Association between Primary Tumor Location and Prognostic Survival in Synchronous Colorectal Liver Metastases after Surgical Treatment: A Retrospective Analysis of SEER Data

The prognostic and predictive role of primary tumor location (PTL) in localized and metastatic colorectal cancer (CRC) is a hotspot issue in recent years. However, its prognostic role is still unclear in synchronous colorectal liver metastases (sCRLM), especially in those receiving surgical treatment of primary tumor and liver metastases. Here, a retrospective survival analysis was performed using the Surveillance, Epidemiology, and End Results Program (SEER) database between 2010 and 2014, on patients who were pathologically confirmed sCRLM, and received surgical treatment of both primary tumor and liver metastases. After stringent exclusive procedure, a total of 1508 patients with sCRLM (872 men [57.8%] and 636 women [42.2%]; mean age, 60.9 years) were eligible for the final study. Compared with sCRLM with left-sided PTL, cases with right-sided PTL were more likely to be T4 (31.3% vs. 20.1%, p<0.001), N2 (42.5% vs. 31.8%, p<0.001) and poorly differentiated (30.5% vs. 15.1%, p<0.001). Furthermore, right-sided sCRLM showed significantly shorter cancer specific survival (CSS) than those from left-side (p<0.001). After Cox hazard regression analysis, right-sided PTL still remained to be a strong independent predictor for poor prognosis in this cohort of sCRLM patients (OS, HR=1.75, 95% CI 1.34-2.29; CSS, HR=1.76, 95% CI 1.33-2.35). In conclusion, according to this population-based cohort from the SEER database, PTL was a critical prognostic factor that affect long-term OS and CSS in patients with sCRLM after surgical treatment of primary tumor and liver metastases.