What is RECIST?
RECIST (Response Evaluation Criteria In Solid Tumors) is a set of standardized guidelines used to assess and quantify the response of solid tumors to treatment in clinical trials. Introduced in 2000 and revised as
RECIST 1.1 in 2009, these criteria provide a consistent method to measure tumor size and response, which is critical for evaluating the efficacy of
oncological therapies.
Why is RECIST Important?
RECIST is crucial for ensuring uniformity and reproducibility in clinical trials. By providing a standardized framework, it allows for the comparison of results across different studies and aids in the regulatory approval process for new cancer treatments. This standardization helps in making informed decisions about the efficacy of new drugs and therapies.
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 and Non-Target Lesions?
In the context of RECIST,
target lesions are selected based on their size and visibility and are used to quantitatively evaluate treatment response. Typically, up to five lesions total (and no more than two per organ) are identified as target lesions.
Non-target lesions are all other lesions that are not selected as target lesions and are assessed qualitatively.
How are Changes in Tumor Size Calculated?
The changes in tumor size are calculated using the sum of the longest diameters of the target lesions at baseline and during follow-up. This sum is compared to the sum at baseline to determine the percentage change, which then categorizes the response as CR, PR, SD, or PD.
What are the Limitations of RECIST?
While RECIST is widely used, it has limitations. It primarily focuses on
tumor size and may not fully capture the complexities of tumor biology, such as changes in tumor density or metabolic activity. Additionally, RECIST may not be as effective in evaluating the response of certain cancers, such as
sarcomas or
lymphomas, which require different assessment criteria.
How Has RECIST Evolved?
Since its inception, RECIST has undergone revisions to address its limitations and incorporate new understanding of tumor biology. RECIST 1.1, the latest version, introduced several updates, including the reduction in the number of target lesions and more precise definitions of progressive disease. These changes aim to improve the accuracy and reliability of response assessments.
Future Directions for RECIST
Ongoing research aims to further refine RECIST criteria to better capture the complexity of tumor response. The incorporation of advanced imaging techniques and biomarkers, such as
PET scans and
liquid biopsies, is being explored to provide a more comprehensive assessment of treatment efficacy.
