A novel tumor-node-metastasis (TNM) staging system of diffuse malignant peritoneal mesothelioma using outcome analysis of a multi-institutional database*.

Abstract

Currently, no tumor-node-metastasis (TNM) staging system exists for patients with diffuse malignant peritoneal mesothelioma (DMPM). The primary objective was to formulate a clinicopathological staging system through the identification of significant prognostic parameters. Eight international institutions with prospectively collected data on patients who underwent cytoreductive surgery and hyperthermic intraperitoneal chemotherapy contributed to the registry. Two hundred ninety-four patients had complete clinicopathological data and formed the basis of this staging project. Peritoneal cancer index (PCI) was categorized into T(1) (PCI 1-10), T(2) (PCI 11-20), T(3) (PCI 21-30), and T(4) (PCI 30-39). Twenty-two patients had positive lymph nodes (N(1) ) and 12 patients had extra-abdominal metastases (M(1) ). The survival for patients with T(1) (PCI 1-10) N(0) M(0) was significantly superior to the other patients. This group of patients is therefore designated as Stage I. The survival of patients with T(2) (PCI 11-20) and T(3) (PCI 21-30), in absence of N(1) or M(1) disease, was similar. This group of patients was categorized as Stage II. The survival of patients with T(4) (PCI 30-39), N(1,) and/or M(1) was similarly poor. This group of patients was therefore categorized as Stage III. Three prognostic factors were independently associated with survival in the multivariate analysis: histological subtype, completeness of cytoreduction, and the proposed TNM staging. The 5-year survival associated with Stage I, II, and III disease was 87%, 53%, and 29%, respectively. The proposed TNM staging system resulted in significant stratification of survival by stage when applied to the current multi-institutional registry data.