In contrast, Ki67 immunohistochemistry levels, as well as Ki67 ( MKI67 ) mRNA expression, were overall higher in younger patients with a decreasing trend with increasing age (Kruskal-Wallis p = 4e−05 and p = 0.0009, respectively, Additional file 1 B-C).
For tumor mutational burden, there was no consistent change in the number of substitutions and indels per Mb sequence between age groups that was matched with a significant trend (increase/decrease) in any of the tested patient groups (groups: all patients, HRDetect-high, HRDetect-low/intermediate, and PAM50 basal-like, all Kruskal-Wallis p > 0.05 and linear regression modeling p > 0.05, Additional file 1 O).
Similarly, for patient subsets defined by DNA repair deficiency, patients with HRD-high tumors (assessed by HRDetect) showed a trend towards a younger age at diagnosis compared to non-HRD patients (Fig. 2 b).