Nomogram to predict subsequent brain metastasis in patients with metastatic breast cancer

Abstract

PURPOSE Brain metastasis is usually a fatal event in patients with stage IV breast cancer. We hypothesized that its occurrence can be predicted if a clinical nomogram can be developed, thus allowing for selection of enriched patient populations for prevention trials. PATIENTS AND METHODS Electronic medical records of patients with metastatic breast cancer were retrospectively reviewed for the period between January 2000 and February 2007 under a study approved by the institutional review board. A multivariate logistic regression analysis of selected prognostic features was done. A nomogram to predict brain metastasis was constructed and validated in a cohort of 128 patients with brain metastasis treated at the Cross Cancer Institute (Edmonton, Alberta, Canada). Results Of 2,136 patients with breast cancer, 362 developed subsequent brain metastasis. Age, grade, negative status of estrogen receptor and human epidermal growth factor receptor 2, number of metastatic sites (one v > one), and short disease-free survival were significantly and independently associated with subsequent brain metastasis. The nomogram showed an area under the receiver operating characteristic curve (AUC) of 0.68 (95% CI, 0.66 to 0.69) in the training set. The validation set showed a good discrimination with an AUC of 0.74 (95% CI, 0.70 to 0.79). The nomogram was well calibrated, with no significant difference between the predicted and the observed probabilities. CONCLUSION We have developed a robust tool that is able to predict subsequent brain metastasis in patients with breast cancer with nonbrain metastatic disease. Selection of an enriched patient population at high risk for brain metastasis will facilitate the design of trials aiming at its prevention.