Adjuvant T-DM1 versus trastuzumab in patients with residual invasive disease after neoadjuvant therapy for HER2-positive breast cancer: subgroup analyses from KATHERINE

•Baseline PN was associated with longer on-study and a lower resolution rate in both study arms.•Prior platinum more grade 3-4 thrombocytopenia T-DM1, but not ?3 hemorrhage.•IDFS benefit T-DM1 versus trastuzumab similar irrespective of neoadjuvant therapy containing anthracyclines.•T-DM1 an increased overall risk CNS recurrence.•The IDFS maintained high-risk tumors defined by operable status, nodal involvement, HR status. BackgroundIn the KATHERINE (NCT01772472), patients residual invasive early breast cancer (EBC) after chemotherapy (NACT) plus human epidermal growth factor receptor 2 (HER2)-targeted had 50% reduction recurrence or death adjuvant emtansine (T-DM1) trastuzumab. Here, we present additional exploratory safety efficacy analyses.Patients methodsKATHERINE enrolled HER2-positive EBC disease breast/axilla at surgery NACT taxane (± anthracycline, ± platinum) pertuzumab). Patients were randomized to (n = 743) for 14 cycles. The primary endpoint disease-free survival (IDFS).ResultsThe incidence peripheral neuropathy (PN) regardless type. Irrespective treatment arm, baseline duration (median, 105-109 days longer) (?65% ?82%). Prior arm (13.5% 3.8%), there no hemorrhage these patients. Risk decreased who received anthracycline-based [hazard ratio (HR) 0.51; 95% confidence interval (CI): 0.38-0.67], non-anthracycline-based (HR 0.43; CI: 0.22-0.82), presented cT1, cN0 (0 6 events), particularly (HRs ranged from 0.43 0.72). central nervous system (CNS) often site first (5.9% 4.3%), difference recurrence.ConclusionsT-DM1 provides clinical across patient subgroups, including small does increase recurrence. type minimal impact on safety. In analyses. (IDFS).