Abstract 6519: Patient, primary colorectal tumor and liver metastases factors which influence survival after liver metastasectomy and therefore should be considered at the preoperative tumor board
Authors: Scherman Peter , Naredi Peter , Syk Ingvar , Holmberg Erik , Rizell Magnus 
Published: September 2020

Abstract
Aim of the study: Patients with colorectal liver metastases (CRLM) should be considered for liver surgery and this study illuminate important factors to be considered at the preoperative multidisciplinary tumor board.
Background: Survival after surgical resection or ablation of colorectal liver metastases is increasingly favorable but only a minority of patients undergo curatively intended treatment. Several studies have shown the importance of assessing resectability by liver surgeons. Which prognostic factors to consider before liver surgery is not fully understood.
Methods: The Swedish colorectal cancer registry (SCRCR) and the Swedish registry for liver tumors (SweLiv) were linked to identify radically resected primary colorectal cancer patients during the years 2009-2013 also surgically treated for liver metastases, synchronously or metachronously. CRLM characteristics and treatment strategies as well as primary tumor and patient factors were analyzed for prognostic impact. 5-year age-standardized relative survival (RS) and 5-year excess mortality rate ratio (EMRR) were calculated. Treatment with ablation only for tumors with maximum size of 30 mm was analyzed in a propensity score weighted cox regression.
Results: 1325 patients were included in the study cohort, whereof 300 were 75 years or older. 1200 were treated with resection and 125 were treated with ablation only. Age-standardized relative five-year survival after open resection of colorectal liver metastases was 54.8 % (95 % CI: 50.6-58.7) and after ablation 32.4 % (95 % CI: 23.3-41.9). Multivariate analysis identified age ≥75 years, tumor size &gt;20 mm, location in segment 4, 6, 7 or 8, multiple metastatic sites and progress after chemotherapy as important risk factors with more than 25 % higher EMRR. Only when analyzed without segments included in the multivariate model was the number of metastases a significant risk factor. Vascular invasion, lymph node ratio and complications at time of primary tumor resection were also important negative prognostic factors. Ablation of small metastases compared to resection was a significant risk factor (HR 2.25 (95 % CI 1.61-3.15)).
Conclusion: Tumor size over 20 mm and location of metastases as well as lymph node status and complications after resection of the primary tumor are important risk factors for survival outcome after liver surgery of CRLM. Progress after preoperative chemotherapy and ablation compared to resection more than doubled the risk of death within 5 years.
Citation Format: Peter Scherman, Peter Naredi, Ingvar Syk, Erik Holmberg, Magnus Rizell. Patient, primary colorectal tumor and liver metastases factors which influence survival after liver metastasectomy and therefore should be considered at the preoperative tumor board [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6519.