Efficacy and safety of trastuzumab emtansine (T-DM1) in patients with HER2-positive breast cancer with brain metastases

Few data are currently available regarding the efficacy and safety of T-DM1 in breast cancer (BC) patients with unselected brain metastases (BM), since most clinical trials have excluded BM patients or have only included highly selected patients. HER2 + BC patients with BM treated with T-DM1 in 5 French centers were included in this retrospective study. Clinical management was performed according to the product guidelines. Efficacy was evaluated recording tumor response rates, progression-free (PFS) and overall survival, treatment compliance, and safety. Thirty nine patients received T-DM1, among whom 82 % presented with concomitant extra-cerebral disease. Median number of previous metastatic chemotherapy and HER2-directed targeted therapy regimens was 2 (range 0-8) and 1 (0-7), respectively. Thirty six patients had received BM loco-regional treatment (72 % whole-brain radiation therapy). After a median follow-up of 8.1 months (1.4-39.6), 24 patients had progressed (first site of progression: brain 14; meningeal 2; outside of the central nervous system 5; both intra- and extra-cerebral 3), 12 patients had died (disease progression), and 27 patients were still alive. Median number of T-DM1 cycles was 8 (1-43). There were 17 partial responses (44 %) and 6 patients achieved disease stabilization (59 % clinical benefit rate). Median PFS was 6.1 months (95 %CI 5.2-18.3), with one- and two-year PFS rates of 33 and 17 %, respectively. Treatment was well tolerated, without unexpected toxicities, treatment delay, or dose reduction. In this retrospective study, T-DM1 appeared to be an effective and well-tolerated therapeutic option in unselected HER2 + BC patients with BM. These findings require a prospective validation.