Introduction: Patients with peritoneal carcinomatosis (PC) of appendiceal origin demonstrate variable oncologic outcomes, despite aggressive cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS–HIPEC). We sought to devise a prognostic risk stratification system for oncologic outcomes following CRS–HIPEC. Methods: A total of 197 patients undergoing CRS–HIPEC for the treatment of appendiceal PC were reviewed from a prospective database. Kaplan–Meier survival curves and multivariate Cox regression models were used to identify prognostic factors affecting oncologic outcomes. Clinicopathologic variables affecting overall survival (OS) were utilized to develop a prognostic staging system and nomograms. Results: Univariate and multivariate Cox regression analysis indicated that high-grade tumor histology, lymph node metastasis, and incomplete cytoreduction were high-risk features, adversely affecting OS. Patients were stratified on the presence of high-risk features as follows: low-risk patients had no risk factors (n = 102); intermediate-risk patients had one risk factor (n = 49); and high-risk patients had more than one risk factor (n = 46). Median OS for low-risk patients was not reached, and was 43 and 22 months for intermediate-risk and high-risk patients, respectively. Five-year OS was 72, 43, and 13 % for low-, intermediate- and high-risk patients, respectively (p < 0.0003 for low vs. intermediate risk, and p = 0.06 for intermediate vs. high risk). Conclusions: We propose a three-tier staging system for appendiceal PC following CRS–HIPEC, based on histologic grade, lymph node involvement, and completeness of cytoreduction. The presence of any one or more of these high-risk features significantly decreased survival in our single-institution database and provided the basis for a prognostic staging system and corresponding nomograms.
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