Systematic review: brain metastases from colorectal cancer—Incidence and patient characteristics

BACKGROUND: Brain metastases (BM) from colorectal cancer (CRC) are a rare event. However, the implications for affected patients are severe, and the incidence has been reported to be increasing. For clinicians, knowledge about the characteristics associated with BM is important and could lead to earlier diagnosis and improved survival. METHOD: In this paper, we describe the incidence as well as characteristics associated with BM based on a systematic review of the current literature, following the PRISMA guidelines. RESULTS: We show that the incidence of BM in CRC patients ranges from 0.6 to 3.2 %. BM are a late stage phenomenon, and young age, rectal primary and lung metastases are associated with increased risk of developing BM. Molecular markers such as KRAS, BRAF, NRAS mutation as well as an increase in CEA and CA19.9 levels are suggested predictors of brain involvement. However, only KRAS mutations are reasonably well investigated and associated with an increased risk of BM. CONCLUSION: The incidence of BM from CRC is 0.6 to 3.2 % and did not seem to increase over time. Development of BM is associated with young age, lung metastases, rectal primary and KRAS mutation. Increased awareness of brain involvement in patients with these characteristics is necessary.