Statistical analysis
primary tumor, death, SRS
EVENT, DISEASE, LUNG METASTASES, PRIMARY TUMOR, METASTASES
Time to RN was defined as starting from the day of SRS up to the date of the MRI evaluation. Time to progression was defined as the interval from the date of SRS to the documentation of progression and evaluated for CNS progression (DBF), local progression and DFS, according to the different kinds of failures. Local progression and RN were computed on a per-lesion basis, whereas all other analyses were on a per-patient basis. OS was defined as the interval from SRS to death of any cause. The impact of RN and local progression was estimated by competing risk analysis and cumulative incidence approach considering death as the competing event [The difference in time to RN and local progression was compared between treatment arms using the method developed by Gray [Variables considered were prescribed dose, number, and the dimension of CNS lesions. As further clinical predictors, gender, KPS score (1 for 70, 2 for 80, and 3 for 90–100), histology of primary tumor (non-lung vs lung metastases), stage of disease (1 for stages I and II, and 2 for stages III and IV), presence of extra-cranial metastases (yes/no), RPA class (I vs II), presence of systemic therapy (yes/no), number of BMs (1 for single lesions, 2 for more), and dose prescription were considered as categorical variables. Target volume and diameter were treated as continuous variables.For each variable, HR and For all endpoints, All analyses were conducted using the Stata software (StataCorp. 2017. Stata Statistical Software: Release 15. College Station, TX: StataCorp LLC).