Patient information: Early stage breast cancer treatment in postmenopausal women (Beyond the Basics)

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 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). The first of these, endocrine therapy, is used in women who have what is called hormone-responsive cancer, meaning it grows in response to the female hormone estrogen. This article will focus on adjuvant therapy forpostmenopausal 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)”.)


Some breast cancers require the female hormone estrogen to grow, while other breast cancers are able to grow without estrogen. Whether a tumor is hormone responsive is determined by checking if it contains hormone receptors, namely estrogen receptors (ER), progesterone receptors (PR), or both.

If you have a tumor that contains hormone receptors (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.


The goal of endocrine therapy is to prevent breast cancer cells from being stimulated by estrogen. In postmenopausal women with early hormone-responsive breast cancer, the two endocrine treatments most often used are the class of drugs called selective estrogen receptor modulators (SERMs) or another class called aromatase inhibitors (AIs). Among the SERMs, tamoxifen (brand name: Nolvadex) is the most commonly prescribed.

The SERMs were the first agents used as a treatment for breast cancer, and while both SERMs and AIs reduce the risk of recurrence and death due to breast cancer, research indicates that AIs are more effective than tamoxifen and should be preferentially administered. That said, multiple options exist, and you should talk with your doctor about the one that is most appropriate for your situation.

Aromatase inhibitors — Aromatase inhibitors are a type of medicine that block estrogen from being produced in postmenopausal women. Examples of these medications include anastrozole (brand name: Arimidex), letrozole (brand name: Femara), and exemestane (brand name: Aromasin).

Studies comparing the effects of tamoxifen with those of AIs as a primary treatment when taken for five years find that AIs are superior. In addition, studies show that for women who have been on tamoxifen for two or three years, there is also a benefit of switching to an AI. Finally, for women who have completed a five-year course of tamoxifen, there are benefits to taking an AI as compared with stopping all treatment. In all cases where an AI is used, treatment with AIs should last five years regardless of whether it is preceded by tamoxifen treatment.

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). Unlike tamoxifen, it does not increase the risk that one could develop cancer of the uterus.

Tamoxifen — Tamoxifen (brand name: Nolvadex) is a SERM and prevents estrogen from binding to the estrogen receptor, thereby preventing estrogen from stimulating the growth of the breast cancer cells. Although it has typically been recommended that women remain on it for five years, studies now show that for women who choose to take tamoxifen rather than an AI, treatment should be for 10 years. However, whether all women require a 10-year course of tamoxifen is unclear, and you should talk with your doctor about whether a longer course of tamoxifen is advised.

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)”)

There has been some suspicion that tamoxifen might also increase a woman’s risk of stroke, but studies have not confirmed this.

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.


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 determine what your chances are of having a recurrence (ie, your prognosis), in which case your doctor may feel chemotherapy is indicated. Ask your doctor or nurse if these tools would be helpful:

Adjuvant! Online is website ( 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.


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:

Videos addressing common questions about clinical trials are available from the American Society of Clinical Oncology (


A summary of the American Society of Clinical Oncology’s recommendations for doctors that covers what may be components of surveillance after breast cancer treatment is provided in the following table (table 1).


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 ( 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 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.