Limitations of RECIST guidelinesLimitations of RECIST guidelines

Srinivasa R Prasad MDSrinivasa R Prasad MDAssociate Professor, RadiologyAssociate Professor, Radiology

University of Texas Health Science Center at University of Texas Health Science Center at San AntonioSan Antonio

RECIST GuidelinesRECIST Guidelines

• Response Evaluation Criteria In Solid Tumors

• Assumes spherical growth of round / ovoid tumors

• Uni-dimensional measurement technique– Less cumbersome, Simple math

• Arbitrary number of measurable lesions– 5/organ; 10/patient

• Target lesions: >1cm (Helical); >2cm (Non-helical)

• Measurement on axial images

• Increase in the threshold for classifying response as disease progression

• Primary modality: CT scan

RECIST GuidelinesRECIST Guidelines

Limitations of RECIST guidelinesLimitations of RECIST guidelines

• No criteria for non-solid tumors • No toxicity criteria• Lower rate of disease progression?• Not applicable to Non-Cytotoxic drugs?

Change in Tumor Form: Change in Tumor Form: From Solid to Non-SolidFrom Solid to Non-Solid

• Tumor morphology– Confluent, Irregular borders– Unusual configuration; Circumferential (eg.

mesothelioma)– Lesion length > 1.5-2 times lesion width

• Discordant results due to RECIST technique– Uni-dimensional measurement– Shape changes may confound results

Limitations of RECIST guidelinesLimitations of RECIST guidelines

Lesion Confluence and Lesion Confluence and Relationship to Normal Relationship to Normal Anatomical StructuresAnatomical Structures

Unusual Lesion Unusual Lesion ConfigurationConfiguration

Lesion Morphology: Mesothelioma

• Non-spherical, asymmetric tumor growth

• Tumor size: Sub-centimeter tumors

• Choosing representative tumor burden– Problematic when tumor burden is substantial

– Differential tumor response

Limitations of RECIST guidelinesLimitations of RECIST guidelines

Differential tumor Differential tumor behaviorbehavior

Pre

Post

• Discordant results due to RECIST technique– Unusual Tumor morphology

• Confluent tumors, Unusual growth pattern

• Lesion length > 2 times lesion width

• Lesions with irregular / infiltrative borders

– Unpredictable Tumor Behavior

• Differential tumor shrinkage/growth

Limitations of RECIST guidelines

Differential tumor behavior

Change in Tumor Change in Tumor Form: From Form: From Solid to Non-SolidSolid to Non-Solid

• Updated imaging technology not considered

– Multiplanar capability

– Automated tumor detection

– 3-D data acquisition: volumetric tumor measurement

Limitations of RECIST guidelinesLimitations of RECIST guidelines

• Criteria for tumors treated by Non-drugs? (eg: Radio-frequency ablation)

• Metabolic and physiological changes predate tumor size change

Limitations of RECIST guidelinesLimitations of RECIST guidelines

Non-Drug treatment of tumors: Response criteria?Non-Drug treatment of tumors: Response criteria?

Imaging Pitfalls: Scanning & Visualization Techniques

Future?Future?

WHO-Bidimensional

RECIST-Unidimensional

Volumetric