Simultaneous resection of colorectal cancer and synchronous liver metastases: what determines the risk of unfavorable outcomes? An international multicenter retrospective cohort study
Authors: Sijberden Jasper P. , Zimmitti Giuseppe , Conci Simone , Russolillo Nadia , Masetti Michele , Cipriani Federica , Lanari Jacopo , Görgec Burak , Benedetti Cacciaguerra Andrea , Rotellar Fernando , D’Hondt Mathieu , Edwin Bjørn , Sutcliffe Robert P. , Dagher Ibrahim , Efanov Mikhail , López-Ben Santi , Primrose John N. , Giuliante Felice , Spinelli Antonino , Chand Manish , Alvarez Salud , Langella Serena , Nicosia Simone , Ruzzenente Andrea , Vivarelli Marco , Cillo Umberto , Aldrighetti Luca , Jovine Elio , Ferrero Alessandro , Guglielmi Alfredo , Besselink Marc G. , Abu Hilal Mohammad 
Published: April 2023

Background:
The use of a simultaneous resection (SIMR) in patients with synchronous colorectal liver metastases (sCRLM) has increased over the past decades. However, it remains unclear when a SIMR is beneficial and when it should be avoided. The aim of this retrospective cohort study was therefore to compare the outcomes of a SIMR for sCRLM in different settings, and to assess which factors are independently associated with unfavorable outcomes.

Methods:
To perform this retrospective cohort study, patients with sCRLM undergoing SIMR (2004–2019) were extracted from an international multicenter database, and their outcomes were compared after stratification according to the type of liver and colorectal resection performed. Factors associated with unfavorable outcomes were identified through multivariable logistic regression.

Results:
Overall, 766 patients were included, encompassing colorectal resections combined with a major liver resection (n=122), minor liver resection in the anterolateral (n=407), or posterosuperior segments (‘Technically major’, n=237). Minor and technically major resections, compared to major resections, were more often combined with a rectal resection (29.2 and 36.7 vs. 20.5%, respectively, both P=0.003) and performed fully laparoscopic (22.9 and 23.2 vs. 6.6%, respectively, both P = 0.003). Major and technically major resections, compared to minor resections, were more often associated with intraoperative transfusions (42.9 and 38.8 vs. 20%, respectively, both P = 0.003) and unfavorable incidents (9.6 and 9.8 vs. 3.3%, respectively, both P≤0.063). Major resections were associated, compared to minor and technically major resections, with a higher overall morbidity rate (64.8 vs. 50.4 and 49.4%, respectively, both P≤0.024) and a longer length of stay (12 vs. 10 days, both P≤0.042). American Society of Anesthesiologists grades ≥3 [adjusted odds ratio (aOR): 1.671, P=0.015] and undergoing a major liver resection (aOR: 1.788, P=0.047) were independently associated with an increased risk of severe morbidity, while undergoing a left-sided colectomy was associated with a decreased risk (aOR: 0.574, P=0.013).

Conclusions:
SIMR should primarily be reserved for sCRLM patients in whom a minor or technically major liver resection would suffice and those requiring a left-sided colectomy. These findings should be confirmed by randomized studies comparing SIMR with staged resections.