- Breast cancer can spread from the breast tissue to other parts of the body via the lymph system, bloodstream, or directly to adjacent areas.
- Assessing the progression of your disease can offer clues about how rapidly your cancer might spread.
- Symptoms of metastatic breast cancer vary depending on what other organs or regions of the body are affected.
- Treatment of metastatic breast cancer may include a variety of therapies targeting both the initial tumor in the breast and cancerous tumors that have spread to other organs or tissues.
Breast cancer can remain localized in the breast, or it can spread throughout the body. When it spreads, it’s called metastatic breast cancer (MBC), or stage 4 breast cancer.
How quickly your cancer spreads depends on a number of factors, some of which you’ll learn through your doctor’s assessment of your illness.
Like all cells, breast cancer cells grow by cellular division. But because cancer cells are mutated, their growth rate can be difficult to predict.
According to the Robert W. Franz Cancer Research Center at Providence Portland Medical Center, breast cancer cells need to divide at least 30 times before they are detectable by physical exam.
Each division takes about 1 to 2 months, so a detectable tumor has likely been growing in the body for 2 to 5 years.
Generally speaking, the more cells divide, the bigger the tumor grows. The larger the tumor, the greater the odds that it may invade nearby tissues, the lymphatic system, or the circulatory system, and spread to other organs.
Breast cancer grading and staging can provide some clues to how aggressive your cancer is.
Grade 3 breast cancer is likely to spread faster than grade 1 or 2, for example.
By definition, stage 4 breast cancer is the fastest spreader, since it already has metastasized beyond the breast tissue.
Grading is particularly important in predicting how fast breast cancer may spread.
To grade your breast cancer, your doctor will conduct a biopsy to remove cancer cells from your breast. The biopsied cells are graded based on how similar or different they look compared to normal cells.
Breast cancer cells are graded on a scale of 1 to 3:
- Grade 1, or well differentiated. The cancer cells appear to be slower-growing and resemble normal breast tissue.
- Grade 2, or moderately differentiated. Cancer cells are moderately different from normal cells and likely to grow at a medium rate of speed.
- Grade 3, or poorly differentiated. Cancer cells look very different from normal cells, meaning they are likely to grow and spread faster.
Staging assesses whether your breast cancer has spread, and if so, how far. Staging can give your healthcare team information to predict:
- how fast your cancer might spread
- how survivable it is
- what treatment options are available
In addition to looking at the size and location of the tumor, doctors also consider whether the tumor tests positive for estrogen receptors, progesterone receptors, or HER2 proteins.
Each of these proteins can cause tumors to grow and possibly spread more rapidly.
Stages of breast cancer and what they mean
Breast cancer stages are usually expressed on a scale of 0 to 4.
Stage 0 is considered non-invasive (in situ) breast cancer, with no evidence that the cancer (or other abnormal cells) has spread beyond the part of the breast where it began to grow, including to nearby lymph nodes.
Stages 1 to 3 generally describe breast cancer that may have spread to other parts of the breast and nearby lymph nodes, with stages increasing with the size of tumors and extent of spread.
Cancer that remains localized to the breasts is the most treatable.
Breast cancer tumors can grow directly from breast tissue to other nearby locations, such as the chest wall or the skin of the breast. This is considered stage 3 breast cancer.
Stage 4 is metastatic breast cancer (MBC), meaning that cancer that originated in the breast has now spread to other parts of the body.
In stage 4 breast cancer, cancer cells can spread beyond the breasts by invading lymph nodes near the breast and traveling to other parts of the body via the lymphatic system.
Cancer cells also can move through the bloodstream to inhabit other organs and regions of the body.
The most common destinations for MBC or advanced breast cancer cells are the brain, bones, lungs, and liver.
The outcome for Stage 4 breast cancer that has metastasized, or spread to distant organs of the body, is considerably lower than for earlier stages, with a 28 percent 5-year survival rate.
However, with prompt diagnosis and proper treatment, both quality of life and longevity may be improved for those with stage 4 breast cancer.
The symptoms of MBC can vary, depending on where the cancer has spread.
- Breast cancer that has spread to the bones may cause pain, swelling, or bones that break or fracture easily.
- Lung cancer metastasized from the breast can cause shortness of breath, breathing difficulties, chronic cough, and chest pain.
- When breast cancer spreads to the liver, it can trigger abdominal pain, loss of appetite, nausea, unusually high levels of enzymes in the liver, and yellow skin due to jaundice.
- Brain or spinal tumors caused by breast cancer that’s spread can lead to persistent headaches, blurred or double vision, nausea or vomiting, seizures, and behavioral changes.
It’s important to keep in mind that while several nonspecific symptoms, such as fatigue, weight loss, and poor appetite, may be related to MBC, they can also be caused by other factors, like depression or medication.
If you have concerns about specific symptoms, talk with your doctor to make sure they aren’t related to MBC.
Treatment for stage 4 or metastatic breast cancer will depend on where it has spread. It will also vary depending on the following factors:
- the level of hormone receptors and/or HER2 in the tumor
- gene mutations in the tumor
- specific symptoms
- previous cancer treatments
- whether women are still menstruating
- overall health
For those with stage 4 breast cancer, the primary treatments are systemic or drug therapies. These options include chemotherapy, hormone therapy, immunotherapy, and targeted therapy, or some combination of the four.
While there is no cure for MBC, the goal of these treatments is to shrink or slow tumor growth, improve quality of life, and help people with the condition live longer.
Chemotherapy may be used prior to breast cancer surgery to reduce tumor sizes, or it may be used to destroy any cancer cells remaining after surgery. In general, it is used to destroy or damage cancer cells as much as possible.
The type of chemotherapy used for stage 4 breast cancer will depend on various factors such as how fast the cancer is growing despite previous treatment, and if there is a lot of cancer in organs such as the liver and or lungs.
These treatments include:
- doxorubicin (Adriamycin)
- pegylated liposomal doxorubicin (Doxil, Caelyx)
- epirubicin (Ellence)
- capecitabine (Xeloda)
- carboplatin (paraplatin)
- taxol (placlitaxel)
- cyclophosphamide (Cytoxan)
Chemotherapy is often used in combination with targeted therapies, which are medications that specifically target cancer cells. Every person’s chemotherapy plan will be different.
Your healthcare team is guided by information about your experience with side effects, previous treatment, and the fact that some chemotherapies work better as combination regimens.
Although side effects from chemotherapy can be unpleasant, they can often be successfully managed or even prevented. They usually go away after treatment is finished.
Hormone therapy (also known as endocrine therapy) can be an effective treatment for estrogen receptor-positive (ER-positive) or progesterone receptor-positive (PR-positive) tumors.
In general, hormone therapy is recommended for those with hormone receptor-positive (HR-positive) breast cancer because it blocks estrogen receptors in cancer cells, causing them to stop growing and dividing.
Hormone therapy can also be used to block the body’s production of estrogen to starve cancer cells. Treatments include:
- aromatase inhibitors (Arimidex, Aromasin, or Femara)
- tamoxifen (Soltamox)
- fulvestrant (Faslodex)
- ovarian suppression: using drugs to stop the ovaries from producing estrogen
Immunotherapy, also called biologic therapy, boosts the body’s natural defenses so it can fight cancer.
Drugs that target the proteins on immune cells can help restore the immune response against breast cancer cells and keep the body’s immune system from attacking normal cells in the body.
Patients with particular genetic profiles may benefit from one of the two main types of immunotherapy that target these “checkpoint” proteins:
- PD-1 inhibitors: pembrolizumab (Keytruda)
- PD-L1 inhibitors: atezolizumab (Tecentriq)
Targeted therapy drugs specifically seek out the changes in cells that cause cancer. These treatments block the growth and spread of cancer cells while limiting damage to healthy cells.
Different types of tumors have different targets. Your doctor may need to run tests to identify the specific genes, proteins, and other factors related to your tumor, which will help them determine the most effective treatments.
There are a number of specific targeted therapies for:
- HER2-positive breast cancer
- HR-positive breast cancer
- triple-negative breast cancer
- those with BRCA gene mutations
Local or regional treatments
The systemic therapies described above are the main treatments for metastatic breast cancer.
However, local and regional treatments, including radiation, surgery, and chemotherapy can also be used to help treat metastatic cancer in a specific part of the body, but they’re unlikely to completely eradicate it.
Usually, these therapies are used to treat symptoms or complications of the cancer.
For example, radiation and surgery may be used in these situations:
- when a breast tumor causes an open wound in the breast (or chest)
- to treat a small number of metastases in a specific area, such as the brain
- to help prevent bone fractures
- when a tumor is pressing on the spinal cord
- to treat a blood vessel blockage in the liver
- to provide pain relief or to relieve other symptoms
Chemotherapy can also be delivered directly to a certain area (such as into the fluid around the brain or spinal cord), to help relieve symptoms or complications.
Not all breast cancer spreads beyond the breast. But when it does spread, it’s typically via the lymph system or bloodstream.
MBC is cancer that has spread to distant parts of the body, most frequently the lungs, brain, liver, or bones.
The speed with which breast cancer spreads depends on a number of factors, including:
- how mutated your breast cancer cells are
- how fast they grow
- whether your cancer is localized or metastasized
- your age
- lifestyle and environmental factors
- how well you respond to treatment