Long-Term Cardiac Safety and Efficacy of SB3 Trastuzumab Biosimilar vs Reference Trastuzumab in HER2-Positive Early Breast Cancer

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In a secondary analysis of the phase III SB3-G31-BC trial, Pivot et al found that perioperative use of the trastuzumab biosimilar SB3 was associated with a similar cardiac safety profile and similar efficacy outcomes compared with reference trastuzumab after up to 6 years of follow-up in patients with early or locally advanced HER2-positive breast cancer. The new data were reported in JAMA Network Open.

Study Details

In the international trial, 538 patients were randomly assigned between April 2016 and February 2017 to either SB3 (n = 267) or trastuzumab (n = 271) with concomitant neoadjuvant chemotherapy consisting of 4 cycles of docetaxel followed by 4 cycles of fluorouracil, epirubicin, and cyclophosphamide. After surgery, patients continued SB3 or trastuzumab monotherapy for 10 cycles of adjuvant treatment. The primary outcome measures in the current analysis were incidence of symptomatic congestive heart failure and asymptomatic, significant decrease in left ventricular ejection fraction. Secondary outcome measures were event-free survival and overall survival.

Key Points

Median follow-up was 68 months (range = 8.5–78.1 months). Cardiac safety was monitored in 367 patients, including 186 in the SB3 group and 181 in the trastuzumab group. No symptomatic congestive heart failure was reported in either group. Asymptomatic, clinically significant left ventricular ejection fraction decreases were observed in one patient (0.4%) in the SB3 group vs two patients (0.7%) in the trastuzumab group. No patients experienced symptomatic cardiac failure or death due to cardiovascular events.

In the total population, no significant differences for the SB3 group vs the trastuzumab group were observed in event-free survival (hazard ratio [HR] = 0.84, 95% confidence interval [CI] = 0.58–1.20, P = .34) or overall survival (HR = 0.61, 95% CI = 0.36–1.05, P = .07). At 5 years, event-free survival was 79.8% (95% CI = 74.8%–84.9%) in the SB3 group vs 75.0% (95% CI = 69.7%–80.3%) in the trastuzumab group and overall survival was 92.5% (95% CI = 89.2%–95.7%) vs 85.4% (95% CI = 81.0%–89.7%).

The investigators concluded: “In this secondary analysis of a randomized clinical trial, SB3 demonstrated cardiac safety and survival comparable to those of [reference trastuzumab] after up to 6 years of follow-up in patients with ERBB2-positive early or locally advanced breast cancer.”

Xavier Pivot, MD, PhD, of the Institut de Cancerologie Strasbourg Europe, Strasbourg, France, is the corresponding author for the JAMA Network Open article.

Disclosure: The study was sponsored by Samsung Bioepis. For full disclosures of the study authors, visit

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