Dr. Rugo on the Phase III SOPHIA Trial in HER2+ Breast Cancer

Hope S. Rugo, MD, director, Breast Oncology and Clinical Trials Education, University of California San Francisco Helen Diller Family Comprehensive Cancer Center, discusses the phase III SOPHIA trial of margetuximab plus chemotherapy versus trastuzumab (Herceptin) plus capecitabine in patients with HER2-positive metastatic breast cancer after prior anti—HER2-targeted therapies.

The trial enrolled more than 500 patients; results showed that the median progression-free survival by blinded independent central review was longer in patients who received the margetuximab regimen compared with trastuzumab, with a difference of approximately 1 month. Based on the hypothesis and the preplanned exploratory subset analysis, it was found that the CD16a alleles may impact the efficacy of margetuximab. Approximately 85% of this patient population has a lower-infinity allele, whereas the remaining population has the higher-infinity allele.

SOPHIA is the first prospective trial to explore the impact of these Fc-gamma receptor alleles, Rugo explains. In the analysis by Fc-gamma receptor genotype, the PFS appeared to be enhanced with margetuximab in patients who were carriers of the CD16A-F allele compared with that in the intent-to-treat population. In those with the CD16A-F allele, the median PFS was 6.9 months in patients randomized to margetuximab compared with 5.1 months in those randomized to trastuzumab (HR, 0.68; P = .005).

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