Immune-Modified 18F-FDG PET Response Criteria—PECRIT, PERCIMT, and imPERCIST

ParameterPECRIT (15)PERCIMT (17)imPERCIST 5 (18)
Tumor typeMelanomaMelanomaMelanoma
Timing3–4 wk3 mo3 mo
Standard of referenceClinical benefit: PR or CR at 4 mo or SD ≥ 6 mo per RECIST 1.1 (45)Clinical benefit: composite of clinical follow-up, 18F-FDG PET/CT, brain MRI, and LDHFollow-up and overall survival
Definition of responseCR or PR: per RECIST 1.1CR: resolution of all lesions on PE, 18F-FDG PET/CT, and brain MRI; decrease or no increase in LDH; no new lesionCR, PR, or SD: per PERCIST in 5 lesions
PR: decrease in size or resolution of lesions on PE, 18F-FDG PET/CT, and brain MRI; decrease or no increase in LDH; no new lesion
SD: per RECIST 1.1 and >15.5% increase in SULpeak per PERCIST (46)SD: neither CR/PR nor PD
Definition of progressionPer RECIST 1.1No clinical benefit and new lesions on 18F-FDG PET/CT as followsChange in sum of SULpeak in 5 lesions > 30%
For lesions < 1 cm require ≥ 4 new lesions
For lesions 1–1.5 cm require ≥ 3 new lesionsNew lesions can be incorporated
For lesions > 1.5 cm require ≥ 2 new lesions
Emphasis and advantagesCombining anatomic and metabolic criteriaIncorporation of clinical benefit in criteriaNew lesions are incorporated to sum of metabolic activity of lesions and not immediately considered PD
Early response assessmentNumber and metabolic size of new lesions on 18F-FDG PET/CT
  • PECRIT = PET/CT Criteria for Early Prediction of Response to ICI Therapy; PERCIMT = PET Response Evaluation Criteria for Immunotherapy; imPERCIST = Immunotherapy-Modified PERCIST; LYRIC = Lymphoma Response to Immunotherapy Criteria; iPERCIST = Immune PERCIST; HL = Hodgkin lymphoma; PR = partial response; CR = complete response; SD = stable disease; LDH = lactate dehydrogenase; PE = physical examination; CMR = complete metabolic response; PMR = partial metabolic response; SMD = stable metabolic disease; PD = progressive disease; SULpeak = lean body mass–corrected SUVpeak; PMD = progressive metabolic disease; UPMD = unconfirmed PMD; IR = indeterminate response; SPD = sum of product of diameters; CPMD = confirmed progressive metabolic disease; PPD = product of perpendicular diameters.