Tumour response — CT / MRI (RECIST 1.1)

CTMRIRECIST 1.1 (2009)

Objective tumour-response assessment at a follow-up scan against baseline and the prior nadir.

Applies to

Follow-up CT or MRI in a patient with measurable baseline target disease

Does not apply to

Patients with non-target disease only (RECIST uses a separate response table)
Best-overall-response, response confirmation, and progression-free survival (trial-protocol concepts)
Response criteria other than RECIST 1.1 (e.g. iRECIST, mRECIST, Lugano, PERCIST)

What to report

Tap an item to check it off while dictating.

1.Measurable baseline disease
Confirm the assessment is anchored to a baseline with measurable target disease; use the same modality and technique at every timepoint.
2.Target lesion selection
Up to 5 lesions total, ≤2 per organ, representative of all involved organs. Non-nodal ≥10 mm (long axis); lymph node ≥15 mm short axis. Prefer reproducible lesions.
Pitfall: A node with short axis 10–<15 mm is non-target; <10 mm is normal. A lesion in a previously irradiated field is a target only if it has since progressed.
3.Measurement technique
Long axis for non-nodal lesions, short axis for nodes (kept in the sum even after normalising). On CT the 10 mm threshold assumes slice ≤5 mm; for thicker slices use twice the slice thickness. A lesion too small to measure defaults to 5 mm; a disappeared lesion is 0 mm.
Pitfall: Do not enter 0 for a faint, too-small lesion — that means 'disappeared' and can produce a false CR/PR.
4.Sum of diameters
Report the current sum of target diameters and compare it with the baseline sum and the prior nadir (smallest sum on study).
5.Non-target lesions
Assess qualitatively: CR (all resolved, nodes <10 mm, markers normal), Non-CR/Non-PD, or unequivocal PD. Unequivocal progression means substantial overall worsening — not a modest increase in one lesion.
6.New lesions
Any unequivocal new lesion means PD, including disease in a region not imaged at baseline. An equivocal finding is clarified on follow-up before being called new.
7.Overall response
Combine target response, non-target response, and new lesions into the overall category (CR / PR / SD / PD / NE).

Response calculator

RECIST 1.1 response

RECIST 1.1 (2009)

For patients with baseline target disease. Assesses one follow-up timepoint against baseline and the prior nadir.

Target lesions

OrganTypeBaseline long axisCurrent

Baseline sum: —

Prior nadir sum

Smallest sum on study before this scan, including baseline; equals the baseline sum at the first follow-up.Non-target responseUnequivocal PD = substantial overall worsening, not a modest increase in one lesion.New lesionsAn equivocal new lesion is not coded “yes”; confirm on follow-up.

Complete the target lesions, prior nadir, non-target response, and new-lesion status to see the response.

Sources

RECIST 1.1 guideline — Eisenhauer EA et al. Eur J Cancer (2009)
RECIST 1.1 (teaching) — The Radiology Assistant (2015)

Content review: Content pending clinical review · 2026-07-10

Educational reference for trained clinicians. Verify every result against the cited original guideline before use. Not a substitute for clinical judgment or medical advice.