A New Prognostic Model For High-Grade Appendiceal Mucinous Neoplasms With Peritoneal Carcinomatosis.

e16718 Background: Peritoneal carcinomatosis of appendiceal origin (PCAO) is a rare malignancy accounting for less than 1% of all cancers. High-grade appendiceal mucinous neoplasms (HAMN) have a poor prognosis and are often treated with cytoreductive surgery (CRS), with hyperthermic intraperitoneal chemotherapy (HIPEC) followed by adjuvant systemic chemotherapy (ASC). Peritoneal cancer index (PCI) and completeness of cytoreduction score (CCR) are useful prognostic tools in patients with PCAO undergoing CRS/HIPEC. However, neither PCI nor CCR take response to ASC into account. Therefore, we propose an enhanced prognostic scoring system (tumor response index, TRI) that incorporates response to ASC as assessed at the completion of treatment. Methods: We retrospectively reviewed the charts of patients with PCAO who received care at the Van Elslander Cancer Center between January 2011 until December 2018. All patients with HAMN who underwent CRS/HIPEC followed by ASC were included. TRI was assessed by comparing the patients' performance status, tumor markers and imaging at the completion of ASC to those prior to the initiation of ASC. A competing risk model, Kaplan-Meier analysis and multivariate Cox regression analysis were used to estimate correlations between TRI and clinical outcomes (PFS and OS). TRI was also compared to PCI and CCR using the Akaike’s Information Criteria (AIC). Results: A total of 84 charts were reviewed. Patients were divided into groups based on their TRI score. The median age was 57 years with 55% females and 85% Caucasians. Approximately 20% of patients had signet-ring features. The most common ASC regimen used was a combination of 5-fluorouracil, oxaliplatin (FOLFOX) and bevacizumab (65%). The table depicts the median PFS and OS of each TRI group. Lower TRI was associated with significantly better PFS and OS. For all outcomes, AIC was substantially reduced by adding TRI to PCI and CCR, suggesting that TRI is a better predictor of PFS and OS. Conclusions: This study proposes TRI as an effective prognostic tool in patients with PCAO and HAMN after CRS/HIPEC/ASC. [Table: see text]