Outcomes of simultaneous resection for colorectal liver metastases: A nationwide cohort study (2005-2022).

Introduction: The optimal treatment strategy for synchronous colorectal liver metastases (CRLM) has been a topic for ongoing debate. We present a national cohort containing simultaneous resections of the primary tumour and CRLM, with emphasis on postoperative complications, and survival. Method: This population-based national cohort study included consecutive patients who underwent simultaneous resections in Norway between 2005 and 2022. Postoperative complications (Accordion Severity Grading System - ASGS) and overall survival (OS) were analysed in relation to the extent of liver resection and location of the primary tumour. Results: A total of 193 patients underwent simultaneous resection of the primary tumour and liver metastases. Postoperative complications graded as ASGS ≥3 occurred in 48 (24.9 %) while 23 (11.9 %) patients developed ASGS ≥4 complications. Anastomotic leakage was observed in 9 (4.7 %) patients. Among 18 (9.3 %) patients undergoing major liver resections, 10 (55.6 %) and seven (38.9 %) patients experienced ASGS ≥3 and ASGS ≥4 complications, respectively. Major liver resection was an independent predictor for ASGS ≥3, (RR: 2.40; p = 0.002). The 30- and 90-day mortality rates were 0.5 % (n = 1) and 2.1 % (n = 4), respectively. Median, 5- and 10-year OS were 4.8 years, 46.7 % and 35.6 %, respectively. In a multivariable analysis both an increasing number of liver metastases and ASGS ≥4 complications were independently associated with inferior OS. Conclusions: Simultaneous resection for synchronous CRLM was a safe option, particularly in minor liver resections. Major liver resections were associated with increased risk of severe complications and inferior OS.