Patient information: Early stage breast cancer treatment in postmenopausal women

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 (bodywide) 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".)

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, are also presented elsewhere. (See "Patient information: Adjuvant chemotherapy and trastuzumab (Herceptin) for early stage breast cancer".)

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.

Tamoxifen is usually recommended for five years. 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 five years of tamoxifen.

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)")

• Stroke

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 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 in postmenopausal women with early breast cancer. There is no advantage to combined therapy (anastrozole plus tamoxifen).

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

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/clinical_trials/learning/

       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. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

Some of the most pertinent include:

Patient Level Information:
Patient information: Adjuvant chemotherapy and trastuzumab (Herceptin) for early stage breast cancer
Patient information: Breast cancer guide to diagnosis and treatment
Patient information: Early stage breast cancer treatment in premenopausal women
Patient information: Deep vein thrombosis (DVT)

Professional Level Information:
Adjuvant endocrine therapy for postmenopausal women with early stage breast cancer
Adjuvant systemic therapy for older women with early stage breast cancer
An overview of breast cancer and treatment for early stage disease
Clinical decisions in systemic adjuvant therapy for early breast cancer
Endocrine therapy of metastatic breast cancer
General principles of management of early breast cancer in older women
HER2 and predicting response to therapy in breast cancer
Hormone receptors in breast cancer: Measurement and clinical implications
Mastectomy and breast conserving therapy for invasive breast cancer
Mechanisms of action of selective estrogen receptor modulators
Patient information: Breast cancer guide to diagnosis and treatment

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.

• 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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