Pseudomyxoma peritonei: Clinical pathological and biological prognostic factors in patients treated with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC)

Background: Surgical cytoreduction combined with hyperthermic intraperitoneal chemotherapy (HIPEC) has been recently advocated as the standard of care for pseudomyxoma peritonei (PMP). We reviewed our 10-year monoinstitutional case series to identify selection factors predicting postoperative outcome. Methods: One hundred and four patients with PMP were operated on with the aim of performing adequate cytoreduction (residual tumor nodules ≤2.5 mm) and closed-abdomen HIPEC with mytomicin-C and cisplatin. Previously, 26 patients had systemic chemotherapy. PMP was histologically classified into disseminated peritoneal adenomucinosis (DPAM), peritoneal mucinous carcinomatosis (PMCA), and intermediate/discordant group (ID). Immunohistochemical stains were performed for cytokeratin (CK)-7, CK-20, CDX-2, MUC-2, MUC-5AC, CD-44s. The significance of 22 potential clinical, pathological, and biological prognostic variables was assessed by multivariate analysis. Results: Adequate cytoreduction was performed in 89 patients, suboptimal cytoreduction in six, palliative surgery in nine. Operative mortality was 1%. Seventy-eight patients were diagnosed with DPAM, 26 with PMCA, and none with ID. Median follow-up was 37 months (range, 1-110) for the overall series. Five-year overall survival (OS) and progression-free survival (PFS) were 78.3% and 31.1%, respectively. At multivariate analysis, adequate cytoreduction, no previous systemic chemotherapy, and DPAM correlated to better OS and PFS, elevated serum CA19.9 correlated only to better PFS. In most cases, CK20, CDX-2, and MUC-2 were diffusely positive, while CK-7, MUC-5AC, and CD44s were variably expressed. CK20 expression correlated to prognosis at univariate analysis. Conclusions: Favorable outcome after comprehensive treatment can be expected in patients with DPAM, not treated with preoperative systemic chemotherapy and amenable to adequate cytoreduction. MUC-2, CK-20, and CD44s expression may be related to PMP unique biologic behavior.