The majority of baseline tumor and patient characteristics, as well as the proportion of baseline visceral (liver/lung) and central nervous system (CNS) metastases did not differ between the two cohorts, except for a higher proportion of tumors in the T-DM1 cohort with Ki67 ≥ 20% (96.3% versus 77.5%, P = 0.034) and G3 (96.0% versus 77.8%, P = 0.048). This evidence concerns the gene MKI67 and neoplasm.