In patients with human epidermal growth factor receptor 2 (HER2)-positive early breast cancer, addition of pertuzumab to adjuvant trastuzumab and chemotherapy significantly improved invasive-disease-free survival rates.

• Patients randomized to receive pertuzumab or placebo in addition to standard adjuvant chemotherapy and 1 year of trastuzumab treatment
• Primary endpoint: invasive-disease-free survival, defined as time until “recurrence of ipsilateral invasive breast tumor, recurrence of ipsilateral locoregional invasive disease, a distant disease recurrence, contralateral invasive breast cancer, or death from any cause”
• Secondary endpoints: overall survival, disease-free survival, invasive-disease-free survival (per the STEEP definition), relapse-free interval, distant-relapse-free interval, safety, health-related quality of life

• 7.1% of pertuzumab patients (171/2400) experienced disease recurrence vs 8.7% of placebo patients (210/2405) (HR: 0.81; 95% CI: 0.66, 1.00; P=0.045)
• Estimated 3-year rates of invasive-disease-free survival: 94.1% for pertuzumab patients vs 93.2% for placebo patients
• 3-year rate of invasive-disease-free survival for patients with node-positive disease was 92.0% for pertuzumab patients vs 90.2% for placebo patients (HR for an invasive-disease event: 0.77; 95% CI: 0.62, 0.96; P=0.02)
• 3-year rate of invasive-disease-free survival for patients with node-negative disease was 97.5% for pertuzumab patients vs 98.4% for placebo patients (HR for an invasive-disease event: 1.13; 95% CI: 0.68, 1.86; P=0.64)
• Grade 3 or higher diarrhea “occurred almost exclusively during chemotherapy and was more frequent with pertuzumab than with placebo (9.8% vs 3.7%)”