Oncological outcomes associated with primary-first, liver-first and synchronous resection strategies in synchronous colorectal liver metastases.

BACKGROUND: Synchronous colorectal liver metastases (sCRLM) can be managed using primary-first (PF), liver-first (LF), or synchronous resection (SR), but their comparative impact on treatment sequencing, perioperative and oncologic outcomes remains unclear. METHODS: A retrospective analysis of prospectively collected data (2011-2024) from a single tertiary institution compared perioperative complications, oncologic outcomes, and treatment sequencing across strategies. Multivariable regression and propensity score matching were used to adjust for differences in tumor burden and disease severity. RESULTS: Among 531 patients undergoing curative-intent liver resection (PF 42%, LF 36%, SR 22%), primary tumor characteristics and metastatic burden differed across strategies, reflecting selection patterns. Median time to RIOT did not differ significantly between PF, LF, and SR (54.0, 58.0, and 58.5 days, respectively; P = 0.530). In contrast, SR was associated with a shorter overall treatment sequencing (8.5 vs 10.6 and 10.9 months for PF and LF; P < 0.001), remaining independently associated with shorter sequencing time on multivariable analysis (β = -2.81 months; 95% CI, -4.32 to -1.29; P < 0.001). Rates of major postoperative complications (Clavien-Dindo ≥3) were comparable (P = 0.217), and within the SR cohort, did not differ between major and minor hepatectomy (P = 0.624). After adjustment in multivariable analyses and propensity score matching, OS and DFS did not differ between surgical strategies. CONCLUSIONS: Synchronous resection enables more efficient treatment sequencing in appropriately selected patients without compromising perioperative safety or long-term oncologic outcomes.