Evaluation of the clinical TNM staging system for malignant pleural mesothelioma: an assessment in 88 patients.

There is no universally-recognised method for staging malignant mesothelioma, although the use of computed tomograph (CT) scanning has improved the staging of non-invasive disease. The International Union against Cancer has recently proposed using the Tumour Node Metastases (TNM) staging system for mesothelioma, but in clinical practice it is difficult to assess tumour and nodal involvement due to the unique plate-like growth pattern of this tumour. In order to evaluate TNM staging we analysed pre-operative CT scans from 88 patients with histologically-confirmed malignant pleural mesothelioma, all from the same institution. The median age of the patients was 56 years (range 38-79). There were 70 men and 18 women, and 33 had tumours with epithelial histology. The median survival time was 10 months (range 0.2-110), from the date of histological confirmation of mesothelioma. The same radiologist analysed all the CT scans according to the TNM staging system. Actuarial survival curves were constructed by the Kaplan-Meier method. Survival curves for the different TNM categories were compared using the log-rank test. Node evaluation could not be completed in eight cases because the tumour had encompassed the hilum and mediastinum. In multivariate analysis, significant differences in prognosis correlated with the different T categories (P < 0.01), and the different TNM stages (P < 0.05), but not the N categories or the M categories. Larger studies are needed to assess the importance of TNM staging in the selection of treatment and as a prognostic factor for malignant mesothelioma.