A Prognostic Model for Predicting Overall Survival in Patients with Peritoneal Surface Malignancy of an Appendiceal Origin Treated with Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy

Background. Our aim was to develop a prognostic model for predicting overall survival following cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC) in patients with appendiceal adenocarcinoma and peritoneal metastasis. Methods. A retrospective analysis of a prospectively maintained database for all patients treated for appendiceal adenocarcinoma with peritoneal metastasis from 1989 to 2012 was conducted. Results. Overall, 734 (50.7%) males and 715 (49.3%) females, with a mean age at presentation of 48.6 years, were included. Prognostic variables identified in a univariate Cox analysis included sex, tumor recurrence, tumor histology, Peritoneal Carcinomatosis Index, age at diagnosis, lesion size, completeness of cytoreduction (CC) score, distant metastasis, lymph node status, and use of HIPEC. A multivariate Cox analysis identified distant metastasis, CC score, tumor histology, HIPEC use, and sex as independently predictive of survival. A prognostic index was derived and four risk groups were categorized (<= 1, 2-4, 5-10, and >= 10). Median survival for the four risk groups differed significantly: 240 months for patients with a prognostic score <= 1 versus 235, 78.4, and 19.4 months for the cohort of patients with a prognostic score of 2-4, 5-10 and >= 10, respectively (p = 0.000). An internal validation of our prognostic model was carried out on a series of 379 randomly selected patients from our data, which provided corresponding estimates. Conclusions. Our prognostic model demonstrated a significant difference in overall survival for patients stratified by our derived prognostic scores. External validation of this model in other cohorts of patients is needed.