RECIST v1.0 vs v1.1
title: “RECIST v1.0 vs v1.1” type: comparison category: recist/comparison tags: [recist, v11-change, recist-10, recist-11, version-comparison] sources:
- file: “recist_eisenhauer_2009.pdf” page: “228-247”
- file: “recist_sohaib_2012.pdf” page: “entire” date_created: 2025-04-15 date_modified: 2025-04-15 confidence: high anki_deck: “Radiology::RECIST” weak_area: false
Overview
RECIST 1.1 was published in 2009 by the EORTC RECIST Working Group, revising the original RECIST 1.0 (2000) which itself replaced the WHO bidimensional criteria (1981). The revision incorporated evidence from analysis of >6,000 patients and addressed ambiguities that arose in 9 years of clinical use.
Summary of Changes
| Feature | RECIST 1.0 | RECIST 1.1 |
|---|---|---|
| Target lesions | Max 10 total, ≤5 per organ | Max 5 total, ≤2 per organ |
| Lymph node measurement | Longest diameter (all lesions) | Short axis diameter |
| Normal node threshold | Not specified | Short axis <10mm |
| CR definition | Disappearance of all lesions | Disappearance + nodes <10mm SAD |
| Confirmation of CR/PR | Required (4 weeks) | Required only in non-randomized trials |
| New lesion definition | Not specified | Fully operationalized; FDG-PET incorporated |
| Unequivocal progression | Not defined | Clarified for non-target lesions |
| Stable Disease | Not formally defined | Formally defined vs. nadir |
1. Target Lesion Count Reduction (10→5, 5/org→2/org)
v1.0: Up to 10 target lesions total, maximum 5 per organ v1.1: Up to 5 target lesions total, maximum 2 per organ
Rationale: Analysis showed 5 lesions capture equivalent information to 10, with less measurement burden and lower inter-reader variability. The 2-per-organ limit ensures disease from multiple organ systems is represented rather than over-sampling one metastatic site.
Impact: With fewer targets, some disease is not numerically tracked. Measurable lesions not selected become non-targets. Overall response assessment remains unchanged.
2. Lymph Node Measurement (Longest → Short Axis)
v1.0: All lesions measured by longest diameter, including lymph nodes v1.1: Lymph nodes measured by short axis diameter (SAD); all other lesions by longest diameter
Rationale: Short axis diameter is the most reproducible nodal measurement — it is least affected by the imaging plane. Nodes are 3D structures; their longest diameter varies significantly with patient positioning and scan angle. Short axis represents the true cross-sectional nodal burden.
Node thresholds established in v1.1:
- <10mm SAD: Normal — not recorded
- 10–14mm SAD: Pathological but non-measurable — non-target only
- ≥15mm SAD: Pathological and measurable — target or non-target eligible
Impact: A node that measured 18mm longest diameter in v1.0 might now measure 14mm short axis — becoming non-measurable. This affects baseline selection and CR criteria.
3. Complete Response Definition (Nodes Added)
v1.0: CR = disappearance of all lesions v1.1: CR = disappearance of all extra-nodal lesions AND all lymph nodes (target and non-target) with short axis <10mm
Rationale: Residual nodes are common after effective treatment, especially in lymphoma and testicular cancer. v1.1 clarified that a node <10mm SAD is normal — satisfying CR even if visible. v1.0’s “disappearance of all lesions” was impossible to meet in many patients with treated nodal disease.
4. Confirmation Requirement
v1.0: CR and PR required confirmation at 4 weeks in ALL trials v1.1: CR and PR confirmation required ONLY in non-randomized trials where response is the primary endpoint
Rationale: In randomized trials, the control arm provides an internal comparison — confirming response is less critical. Removing the confirmation requirement in randomized trials reduces trial duration and patient burden. In single-arm phase II trials where ORR is the sole basis for drug approval, confirmation remains essential to prevent transient measurement variability from inflating response rates.
5. New Lesion Definition and FDG-PET Integration
v1.0: New lesions mentioned as PD trigger but never formally defined or operationalized v1.1: New lesions fully defined; FDG-PET incorporated for new lesion detection
New lesion rules in v1.1:
- New lesions must be unequivocal — not attributable to technique differences
- Equivocal lesions → repeat scan for confirmation
- Lesions in anatomical locations not imaged at baseline → automatically new
- Ultrasound-detected new lesions → require CT/MRI confirmation
- FDG-PET rules (see New Lesions):
- Baseline PET positive → new PET focus = PD
- Baseline PET negative → new PET focus = PD
- No baseline PET → need CT confirmation
Rationale: FDG-PET detects metabolically active new disease before structural change appears on CT. This is clinically significant — new FDG-avid metastatic deposits represent true disease progression even when CT shows no new anatomical lesion.
6. Unequivocal Progression Clarified
v1.0: Non-target “unequivocal progression” was not defined v1.1: Unequivocal progression of non-target disease is defined as substantial worsening that changes overall tumor burden; modest increases are insufficient
Rationale: The subjectivity of “unequivocal” led to inconsistent application in v1.0. v1.1 clarified that only substantial, unambiguous worsening qualifies — not every size increase.
7. Stable Disease Formally Defined
v1.0: SD implicitly meant “neither PR nor PD” — no formal definition v1.1: SD formally defined as: neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for PD, taking as reference the nadir sum
Clarification (2016): SD must have at least one measurement at a timepoint after study entry. SD cannot be assigned from baseline alone — the patient must have at least one follow-up measurement demonstrating neither PR nor PD.