Where Does Breast Cancer Spread?

Most Common Sites of Distant Breast Cancer Metastases

woman with breast cancer and pink bra with doctor checking x-ray looking for metastases
Istockphoto.com/Stock Photo©AtnoYdur

If you’ve been diagnosed with metastatic breast cancer, or if you had early stage breast cancer in the past and are having new symptoms, it's natural to have questions. Some of the things you may be wondering about include:

  • Where does breast cancer spread?
  • What are the most common sites of breast cancer metastases?
  • How often does breast cancer travel to these regions of the body? 
  • What are the symptoms to be aware of?
  • How is breast cancer treated when it spreads?

Importance of Distant Breast Cancer Metastases

For roughly 85 percent of women, the spread of cancer to distant regions of the body (distant metastases) occurs years and possibly even decades after the original diagnosis. For the remaining 10 to 15 percent of women, distant metastases are already present at the time of diagnosis.

Breast cancer may recur locally (in the breast), regionally (in the lymph nodes in the armpit, above the collarbone, or in the center of the chest) or distantly. In this discussion, we will talk primarily about cancers which have spread to distant sites.

Distant metastases from breast cancer are very important in that they are responsible for around 90 percent of deaths from the disease. That said, even if you develop metastases to one of these sites, treatments are available; treatments which can often extend life.

Breast cancer with distant metastases is referred to as metastatic breast cancer (MBC) or stage 4 breast cancer.

If you are familiar with TNM staging for breast cancer, this would refer to a cancer which is M1 (instead of M0 which means no metastases.) A tumor which is metastatic may have any number for T (the size of the tumor) and N (the number of lymph nodes which are positive and where they are located).

Where Does Breast Cancer Spread?

Breast cancer may spread to nearly any region of the body but is more likely to spread to some regions than others.

Cancers can spread through the bloodstream or through the lymphatic system, and therefore commonly spread to regions which have significant blood or lymphatic flow. (You can learn more about how cancer spreads.)

The areas of the body to which breast cancer spreads can also vary depending on the specific type of breast cancer and the hormonal/HER2 status. The most common sites include:

  • Lymph nodes
  • Bones
  • Lungs (including pleural effusions)
  • Liver
  • Brain
  • Peritoneal metastases (with lobular carcinoma)

The most common first site of metastases was looked at in a 2013 study. Women with early stage breast cancer were evaluated to see what location was the most common first site of metastasis with their cancer. The breakdown was:

  • Bones - 41 percent
  • Lungs - 22 percent
  • Liver - 7.3 percent
  • Brain - 7.3 percent
  • Other sites were the first location of metastasis in the remaining people

Invasive lobular carcinoma tends to have a significantly different pattern of metastases than ductal breast cancer. In one study, almost 70 percent of people with metastases from lobular carcinoma had peritoneal metastases.

For roughly a third of women (and men, as men get breast cancer too), cancer spreads to multiple organs at the same time.

Let’s take a look at these common sites individually, as well as some of the less common sites to which breast cancer may spread. While treatment options for metastatic breast cancer are similar no matter where a cancer has spread, there are some treatments that are used for specific sites of metastasis as well.

Breast Cancer Spread to Lymph Nodes

The spread of breast cancer to lymph nodes does not mean that a breast cancer is metastatic. Even if cancer recurs in lymph nodes (at least lymph nodes near the breast) it is considered a regional recurrence and not a distant recurrence.

We bring up the spread to lymph nodes because many people become confused if they hear they have lymph node-positive breast cancer.

In this case, a pathology report may state: "breast cancer metastatic to lymph nodes" yet as noted, this does mean that the breast cancer is metastatic. Breast cancer which has spread to lymph nodes can be stage II, stage III, or stage IV.

Breast Cancer Spread to Bones (Bone Metastases from Breast Cancer)

The most common site of distant breast cancer metastases, occurring in around 70 percent of people with metastatic breast cancer, is to bones. Of the bones to which breast cancer spread, the most common sites include the spine, the ribs, the pelvis, and the long bones of the arms and legs. Bone metastases tend to have a fairly good prognosis relative to metastases to some other regions of the body.

Bone metastases may be found on a scan done to look for metastases (when no symptoms are present) or found on scans that are done to evaluate symptoms such as pain. Some people are unaware that they have bone metastasis until they suffer a fracture with only minimal trauma. Fractures through a portion of a bone weakened by cancer metastases are called pathologic fractures.

There are several types of treatment available for bone metastases from breast cancer, and some of these can control the disease for quite some time. Radiation therapy is often done when rapid relief is needed, and can be very effective for the local treatment of bone metastases. Drugs such as Strontium 89 include a particle of radiation attached to another chemical which is injected into the bloodstream. These treatments, in contrast to radiation therapy, are often effective when a person has multiple or widespread bone metastases. Sometimes surgery is needed to stabilize a bone which has fractured or is at risk of fracturing due to metastases.

In recent years, bone-modifying medications have been added to the treatments available for bone metastases and can be very effective.

Bisphosphonates such as Zometa (zoledronic acid) are not only effective in reducing pain from metastases but appear to have anticancer effects as well. These medications may also reduce the chance of further bone metastases and improve survival. The medication Xgeva (denosumab) may also be effective in treating bone metastases while improving survival.

Breast Cancer Spread to the Liver (Liver Metastases from Breast Cancer)

Breast cancer metastases to the liver are also very common.

Liver metastases may be present without any symptoms and are often detected on scans such as a PET scan. Sometimes these metastases are suspected based on abnormal liver function tests. Symptoms of liver metastases may include abdominal pain, nausea, itching (which can be severe) and jaundice, a yellowish discoloration of the skin and the whites of the eyes.

General treatments for metastatic cancer (such as chemotherapy, hormonal therapies, and targeted therapies) may decrease these metastases, but since the liver acts as the "detoxification" center of the body, there can be a fine balance, and sometimes liver metastases reduce the ability to tolerate chemotherapy.

Radiation therapy to the liver can decrease pain and may improve survival. At times other local treatments may be used to treat liver metastases such as surgery, radioembolization, chemoembolization, radiofrequency ablation, or stereotactic body radiotherapy.

Breast Cancer Spread to the Lungs (Lung Metastases from Breast Cancer)

Just as the blood is filtered by the liver, blood passes through the lungs, making this a common site of metastasis.

Lung metastates may be suspected based on a scan, which often shows multiple small areas of metastases (in contrast to lung cancer, for example, which is more likely to appear as a single large mass). The most common symptom is shortness of breath, which may be mild and only occur with exercise at first. Other symptoms can include a persistent cough or pain with breathing.

In addition to spreading to the lungs, metastatic breast cancer often causes pleural effusions—a build-up of fluid in the space between the membranes (the pleura) which line the lungs. Pleural effusions occur not only when breast cancer spreads to the lungs, but with spread to the lymph nodes in the area between the lungs (the mediastinum). The fluid may be benign (without cancer cells) and related to inflammatory changes, or instead, contain cancer cells (a malignant pleural effusion).

Lung metastases are often treated by the general treatments for metastatic breast cancer, but radiation therapy may be helpful, especially if the metastases cause an obstruction in the airways (bronchi).

Pleural effusions can be quite large and cause significant shortness of breath. Fluid is often removed by placing a needle through the chest wall and into the pleural cavity to drain the fluid. Unfortunately, pleural effusions often recur. When this happens, a shunt may be placed, or a pleurodesis recommended (a procedure in which the layers of the pleura are scarred together so fluid cannot reaccumulate).

Breast Cancer Spread to the Brain (Brain Metastases From Breast Cancer)

Breast cancer spreads to the brain in about 10 to 15 percent of people with metastatic breast cancer overall. Brain metastases are more common in women with HER2 positive tumors and triple negative breast cancer, with brain metastases occurring in roughly a third of people with HER2/neu positive breast cancers which metastasize.

Symptoms of brain metastases often include headaches, visual changes, dizziness or seizures (sometimes a seizure is the first symptom). Other symptoms may include weakness on one side of the body, problems with coordination, or personality changes.

Unlike metastases to some other regions, treatments such as chemotherapy and targeted therapies are often ineffective against brain metastases due to the blood brain barrier. The blood-brain barrier is a tight network of capillaries designed to protect the brain from toxins (such as chemotherapy).

The treatment of metastases usually includes steroids to decrease swelling in the brain. Whole brain radiation may be used to address the metastases, or if only a single or a few "spots" of metastasis are present, stereotactic body radiotherapy (SBRT) may be used in an attempt to destroy the metastasis completely. SBRT, also known as Cyber knife or gamma knife is a procedure in which high doses of radiation are delivered to a small and very precise area of tissue.

Less Common Sites of Distant Metastases

As noted above, breast cancer can spread to nearly any region of the body. Some of the less common sites (with the exception of lobular carcinoma) of metastasis include:

  • Bone marrow - Breast cancer which has spread to bone often involves the bone marrow as well (bone marrow is commonly produced in the bones most likely to be involved with breast cancer). Symptoms may include a low white blood cell or red blood cell count which is not linked with chemotherapy.
  • Peritoneal metastases - Around two-thirds of people with metastatic lobular carcinoma develop peritoneal metastases.
  • The opposite breast
  • The ovary
  • The adrenal glands
  • The pancreas
  • Skin and soft tissue
  • Uncommon sites of metastases include areas ranging from the uterus to the eye.

Sites of Metastases and Types of Breast Cancer

As noted above, HER2 positive and triple negative breast cancers are more likely to spread to the brain and the liver, whereas estrogen receptor positive tumors more commonly spread to bones. Lobular carcinomas have a tendency to spread to the abdomen.

Why Does Cancer Spread?

We aren't certain why cancer recurs and spreads, nor how it can appear to lie dormant for years and even decades and then recur. Since distant metastases are the cause of death for most cancers, much research is being conducted looking at why metastases occur, as well as methods that might inhibit the spread of cancers.

Coping With Metastatic Breast Cancer

If you have been diagnosed with metastatic breast cancer, you are probably feeling frightened and perhaps overwhelmed by all of the information you've been given. Metastatic breast cancer is different than early stage breast cancer in many ways. Talk with your friends and family. Many people find it helpful to become involved in a support group or support community designed specifically for those with metastatic cancer. Learn all you can about your disease. Treatment, even those for metastatic breast cancer, is improving, and survival is lengthening. One of the most important steps you can take is to be your own advocate in your cancer care. There are many decisions to make about treatments options, and only you know which of the choices are best for you.

For Friends and Family

If your loved one has been diagnosed with distant metastases she (or he) is probably a little overwhelmed. If she or he had breast cancer before, it is a different story the second time around. Your loved one will need your support to be ready to face this yet again.

It's important to quickly point out the treatments options for metastatic breast cancer are different, and the philosophy about treatment for metastatic breast cancer differs significantly from that for early stage breast cancer. With early stage breast cancer, the goal is usually to be as aggressive as possible to reduce the chance that the cancer will come back. With metastatic breast cancer, however, the philosophy is usually to use the minimum amount of treatment needed in order to control the disease. Treating the disease aggressively does not improve survival, but does increase side effects and lessen quality of life.

The lack of widespread understanding of these differences has led to many emotionally painful moments for those coping with metastatic breast cancer. Take a moment to learn about what not to say to someone with metastatic breast cancer.

Sources:

Berman, A., Thukral, A., Hwang, W., Solin, L., and N. Vapiwala. Inidence and Patterns of Distant Metastases for Patients with Early-Stage Breast Cancer After Breast Conservation Treatment. Clinical Breast Cancer. 2013. 13(2):88-94.

Coleman, R. Impact of Bone-Targeted Treatments on Skeletal Morbidity and Survival in Breast Cancer. Oncology (Williston Park). 2016. 30(8):pii:218394.

Inoue, M., Nakagomi, H., Nakada, H. et al. Specific Sites of Metastases in Invasive Lobular Carcinoma: A Retrospective Cohort Study of Metastatic Breast Cancer. Breast Cancer. 2017 Jan 20. (Epub ahead of print).

Yeung, C., Hilton, J., Clemons, M. et al. Estrogen, Progesterone, and HER2/neu Receptor Discordance Between Primary and Metastatic Breast Tumours – A Review. Cancer Metastasis Reviews. 2016. 35(3):427-37.

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