Development and validation of nomograms to predict brain metastasis-free survival in lung and breast cancer

Primary lung cancer (LC) and breast cancer (BC) are among the most common malignancies and are highly prone to brain metastasis (BM). This study aimed to identify risk factors for brain metastasis-free survival in patients with primary LC or BC and to construct clinically simple nomograms. Our study analyzed the independent factors for the occurrence of BM by univariate and multivariate Cox regression based on the training set and then developed nomograms. The performance of the nomogram was determined by the C-index and calibration curve. The results were verified with a validation set. A total of 1739 patients with primary LC and 1150 with primary BC were included in our retrospective study. In primary LC, pathological staging, N stage, targeted therapy, and chemotherapy treatment were significantly associated with BM. In primary BC, the factors significantly associated with BM were TNBC, Ki-67 index, targeted therapy, radiotherapy, and surgery. These two nomograms had discriminatory ability, with C-indices of 0.786 and 0.783 in the training set and 0.809 and 0.843 in the validation set, respectively. We constructed and validated predictive nomograms for the development of BM in patients with primary LC or BC. The proposed nomograms certainly have good performance.