IMPORTANCE

Simultaneous or delayed resection of synchronous liver metastasis (SLM) with primary colorectal cancer (CRC) remains a controversial topic.

OBJECTIVE

To investigate the outcomes of simultaneous vs delayed resection in patients with resectable SLM.

DESIGN, SETTING, AND PARTICIPANTS: This comparative effectiveness research study included 1569 patients with resectable SLM who underwent curative-intent liver resection at 3 independent centers in China between January 1, 2000, to December 31, 2019. A 1:1 propensity score matching was performed. Follow-up was completed on August 31, 2021, and the data were analyzed from April 1 to 30, 2022.

MAIN OUTCOMES AND MEASURES

Primary outcome was the percentage of patients with at least 1 major complication within 60 days after surgery. Secondary outcomes were intraoperative and postoperative complications, overall survival (OS), and cancer-specific survival (CSS) rates.

RESULTS

Among the 1569 patients included, 1057 (67.4%) underwent delayed resection (719 men [68.0%] with a mean [SD] age of 57.4 [11.2] years), and 512 patients (310 men [60.5%] with a mean [SD] age of 57.1 [10.5] years) underwent simultaneous resection. Matching yielded 495 pairs of patients underwent simultaneous resection. The percentage of major perioperative complications did not differ between the simultaneous and delayed resection groups (34.1% vs 30.0%; P = .89). The OS rates were 65.2% at 3 years, 47.1% at 5 years, and 38.0% at 8 years for the delayed resection group and 78.0% at 3 years, 65.4% at 5 years, and 63.1% at 8 years for the simultaneous resection group (hazard ratio [HR], 1.42; 95% CI, 1.10-1.85, P = .003). The CSS rates were 68.3% at 3 years, 48.5% at 5 years, and 37.1% at 8 years for the delayed resection group and 79.2% at 3 years, 67.2% at 5 years, and 65.9% at 8 years for the simultaneous resection group (HR, 1.45; 95% CI, 1.14-1.98; P = .004). On subgroup analysis comparing the 2 strategies according to the KRAS sequence variation status, the OS rates (HR, 1.61; 95% CI, 1.45-2.18; P < .001) and CSS rates (HR, 1.62; 95 CI, 1.40-1.87; P = .003]) in the simultaneous resection group were significantly better than those in the delayed resection group in patients with KRAS wild-type tumors.

CONCLUSIONS AND RELEVANCE

Results of this study suggest that complication rates did not differ when CRC and SLM were resected simultaneously and that the survival benefits of simultaneous resection were restricted to patients with KRAS wild-type tumors. Integrating molecular features into the treatment decision is a basis for accurate, individualized treatments.