According to the Centers for Disease Control and Prevention (CDC), breast cancer is the second most common cancer in women. The American Cancer Society (ACS) estimates that in 2021, there will be 284,000 new cases of breast cancer.
Breast cancer treatment has improved dramatically in recent decades, which helps in part explain why life expectancy is generally so good for most breast cancer patients. But for someone with metastatic breast cancer—an incurable, advanced form of the disease—their treatment story becomes slightly different.
But just because the disease isn't curable in its most advanced stage doesn't mean that there aren't treatments available for metastatic breast cancer. "Treatment options for metastatic cancer are extensive," Evelyn Toyin Taiwo, MD, hematologist and oncologist at Weill Cornell Medicine and New York-Presbyterian Brooklyn Methodist Hospital, tells Health. "There's a whole lot of reasons to treat these patients, even though a cure is unlikely."
Here's what you need to know about treatment options available for metastatic breast cancer, in order to both prolong a person's life with the disease, and to make any symptoms more manageable.
What is metastatic breast cancer?
Metastatic breast cancer is cancer that has spread beyond the breast and surrounding lymph nodes to other parts of the body. It is also known as stage 4 breast cancer. It is the most advanced form of breast cancer, and has no cure.
Metastatic breast cancer can spread to any part of the body, but the most common places for it to go are the bones, lungs, liver, and brain, Dean Tsarwhas, MD, a medical oncologist at Northwestern Medicine, tells Health. Doctors don't fully understand why breast cancer seems to have a proclivity for those locations, he says, or why some cancer subtypes tend to spread to certain locations over others.
How is metastatic breast cancer treated?
Breast cancer is an incredibly complex disease. That's why, in the metastatic phase, there are a lot of factors that inform treatment once a patient is diagnosed.
As with an earlier-stage breast cancer, treatment is influenced by the cancer subtype (such as hormone-receptor positive breast cancer, HER2-positive breast cancer, and triple-negative breast cancer), says Dr. Tsarwhas. For example, you wouldn't give someone estrogen-blocking drugs to fight their cancer if they don't have hormone-sensitive cancer. Certain genetic factors can also affect treatment, he says.
Where a cancer has spread also informs treatment, Dr. Tsarwhas adds. Cancer in the bones, for instance, tends to grow more slowly, he says, so patients often have time to let hormone therapy and other treatments work. On the other hand, cancer in the liver often requires a "rapid-response event," due to the organ's importance. "So sometimes with breast cancer in the liver… we need to go to chemotherapy to get a response right away," says Dr. Tsarwhas. If the cancer has spread to the brain, he says radiation is a better bet since it's harder to get drugs into the brain.
Having a BRCA1 or BRCA2 mutation—genetic mutations that impact how cells grow and divide, which have been linked to an increased risk of breast, ovarian, and pancreatic cancer—can also affect metastatic breast cancer treatment, says Dr. Tsarwhas. While BRCA status doesn't affect treatment for earlier stages of breast cancer, metastatic patients with BRCA mutations are often given specific drugs to help slow tumor growth (more on those later).
Generally speaking, doctors know that their patients can't be cured, so treatment focuses instead on slowing cancer growth and prolonging the quality of life for as long as possible. "[The patient] is going to live with this disease long-term," says Dr. Taiwo—meaning that instead of blitzing someone with an intense round of chemo with lots of debilitating side effects, "we look for the most effective systemic therapy with the least amount of toxicity a patient needs to continue to have a good quality of life."
Treatment then is really personalized based on all of these many factors. That said, there are some pretty universal standards of care that doctors turn to depending on a patient's individual situation. Here's an overview of the different kinds of treatments available for metastatic breast cancer.
These drugs are used to treat hormone-receptor (HR) positive breast cancers, Alberto Montero, MD, clinical director of the Breast Cancer Medical Oncology Program at University Hospitals Seidman Cancer Center and an associate professor of medicine at Case Western Reserve University School of Medicine, tells Health.
Those specific cancer cells have receptors on them that interact with estrogen or progesterone, helping them grow faster, according to the ACS. Hormone therapy drugs block the cancer's access to these hormones in a variety of ways. Drugs like tamoxifen, for example, work to stop the receptors from attaching to estrogen or progesterone, thereby slowing their growth. Other drugs called aromatase inhibitors completely stop the production of estrogen—giving estrogen-receptor positive cancer nothing to work with.
This type of treatment attacks specific elements that make cancer cells grow and function with less damage to healthy cells, according to the National Cancer Institute (NCI). They're often combined with other cancer treatments (like chemotherapy or hormone therapy) to improve their effectiveness. Herceptin and Perjeta, for example, are two IV-administered antibody drugs used on metastatic breast cancer patients with HER2-positive cancer, says Dr. Tsarwhas. They work together to block signaling on HER2 receptors, slowing cancer growth.
Other targeted therapy drugs work to counteract the effects of genetic factors, says Dr. Tsarwhas. PARP (aka poly ADP-ribose polymerase) inhibitors olaparib and talazoparib, for example, block an enzyme that repairs damaged DNA, which slows the growth and spread of metastatic breast cancer in people with BRCA mutations, per the NCI. Postmenopausal patients with a PIK3CA mutation—which can make cancer cells divide uncontrollably and potentially make HR-positive cancers resistant to hormone therapy—can be given the targeted drug Piqray to block the effects of this mutation. It, in combination with anti-estrogen therapy, has been shown in recent clinical trials to extend lifespan and slow cancer growth.
There are now finally some targeted therapies for triple-negative breast cancer, which is incredibly aggressive and hard to treat. Trodelvy, which was approved by the FDA in 2020, binds to the cancer cell and then delivers a "payload" of chemo drugs directly to the cell, says Dr. Tsarwhas. "That's been a new development that has improved options for triple-negative disease," he says.
These treatments work by spurring the immune system to fight the cancer itself, the ACS says. It's used primarily to treat triple-negative breast cancer in combination with chemotherapy, says Dr. Montero. Triple-negative breast cancer is incredibly aggressive and tough to treat, but these drugs (combined with chemo) have been shown in clinical trials to improve patient lifespan and slow the disease's progression.
Radiation therapy uses high doses of radiation (think of it like a super intense X-ray) to kill cancer cells, per the NCI. In metastatic patients, localized radiation is used to help manage pain from bone lesions or to attack cancer that's spread in the brain, says Dr. Tsarwhas.
This is what most people think of when they hear the words "cancer treatment." According to the NCI, chemotherapy uses strong chemicals to kill cancer cells or slow their growth. It can also kill healthy cells, which can result in nausea, hair loss, fatigue, and other side effects. Because of these intense side effects, chemo in the metastatic setting is reserved for fast-moving cancers or cancers that have spread to the brain or liver, says Dr. Tsarwhas. As mentioned earlier, it's often paired with immunotherapy to treat metastatic triple-negative breast cancer.
These are research studies looking into new potential treatment options for metastatic breast cancer that involve real human subjects. "Clinical trials are also ways that we manage our patients with all types of breast cancer but particularly those with metastatic breast cancer," says Dr. Taiwo. "There are tons of clinical trials that are ongoing." (Dana-Farber Cancer Institute, for example, has several active metastatic breast cancer treatment trials.) Participating in these trials helps doctors better understand how breast cancer works, and may provide patients with new treatment options not otherwise available.
Surgery is less common to treat late-stage breast cancer, says Dr. Taiwo, because the goal of surgery is usually to remove the entire cancer. When cancer has spread enough to be metastatic, you can't really do much on that front with a surgery. However, "there are cases where we will consider surgery as a palliative need," she says. For example, if someone has bone lesions that are causing pain or fractures, they might be sent to an orthopedic surgeon to help stabilize their bones.
This is a relatively new field of medicine, which per the National Institute on Aging (NIA) seeks to improve quality of life and manage symptoms of people living with chronic or serious illness. At their hospitals, Drs. Tsarwhas and Montero say that their oncology team often co-manages a patient's care with the palliative medicine team. "[Palliative care doctors] are trained to basically manage side effects from our treatments," says Dr. Montero, "and also help manage symptoms related to cancer such as pain."
"It's important to focus on pain management, focus on proper nutrition, keeping patients physically active to give them more energy to feel better during treatment," adds Dr. Tsarwhas on the palliative approach. "You have to have a holistic approach to the patient." Research has shown that working with a palliative care team as well as a cancer treatment team improves end-of-life care for patients with metastatic breast cancer.
With all of these treatment options, there's a lot of hope for metastatic breast cancer patients to live longer lives. With the right treatment, "we have patients living for up to 10 years," says Dr. Taiwo. Helping patients live out their days with minimal pain or symptoms "is a worthy goal," she says.
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