SABCS 2024: Margetuximab vs Trastuzumab Combinations in Early HER2-Positive Breast Cancer

By: Celeste L. Dixon
Posted: Thursday, December 19, 2024

Investigators comparing the neoadjuvant combination of paclitaxel, margetuximab-cmkb, and pertuzumab (TMP) with paclitaxel, trastuzumab, and pertuzumab (THP) in patients with newly diagnosed stage II to III HER2-positive early breast cancer and a CD16A FF/FV genotype found no statistically significant improvement in pathologic complete response rate. Safety and tolerability were also similar between the two regimens, noted Adrienne Waks, MD, of Dana-Farber Cancer Institute, Boston, and colleagues in their work, presented during the 2024 San Antonio Breast Cancer Symposium (SABCS; Abstract LB1-02).

Between 2020 and 2024, the 171 female patients (median age, 53 years) were randomly assigned on a 2:1 basis to neoadjuvant TMP or THP for four cycles. In this trial, patients could have any hormone receptor (HR) status and CD16A genotype FF or FV by central testing; estrogen receptor status and baseline clinical stage were stratification factors. In all, 65% of patients had HR-positive tumors, 87% had cT1–T2 tumors, and 35% had clinically node-positive disease. Additionally, 77% were White, 10% were Black, and 4% were Asian; 13% were Hispanic. The pathologic complete response rate in the TMP arm was 56%, vs 46% in the THP arm (P = .25).

Here are the key study results:

• Among HR-positive patients (n = 111), the pathologic complete response rate was 48% overall (54% for TMP vs 35% for THP).
• Among HR-negative patients (n = 59), the pathologic complete response rate was 63% overall (60% for TMP vs 71% for THP).
• Among HER2 immunohistochemistry 3+ patients (n = 130), the pathologic complete response rate was 62% overall (66% for TMP vs 55% for THP).
• Among HER2 immunohistochemistry < 3+ patients (n = 40), the pathologic complete response rate was 23% (27% for TMP vs 10% for THP).

Disclosure: For full disclosures of the study authors, visit sabcs.org.

2024 San Antonio Breast Cancer Symposium

---