Response evaluation criteria in solid tumors (RECIST) - Cancer Science

What is RECIST?

The Response Evaluation Criteria in Solid Tumors (RECIST) is a standardized set of criteria used to evaluate the response of solid tumors to treatment. It provides a consistent and reproducible method to measure and compare treatment efficacy across clinical trials and routine practice.

Why is RECIST Important?

RECIST is crucial because it provides a common language for oncologists and researchers to describe tumor response. This standardization helps in determining the efficacy of therapies, comparing results from different studies, and making important decisions about patient care and drug approvals.

How is Tumor Response Measured?

Tumor response is typically measured using imaging techniques like CT scans or MRIs. RECIST defines four categories of response:

Complete Response (CR): Disappearance of all target lesions.
Partial Response (PR): At least a 30% decrease in the sum of the diameters of target lesions.
Progressive Disease (PD): At least a 20% increase in the sum of the diameters of target lesions or the appearance of new lesions.
Stable Disease (SD): Neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for PD.

What are Target Lesions?

Target lesions are specific tumors identified at baseline that are measured over time to assess response. They are chosen based on size, visibility, and suitability for measurement. Non-target lesions are other cancerous growths that are monitored but not measured for response.

What are the RECIST Versions?

There are two main versions of RECIST:

RECIST 1.0: Introduced in 2000, it provided the first standardized criteria for measuring tumor response.
RECIST 1.1: Released in 2009, this version includes updates such as reducing the number of target lesions to a maximum of five and incorporating guidelines for assessing lymph nodes.

How are Lymph Nodes Evaluated in RECIST 1.1?

In RECIST 1.1, lymph nodes are considered target lesions if they are 15 mm or larger in the short axis. Nodes smaller than 10 mm are considered normal, and those between 10 and 15 mm are non-target lesions.

What are the Limitations of RECIST?

While RECIST is widely used, it has limitations. It primarily considers changes in tumor size, which may not fully capture the effectiveness of some treatments like immunotherapy or targeted therapies. These treatments may cause initial tumor swelling or other non-size-related changes. Additionally, RECIST does not account for tumor heterogeneity or the presence of micrometastases.

Are There Alternatives to RECIST?

Yes, other criteria have been developed to address some of RECIST's limitations. These include:

Immune-related Response Criteria (irRC) for evaluating response to immunotherapies.
Choi Criteria for assessing response in gastrointestinal stromal tumors.
PERCIST for evaluating metabolic response using PET scans.

How is RECIST Used in Clinical Trials?

In clinical trials, RECIST is integral for determining primary endpoints such as overall response rate (ORR), progression-free survival (PFS), and overall survival (OS). It helps in assessing the effectiveness of new treatments and in making regulatory decisions.

Conclusion

RECIST remains a cornerstone in oncology for evaluating the response of solid tumors to treatment. Despite its limitations, its standardized approach allows for consistent and objective measurement of tumor changes, facilitating advancements in cancer treatment and research.