Key points
- RECIST: partial response means a 30% decrease from baseline; progression means a 20% increase and at least 5 mm from the smallest value, or a new lesion [1].
- With immunotherapy, confirm the first progression with imaging 4 to 8 weeks later (iRECIST) [2].
- FDG-avid lymphomas are assessed with PET-CT and the Deauville score; a score of 1 to 3 at the end of treatment means complete metabolic response [3].
RECIST 1.1
| Concept | Definition |
|---|---|
| Measurable lesion | Longest diameter of 10 mm or more on CT with a slice thickness of 5 mm or less |
| Target lymph node | Short axis of 15 mm or more; 10 to 15 abnormal but non-target; below 10 normal |
| Target lesions | At most 5 lesions, and 2 per organ |
| CR | Disappearance of all lesions; nodes below 10 mm |
| PR | A decrease of 30% or more in the sum of diameters from baseline |
| PD | An increase of 20% or more from the smallest sum and at least 5 mm, or a new lesion, or unequivocal progression of non-target lesions |
| SD | Neither PR nor PD |
Calculator: RECIST response.
iRECIST in immunotherapy
With immunotherapy, a tumour sometimes looks larger at first and then shrinks (pseudoprogression). iRECIST calls the first progression iUPD; if the patient is clinically stable, treatment continues and imaging is repeated 4 to 8 weeks later; a further increase or another new lesion means iCPD [2].
The Lugano criteria in lymphoma
| Score | FDG uptake |
|---|---|
| 1 | No uptake above background |
| 2 | Less than or equal to mediastinum |
| 3 | Above mediastinum and less than or equal to liver |
| 4 | Moderately above liver |
| 5 | Markedly above liver, or new lesions |
| X | New uptake unlikely to be lymphoma |
At the end of treatment, a score of 1 to 3 is complete metabolic response; a score of 4 to 5 with reduced uptake is partial response, unchanged is stable disease and increased is metabolic progression [3]. On interim PET, the interpretation of a score of 3 depends on the protocol (de-escalation or escalation of treatment). Lymphomas with low FDG avidity are assessed with CT [3].
References
3 referencesShow all references, 1 with a study cardClose the reference list
Numbers in the text, such as [1], refer to these sources. Sources with a “Study card” button are summarised in the site’s evidence library.
- 1
- 2
- 3
This page is based on reputable scientific sources and was last updated on 28 October 2026. The content of this website is for educational and informational purposes only and does not replace consultation, diagnosis or treatment by a specialist physician. Consult your treating physician about any treatment decision.
Printed from the website; the full and up-to-date version: https://drdabiri.com/en/learn/tumor-response-recist-lugano/