About HER2-low Metastatic Breast Cancer

Historically, HER2 status has been viewed in binary terms: positive or negative1

~85% of patients with BC were previously classified as HER2-negative and were not eligible for anti-HER2 therapy1

˜65% of patients with breast cancer may have an actionable level of HER2 expression, and ˜50% of HER2-negative breast cancer tumors can be classified as HER2-low (IHC 1+ or IHC 2+/ISH–)˜65% of patients with breast cancer may have an actionable level of HER2 expression, and ˜50% of HER2-negative breast cancer tumors can be classified as HER2-low (IHC 1+ or IHC 2+/ISH–)

Low HER2 expression occurs in both HR+ and HR– mBC, and had previously not been actionable3

HR+

For patients classified with HR+/HER2-negative mBC, outcomes decline once endocrine therapy (ET) has been exhausted4-6

  • mPFS decreases from ~16-28 months with ET-based options to ~5 months with subsequent chemotherapya
HR–

For patients classified with HR–/HER2-negative mBC who are ineligible for or have exhausted targeted treatment, chemotherapy remains the only option7,8

  • mPFS decreases from ~10 months with first-line options to ~2 months with subsequent chemotherapya

amPFS ranges represent estimates from publicly available clinical trial data. These clinical trials were conducted independently, and their outcomes are not intended to be used as a cross-trial comparison.

The treatment landscape is evolving, and the need to identify additional targetable populations, including patients with HER2-low mBC, has become critical1

BC, breast cancer; HER2, human epidermal growth factor receptor 2; HR–, hormone receptor-negative; HR+, hormone receptor-positive; IHC, immunohistochemistry; ISH, in situ hybridization; mBC, metastatic breast cancer; mPFS, median progression-free survival.