The impact of primary tumor location of colorectal cancer on the survival outcome of patients with brain metastasis: a systematic review and meta-analysis

Abstract Objectives Several prior studies have shown that in metastasized colorectal cancer, the primary cancer’s location influences patients’ survival rates, with left-sided colorectal cancer being associated with longer survival than right-sided colorectal cancer. This study aimed to explore the influence of the primary location of colorectal cancer on survival following brain metastasis. Methods To address this clinical question, we conducted a systematic review and meta-analysis. We included studies focused on patients diagnosed with brain metastasis from colorectal cancer. These studies reported survival outcomes based on different primary tumor sites (right versus left and colon versus rectum). The primary outcome was to aggregate the hazard ratio (HR) of left-sided colorectal cancer when metastasized to the brain compared with right-sided colorectal cancer. The secondary outcome was to aggregate the HR of rectal cancer when it metastasized to the brain compared with colon cancer. Results Ten studies with a total of 1792 patients were included in the meta-analysis, and combined HR was calculated. Left-sided colon cancer showed higher overall survival compared with right-sided colon cancer when metastasized to the brain (HR: 0.71, 95% CI: 0.54–0.94, I2 = 0%). Rectal cancer did not show a statistically significant difference in overall survival compared with colon cancer (HR: 0.75, 95% CI: 0.40–1.41, I2 = 81%). Conclusions Concordant with lung and liver metastases, the primary location of colorectal cancer influenced overall survival when metastasized to the brain. Left-sided colon cancer demonstrated higher overall survival than right-sided colon cancer.