The Utility of Preoperative Tumor Markers in Peritoneal Carcinomatosis from Primary Appendiceal Adenocarcinoma: an Analysis from the US HIPEC Collaborative.

BACKGROUND Prognostication based on preoperative clinical factors is lacking in patients undergoing cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC). This study aims to determine the value of preoperative tumor markers as predictors of progression-free survival (PFS) and overall survival (OS) for patients with peritoneal carcinomatosis from a primary mucinous adenocarcinoma of the appendix (MACA). METHODS We queried the United States HIPEC Collaborative, a database of patients with peritoneal carcinomatosis treated with CRS/HIPEC at twelve institutions between 2000 and 2017, identifying 409 patients with MACA. Multivariate analysis was used to identify independent predictors of disease progression. Subgroup analysis was conducted to evaluate the impact of tumor grade on the predictive value of tumor markers. RESULTS CA19-9 [HR 2.44, CI 1.2-3.4] emerged as an independent predictor of PFS while CEA [HR 4.98, CI 1.06-23.46] was independently predictive of OS (p <0.01). Tumor differentiation was the most potent predictor of both PFS (poorly differentiated vs well, [HR 4.5 CI 2.01-9.94]) and OS ([poorly differentiated vs well-differentiated: [HR 13.5, CI 3.16-57.78]), p <0.05. Among patients with combined CA19-9 elevation and poorly differentiated histology, 86% recurred within a year of CRS/HIPEC (p < 0.01). Similarly, the coexistence of CEA elevation and unfavorable histology led to the lowest survival rate at two years [36%, p < 0.01]. CA-125 was not predictive of PFS or OS. CONCLUSION Elevated preoperative CA19-9 portends worse PFS, while elevated CEA predicts worse OS after CRS/HIPEC in patients with MACA. This study provides additional evidence that CA19-9 and CEA levels should be collected during standard preoperative bloodwork, while CA-125 can likely be omitted. Tumor differentiation, when added to preoperative tumor marker levels, provides powerful prognostic information. Prospective studies are required to confirm this association.