Diffuse malignant mesothelioma of the pleura in Ontario and Quebec: a retrospective study of 332 patients.

Three-hundred thirty-two cases of pleural diffuse malignant mesothelioma (DMM) seen at large centers in Ontario and Quebec from 1965 to 1984 were reviewed retrospectively. Previous asbestos exposure was found in 44% of patients. Diagnosis was most often made by exploratory thoracotomy; pleural biopsy or cytology were rarely contributory. The delay in diagnosis was often long (median time, 3.5 months) and thrombocytosis (platelets greater than or equal to 400,000/microL) was common (41% of cases). The median survival (MS) was only 9 months. Eleven clinical variables were analyzed for prognostic significance. The three most important prognostic factors using a univariate analysis were stage, weight loss, and histologic type. For 118 patients with complete data, multivariate analysis showed that the stage of disease, high platelet count, and asbestos exposure were the most important prognostic factors. There was no cure of DMM, and we did not find any drastic differences in survival among groups of patients subjected to the different therapeutic measures. Radical surgery and radiotherapy were ineffective and we confirmed the low response rate to chemotherapeutic agents. This large retrospective trial can serve as a baseline for future studies in this field. In particular, it provides the basis for appropriate stratification variables to be used in future therapeutic trials.