Many women with metastatic hormone receptor-positive (HR+) breast cancer have experienced improved clinical outcomes with alpelisib, a PIK3CA inhibitor. A new study led by researchers at Memorial Sloan Kettering Cancer Center has demonstrated that the Guardant360 liquid biopsy test from Guardant Health, Redwood City, Calif, effectively identifies patients with PIK3CA mutations along with other mutations that correlate with treatment resistance.1

The phase I/II study—a longitudinal analysis of tumor and blood-based circulating tumor DNA in metastatic patients treated with alpelisib plus fulvestrant—showed 89% concordance between tissue and blood for PIK3CA mutations. In the study, the Guardant360 liquid biopsy also detected significantly more potential resistance alterations when compared to tissue biopsy.

“While the introduction of PI3K inhibitors in combination with endocrine therapy has made a significant difference in improving progression-free survival, the findings of this new study indicate the need for more comprehensive genomic profiling in hormone receptor-positive metastatic breast cancer patients,” says Pedram Razavi, MD, PhD, a lead study investigator and a medical oncologist at Memorial Sloan Kettering Cancer Center. “Testing more broadly beyond PIK3CA can help identify potential mechanisms of resistance to therapy and determine those patients most likely to respond to a PI3K inhibitor.”

For more information, visit Guardant Health.


1. Razavi P, Dickler MN, Shah, PD, et al. Alterations in PTEN and ESR1 promote clinical resistance to alpelisib plus aromatase inhibitors. Nat Cancer. 2020;1:382–393;  doi:10.1038/s43018-020-0047-1.

Featured image: Metastatic cancer cells spreading on the surrounding tissue. Image © Nicola Ferrari, courtesy Dreamstime ( ID 45971826).