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

## TL;DR

This study finds that left-sided colorectal cancer has better survival rates than right-sided cancer when it spreads to the brain.

## Contribution

The study is the first to meta-analyze the impact of primary tumor location on survival in colorectal cancer brain metastases.

## Key findings

- Left-sided colorectal cancer showed higher overall survival than right-sided cancer when metastasized to the brain (HR: 0.71).
- Rectal cancer did not show a significant survival difference compared to colon cancer when metastasized to the brain (HR: 0.75).

## Abstract

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.

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.

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%).

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.

The online version contains supplementary material available at 10.1186/s40001-025-03614-z.