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.