Oncologic Imaging
Live dataRECIST 1.1 Response
Classifies target-lesion tumour response from baseline, nadir and current sums of longest diameters.
The Response Evaluation Criteria In Solid Tumours (RECIST 1.1) provide a standardised measure of tumour burden change using the sum of longest diameters of target lesions, enabling reproducible categorisation of therapeutic response.
📐 Formula
CR / PR (≥30% ↓ from baseline) / PD (≥20% ↑ and ≥5 mm from nadir) / SD
🎯 When to Use
- Assessing target-lesion response of solid tumours on serial cross-sectional imaging.
- Oncology trial reporting and routine treatment-response follow-up.
- Determining progression to trigger a change in management.
⚙️ How It Works
- Sum the longest diameters of target lesions (short axis for nodal disease) at each time point.
- Percent change from baseline drives partial response; percent change from nadir drives progression.
- Complete Response (CR): disappearance of all target lesions (current sum = 0).
- Partial Response (PR): ≥30% decrease in sum relative to baseline.
- Progressive Disease (PD): ≥20% increase relative to nadir AND ≥5 mm absolute increase.
- Stable Disease (SD): neither sufficient shrinkage for PR nor sufficient increase for PD.
📊 Interpreting the Result
- CR and PR represent objective response; SD may still reflect clinical benefit.
- PD requires both the 20% relative and the 5 mm absolute thresholds to avoid over-calling small nadir changes.
- Non-target lesions and new lesions (assessed separately) can also define progression regardless of target-lesion sum.
⚠️ Limitations & Pitfalls
- Only reflects size change; does not capture necrosis, metabolic or functional response.
- Anatomic criteria may under-represent response to immunotherapy (see iRECIST).
- Measurement variability and lesion selection affect reproducibility.
📚 References
- Eisenhauer EA, Therasse P, Bogaerts J, et al. New response evaluation criteria in solid tumours: revised RECIST guideline (version 1.1). Eur J Cancer. 2009;45(2):228-247.
⚕️ For clinical decision support only. Always verify calculations and apply clinical judgment.