INTRODUCTION

Breast cancer is the most common female cancer in the United States. Finding and treating breast cancer in the early stages allows many women to be cured.

After surgery, systemic (body-wide) anticancer treatment may be given to eliminate any microscopic tumor cells that might remain in the body. This type of therapy is called adjuvant therapy, and it is a very important component of breast cancer treatment. Adjuvant therapy significantly decreases the chance that the cancer will return (or recur), and it also improves a woman's chance of surviving her cancer.

There are three options for systemic adjuvant therapy of breast cancer: endocrine therapy, chemotherapy, and trastuzumab (Herceptin). This article will focus on adjuvant therapy for postmenopausal women with hormone-responsive breast cancer. Adjuvant treatment for premenopausal women with hormone-responsive breast cancer is discussed in a separate monograph. (See "Patient information: Early stage breast cancer treatment in premenopausal women (Beyond the Basics)".)

Adjuvant treatment for women with hormone-nonresponsive breast cancers, as well as a discussion about the side effects and indications for chemotherapy and trastuzumab in women with HER2-positive breast cancer, is presented elsewhere. (See "Patient information: Adjuvant medical therapy for HER2-positive breast cancer (Beyond the Basics)".)

DEFINING HORMONE-RESPONSIVE BREAST CANCER

Some breast cancers require the female hormone estrogen (estradiol) to grow, while other breast cancers are able to grow without estrogen. These hormone receptors can be estrogen receptors (ER), progesterone receptors (PR), or both.

If hormone receptors are present within a breast cancer (called hormone responsive), you are more likely to benefit from treatments that lower estrogen levels or block the actions of estrogen. These treatments are referred to as endocrine or hormone therapies.

ENDOCRINE THERAPY OPTIONS

The goal of endocrine therapy is to prevent breast cancer cells from being stimulated by estrogen. In postmenopausal women with early breast cancer, two endocrine treatments are possible: tamoxifen and a class of drugs called aromatase inhibitors (AIs).

Tamoxifen — Tamoxifen (Nolvadex) prevents estrogen from binding to the estrogen receptor, thereby preventing estrogen from stimulating the growth of the breast cancer cells. It is usually recommended for five years, but the benefits of taking tamoxifen last for at least ten years after the drug is stopped. Taking tamoxifen for more than five years does not add further benefit, and the risk of side effects such as uterine cancer increases with longer treatment. However, there is added benefit from switching over to an aromatase inhibitor after taking tamoxifen for two to three or five years. (See 'Aromatase inhibitors' below.)

Side effects — Tamoxifen may increase the risk of the following, particularly in women over age 50 years:

• Cancer of the uterus (endometrial cancer and sarcoma)
• Blood clots within deep veins (deep vein thrombosis), usually in the legs, which can travel to the lungs (pulmonary embolism) (see "Patient information: Deep vein thrombosis (DVT) (Beyond the Basics)")
• Whether tamoxifen increases the risk of stroke is controversial.

For most women, the benefits of tamoxifen in preventing a recurrence of breast cancer far outweigh the risks of uterine cancer, blood clots, or other long-term effects. However, the risks may be higher for women with risk factors for blood clots or a stroke (eg, prior history of blood clots in the leg or lung, history of smoking), and for those who take tamoxifen for longer than five years.

Tamoxifen may cause other side effects, particularly hot flashes and vaginal discharge.

Aromatase inhibitors — Aromatase inhibitors are a type of medicine that block estrogen from being produced in postmenopausal women.

Studies suggest that aromatase inhibitors such as anastrozole (Arimidex), letrozole (Femara), and exemestane (Aromasin) are at least as effective and may be more effective than five years of tamoxifen alone in postmenopausal women with early breast cancer. There also appears to be added benefit from switching over to an aromatase inhibitor after taking tamoxifen for two to three or five years.

Side effects — Side effects of aromatase inhibitors include bone loss and bone fractures, pain in the muscles and joints, blood clots, and cardiovascular events (heart attack, heart failure).

CHEMOTHERAPY IN ADDITION TO ENDOCRINE THERAPY

Chemotherapy provides benefit for some women with ER-positive early breast cancer, especially women with positive lymph nodes. It is less clear which women with ER-positive and lymph node negative breast cancer need chemotherapy.

Two tools are available to help decide if chemotherapy is needed. Ask your doctor or nurse if these tools would be helpful in deciding whether chemotherapy is needed in your case.

• Adjuvant! Online is website (www.adjuvantonline.com) that can help to determine your risk of a breast cancer relapse and the possible benefits of chemotherapy and endocrine therapy.
• Oncotype DX assay™, also known as 21 gene recurrence score assay, can help to estimate your risk of a breast cancer relapse, which can help to predict if there is a benefit of having chemotherapy.

CLINICAL TRIALS

Progress in treating breast cancer requires that better treatments be identified through clinical trials, which are conducted all over the world. A clinical trial is a carefully controlled way to study the effectiveness of new treatments or new combinations of known therapies. Ask for more information about clinical trials, or read about clinical trials at:

www.cancer.gov/clinicaltrials/learningabout

http://clinicaltrials.gov/

FOLLOW UP AFTER TREATMENT

A summary of the American Society of Clinical Oncology's recommendations for surveillance after breast cancer treatment is provided in the following table (table 1).

WHERE TO GET MORE INFORMATION

Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient information: Breast cancer (The Basics)
Patient information: Breast reconstruction after mastectomy (The Basics)
Patient information: Choosing treatment for early-stage breast cancer (The Basics)
Patient information: Ductal carcinoma in situ (DCIS) (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient information: Breast cancer guide to diagnosis and treatment (Beyond the Basics)
Patient information: Adjuvant medical therapy for HER2-positive breast cancer (Beyond the Basics)
Patient information: Early stage breast cancer treatment in premenopausal women (Beyond the Basics)
Patient information: Lymphedema after breast cancer surgery (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Adjuvant endocrine therapy for hormone receptor-positive breast cancer
Overview of the treatment of newly diagnosed, non-metastatic breast cancer
Treatment approach to metastatic hormone receptor-positive breast cancer: Endocrine therapy
General principles on the treatment of early stage and locally advanced breast cancer in older women
HER2 and predicting response to therapy in breast cancer
Hormone receptors in breast cancer: Clinical utility and guideline recommendations to improve test accuracy
Breast conserving therapy
Mechanisms of action of selective estrogen receptor modulators

The following organizations also provide reliable health information.

• National Cancer Institute

      1-800-4-CANCER
      (www.nci.nih.gov)

• The American Society of Clinical Oncology

     (www.cancer.net/portal/site/patient)

• National Comprehensive Cancer Network

     (www.nccn.com)

• American Cancer Society

      1-800-ACS-2345
     (www.cancer.org)

• National Library of Medicine

     (www.nlm.nih.gov/medlineplus)

• Adjuvant! online

     (www.adjuvantonline.com/)

• Susan G. Komen Breast Cancer Foundation

     (www.komen.org)

Patient support — There are a number of online forums where patients can find information and support from other people with similar conditions.

• About.com Breast Cancer Forum

     (http://breastcancer.about.com/forum)

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