Development and validation of a prognostic nomogram for survival in patients with brain metastases from colorectal cancer

Brain metastases from colorectal cancer are rare but carry a dismal prognosis. This study aimed to develop and externally validate a prognostic model for individualized survival prediction in affected patients. The model was constructed using a training cohort of 112 patients diagnosed with brain metastases after initial colorectal cancer treatment at our institution between 1985 and 2017, and validated in an external cohort of 114 patients referred for brain metastasis treatment between 1987 and 2017. A nomogram was developed incorporating five variables: age, performance status assessed by the Karnofsky Performance Status scale, number of brain metastases, maximum size of brain lesions, and number of prior systemic chemotherapy regimens. In the training cohort, the median survival was 6.6 months, with 1-year and 3-year survival rates of 29.0% and 7.2%. Poorer performance status, multiple metastases, and higher number of chemotherapy regimens were associated with worse prognosis. In the validation cohort, median survival was 5.8 months, with 1-year and 3-year survival rates of 27.0% and 8.4%. Harrell's concordance index was 0.70 for internal validation and 0.63 for external validation. This model may provide a clinically useful tool for individualized survival estimation in patients with brain metastases from colorectal cancer.