The positive findings for the trastuzumab biosimilar Ontruzant in patients with human epidermal growth factor receptor 2 (HER2)–positive early or locally advanced breast cancer were presented at the European Society for Medical Oncology (ESMO) Congress 2021.
Samsung Bioepis reported results of what it called the longest follow-up study of patients with human epidermal growth factor receptor 2–positive early or locally advanced breast cancer treated with a trastuzumab biosimilar. The findings will be formally presented in poster form at the European Society for Medical Oncology (ESMO) Congress 2021.
Investigators said 5-year event-free survival rates in the phase 3 study were 82.8% in the biosimilar (Ontruzant) cohort and 79.7% in the reference trastuzumab (Herceptin) group.
Five-year overall survival rates were 93.1% and 86.7% for the biosimilar (HR 0.62; 95% CI, 0.32-1.22; P = .17) and originator drug cohorts, respectively.
Investigators reported 3 cases of asymptomatic significant left ventricular ejection fraction (LVEF) decrease (Ontruzant, n = 1). Each of these patients recovered with LVEF ≥ 50%. There were no cases of symptomatic congestive heart failure or cardiac death in either cohort.
Events of recurrence, progression and death were reported for 17.2% of patients in the biosimilar group (HR 0.78; 95% CI, 0.48-1.25; P = .30) and 21% in the reference cohort.
Patients in the biosimilar cohort (n = 186) and the reference group (n = 181) received 8 cycles of trastuzumab concurrently with chemotherapy in the neoadjuvant setting. After surgery, they received 10 cycles of trastuzumab over 1 year. Median follow-up duration was 68 months from the point of randomization.