A nomogram for predicting survival in patients with breast cancer brain metastasis

Abstract

Brain metastasis (BM) is common in patients with breast cancer. Predicting patient survival is critical for the clinical management of breast cancer brain metastasis (BCBM). The present study was designed to develop and evaluate a prognostic model for patients with newly diagnosed BCBM. Based on the clinical data of patients with BCBM treated in the Affiliated Hospital of Academy of Military Medical Sciences (Beijing, China) between 2002 and 2014, a nomogram was developed to predict survival using proportional hazards regression analysis. The model was validated internally by bootstrapping, and the concordance index (c-index) was calculated. A calibration curve and c-index were used to evaluate discriminatory and predictive ability, in order to compare the nomogram with widely used models, including recursive partitioning analysis (RPA), graded prognostic assessment (GPA) and breast-graded prognostic assessment (Breast-GPA). A total of 411 patients with BCBM were included in the development of this predictive model. The median overall survival time was 14.1 months. Statistically significant predictors for patient survival included biological subtype, Karnofsky performance score, leptomeningeal metastasis, extracranial metastasis, the number of brain metastases and disease-free survival. A nomogram for predicting 1- and 2-year overall survival rates was constructed, which exhibited good accuracy in predicting overall survival with a concordance index of 0.735. This model outperformed RPA, GPA and Breast-GPA, based on the comparisons of the c-indexes. The nomogram constructed based on a multiple factor analysis was able to more accurately predict the individual survival probability of patients with BCBM, compared with existing models.

Keywords: brain metastasis; breast cancer; nomogram; predictive model.

Figure 1.

The nomogram for predicting overall survival was established for patients with breast cancer brain metastasis. The predictor points of each variable were observed on the upper-most point axis. There was a Total Points line at the bottom of the nomogram, and each variable score was summed to give the total points. A vertical line down to the 1-, 2- and 3-year survival lines allowed for the determination of probabilities for each individual. 1, luminal A; 2, luminal B; 3, HER-2 positive; 4, Triple negative; KPS, Karnofsky performance score (22); DFS, disease-free survival.

Figure 2.

The calibration plots to predict the 1-year and 2-year OS rates for all patients. The x-axis represents the predicted OS and the y-axis represents the actual OS. The 45-degree line indicated an ideal reference line, which implies that the predicted OS rates were equal to the observed results. OS, overall survival.

Figure 3.

Overall survival of 411 patients according to the (A) RPA, (B) GPA and (C) Breast-GPA models. RPA, recursive partitioning analysis; GPA, graded prognostic assessment.