A proposed staging system for diffuse malignant peritoneal mesothelioma patients undergoing cytoreductive surgery and perioperative intraperitoneal chemotherapy

Abstract

4150 Background: There is no staging system available for diffuse malignant peritoneal mesothelioma (DMPM). This study evaluated seven clinical, seven radiological and twelve histopathologic prognostic parameters for survival of patients with DMPM. Methods: Between September 1989 and September 2005, sixty-two DMPM patients who were treated in a uniform fashion utilizing cytoreductive surgery combined with heated intraoperative intraperitoneal chemotherapy, with cisplatin and doxorubicin, followed by early postoperative intraperitoneal paclitaxel from postoperative day 1 to day 5 were included in this study. All prognostic parameters were analyzed in univariate and multivariate analyses using overall survival as the endpoint. The clinical and radiological data were obtained prospectively. A review of the histopathological features of DMPM was performed by two experienced pathologists, who individually evaluated each case. The mean number of specimens taken from separate anatomic sites was 11 ± 4 per patient. The mean number of slides studied was 20 ± 8 per patient. Results: The median follow-up was 37 months (range 8 to 143 months). The overall survival was 79 months (range 1 to 143 months) and 5-year survival was 50%. The following 14 prognostic variables were significant for survival in the univariate analysis: gender (p = 0.045), peritoneal cancer index (p = 0.038), completeness of cytoreduction score (p = 0.010), interpretive CT findings of the small bowel (p = 0.001), histologic type (p < 0.001), nuclear size (p < 0.001), nuclear/cytoplasmic ratio (p < 0.001), mitotic count (p < 0.001), atypical mitosis (p < 0.001), chromatin pattern (p < 0.001), cellular necrosis (p < 0.001), perineural invasion (p = 0.037), stroma pattern (p < 0.001) and depth of invasion (p = 0.014). In the multivariate analysis, the only factor that was independently associated with an improved survival was nuclear size. The 3-year survival rates with nuclear size of 10–20 μm, 21–30 μm, 31–40 μm and > 40 μm were 100%, 87%, 27% and 0%, respectively. Conclusions: Nuclear size was the dominant factor determining overall survival in patients with DMPM. A histopathological staging system based on measurement of the nuclear size was proposed. No significant financial relationships to disclose.