A presentation at the American Society of Clinical Oncology (ASCO) Annual Meeting (May 31 – June 4, 2019; Chicago, IL) provided further support for the safety and efficacy profile of trastuzumab-dkst for patients with HER2-positive metastatic breast cancer.
HERITAGE was a multicenter, double-blind, randomized, parallel-group, phase III trial designed to evaluate the efficacy and safety of trastuzumab-dkst vs trastuzumab as first-line options for patients with HER2-positive metastatic breast cancer. Previously, overall response at week 24 and progression-free survival (PFS) at week 48 were reported.
Cornelius F Waller, PhD, University of Freiburg Medical Center (Germany), and colleagues randomized 500 patients (1:1) to trastuzumab-dkst or trastuzumab. Both patients groups received taxane after initial therapy. After 24 weeks, patients with responding and stable disease continued monotherapy per randomization. Safety and overall survival (OS) during maintenance, as well as through 36 months of follow-up, were reported at the ASCO Annual Meeting.
Among the total patient population, 343 received monotherapy after 24 weeks (trastuzumab-dkst, n = 179; trastuzumab, n = 164). A total of 128 patients discontinued monotherapy (trastuzumab-dkst, n = 63; trastuzumab, n = 65), and mean time to discontinuation was 19 months in both groups.
Dr Waller and colleagues reported that treatment-related adverse events during monotherapy were similar for trastuzumab-dkst (69%) and trastuzumab (73%). Most treatment-related adverse events were low grade, and serious adverse event rates were only 6% in both groups. The cumulative rates of treatment-related adverse events of special interest were similar for hypersensitivity, pulmonary, and cardiac events, they acknowledged.
Furthermore, researchers noted that at 36 months, 169 patients had received further lines of therapy – with similar distribution of HER2-specific treatments, endocrine therapies, and chemotherapies. Median PFS was 11.1 months in both groups. Similarly, median duration of response was 9.9 and 9.8 months for trastuzumab-dkst and trastuzumab, respectively, and median OS was 35.0 and 30.2 months.
“Long-term safety data with similar median OS compared with originator trastuzumab further support the safety and efficacy profile of trastuzumab-dkst,” authors of the study concluded.—Zachary Bessette