Metastatic Breast Cancer

Overview

Metastatic breast cancer, classified as Stage IV disease and also known as “advanced,” is cancer that has spread beyond the breast and surrounding lymph nodes into other areas of the body. Metastatic disease is usually diagnosed when breast cancer has recurred (returned), months or even years after treatment for earlier-stage disease, but it can also be diagnosed as advanced at the original diagnosis as well.

At one time, the prognosis for women with metastatic breast cancer was poor, but through research and advances in treatment, women are living longer with advanced disease. Studies have shown that new treatments have led to a 30-percent increase in the average survival for women with metastatic breast cancer. In fact, survival now varies widely, with some women living for 20 years or more after a diagnosis of metastatic breast cancer. Quality of life has also improved, and many women live full, active lives while being treated for the disease.

Development of metastasis

Breast cancer metastasizes (spreads) when cancer cells break away from the breast tumor and enter the bloodstream, where they can then travel to other parts of the body. The most common site of metastasis is bone. Other common sites of metastasis include the lungs, liver and brain.

Metastasis is typically found either through routine follow-up tests or because of symptoms such as bone pain or shortness of breath. Even though the cancer is now in a different organ, the cells are still breast cancer cells, and so many of the same treatments used for earlier-stage breast cancer are used for metastatic disease, no matter where the metastatic lesions are located in the body. No current treatment cures metastatic breast cancer; treatment may only slow or stop the growth of the disease.

Differences in breast cancers

You may have heard that no two breast cancers are alike. This is true. Advances in technology have enabled researchers to gain a better understanding of breast cancer, and they have found that many features of breast cancers differ. The disease is now categorized into several different subtypes on the basis of the molecular makeup of the tumor (Table 1). These differences have important implications for treatment, with some treatments being effective for only certain subtypes.

Tumor markers, also called biomarkers, are substances found in the body when cancer is present. These markers help doctors know more about an individual tumor to help them make more informed decisions about treatments. Common biomarkers are proteins either produced by cancer cells themselves or by other cells in response to cancer, as well as genetic alterations linked to the development of some cancers.

Biomarkers help doctors personalize treatment by classifying breast cancer tumors according to a molecular subtype. The distinction between these subtypes is important because results – such as the length of time without progression, survival and response to therapy – vary according to subtype.

Among the most well-known biomarkers are estrogen receptor (ER) and progesterone receptor (PR) and the HER2 gene.

ER and PR

Your breast cancer may be sensitive to the natural hormones of your body – estrogen and progesterone. These breast cancer cells contain receptors that can pick up these hormones as they circulate through your body. These two hormones can tell some breast cancer cells (those that carry the estrogen receptor and/or the progesterone receptor) to “turn on” the growth of breast cancer cells. Breast cancers are classified on the presence (ER+/PR+) or absence (ER-/PR-) of these receptors in the cells, and the amount of receptors (or expression) is also measured. ER and/or PR are expressed in up to 80 percent of breast cancers. A test may also show that you are hormone-receptor-negative (HR-), which means the cancer lacks these receptors and won’t be affected by treatments that block the hormones in your body.

HER2

When multiple copies of the human epidermal growth factor receptor-2 (HER2) gene are present (known as gene amplification), an excess production of the HER2 protein occurs. The protein sends signals that increase the growth of breast cancer cells, and high levels of HER2 are associated with fast-growing tumors. About a fourth of breast cancers have a high level of the HER2 protein and/or gene and are therefore classified as HER2+ (positive). About 75 percent of all breast cancers are classified as HER2- (negative) because they lack a high level of HER2.

Take control

Women with metastatic breast cancer often feel isolated, but you are not alone. And the disease is not being ignored, as researchers are working every day to improve treatments.

Uncertainty will likely be one of your biggest challenges. It’s very difficult for doctors to predict survival for women with metastatic breast cancer because every woman and every breast cancer is different. You can feel more in control by learning as much as you can about the specific characteristics of your breast cancer, your treatment options and ways you can help yourself, both physically and emotionally. Many women living with advanced breast cancer credit regular exercise, yoga, healthy nutrition, time with family and friends, support groups and spirituality with helping them during treatment for metastatic breast cancer.

This content

This content is primarily for women who have metastatic breast cancer either as a new diagnosis or as recurrence of a previous breast cancer. Family and friends of women with metastatic breast cancer can also gain insight and knowledge that will help them provide support to their loved ones.

In the pages that follow, you will find information about the treatment options for metastatic breast cancer, tests used to assess whether treatment is effective, and ways to manage the physical and emotional side effects of the disease. Throughout the guide you will also be directed to websites with more details to help you better understand metastatic breast cancer.

Table 1. Molecular subtypes of breast cancer

Subtypes Prevalence Typical characteristics
Luminal A (Usually ER+ and/or PR+, HER2-) 42-59% Low proliferation rate (percentage of cancer cells actively dividing); typically responds to hormone (antiestrogen) therapy
Luminal B (Usually ER+/PR+, sometimes HER2+) 6-19% High proliferation rate; typically responds to hormone therapy and anti-HER2 treatments
Triple-negative/basal-like (Usually ER-/PR-, HER2-) 13-28% Most BRCA1 mutations are in this group; usually aggressive, with a high risk of recurrence; typically treated with chemotherapy
HER2+ 7-12% Usually responds to anti-HER2 treatments

* Reflects the prevalence among all breast cancer cases. ER = estrogen receptor, PR = progesterone receptor, HER2 = human epidermal growth factor receptor 2, BRCA1 = breast cancer susceptibility gene 1

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