Run the technical gate before the response thresholds. Keep pretreatment-baseline PERCIST 1.0 separate from nadir, immune and multi-lesion variants, and always pair the hottest-lesion calculation with whole-study review.
{
"categories": [
{
"outcome_code": "CMR",
"label": "complete_metabolic_response",
"core_state": "all_tumor_uptake_resolved_to_background_without_new_cancer_typical_FDG_avid_lesions"
},
{
"outcome_code": "PMR",
"label": "partial_metabolic_response",
"core_state": "hottest_evaluable_lesion_SULpeak_decrease_at_least_30_percent_and_0.8_SUL_units_without_progression_override"
},
{
"outcome_code": "SMD",
"label": "stable_metabolic_disease",
"core_state": "does_not_meet_CMR_PMR_or_PMD_after_full_study_review"
},
{
"outcome_code": "PMD",
"label": "progressive_metabolic_disease",
"core_state": "qualifying_SULpeak_increase_or_new_cancer_typical_lesion_or_unequivocal_extent_or_nontarget_progression"
}
],
"applicability": {
"use_for": "Objective metabolic response assessment of FDG-avid solid malignancy on paired whole-body 18F-FDG PET or PET/CT examinations acquired with a protocol suitable for quantitative comparison.",
"classification_unit": "one_patient_at_one_follow_up_timepoint_relative_to_the_declared_pretreatment_baseline",
"required_inputs": [
"tumor_type_and_therapy",
"therapy_start_date",
"pretreatment_FDG_PET",
"follow_up_FDG_PET",
"lean_body_mass_normalized_SUL",
"liver_or_aortic_reference_measurements",
"injection_to_scan_times",
"serum_glucose",
"scanner_and_reconstruction_comparability",
"whole_study_new_lesion_review"
],
"outside_scope": [
"non_FDG_tracers",
"non_FDG_avid_tumors",
"lymphoma_when_disease_specific_Lugano_Deauville_is_required",
"brain_tumor_RANO_response",
"therapy_selection_or_prognosis_from_category_alone"
]
},
"baseline_measurability_gate": {
"tumor_metric": "SULpeak, the mean lean-body-mass-normalized uptake in the hottest approximately 1 mL spherical volume of interest, not SUVmax from one voxel.",
"normal_liver_reference": {
"region": "approximately_3_cm_spherical_VOI_in_normal_right_hepatic_lobe",
"minimum_tumor_SULpeak_formula": "1.5_times_liver_mean_SUL_plus_2_times_liver_SUL_standard_deviation"
},
"diseased_liver_alternative": {
"region": "descending_thoracic_aortic_blood_pool_tubular_VOI",
"minimum_tumor_SULpeak_formula": "2_times_aortic_mean_SUL_plus_2_times_aortic_SUL_standard_deviation"
},
"failure_rule": "If no tumor focus reaches the applicable baseline threshold, PERCIST 1.0 quantitative response is not assessable; describe the visual findings without manufacturing CMR, PMR, SMD or PMD.",
"lesion_size_note": "The method is uptake-defined. Small lesions can be limited by partial-volume effects; retain lesion size and technical confidence rather than treating a noisy value as exact."
},
"serial_acquisition_and_comparability_gate": {
"patient_preparation": [
"fast_at_least_4_hours",
"serum_glucose_below_200_mg_per_dL",
"record_glucose_and_injected_activity"
],
"uptake_timing": [
"both_scan_starts_50_to_70_minutes_after_injection_under_original_PERCIST",
"baseline_to_follow_up_uptake_time_difference_not_greater_than_15_minutes"
],
"equipment_and_processing": [
"same_scanner_at_same_site_when_possible",
"same_acquisition_protocol",
"same_reconstruction_protocol",
"same_software_version",
"injected_FDG_activity_difference_not_greater_than_20_percent"
],
"reference_stability": "Baseline and follow-up liver mean SUL must differ by no more than 20 percent of the larger measurement and no more than 0.3 SUL units.",
"noncompliance_rule": "State every failed comparability condition. Do not return a definitive threshold-based category when the protocol or reference instability makes the SUL change non-comparable; preserve a technical-not-assessable state for agent output."
},
"target_and_measurement_model": {
"primary_one_lesion_method": "Select the single hottest evaluable malignant focus at each timepoint. The follow-up focus need not be the same anatomic lesion as the baseline focus.",
"VOI": "Place an approximately 1 mL spherical VOI to obtain the highest mean SUL within the tumor and retain lesion identity, coordinates, image and SULpeak.",
"whole_study_guard": "The one-lesion calculation never replaces review of every imaged site for new malignant uptake, discordant nontarget progression, treatment effect, infection and physiologic uptake.",
"exploratory_five_lesion_method": "If a protocol prespecifies up to five lesions and no more than two per organ, retain that implementation separately and use the same declared aggregation method throughout; do not mix it with the core one-lesion result.",
"exploratory_TLG_boundary": "Metabolic tumor volume and total lesion glycolysis are exploratory in PERCIST 1.0. Do not silently substitute a whole-body TLG threshold for the core SULpeak categories."
},
"calculation_and_reference_rules": {
"percent_change_formula": "100_times_follow_up_hottest_SULpeak_minus_baseline_hottest_SULpeak_divided_by_baseline_hottest_SULpeak",
"absolute_change_formula": "follow_up_hottest_SULpeak_minus_baseline_hottest_SULpeak",
"reference_scan": "PERCIST 1.0 specifies the pretreatment baseline as the response reference. A nadir-based longitudinal variant must be named as a modification and reported separately.",
"timing_output": "Retain the number of weeks from therapy start with the percent and absolute SULpeak change; the categorical label alone discards important continuous information.",
"baseline_timing": "A practical implementation suggests obtaining the baseline examination within 21 days before therapy starts when feasible."
},
"patient_level_algorithm": [
{
"priority": 1,
"if": "technical_or_reference_comparability_gate_fails_or_no_measurable_baseline_tumor",
"output": "not_assessable_with_reasons"
},
{
"priority": 2,
"if": "credible_new_FDG_avid_lesion_typical_of_cancer_or_unequivocal_metabolic_or_anatomic_progression",
"output_code": "PMD"
},
{
"priority": 3,
"if": "all_known_tumor_uptake_is_below_mean_liver_and_indistinguishable_from_surrounding_background_and_no_new_lesions",
"output_code": "CMR"
},
{
"priority": 4,
"if": "SULpeak_decrease_at_least_30_percent_AND_absolute_decrease_at_least_0.8_SUL_units_AND_no_target_size_increase_over_30_percent_AND_no_new_or_unequivocally_progressive_disease",
"output_code": "PMR"
},
{
"priority": 5,
"if": "SULpeak_increase_at_least_30_percent_AND_absolute_increase_at_least_0.8_SUL_units_in_the_hottest_target_or_other_qualifying_progression",
"output_code": "PMD"
},
{
"priority": 6,
"if": "assessable_and_does_not_meet_CMR_PMR_or_PMD",
"output_code": "SMD"
}
],
"category_and_override_rules": {
"CMR_rule": "CMR requires metabolic resolution of every known lesion to background and no new cancer-typical focus; SULpeak need not become zero and a morphologic residual may remain.",
"PMR_AND_rule": "Both the relative decrease of at least 30 percent and the absolute decrease of at least 0.8 SUL units are required. Meeting only one threshold remains SMD unless another category applies.",
"PMD_AND_rule": "For the quantitative SULpeak branch, both the relative increase of at least 30 percent and the absolute increase of at least 0.8 SUL units are required.",
"new_lesion_override": "A new focus must be in a distribution typical of cancer and not better explained by infection, inflammation, treatment effect or physiologic activity. Confirm an equivocal focus before final PMD and retain the first-suspicion date if later confirmed.",
"nontarget_guard": "A modest isolated nontarget change does not automatically override PMR. An unequivocally progressive discordant lesion can establish PMD, but its lesion, magnitude and rationale must be recorded.",
"extent_and_size_guard": "An unequivocal increase in metabolic extent or a reproducible anatomic size increase can establish progression even when the hottest SULpeak branch alone is insufficient; label the progression mechanism."
},
"variant_boundaries": {
"PERCIST_1_0": "FDG SULpeak framework with the pretreatment baseline reference and four metabolic categories.",
"EORTC_PET": "Uses different SUV percentage thresholds and must not be labeled PERCIST.",
"immune_modified_PET_criteria": "iPERCIST, imPERCIST and disease-specific immunotherapy rules can require confirmation or different new-lesion handling. Never import those rules into conventional PERCIST 1.0 without naming the variant.",
"RECIST_boundary": "RECIST 1.1 measures anatomic diameters. Return metabolic PERCIST and anatomic RECIST results independently when both are requested.",
"lymphoma_boundary": "Use the protocol-specified Lugano and Deauville framework for FDG-avid lymphoma rather than assuming generic solid-tumor PERCIST."
},
"management_and_risk_context": {
"management_rule": "PERCIST is a response measurement framework, not an instruction to continue, stop or change therapy. The oncology team integrates pathology, regimen, timing, symptoms, laboratory data, anatomic imaging, toxicity and trial rules.",
"discordance_rule": "When metabolic and anatomic or clinical response disagree, return both supported results with their techniques and trigger expert review rather than forcing a blended category.",
"risk_rule": "The four labels are not individualized probabilities of survival, cure or future progression. Protocol variation, low avidity and biologic heterogeneity limit direct prognostic inference."
},
"output_contract": [
"PERCIST_1_0_and_any_named_modification",
"therapy_and_response_dates_with_weeks_since_start",
"baseline_and_follow_up_scanner_protocol_glucose_dose_and_uptake_times",
"liver_or_aortic_reference_mean_SD_and_stability",
"hottest_lesion_identity_at_each_timepoint_and_one_mL_SULpeak",
"relative_and_absolute_SULpeak_change",
"new_lesions_nontarget_discordance_and_progression_mechanism",
"CMR_PMR_SMD_PMD_or_not_assessable_with_reason",
"continuous_measurements_retained_with_category",
"no_autonomous_treatment_or_prognostic_claim"
],
"missing_input_behavior": [
"If lean-body-mass SULpeak or the baseline reference threshold is unavailable, do not substitute SUVmax or guess quantitative response.",
"If preparation, uptake timing, scanner, reconstruction or liver stability is not comparable, return technical limitation and withhold a definitive threshold category.",
"If a new focus is equivocal for tumor versus inflammation, infection, fracture healing or treatment effect, preserve possible progression and request corroboration.",
"If only one of the 30-percent and 0.8-SUL thresholds is met, do not round the case into PMR or PMD.",
"If the comparator is a nadir rather than pretreatment baseline, name the method as modified and do not present it as the unqualified PERCIST 1.0 result."
],
"interpretation_limits": [
"PERCIST depends on FDG avidity and technically comparable quantitative PET; it is not applicable to every tumor, tracer or therapy.",
"The hottest-lesion method can conceal interlesional heterogeneity unless the whole study and discordant lesions are explicitly reviewed.",
"Metabolic change can reflect inflammation, infection, glucose and uptake-time variation, scanner reconstruction or treatment effect rather than viable-tumor change."
],
"supporting_sources": [
{
"role": "primary_framework",
"citation": "Wahl et al. J Nucl Med. 2009;50 Suppl 1:122S-150S",
"doi": "10.2967/jnumed.108.057307",
"pmcid": "PMC2755245"
},
{
"role": "practical_clarification",
"citation": "O et al. Radiology. 2016;280:576-584",
"doi": "10.1148/radiol.2016142043",
"pmcid": "PMC4976461"
},
{
"role": "current_reference_catalog",
"citation": "US National Cancer Institute Imaging Response Criteria resource",
"url": "https://dctd.cancer.gov/research/research-areas/imaging/resources/response-criteria"
}
],
"source_locator": "Wahl et al. 2009, PMC2755245, Quantitative Approaches and Table 7 for baseline measurability, SULpeak, category thresholds and exploratory metrics; O et al. 2016, PMC4976461, Target Lesion at Baseline, Assessable FDG PET Study, Objective Response, PERCIST Categories, Nontarget Lesions and Unequivocal Progression for operational clarification."
}