Metastatic Breast Cancer: 8 Things Doctors Want You to Know

Nearly 270,000 people in the United States—almost all women—are expected to be diagnosed with invasive breast cancer in 2018, and about 40,000 will die from it. Breast cancer is the second most common cause of cancer death in American women, and most of those cases are due to metastatic cancer that has spread beyond the breast to other areas of the body. Yet, new treatments over the past few years are making a big difference in transforming metastatic breast cancer into a chronic, manageable disease—and extending survival rates significantly. Two breast cancer oncologists who both treat and research this cancer explain more about these promising new treatments.

A variety of new drugs approved in recent years to treat metastatic breast cancer "really have been game-changers," says Cesar A. Santa-Maria, MD, a breast oncologist and researcher at the Sidney Kimmel Cancer Center at Johns Hopkins. These targeted therapies attack tumors based on their specific metabolic characteristics, preventing cancer cells from growing and spreading. As a result, many patients have experienced "good disease control in the metastatic setting for long periods of time," Dr. Santa-Maria says, with fewer side effects than with older medications and chemotherapy.

Breast cancer is "not one disease—it's a bunch of different diseases," says Kathy Miller, MD, oncologist, researcher and professor of oncology at Indiana University School of Medicine. Most breast cancers (about 70%) are sensitive to hormones, such as estrogen and progesterone. Some cancers (about 15% to 20%) may also contain an extra growth factor called HER2 (human epidermal growth factor), which Dr. Miller says is "like a gas pedal stuck in the 'on' position," causing tumors to grow very quickly. About 10% to 15% of breast cancers aren't sensitive to estrogen, progesterone or HER2, so they are called triple-negative. Your treatment will vary depending on your metastatic breast cancer's type.

Dr. Miller says before the advent of HER2-positive targeted therapy, she'd pray a patient's tumor would not turn out to be HER2-positive, because of the poor prognosis. "Now it's exactly the opposite," says Dr. Miller. "You find yourself praying, 'Please let it be HER2-positive, because I have so much more I can do for this woman.' It's really changed." Dr. Miller says newer targeted therapies have boosted average survival from 18 months to 5 years—with some women living many years longer. "It's really been phenomenal," she says.

Patients with hormone receptor-positive breast cancer are typically given anti-hormone therapy to block hormonal effects, but over time, "The cancer will outsmart the drug and it will be able to grow despite treatment," says Dr. Santa-Maria. However, in the past few years, drugs have become available that help fight this hormone resistance, making the hormone therapy last longer. Drugs such as CDK4/6 inhibitors are given along with anti-hormone therapy and have "really changed the treatment landscape" for metastatic hormone-receptor positive breast cancer, he says. In some patients, these newer treatments have doubled the amount of time they can be on hormone therapy, from about a year on average to two years, with generally manageable side effects (such as low white blood cell counts and being tired).

Dr. Miller dislikes the term "triple-negative breast cancer," which patients may mistakenly think is "three times as bad" as other breast cancers, she says. However, because this subtype doesn't respond to the targeted therapies currently available, it is "historically the toughest breast cancer to treat," says Dr. Santa-Maria. Right now, the standard treatment is chemotherapy. One promising area of research, though, is immunotherapy for triple-negative breast cancer. Dr. Santa-Maria says some patients in clinical trials are responding very well to this treatment, which he hopes will be available "sooner rather than later."

Some patients with breast cancer have genetic defects in the BRCA1 or BRCA2 genes. Researchers have found that patients with BRCA mutations who have metastatic breast cancer may benefit from treatment with PARP inhibitors, says Dr. Santa-Maria. Because of this new treatment, doctors may recommend some women with metastatic breast cancer undergo genetic testing to see if they have the BRCA mutation. "That's the only way to know if they might benefit from this group of targeted therapies," says Dr. Miller. Dr. Santa-Maria says several top universities have recently begun studying whether cancer caused by other mutations, not just BRCA, may also respond to PARP inhibitors.

Metastatic breast cancer is a "systemic disease," says Dr. Santa-Maria. It uses your bloodstream and lymphatic system to travel around your body, and may cause tumors to grow in various organs. Doctors typically won't do surgery on these tumors or radiate them because, Dr. Santa-Maria says, "It's almost like whack-a-mole—as you get one lesion out, you'd likely have another lesion develop elsewhere." Instead, other treatments, such as chemotherapy and targeted therapy, or combinations of these drugs, are used to shrink and control the tumors. If, however, a tumor is painful or causing symptoms, doctors may remove it, he says.

Some patients think if they enroll in a clinical trial, they risk getting stuck in the control group and receiving just "a placebo or a sugar pill," says Dr. Miller. But clinical trial patients typically get either experimental treatment or the current standard of care for their cancer. It's also often the only way to access many of the new drugs being studied, such as immunotherapy for breast cancer, says Dr. Santa-Maria. Both he and Dr. Miller strongly encourage cancer patients to look into clinical trials (found via the American Cancer Society website Trusted Source American Cancer Society Highly respected international organization Go to source or by contacting your physician). Besides helping yourself, research also moves cancer treatment forward, points out Dr. Miller, enabling future patients with metastatic breast disease to find better, more long-lasting, and perhaps even curative treatments.