Background: The aim of this study was to evaluate the Dutch regional practice variation in treatment of synchronous colorectal liver metastases (CRLM) over time and assess their impact on patients survival. Methods: Two cohorts of patients with synchronous CRLM were selected from the Netherlands Cancer Registry (NCR). All patients diagnosed between 2014 and 2018 were selected to analyze interregional practice variations in local therapy (LT) with multivariable logistic regression. Overall survival (OS) was assessed for patients diagnosed from 2008 to 2013 using Kaplan Meier method and Cox regression analyses. Results: The proportion of patients who underwent LT increased from 15.5% to 21.9%. Interregional use of LT varied from 19.1% to 25.0%. Multivariable logistic regression showed significant differences between regions in the use of LT (p = 0.001) in 2014–2018. There was no association between OS and region of diagnosis for patients who underwent LT after correction for confounders.The use of LT for CRLM increased from 15.5% in 2008–2013 to 21.9% in 2014–2018. Three-year OS increased from 16% to 19% respectively. Conclusion: Interregional practice variations have decreased. The remaining differences are not associated with OS. The use of local therapy and 3-year overall survival have increased over time. Local practice should be monitored to prevent undesirable variation in outcomes.
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