Tumor response under RECIST is primarily measured through imaging techniques such as CT scans and MRI. RECIST categorizes tumor responses into four main categories:
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.
