HJNO Sep/Oct 2022

52 SEP / OCT 2022 I  HEALTHCARE JOURNAL OF NEW ORLEANS ONCOLOGY DIAL GUE COLUMN ONCOLOGY BREAST CANCER is the most common cancer and is one of the leading causes of cancer-related deaths worldwide and in the United States. More than 290,000 new cases in the U.S. are expected to be diagnosed in 2022, resulting in more than 43,000 deaths. Breast cancer is well recognized as a highly heterogeneous disease in terms of biological features, prognosis, and treatment sensi- tivity. In past decades, access to anti-HER2 drugs in the context of pivotal trastuzum- ab trials has driven the dichotomy between HER2-positive and HER2-negative breast cancer. Under current treatment guidelines, only patients with HER2-positive metastatic breast cancer show benefits from HER2- directed therapy. Historically, HER2 status has been defined as positive versus nega- tive. Still, we know that a large proportion of cancers within the HER2-negative clas- sification also express low levels of HER2 — which we commonly refer to as HER2-low breast cancers (BCs) — and this low level of HER2 may still be targetable. About 50% of all primary breast can- cers show a low-level expression of HER2 (HER2-low), defined as immunohistochemi- cally 1+ or 2+ and lack of HER2 gene ampli- fication measured by in situ hybridization. This low HER2 expression is a promising The Exciting New Field of HER2-Low Breast Cancer Treatment