed in both patient subgroups.Only 15% of tumor specimens were assessed for BRAF status— a patient cohort that was not sufficient to determine the extent of the benefit of TAS-102 in these cases. In summary, TAS-102 was shown to have clinical activity in a large population of Japanese and Western patients with heavily pretreated metastatic colorectal cancer, including those whose disease was refractory to fluorouracil. Such benefit was observed across essentially all prespecified
patient subgroups and was validated by means of a multivariate analysis. TAS-102 was associated with few serious adverse events, with neutropenia being the most frequently observed adverse event.