Germline and Somatic Biomarker Testing (Including Liquid Biopsy) for Targeted Treatment and Immunotherapy in Breast Cancer

Multiple biomarkers are being evaluated to predict response to targeted treatments for patients with advanced or high-risk breast cancer. These include tissue-based testing as well as circulating tumor DNA and circulating tumor cell testing (known as liquid biopsy). The objective of this evidence review is to examine whether biomarker testing for BRCA variants, PIK3CA, ESR1, Ki-67, RET, BRAF, circulating tumor DNA, or circulating tumor cells improves the net health outcome in patients with breast cancer who are considering targeted therapy.