Where Breast Cancer Spreads

Metastatic breast cancer presents new treatment challenges. Find out where breast cancer spreads and how doctors treat it.

By Darcy Lewis, Healthgrades

Advanced or metastatic breast cancer means the cancer has spread beyond the breast and surrounding lymph nodes into other parts of the body. Another name for it is stage IV (4) breast cancer. Stage IV breast cancer is one of four breast cancer stages (not including stage 0). Once the cancer has traveled to distant sites, it is considered incurable. But advanced breast cancer is more treatable today than ever before—more than 150,000 women in the United States are living with metastatic breast cancer, also known as MBC. Metastatic breast cancer treatment is highly individualized based on where the breast cancer has spread, the cancer’s hormone receptor and HER2 status, and patient preference.

How Breast Cancer Spreads

Approximately 30% of women treated for early stage breast cancer will develop metastatic breast cancer. Researchers are actively studying why tumors that initially respond to certain cancer treatments begin growing again. Much of it has to do with the genetic traits of the tumor. In some cases, breast cancer has already metastasized at the time of initial breast cancer diagnosis and staging, before treatment.

Although the factors that contribute to metastasis are under investigation, doctors know how breast cancer cells spread: by breaking off from the main tumor—the primary site—and traveling to other parts of your body through your bloodstream and lymphatic system. The most common sites for breast cancer metastasis are the bones, liver, lungs, and brain, but breast cancer can spread to any part of the body.

If you have breast cancer, your doctor will continually monitor you for signs and symptoms of cancer metastasis. Doctors monitor breast cancer patients with blood and imaging tests, such as a CT or PET scan. It’s also important to be aware of new or unusual symptoms and share them with your oncologist.

Systemic Treatment for Metastatic Breast Cancer

The goal of metastatic breast cancer treatment is to shrink the tumor(s), limit further spread, and extend life as much as possible. When deciding on treatment, oncologists consider the patient’s previous breast cancer treatments, including the type of surgery and lymph node removal, as well as the type and amount of radiation therapy, chemotherapy, and targeted therapy. However, most women with stage IV breast cancer receive systemic therapy—treatment that affects the entire body. Systemic therapy may include hormone therapy, chemotherapy, or targeted therapy, alone or in combination. Keep in mind that no matter where breast cancer spreads, it is still breast cancer and is treated as such.

Hormone therapy like tamoxifen or an aromatase inhibitor is for women who have hormone receptor-positive disease. It will likely be used as a first-line treatment, either alone or with a targeted therapy. These patients may also receive chemotherapy to help with symptom control.

The targeted drug Herceptin (generic name trastuzumab) is administered to women with HER2-positive cancers. It is usually in combination with chemotherapy. Treatment may also include hormonal therapy or additional targeted therapies.

Oncologists must consider many factors when planning treatment for advanced or metastatic breast cancer, so each patient’s treatment plan will be different. In general, expect your doctor to continue with a successful treatment plan until the cancer grows despite treatment or you develop excessive side effects. In either case, your doctor still has other drugs and drug combinations to try.

Your doctor may also recommend local treatments, such as surgery or radiation, to help prevent or treat metastatic breast cancer symptoms. Specific treatments vary by the location of the tumor(s).

Bone Metastases

Bones metastases are most often in the ribs, spine, pelvis, and long bones of the legs. Bone tumors cause pain, weaken the bones, and can lead to fractures and spinal cord compression. Another complication is hypercalcemia of malignancy, which means that too much calcium has leached from the bones into the blood.

Doctors commonly use radiation therapy to control pain and other symptoms. Both oral and intravenous (IV) medications can strengthen bones. Procedures including bone cement, tumor ablation, and even surgery are other options.

Brain Metastases

Both surgery and radiation therapy can be used to treat metastatic breast cancer that has spread to the brain. Your oncologist will make his or her recommendation based on how many tumors you have and whether they are causing symptoms.

If you have only one brain metastasis and are generally healthy, surgery followed by radiation therapy may be the most effective option. Stereotactic radiosurgery, a single high-dose radiation treatment, may be used if conventional neurosurgery is not an option or if the woman has several brain metastases.

For women whose breast cancer has spread throughout the brain, doctors may recommend whole-brain radiation therapy. Chemotherapy or HER2-targeted therapy may also be options when surgery or radiation therapy is not enough.

Liver Metastases

More than half of women with stage IV breast cancer eventually develop liver metastasis, according to Breastcancer.org. Most women with metastatic breast cancer that has spread to the liver also have metastases in other places like the bones or brain.

In most cases, oncologists choose systemic treatment like chemotherapy, hormone therapy, or targeted therapy when breast cancer spreads to the liver. For people whose only metastasis is in the liver, some doctors will consider surgery. Additional options include stereotactic radiosurgery, radioembolization, ablation, and even localized chemotherapy delivered directly into the liver.

Lung Metastases

As with liver metastases, oncologists typically recommend systemic therapies when advanced breast cancer has spread to the lung.

Fortunately, lung metastases often do not cause any symptoms. When symptoms occur, some physicians will recommend surgery if the patient is in overall good health. Otherwise, stereotactic body radiation therapy is more common because it is not invasive.

Learning that you or a loved one has metastatic breast cancer, either as a first-time diagnosis or after going through one or more treatment regimens, can be devastating news. In this delicate situation, it’s important to take time to consider all your treatment options, stay positive, and seek and accept comfort from those around you, including your oncologist. If your treatment options are more limited, ask your doctor about a clinical trial. Metastatic breast cancer is one of the most well-studied of cancers, and there are dozens of clinical trials in progress.