Modified RECIST criteria for assessment of response in malignant pleural mesothelioma.

BACKGROUND The growth pattern of malignant pleural mesothelioma makes the use of RECIST (response evaluation criteria in solid tumours) response criteria difficult. We have developed and validated Modified RECIST criteria adapted to the growth pattern of malignant pleural mesothelioma. PATIENTS AND METHODS We evaluated 73 patients from two clinical trials of cisplatin/gemcitabine chemotherapy in malignant pleural mesothelioma. Tumour thickness perpendicular to the chest wall or mediastinum was measured in two positions at three separate levels on thoracic CT scans. The sum of the six measurements defined a pleural unidimensional measure. Bidimensionally measureable lesions were measured unidimensionally as for RECIST. All measurements were added to obtain the total tumour measurement. A reduction of at least 30% on two occasions 4 weeks apart defined a partial response; an increase of 20% over the nadir measurement, progressive disease. The validity of the modified criteria was gauged by evaluating survival and pulmonary function. RESULTS Response according to these criteria predicted for superior survival (15.1 versus 8.9 months; P = 0.03) and forced vital capacity (FVC) increase during treatment (P <0.0001). A significant correlation between change in linear tumour measurement and FVC was seen (R = 0.63; P = 0.0001). CONCLUSION These Modified RECIST criteria for tumour response correlate with survival and lung function and can be used to measure outcome in pleural mesothelioma.