A CT-Based Nomogram for Preoperative Prediction of Synchronous Peritoneal Metastasis in Colorectal Cancer

1. Introduction
Colorectal Cancer (CRC) is the third most common cancer with estimated 1000,000 of new cases worldwide each year, ranking the third cause of cancer-related death [1]. Peritoneal Metastasis (PM) is considered to be a terminal stage of CRC metastasis with unfavorable fatal outcome [2, 3]. The incidence of synchronous PM is about 5-10% of CRC at the initial diagnosis, while 5% of PM are presented with metachronous PM after radical resection, and approximately 25-44% of patients occur in recurrent disease [2]. Recently, Cytoreductive Surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) become popular options and are widely adopted for treating PM in many centers worldwide and the median OS increase to 42 months with this treatment [2,4,5].
Early diagnosis of synchronous PM with a Peritoneal Cancer Index (PCI) < 20 points, can increase the probability of complete CRS procedure [2, 4]. If CRS is incomplete, namely palliative surgery in late-stage PM, the median OS is less than 10 months [2, 6]. Palliative surgery comes with high mortality and substantial hospitalizations and limited survival, especially those with poor prognostic features like ascites or palpable masses with a median survival of 36 days, while early PM with favorable prognostic features obtained a median survival of 154 days [3, 7].