Several drugs have been developed to treat breast cancer that is responsive to estrogen. Selective estrogen-receptor modulators (SERMs; e.g., tamoxifen, raloxifene) inhibit the effects of estrogen on breast cancer cells.
Tamoxifen is taken in pill form once or twice per day, usually for 5 years after breast cancer surgery, radiation and/or chemotherapy to prevent recurrence. Tamoxifen can cause serious side effects, including early stage cancer of the lining of the uterus (this risk increases after 5 years of taking the drug), blood clots and stroke. Common side effects include the following:
- Bone pain
- Hair loss
- Hot flashes
- Pain or redness at the tumor site
- Weight loss
Results of a large international clinical trial indicate taking tamoxifen for 10 years following primary treatment for breast cancer, instead of 5 years, may reduce recurrences and deaths from the disease further. However, at least one other study did not support this evidence. Research is ongoing; talk to your health care provider about follow up breast cancer treatment.
Studies are being conducted to determine if raloxifene (Evista) can effectively reduce the risk for breast cancer. Side effects include hot flashes and leg cramps.
Fulvestrant (Faslodex) destroys estrogen receptors in breast cancer cells. It is used to treat metastatic breast cancer in postmenopausal women who have been treated unsuccessfully with tamoxifen. This treatment is administered once a month by intramuscular injection. Side effects include nausea, hot flashes, and weight gain.
Goserelin (Zolodex) is a synthetic form of luteinizing hormone-releasing hormone (LHRH) that is prescribed to treat metastatic breast cancer in premenopausal women. This medication signals the body to stop producing estrogen, depriving the tumor of the estrogen it needs to grow. Several weeks of treatment are needed before tumor growth slows. Side effects include hot flashes, sexual dysfunction, increased pain, and rash.
Aromatase inhibitors (e.g., anastozole [Arimidex], letrozole [Femara], exemestane [Aromasin]) inhibit the action of the enzyme aromatase, which is involved in estrogen production in postmenopausal women. These drugs may be prescribed for postmenopausal women with advanced breast cancer that has been unsuccessfully treated with tamoxifen, or to extend treatment after tamoxifen.
Side effects include the following:
- Hot flashes
- Increased appetite
Biological therapy (also called immunotherapy) involves using trastuzumab (Herceptin) to inhibit tumor growth and enhance the immune system's ability to fight cancer. It also may be combined with chemotherapy as a first line treatment for metastatic breast cancer and may be used after chemotherapy or anti-estrogen therapy to improve the effectiveness of the treatment.
When used alone or in combination, side effects include the following:
- Cardiac dysfunction (causes severe cough, shortness of breath, difficulty performing physical activities)
- Congestive heart failure
- Low blood cell count (e.g., anemia, neutropenia)
In November 2006, the Food and Drug Administration approved Herceptin® for the treatment of HER2 positive breast cancer, following surgery and in combination with standard chemotherapy.
In studies conducted by the National Cancer Institute, patients who received Herceptin had a reduced risk for recurrence as many as 3 years after surgery. Due to the risk for heart damage, patients must be screened for heart function before beginning and during this treatment.
In March 2007, the FDA approved lapatinib (Tykerb) in combination with capecitabine (Xeloda) for the treatment of advanced or metastatic HER2 positive breast cancer that has not responded to other treatments.
Side effects include diarrhea, nausea, rash, vomiting, and fatigue. This treatment also carries a risk for heart damage and patients are monitored before beginning and during treatment.
In June 2012, the FDA approved pertuzumab (Perjeta) to treat advanced HER2 positive breast cancer. This medication is intended for use in patients who have not yet been treated for metastatic breast cancer with an anti-HER2 therapy or chemotherapy. It is used in combination with trastuzumab (Herceptin) and the chemotherapy drug docetaxel. Common side effects of pertuzumab include diarrhea, hair loss, decreased white blood cell counts, nausea, fatigue, rash and nerve damage (neuropathy).