CT, RECIST, and malignant pleural mesothelioma
Section snippets
Challenges of tumor measurement in pleural mesothelioma
Tumor measurement in pleural mesothelioma provides many challenges for clinical investigators. Firstly, mesothelioma has a unique growth pattern, growing as a ‘rind’ around the hemithorax, and along interlobar fissures. It does not conform to the roughly spherical growth pattern of many other malignancies. Multiple thoracic levels may be involved, and while anatomical landmarks for measurement are available in the upper and mid thorax (carina, arch of the aorta), there are few landmarks in the
Why measure tumor response?
When discussing tumor measurement, it is important to remember why we want to measure response. Palliative chemotherapy aims to benefit patients by decreasing symptoms and prolonging survival, rather than to decrease tumor size alone. A decrease in tumor size may or may not achieve palliation in individual patients. However, tumor response is an important surrogate for patient benefit in non-randomized clinical trials where symptom improvement and increased survival are difficult to assess.
The WHO criteria and pleural mesothelioma
The previously widely-used WHO tumor response criteria were poorly suited to the growth pattern of pleural mesothelioma [1]. These response criteria were most useful for measuring bi-dimensional lesions, taking the sum of the products of the longest diameter of each lesion and its perpendicular diameter as the baseline tumor measurement. A partial response (PR) was defined by a 50% decrease in the sum of these products. Whilst uni-dimensional measurements were allowed, the required 50% decrease
The RECIST criteria and pleural mesothelioma
In contrast, the RECIST criteria, which are becoming increasingly widely used in clinical trials, use uni-dimensional measurements only [2]. A partial response is defined as a 30% decrease in the sum of uni-dimensional tumor measurements.
Despite the use of uni-dimensional measurements, application of the RECIST criteria is not simple in pleural mesothelioma. The RECIST criteria evolved from measurement of the roughly spherical lesions common in other solid malignancies, and assume concordant
The history of uni-dimensional measurement in pleural mesothelioma
Michael Byrne, from Perth, Western Australia, first developed a modification of the WHO criteria in 1997, to assess response in a clinical trial of cisplatin and gemcitabine in pleural mesothelioma [4]. In this study, both bi-dimensionally and uni-dimensionally measurable disease was considered in assessment of response, but the uni-dimensional response criteria differed from the WHO criteria in being mathematically more equivalent to a 50% decrease in the sum of the perpendicular diameters. In
The ‘modified RECIST criteria’ for pleural mesothelioma
With the widespread adoption of the RECIST criteria in other malignancies, the need to use both uni-dimensional and bi-dimensional lesions to assess response in mesothelioma became less important. We then concentrated on clarifying the use of uni-dimensional response criteria as per RECIST, with more explicit definitions for the number and choice of measurement sites and how to measure the longest diameter. These criteria have been recently published as the ‘modified RECIST criteria’ [7].
The
Validation of the ‘modified RECIST criteria’
There were subtle differences between the modified RECIST criteria and the original criteria used in the two clinical trials from Western Australia, which pre-dated RECIST. These two patient data sets were re-assessed and used to validate the modified RECIST criteria.
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Single-centre phase II trial of cisplatin and gemcitabine in 21 patients, 48% ORR [4].
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Multicentre phase II trial of cisplatin and gemcitabine in 53 patients, audited ORR 33% [5].
The complete CT scan series was available for 73
Moving forward with the ‘modified RECIST criteria’
Although the ‘modified RECIST criteria’ are already being used in current and proposed clinical trials, ideally, they should be further evaluated. Tests of inter-observer variability are important, as has been demonstrated in the assessment of response in lung cancer [8]. To confirm the practicality of the criteria they should be tested by clinicians both with and without extensive experience in the measurement of mesothelioma in clinical trials. There are opportunities for international
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Cited by (34)
Specialty Imaging: Thoracic Neoplasms
2016, Specialty Imaging: Thoracic NeoplasmsOptimization of response classification criteria for patients with malignant pleural mesothelioma
2012, Journal of Thoracic OncologyFolylpoly-glutamate synthetase expression is associated with tumor response and outcome from pemetrexed-based chemotherapy in malignant pleural mesothelioma
2012, Journal of Thoracic OncologyCitation Excerpt :Tumor staging was based on the tumor, node, and metastasis (TNM) staging system as proposed by the International Mesothelioma Interest Group (IMIG).26 As MPM is difficult to quantify radiographically because of nonradial and variable patterns of growth and response to therapy,2,27–30 modified Response Evaluation Criteria in Solid Tumors were applied for evaluation of response. These criteria were used to classify the tumor response to treatment as: complete response (CR), partial response (PR), stable disease (SD), or progressive disease (PD).27–30
Assessment of objective responses using volumetric evaluation in advanced thymic malignancies and metastatic non-small cell lung cancer
2011, Journal of Thoracic OncologyAssessment of tumor response in malignant pleural mesothelioma
2007, Cancer Treatment ReviewsCitation Excerpt :However, the recent development of more active regimens underlines the need for accurate techniques for evaluating response in this disease. Several response criteria have been proposed.20 In 1981, the World Health Organization (WHO) established the first quantitative criteria for measurement of solid tumors on imaging studies before and after chemotherapy.22