While intrinsic mutations, like PIK3CA, are present at the outset and can be identified upfront in patients with HR+/HER2- metastatic breast cancer, acquired mutations, like ESR1, cannot be detected on baseline tumor profiling. That’s why longitudinal monitoring with liquid biopsies over the course of treatment is required. Learn more about these key differences in testing for acquired versus intrinsic mutations with Dr. Megan Kruse, a breast medical oncologist at the Cleveland Clinic.