Introduction:
Surgical resection of metastases, especially in the liver and lung, is a potentially curative treatment option for certain patients with Stage IV colorectal cancer, requiring multidisciplinary care. Our study aimed to identify facility factors associated with receipt of and survival rates following metastasectomy for patients with stage IV colorectal cancer.

Methods:
The National Cancer Database was queried for patients diagnosed with Stage IV colorectal adenocarcinoma from 2010-2020. Patients were identified as having metastases in the liver, lung, both liver and lung, or other sites. Patient, tumor, and facility-level factors (e.g. case volume, safety net burden) associated with receipt of non-palliative intent metastasectomy were analyzed by logistic regression. High safety-net burden facilities were those in the top quartile for patients without insurance or with Medicaid insurance. Instrumental variable analysis, using hospital-level metastasectomy rate as the instrument, was used to control for selection bias (e.g. disease burden) associated with standard regression. Cox regression analysis was utilized to compare survival outcomes.

Results:
In total, 81,989 patients were included, with 37,082 (48.5%) having liver metastases, 4,461 having lung metastases (5.4%), 10,570 having liver and lung metastases (12.9%), 11,803 (14.4%) having other sites of metastatic disease, and the remaining 18,073 having a combination of liver/lung metastases with other sites. Using standard Cox regression, metastasectomy was associated with a significant reduction in mortality (HR 0.61, 95% CI 0.59-0.63, p<0.001). After controlling treatment selection by instrumental variable analysis, the significant survival benefit (relative mortality rate 0.67, 95% CI 0.60-0.74, p<0.001) persisted. However, patients were less likely to receive metastasectomy if they were Black (OR 0.76, p<0.001), older than 75 years (OR 0.41, p<0.001), or lived in a zip-code with lowest quartile annual median income (OR 0.84, p<0.001). Compared to patients with lung metastases, patients with liver metastases (OR 2.64, p<0.001) were more likely to receive a metastasectomy. After adjusting for patient-level factors, high safety-net burden facilities were less likely to perform metastasectomy (OR 0.87, p<0.001), but academic facilities (OR 2.40, p<0.001) and those in the top quartile of colorectal cancer patient volume (OR 2.04, p<0.001) were more likely to perform these resections.

Conclusion:
Metastasectomy is associated with significant improvements in survival, even after accounting for patient selection bias. Receipt of metastasectomy was associated with patient socioeconomic factors. Safety-net facilities were less likely to perform these resections, suggesting that limited financial and medical resources at multiple levels may be a significant influence on this type of resection.

Chung-Yuan Hu

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