Introduction to RECIST 1.1 (1)

Based on the revised RECIST 1.1 guidelines, the derivation of overall response depends on the classification of disease at baseline and the evaluation of three distinct categories: target lesions, non-target lesions, and the appearance of new lesions.


1. Categorization of Lesions at Baseline

To determine response, overall tumor burden must be estimated at baseline:

  • Target Lesions: Up to a maximum of five measurable lesions total (and no more than two per organ) are identified to be followed quantitatively. A "sum of diameters" is calculated for these lesions.

  • Non-Target Lesions: All other disease sites, including non-measurable lesions and pathological lymph nodes not selected as target lesions, are recorded qualitatively.

  • Measurability: Non-nodal lesions are measurable if they are >=10 mm; lymph nodes must have a short axis of >=15 mm to be considered target lesions.

2. Time Point Response Derivation

At each evaluation, an overall response status is determined based on the combined assessment of all lesion categories.

Patients with Target Disease

Target LesionsNon-Target LesionsNew LesionsOverall Response

Complete Response (CR): Disappearance of all lesions; nodes <10 mm 

CR 

No 

CR 

CR 

Non-CR/Non-PD 

No 

Partial Response (PR) 

PR: >=30% decrease in sum of diameters 

Non-PD or not all evaluated 

No 

PR 

Stable Disease (SD): Neither PR nor PD 

Non-PD or not all evaluated 

No 

SD 

Progressive Disease (PD): >=20% relative increase AND >=5 mm absolute increase in sum 

Any 

Yes or No 

PD 

Any 

Unequivocal PD 

Yes or No 

PD 

Any 

Any 

Yes 

PD 


Patients with Non-Target Disease Only

For trials allowing patients without measurable disease, response is primarily qualitative:

  • CR: Disappearance of all non-target lesions and normalization of tumor markers.

  • Non-CR/Non-PD: Persistence of one or more non-target lesions.

  • PD: Unequivocal progression of existing non-target lesions or appearance of new lesions.

3. Determining Best Overall Response (BOR)

The BOR is the best response recorded from the start of treatment until the end of study.

  • Confirmation: In non-randomized trials where response is the primary endpoint, a CR or PR must be confirmed by a second assessment, generally at least 4 weeks later.

  • SD Requirements: To be assigned a BOR of SD, the patient must follow the protocol-specified minimum interval for SD (typically not less than 6–8 weeks).

  • Progression Rules: If a patient achieves SD or PR at the first time point but progresses before the minimum duration for SD is met, the BOR is PD






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