Breast Cancer Basics
What You Need to Know About Hormone Receptor Status
Understanding hormone receptors can be essential for breast cancer patients, allowing them to ask the right questions and better understand their treatment options.
Hormone receptor (HR) status helps physicians determine which drug therapies will be most effective in combating an individual’s breast tumor. HR status also serves as an important predictor of overall patient outcome for women with breast cancer. Understanding the biology behind this key characteristic of breast tumors can empower breast cancer patients to become more proactive in their cancer treatment strategies.
One Disease, Many Types
Breast cancer is the most common cancer among women in the United States today, with 180,000 new cases diagnosed every year. In fact, approximately one in every eight American women can expect to develop breast cancer within her lifetime. While a potentially staggering number of women are affected by the disease, the term breast cancer actually encompasses a number of diverse tumor subtypes. Breast tumors can differ in the types of genes that become expressed inappropriately (either at levels higher than or lower than normal), a trait referred to as a tumor’s molecular signature. Tumors also differ in their behavior, such as growth rate (slow versus fast-growing) and potential to spread to other organs in the body (a process called metastasis). While all of these distinctions hold important implications for patient survival, one key feature of breast tumors that newly-diagnosed patients are generally unfamiliar with is hormone receptor status.
Hormone Receptor Status Explained
Hormones in the blood, such as estrogen and progesterone, bind to hormone receptors on the surface of breast cells, triggering them to grow. Under normal circumstances (such as breast growth during puberty or pregnancy), hormone-induced tissue growth proceeds as directed by the body and halts naturally. These hormonal cues become problematic when an abnormal breast cell fails to respond to the body’s anti-growth signals. Thus, a pre-malignant breast cell can use estrogen and progesterone to grow unchecked, leading to the development of a tumor.
About two-thirds of breast cancers have some degree of hormone receptor positivity, meaning that they are responsive to hormonal growth signals. Thus, if a breast tumor is estrogen-receptor positive (ER+) and/or progesterone-receptor positive (PR+), it is these hormones that fuel the tumor’s growth. Such tumors are said to be hormone-sensitive and tend to respond well to drugs which suppress these hormones (such as tamoxifen), which block the tumor cells from receiving additional growth signals. Additionally, ER+/PR+ tumors also tend to be somewhat slower growing than tumors which are hormone insensitive, making HR status a helpful predictor of tumor behavior.
Determining Hormone Receptor Status
In the clinic, microscopic examination of a biospied tumor sample can determine whether or not a breast tumor expresses estrogen and/or progesterone receptors. Tumor samples are typically scored for hormone receptivity on a scale of 0-3 depending on the amount of hormone receptors present, where 0 = none, 1 = few, 2 = moderate, and 3 = numerous. The pathologist also estimates the number of cells within the tumor sample that express these receptors, as this can vary by tumor. Even tumors with a low receptor score may respond to hormone treatment, so patients may want to ask their physician for their numerical ER/PR scores and discuss if hormone treatment is a good option. In contrast, patients with hormone-insensitive tumors (ER-/PR-) are more effectively treated with drugs that halt tumor growth in ways other than blocking hormone signaling. For example, targeting the Her2/neu oncogene, which is overexpressed in many ER- breast cancers, has proved effective in treating women with hormone-insensitive breast tumors.
For more information visit the American Cancer Society: http://www.cancer.org/docroot/lrn/lrn_0.asp
