Fig. 3

HER2/CEP17 ratio investigated with subpopulation treatment effect pattern plot (STEPP) and survival analysis. STEPP investigated the relationship between manually- (A) and digital image analysis (DIA) algorithm-scored (C) mean HER2/CEP17 ratio and the probability of being recurrence-free at the median recurrence-free survival (RFS) (8.7 years). The lower left corners in A, C show the cutoff levels suggested by STEPP analysis and identified by positional scanning (PS). These cutoffs divided the cohort into three subgroups, namely low, intermediate and high. The locally estimated scatterplot smoothing curve fit is shown with the blue line. Kaplan–Meier estimates and multivariable Cox regression model of manually- (B) and DIA algorithm-scored (D) HER2/CEP17 ratio related to RFS. The study cohort was divided into three subgroups according to the suggested optimal first and second cutoffs for the manually scored HER2/CEP17 ratio and the DIA algorithm scored HER2/CEP17 ratio as shown in A, C. *The multivariable Cox regression model for manual HER2/CEP17 ratio was adjusted for lymph node status, tumor size and stratified for estrogen receptor status. Adjusted hazard ratios (HR) with 95% confidence interval (CI) are presented