October 2021 is Breast Cancer Awareness Month-
Up to 30% of patients with early-stage breast cancer will go on to develop a metastatic form of the disease—here’s what to know.
The following written content by Jessie Van Amburg
Breast cancer is one of the most common cancers in the world, making up an estimated 11.7% percent of new diagnosed cancer cases globally in 2020, according to data from the American Cancer Society. The National Institutes of Health also estimates that about 13% of women (or those assigned female at birth) in the US will be diagnosed with breast cancer at some point in their lives. The gist: The odds that you or someone you know have, will have, or have had breast cancer are relatively high.
That’s not supposed to be a scary statement. Thanks to incredible advancements in treatment over the course of decades, most people are able to successfully treat their breast cancer and never look back. The exception here is with a diagnosis of metastatic breast cancer—either as an initial diagnosis or a subsequent one following an earlier diagnosis.
Metastatic breast cancer is an incurable form of the disease, but that doesn’t mean there are no options for treatment, or that everyone who gets the advanced form of the disease will follow the same timeline. Here’s an overview of everything you need to know about metastatic breast cancer, straight from top oncologists.
What is metastatic breast cancer?
Metastatic breast cancer, also known as stage 4 breast cancer, is the most advanced form of the disease. “Metastatic breast cancer starts in the breast and spreads beyond the breast and lymph nodes to go to other organs,” Dean Tsarwhas, MD, medical director of cancer services for Northwestern Medicine Lake Forest Hospital, tells Health. He says breast cancer most commonly spreads to the bones, liver, lungs, and brain, although it can go anywhere in the body.
There are an estimated 155,000 women living with metastatic breast cancer in the US, according to 2017 data published in Cancer Epidemiology, Biomarkers & Prevention. Most of those cases occur in patients who had previously been diagnosed with an earlier stage of breast cancer, Nancy Lin, MD, an oncologist who specializes in breast cancer at Dana-Farber Cancer Institute in Boston, tells Health. In fact, a 2020 review in the British Journal of Cancer shared that 20%-30% of patients diagnosed with an earlier-stage breast cancer still die of a metastatic form of the disease. This can happen either because breast cancer doesn’t respond to treatment and spreads, or because it is recurrent, meaning that it returns after going into remission.
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Less commonly, patients can be diagnosed with metastatic breast cancer at their initial diagnosis, which means doctors only find the disease when it’s already spread to areas outside of the breast. This is known as de novo or primary metastatic breast cancer, and it affects only about 6% of patients with metastatic breast cancer, per the American Cancer Society.
How does breast cancer spread?
For the majority of patients with metastatic breast cancer, it means an initial earlier-stage diagnosis spread to distant parts of the body. According to the National Cancer Institute (NCI), cancer cells spread throughout the body in a series of steps.
The first step of metastasis for any type of cancer—not specifically breast cancer—is when cancer spreads to nearby healthy tissue in the body. The cancer can then continue to spread to nearby lymph nodes or blood vessels in the body, per the NCI. Once cancer cells move into the body’s lymph nodes or blood vessels, they essentially gain access to the body’s lymphatic system (which moves a fluid called lymph throughout the body) and bloodstream. With that access, cancer cells can stop in a distant location in the body, invade blood vessel walls, and then move into surrounding tissue, growing there until a new tumor forms. New blood vessels then grow to create a blood supply to the new tumor to help it continue to grow.
It’s important to note that this doesn’t happen with every cancer diagnosis—most cancer cells will die during this process. But, per the NCI, as long as conditions in the body are “favorable,” metastasis can happen. Some metastatic cancer cells can also remain at a distant site for years, inactive, before they begin to grow again (or at all). Read more from Health.
