Pseudomyxoma peritonei: biological features are the dominant prognostic determinants after complete cytoreduction and hyperthermic intraperitoneal chemotherapy.

OBJECTIVE To investigate outcome and prognostic factors in patients with pesudomyxoma peritonei (PMP) treated by complete cytoreduction and hyperthermic intraperitoneal chemotherapy. BACKGROUND After comprehensive treatment, prognosis of PMP is predominantly dependent on the completeness of cytoreduction. Once complete cytoreduction is achieved, additional factors predicting long-term outcome are still poorly understood. METHODS From a prospective database, we selected 102 patients undergoing complete cytoreduction (residual tumor nodules < or =2.5 mm) and closed-abdomen hyperthermic intraperitoneal chemotherapy with mitomycin-C and cisplatin. Previously, 22 patients had systemic chemotherapy. PMP was histologically classified into disseminated peritoneal adenomucinosis, peritoneal mucinous carcinomatosis (PMCA), and intermediate/discordant group. Twenty-one patient-, tumor-, and treatment-related variables were assessed by multivariate analysis with respect to overall (OS) and progression-free (PFS) survival. The following immunohistochemical markers were tested: cytokeratin (CK)-7, CK-20, CDX-2, MUC-2, and MUC-5AC. RESULTS Operative mortality was 1%. Seventy-eight patients were diagnosed with disseminated peritoneal adenomucinosis, 24 with PMCA, none with intermediate/discordant group. For the overall series, median follow-up, 5-year OS, and PFS were 45 months (range 1-110), 84.4%, and 48.3%, respectively. In most cases, CK20, CDX-2, and MUC-2 were diffusely positive, whereas CK-7 and MUC-5AC were variably expressed. At multivariate analysis, previous systemic chemotherapy and PMCA correlated to both worse OS and PFS, elevated serum CA125 only to worse PFS. CK20, CDX-2, and MUC-2 expression correlated to prognosis at univariate analysis. CONCLUSIONS After complete cytoreduction and hyperthermic intraperitoneal chemotherapy, prognosis of PMP is primarily dependent on pathologic and biologic features. MUC-2, CK-20, and CDX-2 may be related to the disease biology. Understanding PMP molecular basis may facilitate personalized treatment.