Understanding metastatic breast cancer
Being diagnosed with metastatic breast cancer can happen to anyone at any time, regardless of previous cancer stage or type. In this section, we’ll walk you through how metastatic breast cancer happens and how the characteristics of the cancer can help you and your healthcare team decide on the best treatment options for you.
How metastatic breast cancer happens
When breast cancer metastasizes, the cancer cells enter the lymphatic channels or the bloodstream and spread to the lymph nodes or other parts of the body, such as the bones, lungs, liver or brain. Though cancer at any stage can become metastatic, metastatic cancer is the term used to refer to stage IV cancer.
Metastatic breast cancer may be your very first breast cancer diagnosis, or it may be an earlier breast cancer that has come back.
- If this is your first cancer diagnosis, you may hear your healthcare team use the term “de novo metastatic breast cancer” to describe it. It’s possible your doctors discovered you have breast cancer because you had symptoms in a different area of your body, such as your bones. Breast cancer cells remain breast cancer cells no matter where they are. Even when cancer cells spread to a different area of the body, your doctors will still treat them as breast cancer.
- If you had breast cancer in the past, this new diagnosis may be referred to as “recurrent” breast cancer. In a recurrence, some of the primary cancer cells survived the treatments you may have had after your early-stage diagnosis. Your doctors may decide to do a confirming biopsy (surgical removal and testing of a piece of cancerous tissue) to ensure the tumor cells remain similar to those at your original diagnosis. If the characteristics of the cancer have changed, you and your doctor can choose treatments that target those characteristics.
With stage IV disease, it’s difficult to fully remove cancer with surgery or medicine. New tumors may appear over time, or cells may stop responding to different treatments. While there is currently no cure for metastatic breast cancer, it’s possible to experience periods during which tests show no evidence of disease (NED). While reaching NED may not always be possible, it’s likely that you will have periods when the cancer does not grow. This is called stable disease.
While your experience of ongoing treatment may shift and change over time, enjoying activities, discoveries, and connections that feel good can always be part of your life.
Understanding the cancer’s subtype and behavior
Breast cancer subtypes are determined by the cancer cells’ reaction to the hormones estrogen and progesterone — usually recognized by the presence of hormone receptors in the cells (referred to as hormone receptor status) — or too much of the HER2 protein, called the HER2 status.
Breast cancer treatment is often tailored to specific subtypes so it can directly disrupt the processes that make the cancer grow. Your pathology report will include the type of cancer you have, and whether it is a single type or a combination of types.
In recurrent breast cancer, the original subtype can sometimes change by the time the cancer metastasizes. Between 15 and 20 percent of metastatic cancers have different pathology traits than at early-stage diagnosis. If you’ve been diagnosed with recurrent metastatic breast cancer, ask your doctor about performing a new biopsy and new subtype tests. The results can help ensure you’re getting the most effective treatment options for your type.
Here are the known breast cancer subtypes:
- Hormone receptor-positive or negative: Normal cells have high levels of both estrogen and progesterone receptors. Cancer cells that grow in response to certain hormones test positive for those hormone receptors; those that do not test negative. For the hormones estrogen and progesterone, hormone-receptor status is often expressed as “ER+/-” and “PR +/-.”
- Hormone-sensitive cancers may respond to medicines called hormonal therapies. Hormonal therapies block estrogen from binding to cancer cells, lower estrogen levels, or reduce the number of estrogen receptors on the cells.
- In some cases, the cell will have high levels of estrogen receptors but few or no progesterone receptors. Tumors that are ER+ but PR- may be more aggressive and less sensitive to hormonal therapies.
- Tumors that are both ER+ and PR+ usually respond to hormonal therapies. Any hormone sensitivity makes you a candidate for hormonal therapy.
- Human epidermal growth factor receptor 2-positive or negative (HER2 +/-): The HER2 protein is part of normal cell growth, but in some cancer cells the amount of HER2 proteins is too high. This is called HER2-positive breast cancer and can be treated with anti-HER2 therapies.
- Triple-negative breast cancer: These types of cancers test negative for estrogen and progesterone receptors and HER2, which means the cancer cells grow without estrogen, progesterone, or HER2 proteins present. These cancers do not respond to anti-HER2 or hormonal therapies. Triple-negative cancers usually respond to chemotherapy.
In addition to subtype, your doctor will also note how the cancer grows (in a sheet or in a mass) and the proliferation index, which tells what percentage of the cancer cells are actively dividing.
Your pathology report
If you have a surgical biopsy to test the cancer tissue, the information collected becomes part of your pathology report, a profile of the tissue-testing results. These results include information about the cancer’s hormone-receptor and HER2-receptor status, and they help determine the most effective treatment.
In some cases, such as in brain or bone metastases, the location may make biopsy difficult, so your doctors will rely on scans, symptoms, and blood work to confirm your diagnosis instead.
Understanding new terms
Like any illness, cancer has its own vocabulary. If this is your first diagnosis, it may be helpful to keep a running list of terms you want defined to help you make sense of everything. Don’t be afraid to ask your doctor, nurse, or other medical professional to explain what they mean more clearly.