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Response
Evaluation Criteria
in Solid Tumor

RECIST provides simple and pragmatic standardised criteria to assess new cancer treatments by measuring changes in tumour size, with validation and updates overseen by the RECIST Working Group.

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Guidance for Cancer
Treatment Evaluation

The mission of the RECIST Working Group is to ensure that RECIST undergoes continued testing, validation and updating.

The evolving landscape of oncology

RECIST continuously adapts to advancements in diagnostics, treatments, and patient care, ensuring its relevance in the fight against cancer.

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Precision medicine

How to adapt to therapies targeting individual tumor genetics for accurate treatment assessment?

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Beyond tumour size

How to integrate functional and metabolic changes to assess advanced targeted agent efficacy?

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Advanced imaging

How to incorporate PET-CT and advanced MRI for deeper insights into tumor biology and response?

Frequently asked questions

RECIST (Response Evaluation Criteria in Solid Tumors) provides standardized guidelines to assess tumor response in oncology trials using imaging. It defines measurable lesions, specifies how to select target and non-target lesions, and outlines criteria for response categories: Complete Response (CR), Partial Response (PR), Stable Disease (SD), and Progressive Disease (PD). Measurements are typically based on the sum of the longest diameters of target lesions on CT or MRI. Changes in this sum over time determine response status, ensuring consistency across sites and studies. RECIST is applied at predefined time points during the trial and is critical for evaluating treatment efficacy, supporting regulatory submissions, and enabling comparison between therapies.

RECIST is freely available. To apply RECIST in your trial:

1. Include RECIST in the protocol: Specify that tumor response will be assessed according to RECIST (e.g., RECIST 1.1 or iRECIST) and outline key principles such as lesion selection, measurement schedule, and response categories.

2. Define imaging requirements: Detail imaging modalities (CT, MRI), timing of scans, and anatomical coverage to ensure consistency.

3. Provide guidance in CRFs: Design case report forms to capture all necessary data—target lesion measurements, non-target lesion status, and new lesion documentation—at each assessment time point. An example is provided here.

4. Train investigators and radiologists: Ensure all involved personnel understand RECIST rules and protocol-specific instructions.

Proper planning guarantees standardized, reproducible response evaluation across sites.

iRECIST (immune RECIST) was developed to address unique response patterns seen with immunotherapies, such as pseudoprogression (initial tumor enlargement or new lesions followed by regression). Under RECIST 1.1, such changes would be classified as progression, potentially leading to premature discontinuation of effective treatment. iRECIST introduces concepts like unconfirmed progression (iUPD) and confirmed progression (iCPD), requiring additional imaging to verify progression before stopping therapy. This ensures patients are not withdrawn from immunotherapy too early.

In short: RECIST is for conventional therapies; iRECIST captures what happens after RECIST progression in immunotherapy trials to account for atypical response patterns.

The guidelines and examples of CRFs for RECIST 1.1 can be found here.
The guidelines and examples of CRFs for iRECIST can be found here.

There is currently no software available through the RECIST Working Group

You can leave a question on the contact page.

This contact form should not be used to ask for advice on individual cases. While we are happy to provide advice on how to use the guidelines, we cannot provide interpretation for cases in a trial. This mailbox is not monitored on a daily basis. There may be delay in responses. Therefore, please consult an experienced radiologist or a panel of experts to look at your specific case.

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