target lesion
Measurable lesion selected for quantitative monitoring in treatment response assessment protocols.
Full Definition
A target lesion is a measurable tumor lesion selected for quantitative monitoring during treatment response assessment according to standardized criteria such as RECIST. Target lesions must be accurately measurable in at least one dimension, clearly defined, and representative of the overall tumor burden. Typically, up to five lesions per organ and ten lesions total are selected as targets, prioritizing the largest lesions. Target lesions are measured at baseline and follow-up imaging to calculate overall response. The selection and measurement of target lesions must follow strict protocols to ensure reproducible and meaningful response assessment.
Usage
Usage note: Always specify measurement methodology and comparison timepoint.
In Context
- "Five target lesions were identified for RECIST assessment, including the large hepatic metastasis." — Baseline staging report
- "The sum of target lesion diameters decreased by 35% compared to baseline measurements." — Response evaluation report