BRAIN METASTASES (BM) from colorectal cancer (CRC) were uncommon but associated with poor outcomes, particularly when they developed close to the initial CRC diagnosis, according to a study of 5,617 patients. Researchers identified 94 patients with radiologically confirmed BM, representing 1.7% of the screened population.
The median age of patients with CRC and BM was 60 years, and 60.6% were male. Primary tumours were located in the rectum in 44.7% of cases, the left sided colon in 33.0%, and the right sided colon in 22.3%. Together, left sided and rectal tumours accounted for 77.7% of cases.
These findings indicated that BM occurred predominantly among patients with left sided or rectal CRC within the study population. The analysis also examined molecular characteristics, including microsatellite instability, RAS mutations, BRAF mutations and HER2 positivity.
The median overall survival (OS) from CRC diagnosis was 36.1 months. The median time from CRC diagnosis to BM was 21.8 months, with an interquartile range of 7.3–41.1 months. Following BM development, median post BM OS was 5.8 months.
The timing of BM was strongly associated with survival. De novo BM, defined as disease diagnosed within 90 days of CRC diagnosis, was associated with substantially shorter OS than interval BM, which was defined as disease developing more than 90 days after CRC diagnosis.
Median OS was 18.7 months among patients with de novo BM compared with 42.5 months among those with interval BM. The difference between groups was statistically significant (p<0.001).
After adjustment for age, sex and Eastern Cooperative Oncology Group performance status, de novo BM remained independently associated with poorer OS (adjusted hazard ratio: 6.86; p<0.001).
Among patients with available molecular data, deficient mismatch repair or microsatellite instability high status was identified in 5 of 81 patients. RAS mutations were detected in 37 of 82 patients, while BRAF mutations were identified in 6 of 74 patients. HER2 positivity was reported in 8 of 74 patients.
The data suggested that the timing of BM could provide clinically meaningful prognostic stratification in CRC. Despite differences according to timing, outcomes following BM remained poor, with a median post BM OS of 5.8 months.
The researchers highlighted the need for prospective studies incorporating standardised molecular profiling, treatment data and longitudinal neuroimaging. Such studies could help refine risk stratification and support risk adapted surveillance for patients with CRC at risk of BM.
Reference
Kemik F et al. Clinicopathologic and molecular characteristics of colorectal cancer patients with brain metastases: a multicenter cohort study. Sci Rep. 2026;DOI: https://doi.org/10.1038/s41598-026-69206-x.
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