1. Data collection:
Age at BC diagnosis, tumor size, axillary adenopathy, clinical stage, HER2 status, Ki67 proliferation index and the modified Scarff-Bloom-Richardson grade of differentiation.
2. Analysis Plan:
Continuous variables as means and standard deviation (SD) if they follow a normal distribution; if not, as medians and IQR (interquartile range). Numbers and percentages display categorical variables.
3. Model validation:
The association between covariates and the diagnosis of brain metastases by performing logistic regression analyses; odds ratio (OR), 95 % confidence intervals (CI), and p-value will be estimated. Variables with a p-value \< 0.05 in the univariate logistic regression analysis will be further assessed in a multivariate logistic regression analysis.
For the clinical use of the model, we will use a score to each variable as that designed by Cacho-Díaz B. et. al. then, we will categorize patients into three risk groups according to the sum of the scores. We will employe a Cox regression analysis to assess each group's risk of developing brain metastases. Adjusted hazard ratios (aHRs), 95 % CIs, and p values will be evaluated.
