Studying Changes in Ki-67 Expression in Patients with Breast Cancer Receiving Endocrine Therapy Before Surgery
This trial studies Ki-67 expression changes after patients undergo cancer removal surgery and receive at least two weeks of endocrine therapy (ET) for estrogen receptor positive (ER+)/human epidermal growth factor receptor 2-negative (HER2-) breast cancer. This study will compare changes in Ki67 expression between patients who are carriers vs. noncarriers of BRCA2 mutation. Everyone has the BRCA2 gene. However, some people have a change (mutation) in this gene that increases the risk of breast cancer. Estrogen plays a role in cancer growth in people with ER+ breast cancer. BRCA proteins influence estrogen signaling and a BRCA2 gene mutation may have a negative influence on response to ET. Anastrozole is standard ET treatment for patients with ER+/HER2- breast cancer, and they work by lowering the levels of estrogen in the body. A standard treatment in people with ER+/HER2- breast cancer is endocrine therapy, which blocks or decreases hormones. People usually receive endocrine therapy after surgery rather than before. Researchers have found that Ki67 expression is a helpful tumor marker, meaning it can be helpful in showing whether cancer growth is taking place. By looking at changes in Ki67 expression while receiving ET given before surgery, this study may provide valuable information about effective treatment approaches for patients with ER+/HER2- breast cancer who are carriers or noncarriers of the BRCA2 mutation.