Risk factors for brain metastases in patients with metastatic colorectal cancer

Background: Brain metastases (BM) from colorectal cancer (CRC) are rare, but the incidence is suspected to rise as treatment of metastatic (m) CRC improves. The aim of this study was to identify possible biological and clinical characteristics at initial presentation of mCRC that could predict later risk of developing BM. Furthermore, we wished to estimate the incidence of BM in long-term surviving patients. Material and methods: We conducted a retrospective study on a Danish multicenter cohort of patients with mCRC who received cetuximab and irinotecan (Cetlri) as third-line treatment. All patients had previously progression on 5-FU, irinotecan and oxaliplatin containing regimens and received Cetlri treatment independent of RAS mutations status. We subsequently performed KRAS, NRAS, BRAF, PIK3CA, PTEN, ERBB2 and EGFR sequencing of DNA extracted from primary tumor tissue. Results: Totally, 480 patients were included in our study. BM were diagnosed in 42 [8.8%; 95% confidence interval (CI) 6.4-11.6%] patients. Patients with BM had a significantly longer survival from mCRC diagnosis than non-BM patients (median=32 versus 28 months, p = 0.001). On univariate cox regression analysis, the risk of developing BM was significantly increased in patients with rectal cancer (HR = 3.9; 95% CI = 1.2-13.3), metachronous metastatic disease (HR = 2.3; 95% CI = 1.2-4.4) and lung metastases (HR = 4.2; 95% CI = 2.2-7.9). On multivariate cox regression analysis only lung metastases were significantly associated BM (HR = 3.5; 95% CI = 1.8-6.8 ). None of the investigated mutations were associated with BM. Conclusion: The incidence of BM was 8.8% in patients with mCRC who received third-line therapy. The most important risk factor for developing BM was lung metastases. Furthermore, rectal cancer, metachronous metastatic disease and long survival were linked to BM development.