Response evaluation criteria in solid tumors

The Response Evaluation Criteria in Solid Tumors (RECIST) provide standards for solid tumor response assessments. The resist method requires to measure the overall tumor burden at baseline and use it as comparator for subsequent measurements.

Using the RECIST standard you can obtain the following response for a solid tumor

• Complete Response (CR),
• Partial Response (PR),
• Stable disease (SD),
• Progressive (worsening) disease (PD),

There are 3 types of lesion in the overall tumor response assessment.

• Target lesions are defined as those followed quantitatively. Theye are measured at every visit, and their measurements are added to get the sum of diameters.
• Non-target lesion as defined as those followed qualitatively, as a whole. Theye are evaluated as ‘present’, ‘absent’ or ‘unequivocal progression’.
• New lesions are evaluated in a qualitative and binary fashion, and the appearance of a new lesion is interpreted as progression.

Investigator assessments of the lesion status, along with an overall response assessment have to be reported for each tumor assessment time-point.

The main objective of the exercise is to obtain the response of the tumor to the treatment. To derive the response, we need to have the following information:

• Identify Longest Diameter (LD) for non-nodal target lesions
• Identify Short Axis (SA) for target lymph nodes
• Add up sum of diameters (SOD) from LD and SA
• Calculate percentage change from nadir SOD
• Calculate percentage change from baseline SOD

Please note that the “nadir” is the smallest SOD prior to the current assessment.