Estrogen receptor-sensitive breast cancer
Estrogen receptor-sensitive breast cancer, also known as estrogen receptor-positive (ER+) breast cancer, is a type of breast cancer that is influenced by estrogen stimulation. It primarily arises from the epithelial cells in the breast, with most cases originating in the ducts. Age and gender are significant risk factors, particularly for women over fifty, although younger women may present with more aggressive forms of the disease. Factors such as early menstruation, late menopause, and certain inherited mutations (like BRCA1 and BRCA2) can elevate risk.
The disease depends on estrogen for tumor growth, as the hormone promotes cell division in breast tissue. Symptoms often include palpable lumps, changes in breast shape or size, and unusual discharge from the nipple. Screening methods include breast self-exams, clinical exams, mammograms, and ultrasound, with biopsies necessary for definitive diagnosis.
Treatment typically involves surgery, such as lumpectomy or mastectomy, followed by radiation and chemotherapy. Hormone therapies that block estrogen receptors are also effective. With improved treatments and screening, the survival rates for this type of cancer have increased significantly, although it remains a leading cause of cancer deaths among women. Research continues to explore potential links between lifestyle factors and the disease's development.
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Estrogen receptor-sensitive breast cancer
ALSO KNOWN AS: Estrogen receptor-positive breast cancer, hormone-dependent breast cancer, ER+ breast cancer
RELATED CONDITIONS: Breast cancer, fibroadenomas, breast cysts, fibrocystic breasts
DEFINITION: Estrogen receptor-sensitive breast cancer is the diagnosis given for breast cancer driven by estrogen stimulation. Breast cancer cells are primarily epithelial. Most breast cancers originate in the ducts of the breast, where cells are larger than normal epithelial cells and exhibit various patterns. A smaller percentage originates in the lobules, where cells are smaller, uniform, and appear in rows. Invasive cancers compose the remaining types of breast cancer, though these are rare.
Risk factors: Age and gender are the strongest risk factors, with most cases occurring in women over fifty. However, younger women tend to have more aggressive tumors. Early menstruation (before twelve), late menopause (after fifty-five), and reproductive history (late pregnancy) are associated with higher risk, possibly because of the longer lifetime exposure to growth-stimulating estrogen. Inherited mutations in the tumor-suppressor genes BRCA1 and BRCA2 and a family history of the disease can also increase risk.
Etiology and the disease process: Estrogen appears to be involved with the proliferation and progression of estrogen receptor-sensitive breast cancer. The ovaries, adrenal glands, and some fat tissue produce estrogen. In normal breast cells, especially the milk glands, estrogen stimulates cell division directly and through its influence on other hormones (such as progesterone) and growth factors. Researchers believe that higher-than-normal amounts of estrogen can increase the rate of cell division (and the risk for chance mutations) and trigger the proliferation of cells already harboring genetic mutations. Even after cancer has developed, estrogen receptor-sensitive cells depend on estrogen stimulation for continued growth and possibly for survival.
Incidence: Breast cancer is the most common cancer in women in the United States (excluding nonmelanoma skin cancers). After steadily increasing during the 1980s and 1990s, breast cancer incidence began to decrease between 2001 and 2003 from approximately 100 to 75 per 100,000 in the United States—the incidence rate remained relatively constant through the 2010s. However, by the mid-2020s, research indicated increased incidence rates among younger women. One in eight women develop breast cancer.
Symptoms: The classic symptom of this type of cancer is a palpable lump in the breast. Other symptoms include a noticeable difference in breast size or shape, breast swelling, nipple discharge or inversion, dimpling of the skin, orange peel consistency, and enlarged lymph nodes in the area of the armpit or collarbone.
Screening and diagnosis: The breast self-exam, in combination with the clinical exam and mammogram, during which breast X-rays are taken to detect masses too small to feel, are the best screening tools available. Modern options include ultrasound, which can differentiate between cysts and solid tumors and help diagnose younger women who typically have higher breast density. Magnetic resonance imaging (MRI) helps visualize tumor size and locate additional tumors, and computer-aided detection (CAD) scans a mammogram for undetected tumors. Nuclear medicine studies for breast cancer screening and diagnostics are underway.
A biopsy is necessary to confirm cancer, and the type of selected depends on size, location, and number of masses, as well as the patient’s medical history. A fine-needle biopsy uses a very thin needle to draw out fluid from abnormal tissue, a core biopsy uses a larger needle to remove a tissue sample, a (or vacuum-assisted) biopsy inserts a probe that suctions and slices several tissue samples, and surgical biopsy removes all or part of the abnormal tissue. Surgical biopsy may be ultimately necessary for confirmation of cancer.
Tumors are described using the TNM (tumor/lymph node/metastasis) classification system, which corresponds with four main breast cancer stages.
Treatment and therapy: Treatment options include a breast-conserving lumpectomy (removal of the tumor and part of the surrounding tissue) or a modified radical mastectomyremoval of the breast, lymph nodes, and fatty tissue associated with the breast and lining of the chest. Both surgeries are a drastic improvement over the disfiguring Halstead radical mastectomy that was used until the 1970s. Postoperative radiation is recommended, followed by chemotherapy, which consists of a combination of cyclophosphamide (Cytoxan), methotrexate or doxorubicin (Adriamycin), and 5-fluorouracil (5-FU). Because this type of breast cancer responds to hormone stimulation, hormone therapy that antagonizes the estrogen receptor, like tamoxifen (Nolvadex), Elacestrant (Orserdu), and toremifene (Fareston), are used in addition to chemotherapy. Treatments continue to be developed to improve patient outcomes.
Prognosis, prevention, and outcomes: Due to increased screening and the advantages of hormone therapy, survival rates are greater than 80 percent for women with estrogen receptor-sensitive breast cancer. Since 1990, mortality rates have decreased by 25 percent, although it remains the second leading cause of cancer deaths in women. (Lung cancer is the first.)
Because the cause is unknown, preventive measures are difficult to outline. Researchers are investigating possible links between estrogen receptor-sensitive breast cancer and oral contraceptives, environmental factors, silicone implants, obesity, hormone replacement therapy, smoking, alcohol, and lack of exercise.
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