Gastrointestinaltoxicities(GIT),includingoralmucositis,nauseaandvomiting,anddiarrhea,arecommonsideeffectsofchemotherapyandtargetedagentsinpatientswithadvancedcolorectalcancerandpancreaticcancer.Beingoftenunderreported,itisstilldifficulttopreciselyestablishtheirburdenintermsofbothpatient’squalityoflifeandcancercarecosts.Moreover,withtheuseofmoreintensiveupfrontcombinationregimens,thefrequencyofthesetoxicitiesisrapidlygrowingwithapotentialnegativeeffectalsoonpatient’soutcome,asaresultofdosereductions,delaysorevendiscontinuationofactivetreatments.Thus,identifyingpatientsathigherriskofdevelopingGITaswellasanoptimalmanagementareparamountinordertoimprovepatient’scomplianceandoutcome.Afterthedescriptionofthemaintreatment-inducedGIT,wediscussthecurrentknowledgeonthepathophysiologyofthesesideeffectsandcommentthescalescommonlyusedtoassessandgradethem.WethenprovideacriticalupdateonGITincidencebasedontheresultsofkeyrandomizedtrialsconductedinpatientswithmetastaticcolorectalcancerandadvancedpancreaticcancer.
