Base Treatment Decisions in Metastatic Breast Cancer on Presence of ESR1 Mutations

In this exclusive MedPage Today video, Virginia Kaklamani, MD, DSc, of UT Health Sciences Center in San Antonioand co-director of theSan Antonio Breast Cancer Symposium (SABCS), discusses a subgroup analysis of the phase III EMERALD trial, which examined variant allele frequencies (VAF) of ESR1 and PIK3CA mutations in estrogen receptor-positive, HER2-negative metastatic breast cancer. The findings emphasize that treatment decisions should be based on the presence of ESR1 mutations rather than VAF.

The following is a transcript of her remarks:

So, the subgroup analysis here is looking at variant allele frequency of ESR1 mutations and PIK3CA mutations.

And the reason is we know that when we get liquid biopsy, we get the variant allele frequencies of the different mutations that are seen, and we still are not understanding how to interpret that.

And the bottom line is, at least as of now, we should not look at variant allele frequency to make a decision. Because even though in the majority of cases the VAF for PIK3CA mutations was higher than the VAF for ESR1 mutations, elacestrant [Orserdu] was still more efficacious.

So, don’t look at the VAF; just look at the presence of ESR1 mutations and make your treatment decisions based on that.