What is Metastatic Breast Cancer? Metastatic breast cancer (MBC), also known as Stage IV, recurrent, or chronic cancer breast cancer, occurs when the cancer has spread beyond the breast to distant sites within the body. This process is called metastasis. The most common sites for MBC are the bones, lungs, liver, skin, and brain.(1)

What happens when breast cancer spreads? Breast cancer that metastasizes is still breast cancer and does not become bone cancer or liver cancer or lung cancer. Under a microscope, the tumor cells look and act like breast cancer and will be treated as breast cancer.

Who gets MBC? No one brings MBC on themselves. The difficult truth is that anyone who has had early-stage breast cancer can experience a metastatic recurrence of their disease months, years, or even decades after finishing their treatment. About 6% of MBC cases are discovered at the initial diagnosis.(2) When this happens, it is called de novo MBC.

Why does breast cancer metastasize? At this time, researchers can’t explain why metastasis occurs, but they’re working on finding answers. Early detection is an important tool, but it does not cure or prevent an early-stage cancer from coming back as metastatic disease.

What are the statistics on the incidence of MBC? About 25–30% (3) of those with early-stage breast cancer will experience a metastatic recurrence of their disease months, years, or even decades after they finish treatment.

What is the difference between early-stage breast cancer and MBC? MBC is treatable but no longer curable. Treatment for MBC is lifelong and focuses on preventing further spread of the disease and managing symptoms. The goal is for patients to have the best quality of life for as long as possible.

How is MBC treated? Treatment choices are guided by breast cancer subtype, location, the extent of metastasis, previous treatments, and other individual factors. These treatments may include targeted therapy, chemotherapy, radiation, and in certain cases, surgery.

What are the different subtypes of MBC? Subtypes for early-stage breast cancer and MBC are the same. In order of prevalence, they are hormone receptor-positive/HER2 negative; hormone receptor-negative/HER2 negative; hormone receptor positive/HER2 positive; and hormone receptor-negative/HER2 positive. Hormone receptor-positive means that estrogen and/or progesterone can promote the growth of these tumors. HER2 positive means that tumor cells make high levels of a protein called human epidermal growth factor receptor 2, which presents a treatment target in these cases.(4)

Do men get breast cancer? Yes, men do get breast cancer and are often misdiagnosed initially. They represent about 1% of new cases of breast cancer and 1% of the deaths annually from MBC.

 How many people die of breast cancer each year? It is estimated that over 42,000(5) females and about 530 males(6) will die of breast cancer in 2024. This number is essentially unchanged over the last few decades. Virtually all deaths from breast cancer are caused by MBC.

 How many people are living with MBC in the US? Although the National Cancer Institute collects statistics on patients with de novo MBC diagnoses, they do not count metastatic recurrences of early-stage disease. Studies estimate that over 168,000 women(7) are living with metastatic breast cancer in the U.S.

How much is spent on research funding for MBC? In 2014, the Metastatic Breast Cancer Research Alliance reported that from 2000 to 2013, only 7% of the $15 billion in breast cancer research funds was for MBC. According to their most recent report in 2023, 13% of all breast cancer research dollars were allocated for MBC from 2014 to 2020. This is encouraging news, and the organization continues to advocate for 30% of breast cancer research funds devoted to MBC.(8)

What is National Metastatic Breast Cancer Awareness Day? October 13 was set aside by unanimous House and Senate resolutions in 2009, establishing that one day in October should recognize and bring awareness to metastatic breast cancer. One day is not enough, but it’s a start for year-round awareness of what MBC is and why it’s important for all of us.

Do young women get MBC? Breast cancer incidence in younger women is still low—about 49 per 100,000 in 2019, the most recent data available. Currently, MBC is the leading cause of cancer death in women aged 20 to 49 in the U.S.(9) Women under age 50 have a two-fold higher death rate than average (12.1 vs. 6.5 deaths per 100,000).(10)

How is MBC monitored? Usually, MBC is monitored by periodic imaging tests (e.g., CT scans, PET scans, bone scans, or MRIs), blood tests measuring tumor markers, and assessment of how the patient is feeling.

What is scanxiety? Scanxiety refers to patient anxiety over scans as their scan date approaches and while awaiting results. Good results refer to stable disease (metastases are not growing or spreading) or NED (no evidence of disease).

What is NED and how does it differ from being ‘in remission’ or being ‘cancer free’? NED means the metastases are no longer detectable upon imaging. This is great news! However, breast cancer cells may still be circulating in the body, so treatment continues. ‘In remission’ is an older term that is not usually used in metastatic breast cancer. Once your disease has metastasized, you are never ‘cancer-free.’ Still, being NED or being stable are wonderful words to hear from your oncologist.