Metastatic breast cancer (MBC), also known as stage 4 (sometimes written with Roman numerals as stage IV) breast cancer or advanced breast cancer, is a type of breast cancer that has spread to other parts of the body. When you first receive a breast cancer diagnosis, it could be metastatic or an earlier stage.
If you’re first diagnosed with an earlier stage of breast cancer, it could progress or come back in other parts of the body, called metastatic breast cancer. Depending on your situation, your oncologist will use different tests to make a diagnosis and develop a treatment plan.
If breast cancer has already metastasized when you’re first diagnosed, it’s called de novo MBC. According to the Breast Cancer Research Foundation, only 6 percent to 10 percent of MBC cases are de novo MBC.
The symptoms of de novo MBC vary depending on where it’s spread. Along with early symptoms of breast cancer, you may experience other symptoms that point to a de novo MBC diagnosis. Breast cancer usually metastasizes to the liver, lungs, bones, or brain. Along with a feeling of general discomfort, fatigue, or weight loss, you may have the following symptoms specific to a metastasis site:
If you begin experiencing any of these symptoms, you’ll need to tell your doctor. They’ll likely refer you to an oncologist who will order diagnostic and imaging tests based on your specific symptoms. If you’re undergoing treatment for breast cancer and experience any of these symptoms, tell your doctor right away. These signs could indicate that breast cancer has metastasized.
Your oncologist will perform several different tests to confirm a breast cancer diagnosis. The most common test for breast cancer is a mammogram, which uses X-rays to take several images of your breast at different angles to look for tumors. If you have dense breast tissue, you may also undergo a breast ultrasound.
If your mammogram or ultrasound shows that you may have a tumor, your oncologist may next perform a biopsy to confirm your diagnosis. For this procedure, they’ll use a needle to remove a small amount of tissue or fluid from the suspected tumor to examine under a microscope. The cells are stained with different chemicals and looked at by a specialist to make an official breast cancer diagnosis.
Breast cancer treatment is often guided by the hormone receptors that are on the surface of tumor cells. Your oncologist may order blood tests to determine whether your tumor is hormone receptor-positive. Hormone receptor-positive breast cancer cells have either estrogen (ER) or progesterone (PR) receptors or both. These types of breast cancer can be treated with hormone therapy drugs that lower estrogen levels or block estrogen receptors. Your oncologist will also check if your tumors have high levels of the human epidermal growth factor receptor (HER2) protein, which can also affect the treatments you’ll receive.
CT scans are often the first test used to diagnose and stage cancer. These scans use X-rays to make 3D pictures of your entire body to look for metastases, especially liver, lung, or bone metastases. You may have a contrast dye injected into a vein to help your organs and bones stand out more in the scan.
If your oncologist suspects there’s liver, lung, or bone involvement, they may use a positron emission tomography (PET) scan to look at your entire body. This test uses a small amount of radioactive sugar that’s injected as a liquid into a vein. Tumors use up this sugar faster than healthy cells, creating “hot spots” that are visible on the scan. Sometimes, a PET/CT scan is used to take more detailed pictures of your organs.
If you have symptoms of bone metastases, a bone scan can be used to look for any new tumors in the affected area(s). A bone scan is similar to a PET scan — it also uses a small amount of radioactive tracer that’s injected as a liquid into a vein. After waiting a few hours for it to absorb into your bones, a special camera takes images to look for hot spots, or tumors.
MRI uses strong magnets and radio waves to create highly detailed images of your organs and tissues. Your oncologist may order an MRI to look for brain metastases (if cancer has spread to your brain). Similar to having a CT scan done, you’ll likely get an injection with a contrast agent to improve images of your brain and spinal cord.
If you were previously diagnosed with breast cancer, there’s a chance it may return. Breast cancer that develops outside of the breast and lymph nodes after an initial diagnosis and treatment is called metastatic recurrence. Roughly 30 percent of women diagnosed with early-stage breast cancer will develop metastatic recurrence.
Although any type of breast cancer can metastasize, it’s more common with aggressive subtypes. For example, triple-negative breast cancer (TNBC), which doesn’t have any treatable hormone receptors, is an aggressive type of cancer. Studies show that around 46 percent of women with TNBC will have metastases.
The hormone receptor and HER2 status of breast cancer can also influence where it’s likely to spread. One study from the journal Oncotarget found that hormone receptor/HER2-positive breast cancers are more likely to spread to the liver, whereas hormone receptor-positive/HER2-negative cancers more often spread to the bones.
If your breast cancer is in remission (responding to treatment or under control), you’ll likely still have yearly follow-up visits and mammograms to monitor your health. According to the American Cancer Society, blood and imaging tests like X-rays, bone scans, and CT or PET scans aren’t a part of standard follow-up care for those whose breast cancer is in remission. However, these tests will be done if you have symptoms that indicate the breast cancer has returned or metastasized.
Let your doctor know right away if you begin experiencing signs of liver, bone, lung, or brain metastases. They’ll perform the same diagnostic and imaging tests used to diagnose de novo MBC.
Research shows that the hormone receptor and HER2 status of breast cancer cells can change once they metastasize. For example, if your original breast cancer diagnosis was positive for PR or ER, it may be different in metastases. Your oncologist will likely perform a biopsy on the metastatic tumors to determine their hormone receptor and HER2 status. These results will affect the treatment decisions they make.
Receiving a diagnosis of MBC after remission may be scary and overwhelming, but it’s important to know there are treatments available to help people live longer. Depending on your specific case, your oncologist may recommend chemotherapy, hormonal therapy, and immunotherapy to help manage your MBC.
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