Modeling of mesothelioma growth demonstrates weaknesses of current response criteria

Lung Cancer. 2006 Mar 9; [Epub ahead of print] [Link]

Geoffrey R. Oxnard^a, Samuel G. Armato III^{b, d} and Hedy L. Kindler^{c, d}

^aDepartment of Medicine, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, United States
^bDepartment of Radiology, The University of Chicago, 5841 South Maryland Avenue, MC 2026, Chicago, IL 60637, United States
^cSection of Hematology/Oncology, Department of Medicine, The University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637, United States
^dCancer Research Center, The University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637, United States

Received 7 October 2005;  accepted 20 December 2005.  Available online 10 March 2006.

Abstract

Applicability of the Response Evaluation Criteria in Solid Tumors (RECIST) to the geometry of mesothelioma has been recently investigated. A “modified RECIST” measurement technique developed for mesothelioma proposes measurement of tumor thickness rather than maximum diameter. This study evaluated the volumetric consistency of the RECIST response criteria as applied to the modified RECIST measurement technique. Geometric models were developed to simulate mesothelioma growth, and measurements of these models were calculated. Relationships between change in model measurements and corresponding change in model volume were derived and evaluated. Application of the RECIST response criteria to the typical spherical tumor model results in partial response (PR) classification based on a 66% volume decrease and progressive disease (PD) based on a 73% volume increase; for mesothelioma model thickness measurements, the RECIST criteria result in PR classification based on a 30% volume decrease and PD based on a 20% volume increase. Alternative response criteria for mesothelioma thickness measurement (−66% for PR, +74% for PD) achieve volumetric equivalence with the RECIST criteria for spherical tumor measurement. Application of the RECIST response criteria to mesothelioma thickness measurements yields PR and PD classifications based on smaller volume changes than for spherical tumors.

Keywords: Mesothelioma; Response Evaluation Criteria in Solid Tumors (RECIST); Tumor measurement; Tumor response; Tumor volume