Loibl S et al. -The efficacy and safety of buparlisib plus trastuzumab and paclitaxel as neoadjuvant treatment for HER2+ breast cancer were studied.In the current study it was shown that the addition of buparlisib to taxane-trastuzumab-based therapy in HER2+ early breast cancer was not feasible.

Methods

• Patients with HER2+ breast cancer were randomised based on PIK3CA mutation status.
• Patients were further stratified by ER status to receive buparlisib or placebo plus trastuzumab (first 6 weeks) followed by buparlisib or placebo with trastuzumab and paclitaxel.
• The primary end-point was pathological complete response (pCR).
• The secondary end-point was objective response rate (ORR) at 6 weeks.

Results

• Recruitment was suspended due to liver toxicity after enrolment of 50 of the planned 256 patients.
• 21 patients (84%) had wild type PIK3CA and 4 patients (16%) had mutant PIK3CA.
• The pCR rate was similar between buparlisib and placebo arms (32.0% versus 40%).
• A trend towards higher ORR (68.8% versus 33.3%) and a significant decrease in Ki67 (75% versus 26.7%) was observed in buparlisib versus placebo arm in the ER+ subgroup.