Safety of trastuzumab emtansine (T-DM1) in HER2-positive advanced breast cancer (BC) patients (pts): Primary results from KAMILLA study cohort 1.

1033Background: KAMILLA is a single-arm, open-label, phase 3b safety study of T-DM1 in pts with HER2-positive advanced BC from 278 sites in 40 countries. We report the primary analysis of the first study cohort (N = 2003). Methods: Pts with HER2-positive, locally advanced or metastatic BC (locally confirmed) with progression after prior treatment with chemotherapy and a HER2-directed agent for metastatic BC or within 6 mo of completing adjuvant therapy were enrolled. Pts received T-DM1 3.6 mg/kg every 3 wks until unacceptable toxicity, withdrawal, or disease progression. The primary outcome was safety. Results: A total of 2002 pts were treated (median age 55 yrs, range, 26–88). Most pts had a baseline ECOG score of 0 (n = 1110, 55.4%) or 1 (n = 775, 38.7%), and 1232 (61.5%) had ER and/or PR positive tumors. Median time since initial BC diagnosis was 5 yrs (range, 0–53). Most pts had received ≥2 prior lines of therapy (0–1 prior lines: 29.7%; ≥2: 66.0%); 1855 (92.8%) received prior targeted therapy in the ...