Revised Modified Response Evaluation Criteria in Solid Tumors for Assessment of Response in Malignant Pleural Mesothelioma (Version 1.1)

Introduction: Malignant pleural mesothelioma poses unique difficulties in tumor measurement and response assessment; however, robust and reproducible assessment of response is critically important in the conduct, interpretation, and reporting of clinical trials. Methods: The current de facto standard for the assessment of mesothelioma tumor response, “modified RECIST” (Response Evaluation Criteria in Solid Tumors), was published in 2004 as a research paper. Practical application of the modified RECIST guidelines has suffered from varied interpretations, resulting in inaccuracies and inconsistencies in tumor response assessment across and within mesothelioma clinical trials. The presented “modified RECIST 1.1 for mesothelioma” response assessment guidelines provide a much‐needed update that incorporates recommendations from RECIST 1.1 and approaches to other practical issues, including: (1) definition of minimally measurable disease; (2) definition of measurable lesions; (3) acceptable measurement location; (4) non‐pleural disease considerations; (5) characterization of non‐measurable pleural disease; (6) assessment of pathological lymph nodes; (7) establishing progressive disease; and (8) accommodations for bilateral pleural disease. Results: These modified RECIST 1.1 guidelines for mesothelioma tumor response collate and apply research published since the development of modified RECIST, align modified RECIST with RECIST 1.1, address those aspects of tumor measurement that were neglected or not well characterized in the modified RECIST paper, and clarify ambiguous or difficult measurement issues that have been highlighted through the subsequent decade of clinical trials research. Conclusion: Adoption of the modified RECIST 1.1 guidelines for mesothelioma is recommended to harmonize the application of tumor measurement and response assessment across the next generation of clinical trials in this disease.