1. Limitations of RECIST guidelines Srinivasa R Prasad MD Associate Professor, Radiology University of Texas Health Science Center at San Antonio

2. RECIST 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

3. 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 Guidelines

4. Limitations of RECIST guidelines No criteria for non-solid tumors No toxicity criteria Lower rate of disease progression? Not applicable to Non-Cytotoxic drugs?

5. Change in Tumor Form: From Solid to Non-Solid

6. 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 guidelines

7. Lesion Confluence and Relationship to Normal Anatomical Structures

8. Unusual Lesion Configuration

9. Lesion Morphology: Mesothelioma

10. 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 guidelines

11. Differential tumor behavior Pre Post

12. 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

13. Differential tumor behavior

14. Change in Tumor Form: From Solid to Non-Solid

15. Updated imaging technology not considered –Multiplanar capability –Automated tumor detection –3-D data acquisition: volumetric tumor measurement Limitations of RECIST guidelines

16. Criteria for tumors treated by Non-drugs? (eg: Radio-frequency ablation) Metabolic and physiological changes predate tumor size change Limitations of RECIST guidelines

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

18. Imaging Pitfalls: Scanning & Visualization Techniques

19. Future? WHO-Bidimensional RECIST-Unidimensional Volumetric