The importance of surgical staging in the treatment of malignant pleural mesothelioma.

OBJECTIVES: Progress in the therapy of malignant pleural mesothelioma is limited by the lack of an adequate staging system and controversy about prognostic factors. This surgical series was analyzed to determine whether a new TNM staging system proposed by the International Mesothelioma Interest Group and certain prognostic factors could stratify patients in future clinical trials.
METHODS: Thoracotomy was performed if computed tomographic scans showed resectable tumor confined to one hemithorax. Pleurectomy/decortication was done if visceral pleural tumor was minimal, and extrapleural pneumonectomy was done for more locally advanced disease. Complete resection was defined as no gross residual tumor. Adjuvant therapy was given as required by serial clinical trials. Patients had computed tomographic scans every 3 months until death. Prognostic factors were examined by log-rank and Cox regression analyses.
RESULTS: From October 1983 to July 1994, a total of 131 thoracotomies were performed, resulting in 101 resections, 72 of which were complete. Extrapleural pneumonectomy was done in 50 patients and pleurectomy/decortication in 51. The ratio of men to women was 108:23. Median age was 63 years (range 32 to 80 years). Operative mortality was five of 131 patients (3.8%), three of 50 in the group having extrapleural pneumonectomy (6%). Ninety-five of the 131 tumors were epithelial. Fifty-one of 89 patients (57%) having node dissections had diseased nodes, 45 (50%) N2. By univariate analysis, type of resection, T and N status, stage, histologic type, and adjuvant therapy, but no gender or age, significantly affected survival. Type of resection, stage, and histologic type were significant in a multivariate analysis. Local recurrence occurred mainly after pleurectomy/decortication, and distant metastases developed after extrapleural pneumonectomy.
CONCLUSIONS: (1) N2 nodal disease is more frequent than previously reported; (2) the prognostic importance of histologic type is confirmed; (3) both T and N status influence outcome, and the International Mesothelioma Interest Group staging system successfully identifies patients whose prognosis is poor; (4) despite more locally advanced disease in most patients with extrapleural pneumonectomy, that approach provided better local control than pleurectomy/decortication but failed to improve survival because of distant metastatic disease. Contrary to past practice, future clinical trials should stratify for histologic type, must control for TNM stage, and must consider the impact of type of surgical resection on the pattern of relapse.