Open accessPosition article and guidelinesJournal forImmunoTherapy of CancerSociety for Immunotherapy of Cancer(SITC)consensus definitions forresistance to combinations of immunecheckpoint inhibitorsHarriet Kluger,J Carl Barrett,2 Justin F Gainor,3 Omid Hamid,Michael Hurwitz,Theresa LaVallee,5 Rebecca A Moss,Roberta Zappasodi,7.8.9Ryan J Sullivan ,3 Hussein Tawbi,10 Elad Sharon 11To cite:Kluger H,Barrett JC.ABSTRACTdo not initially respond to ICI monotherapyGainor JF,efa/.Society forImmunotherapy is the standard of care for several(ie,primary resistance)and recurrence mayImmunotherapy of Cancercancers and the field continues to advance at a rapid(SITC)consensus definitions foroccur even after periods of extended diseasepace,with novel combinations leading to indications in anresistance to combinations ofincreasing number of disease settings.Durable responsescontrol(ie,secondary resistance).12immune checkpoint inhibitorsPreviously,the Society for ImmunotherapyJournal for lmmunoTherapyand long-term survival with immunotherapy have beenof Cancer (SITC)developed consensus defi-of Cancer2023;11e005921.demonstrated in some patients,though lack of initialbenefit and recurence after extended disease controlnitions for clinical phenotypes of resistance todoi:10.1136jtc-2022-005921remain major hurdles for the field.Many new combinationsingle-agent checkpoint blockade for thera-Additional supplementaregimens are in development for patients whose diseasepies targeting programmed cell death proteinmaterial is published online only.progressed on initial immunotherapy.To guide clinical trial1 and its ligand (PD-(L)1).3 The definitionsTo view,please visit the joumadesign and support analyses of emerging molecular andidentified minimum drug exposure require-online (http://dx.doi.org/10.cellular data surrounding mechanisms of resistance,thements,best response,and requirements for1136tc2022-005921).Society for Immunotherapy of Cancer (SITC)previouslyconfirmatory scans to define primary resis-generated consensus clinical definitions for resistancetance,secondary resistance,and diseaseAccepted 17 January 2023to single-agent anti-PD-1 immune checkpoint inhibitors(ICIs)in three distinct scenarios:primary resistance,progression after discontinuation of therapysecondary resistance,and progression after treatmentto support standardized study enrolmentdiscontinuation.An unmet need still exists,however,forcriteria and facilitate appropriate compari-definitions of resistance to ICl-based combinations,whichsons in post-anti-PD-(L)1 clinical trials.Therepresent an expanding frontier in the immunotherapySITC-defined resistance phenotypes fortreatment landscape.In 2021.SITC convened a workshopmonotherapy have been shown to be associ-including stakeholders from academia,industry.andated with distinct clinical outcomes includinggovernment to develop consensus definitions fortumor burden,tumor growth,likelihood toresistance to ICl-based combination regimens forreceive further syste
