HER2 status in elderly women with breast cancer

HER2 (human epidermal growth factor receptor 2) is an important biomarker in breast cancer, but its prevalence in elderly women is not well established. Previous studies reported HER2 status based on either immunohistochemistry (IHC) or fluorescent in situ hybridization (FISH) interchangeably. However, the tests may give discordant results. We report the prevalence of HER2 amplification in elderly women using only FISH.

We retrospectively identified women 65 years and older undergoing core biopsy, lumpectomy or mastectomy for primary breast malignancy at a single institution between 2009 and 2011. Data collected included age, histopathological type, hormone receptor status, and HER2 status. Descriptive statistics were performed using SAS Software, Version 9.2.

One hundred fifty-eight women were included in the study. Most had invasive ductal carcinoma (74.7%), and were positive for either estrogen (ER) or progesterone (PgR) receptors (82.3% and 70.0%, respectively). Only 17% were negative for both ER and PgR; 11.4% were triple negative. Nineteen samples (12.0%) were positive for HER2. In univariate analyses, hormone receptor and HER2 status did not vary with age. When stratified by age, 60% of women with hormone receptor/HER2 positive tumors were younger than 70 years, compared with 22.2-33.3% of women in other subgroups. The difference was not statistically significant (p=0.20).

This study adds to the knowledge of the biology of breast cancer in elderly women. Triple negative tumor incidence was similar to that previously reported for women under 70 years old, but HER2 positive tumors were less common. Additional prospective studies are needed to confirm our findings.