Women are by far the primary victims of breast cancer, with 61,000 non-invasive cases and 246,660 invasive cases of the disease expected to be diagnosed in American women in 2016, according to the American Cancer Society.

The malignant disease is caused by an inherited or acquired DNA mutation, but the reasons behind this defect are not fully understood. Patients who suffer from the disease often experience symptoms like a new breast lump or mass, swelling of all or part of the breast, skin irritation or dimpling, breast or nipple pain, nipple retraction, redness, scaliness, thickening of the nipple or breast skin, or a nipple discharge other than breast milk.

The disease is expected to kill 40,450 women this year, according to the ACA. But advancements in the field are resulting in earlier diagnosis, more effective treatments, and greater survival rates. Treatment for breast cancer is divided into two categories — local or systemic treatment. An approach focused on treating the cancer without harming the rest of the body, like surgery or radiation therapy, is known as local treatment, while systemic treatment aims to reach cancer cells anywhere in the body. This includes chemotherapy, hormone therapy, targeted therapy, and bone-directed therapy.

Targeted Therapy for Breast Cancer

“Targeted cancer therapies are drugs or other substances that block the growth and spread of cancer by interfering with specific molecules (molecular targets) that are involved in the growth, progression, and spread of cancer,” according to the National Cancer Institute of the National Institutes of Health.

Targeted therapy is sometimes referred to as molecularly targeted drugs, molecularly targeted therapies, or precision medicine. Its development starts with identifying good targets, which means agents that are crucial for the process of cancer cell growth and survival. This can be done by measuring the levels of a protein in cancer cells compared to healthy cells.

Potential targets are proteins present in great amounts in cancer cells but not in healthy ones, particularly if they are already known to contribute to cell growth or survival. The purpose of a targeted therapy is to address these proteins and attack them or disable their function.

“Many different targeted therapies have been approved for use in cancer treatment,” according to the National Cancer Institute. “These therapies include hormone therapies, signal transduction inhibitors, gene expression modulators, apoptosis inducers, angiogenesis inhibitors, immunotherapies, and toxin delivery molecules.”

The drugs approved by the U.S. Food and Drug Administration (FDA) are Everolimus (Afinitor), tamoxifen (Nolvadex), toremifene (Fareston), Trastuzumab (Herceptin), fulvestrant (Faslodex), anastrozole (Arimidex), exemestane (Aromasin), lapatinib (Tykerb), letrozole (Femara), pertuzumab (Perjeta), ado-trastuzumab emtansine (Kadcyla), and palbociclib (Ibrance).

The different types of targeted therapy are divided into subtypes. Hormone therapies are used to slow or stop the growth of hormone-sensitive tumors, which means that the drugs disable the body’s capacity to produce the hormones needed for the cancer to grow or that it disrupts the hormones’ action. Signal transduction inhibitors block the work of transduction signals from the environment to the cells to stop the expected reaction. Gene expression modulators alter the normal action of the proteins that contribute to the control of gene expression, while apoptosis inducers promote a process that kills cells called apoptosis.

Angiogenesis inhibitors cut the blood supply needed for tumors to grow by block the growth of new blood vessels to the tumors. Immunotherapies promote the destruction of cancer cells by triggering the body’s own immune system. Finally, monoclonal antibodies are used to deliver toxic molecules and promote the death of specific cancer cells.

Benefits and Risks of Targeted Therapy

“Targeted therapies are currently the focus of much anticancer drug development,” notes the Cancer Institute. “They are a cornerstone of precision medicine, a form of medicine that uses information about a person’s genes and proteins to prevent, diagnose, and treat disease.”

The importance given to research in the field of targeted therapy is based on its potential benefits. Breast cancer targeted therapy is expected to have greater results since the treatment is tailored specifically to each patient’s needs and tumor characteristics.

“Many targeted cancer therapies have been approved by the Food and Drug Administration to treat specific types of cancer. Others are being studied in clinical trials (research studies with people), and many more are in preclinical testing (research studies with animals),” the National Cancer Institute states on its website

There are, however, potential risks, side effects, and limitations associated with this approach. One of the greatest challenges is that cancer cells tend to become resistant to targeted therapy, making it no longer effective. Therefore, the results of targeted therapy are often better when it is used as combined therapy with chemotherapy drugs. A common combination known to be effective includes the targeted therapy trastuzumab (Herceptin) in combination with the chemotherapy drug docetaxel for women with metastatic breast cancer that overexpresses the protein HER2/neu. Another limitation is the difficulty in developing targeted therapy drugs.

Regarding side effects, investigators expected to see fewer toxic effects in targeted therapy compared to chemotherapy, but numerous side effects have been reported. The most common are diarrhea and liver problems, including hepatitis and elevated liver enzymes, but patients may see other problems such as skin problems (acneiform rash, dry skin, nail changes, hair depigmentation), problems with blood clotting and wound healing, high blood pressure, and gastrointestinal perforation.
“Certain side effects of some targeted therapies have been linked to better patient outcomes. For example, patients who develop acneiform rash (skin eruptions that resemble acne) while being treated with the signal transduction inhibitors erlotinib (Tarceva) or gefitinib (Iressa), both of which target the epidermal growth factor receptor, have tended to respond better to these drugs than patients who do not develop the rash,” according to the National Cancer Institute.
Note: Breast Cancer News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website. 
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