Brain metastasis in advanced colorectal cancer: results from the South Australian metastatic colorectal cancer (SAmCRC) registry

Objective Brain metastasis is considered rare in metastatic colorectal cancer (mCRC); thus, surveillance imaging does not routinely include the brain. The reported incidence of brain metastases ranges from 0.6% to 3.2%. Methods The South Australian mCRC Registry (SAmCRC) was analyzed to assess the number of patients presenting with brain metastasis during their lifetime. Due to small numbers, a descriptive analysis is presented. Results Only 59 patients of 4,100 on the registry at the time of analysis had developed brain metastasis (1.4%). The clinical characteristics of those with brain metastasis were as follows: the median age was 65.3 years and 51% were female. Where the V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation status of the tumor was known, the majority harbored a KRAS mutation (55%); 31 (53%) underwent craniotomy and 55 (93%) underwent whole-brain radiotherapy. The median survival time from diagnosis of brain metastasis was 4.2 months (95% confidence interval 2.9-5.5). Patients who underwent craniotomy and radiotherapy had superior survival compared to those who underwent whole-brain radiotherapy (8.5 months vs. 2.2 months, respectively). Data from the SAmCRC (a population-based registry) confirm that brain metastases are rare and the median time to development is approximately 2 years. Conclusions Brain metastasis is a rare outcome in advanced CRC. Patients within the registry tended to be female, young in age, and harbored with higher rates of KRAS mutations. Whether routine surveillance brain scanning should be considered remains controversial given the relative rarity of developing brain metastases in mCRC and ultimately, most patients with central nervous system involvement die from their extracranial disease.