HER2-positive breast cancer is an aggressive form of cancer in which the cells produce too much HER2 protein, causing the cancer to multiply rapidly and divide uncontrollably. Metastatic breast cancer is the most advanced stage (stage IV).It describes cancer that has spread the breast's original location to other parts of the body. Thus, HER2-positive metastatic breast cancer describes a rapidly growing cancer that has already spread throughout the body. It is less responsive to traditional treatments such as hormonal therapy and certain chemotherapy agents, and much more likely to recur than other forms of breast cancer. However, treatments such as HER2-targeted therapy allow doctors to target the HER2 proteins specifically and prevent them from accelerating cell growth and the cancer’s capacity to invade and spread.
Your doctor must conduct a biopsy to determine if your breast abnormality is actually cancer. He or she will take a tissue sample and send it to a pathologist, who will examine it under a microscope and make a diagnosis. The pathologist will send a report back to your physician containing their diagnosis and some important characteristics of the cancer, including HER-2 status. The pathologist may conduct the following tests to determine HER2 status.
The IHC test uses antibodies to detect the HER2 protein in cancer cells. These antibodies produce visible stains when they encounter the proteins, allowing the pathologist to determine if the cells contain normal or unusually high amounts of HER2. The results of the IHC test can be 0 (negative), 1+ (negative), 2+ (borderline), and 3+ (HER2-positive).
The FISH test uses DNA to map the genetic makeup of a person's cells. It allows the pathologist to visualize the number of specific genes. The results are either HER2-positive or HER2-negative.
This test is more accurate than IHC and is used when IHC results are inconclusive.
Women with breast cancers that are HER2 amplified (positive) may be eligible to receive medication targeting the HER2 protein.
This test determines if there are too many copies of the HER2 gene using a stain that makes the genes change color. The stain is applied to the tissue sample and examined under a microscope. The results of this test are either HER2-positive or HER2-negative.
The Inform HER2 Dual ISH test also uses a stain to determine the number of HER2 gene copies. The results are either HER2-positive or HER2-negative.
Women should undergo routine HER2 status testing, as the results may affect treatment decisions. HER2-negative breast cancer can rarely change to HER2-positive over time and vice-versa.
Doctors usually treat HER2-positive metastatic breast cancer with a combination of targeted therapy and chemotherapy or hormonal therapy to slow down tumor growth, improve symptom control and quality of life, and extend survival. Targeted therapy is extremely effective in treating this subtype of breast cancer, and has greatly improved the survival rate and quality of life for women with this aggressive form of cancer.
• Targeted therapy specifically targets HER2-positive cancer cells, preventing the HER2 proteins from fueling cell growth. These medications include trastuzumab, lapatinib, pertuzumab, neratinib, tucatinib, trastuzumab, deruxtecan, margetuximab, and ado-trastuzumab emtansine (T-DM1). First-line therapy is often a combination of trastuzumab, pertuzumab, and chemotherapy, Taxotere or paclitaxel. For hormone receptor-positive tumors, first-line therapy may occasionally be hormone therapy plus trastuzumab or lapatinib. However, suppose cancer gets worse or comes back after these treatments. In that case, second-line therapy may include treatment with T-DM1, or another combination of drugs that the patient has not yet received including lapatinib or pertuzumab. Further, after radiation therapy, there are options of using tucatinib, trastuzumab, and capecitabine for brain metastasis. For adjuvant therapy in HER2-positive breast cancer, there are choices of trastuzumab alone, trastuzumab plus pertuzumab, or trastuzumab followed by neratinib. The type of optimal adjuvant anti-HER2 therapy needs discussion with your doctor. Antibody–drug conjugates or ADCs are a class of biopharmaceutical drugs designed as a targeted therapy for treating cancer. Unlike chemotherapy, ADCs are intended to target and kill tumor cells while sparing healthy cells.
Chemotherapy uses drugs that circulate throughout the bloodstream and kill any cancer cells they encounter. It can help shrink metastases and control symptoms of the disease. Chemotherapy medications may be given through the vein (intravenously) or by mouth (orally).
Radiation therapy uses high-energy rays or particles to destroy cancer cells. In stage IV breast cancer, it is given to shrink tumors, relieve pain and ease symptoms.
Clinical trials allow patients to receive a new treatment before it is available to the general public. In some cases, this may be a new drug that has not been used in humans before, or it may be a drug or drug combination that is not currently used for that specific type of cancer. Early phase clinical trials are often used to test the side effects of a drug or drug combination, while later phase clinical trials are used to see how effective a new treatment might be for a certain type of cancer. Clinical trials allow doctors and researchers to improve the treatment of cancers with possibly more effective therapies. A clinical trial may be a new, groundbreaking drug or it may have no effect. It is important to talk with your doctor about the pros and cons of clinical trials for your particular situation. Participation in clinical trials is highly encouraged.
One of your biggest allies in battling HER2+ metastatic breast cancer will be your oncologist. Questions are your primary resource to gain a better understanding of your disease and enhance your quality of care. Well-thought-out questions can help you get the most out of your appointments and can make all the difference.
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