Incidence of Asymptomatic Brain Metastases in Metastatic Colorectal Cancer

Background: Current literature suggests that brain metastasis is an infrequent occurrence in metastatic colorectal cancer. Outside of rare autopsy studies, these retrospective reports describe the incidence of symptomatic brain metastasis and therefore lack a description of the incidence in asymptomatic patients. With improved survival and a lack of routine brain imaging, the true incidence of brain metastasis among patients with metastatic colorectal cancer is likely under-recognized. At our research institution, protocol criteria require brain imaging regardless of neurologic symptoms. Therefore, we aim to describe the incidence of asymptomatic brain metastases in patients with metastatic colorectal cancer.

Patients and methods: This study included patients with metastatic colorectal cancer enrolled onto a clinical trial screening protocol at the National Cancer Institute that underwent brain imaging (n = 171) between 2010 and 2019.

Results: The median age of patients at initial colorectal cancer diagnosis was 48.1 years. Most had stage IV disease with synchronous metastases. Twenty-five (14.6%) patients were identified with brain metastases, of which 19 (76%) were asymptomatic. Those with asymptomatic lesions were more likely to have presented with synchronous metastases, have a shorter time from primary diagnosis to development of metastatic disease, and have smaller brain metastases.

Conclusion: We identified a high number of asymptomatic brain metastasis and subsequently a higher cumulative incidence of brain metastases in patients with metastatic colorectal cancer than historical reports would suggest. This may represent a heretofore unknown aspect of the natural course of disease now being exposed owing to an increasing life expectancy of these patients and could play a pivotal role in therapeutic decisions.