Repeat Biopsies and Likelihood of Identifying HER2-Low Triple-Negative Breast Cancer

By: Celeste L. Dixon
Posted: Friday, July 7, 2023

Knowing how the number of successive biopsies may relate to documented changes in HER2 status in metastatic triple-negative and hormone receptor–positive breast cancer is crucial, because the use of fam-trastuzumab deruxtecan-nxki (T-DXd) is approved to treat HER2-low—but not HER2-0 (ie, HER2-absent)—disease. A study involving 529 consecutive patients with this type of breast cancer at one medical center found that the proportion with a HER2-low result increased with the number of successive biopsies. The results were presented by Yael Bar, MD, PhD, of Massachusetts General Hospital, Boston, and colleagues at the 2023 American Society of Clinical Oncology (ASCO) Annual Meeting (Abstract 1005).

The work supports the concept that “HER2-low is a spectrum, not a specific entity,” wrote the investigators.

Specifically, the proportions of patients with HER2-low results were 60%, 74%, 83%, 87%, and 100% when one (192 patients), two (235 patients), three (52 patients), four (38 patients), and five to nine (12 patients) biopsies were conducted, respectively. Of note, further research is needed to determine whether the dynamic HER2 results represent variations in underlying biology or in facets of the analyses. HER2-low was defined as HER2 immunohistochemistry (IHC) 1+ or 2+ with nonamplified in situ hybridization.

In women with no prior HER2-low result, about one-third were converted to HER2-low with each successive additional biopsy: 322 of 529 at first biopsy; 44 of 131 on second biopsy; 8 of 25 at third biopsy; 3 of 8 at fourth biopsy. Additionally, Dr. Bar and co-researchers continued: “HER2 status distribution did not significantly vary between the different types of biopsy: 58%, 63%, and 54% of patients had a HER2-low result in their core, surgical, or metastatic biopsy, respectively (P = .20).” Nor did HER2 status conversion rates appear to differ between women who had neoadjuvant therapy with residual disease and women who had surgery as their primary intervention.

Disclosure: Dr. Bar reported no conflicts of interest. The other study authors’ disclosure information can be found at coi.asco.org.

2023 ASCO Annual Meeting

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