Which patients with colorectal cancer develop brain metastases? A multicenter analysis of clinical and molecular predictors.

218 Background: Brain metastases from colorectal cancer (CRC) are rare but clinically significant events with limited data available. This study aimed to evaluate the clinicopathological and molecular features, as well as survival outcomes, of CRC patients who developed brain metastases across multiple centers. Methods: We retrospectively reviewed CRC patients treated at eight oncology centers. Clinical variables (age, sex, tumor location, timing of brain metastasis), molecular markers (MSI, KRAS, NRAS, BRAF, HER2), and survival outcomes were analyzed. Overall survival (OS) was calculated from CRC diagnosis, and post-brain metastasis survival from the time of cranial involvement. Results: Among 5617 CRC patients, 94 (1.7%) were identified with brain metastases. The cohort included 57 men (60.6%) and 37 women (39.4%), with a median age of 60 years (range, 26.9–81.3). Primary tumor location was rectum in 42 patients (44.7%), left colon in 31 (33.0%), and right colon in 21 (22.3%). Brain metastases occurred significantly more frequently in left-sided and rectal primaries compared with right-sided tumors (77.7% vs 22.3%, χ²=28.8, p