A new era in metastatic breast cancer treatment

Breast cancer is the most common form of cancer among women.

The American Cancer Society (ACS) estimates more than 300,000 women will be diagnosed with breast cancer in 2025. The average risk for a woman developing breast cancer in her lifetime is 13 percent, or a 1 in 8 chance, according to the ACS.

For some women, the breast cancer has metastasized, or spread to other areas of her body (typically the liver, lungs, bones or brain).

Hearing you have metastatic breast cancer can be overwhelming and frightening. Advances in treatment, however, offer a way to manage the disease and live productive lives for many years.

“The good news is that there is so much research for breast cancer that we have all of these great treatment options that have been changing the outcome for patients,” says Amaryllis Gil, MD, a hematologist and oncologist at Endeavor Health.

Though the cancer has spread to other areas of the body, treatment for metastatic breast cancer still focuses on the origination point. Your diagnosis will include testing to determine what type of breast cancer you have, if the BRCA1 or BRCA2 mutations are present, and next generation sequencing to treat any mutations in the cancer cells.

Typically, breast cancers are treated according to the receptors on the cancer cell surface. Treatments may include chemotherapy, immunotherapy and/or targeted therapy. For women with a BRCA1 or BRCA2 mutation, targeted therapy is often used.

Treatment for metastatic breast cancer varies depending on the type of cancer:

• TN (triple-negative) breast cancer makes up about 15 percent of all breast cancer cases. Among triple-negative breast cancer cases, about 20 percent have a BRCA1 or BRCA2 mutation. For women who no longer are responding to typical chemotherapy drugs, monoclonal antibody chemotherapy drugs provide a way to directly target the cancer cells. If there is a BRCA mutation, this can be targeted with oral drugs.
• HR+ (hormone receptor-positive) cancers (estrogen receptor-positive or progesterone receptor-positive) make up 2 out of 3 breast cancer cases, according to the ACS. In these types of cancers, cancer cells have receptors for estrogen or progesterone cells to help the cancer spread. A hormone blockade, with an oral drug like tamoxifen or an aromatase inhibitor, can help block the receptors and keep the cancer from growing. If you are premenopausal, treatment may also include inducing menopause either through monthly injections or surgery to help suppress hormones. Treatment may also involve the use of CDK4/6 inhibitors or a P13K inhibitor (for particular mutations). Chemotherapy may be used if hormone therapy fails.
• TP+ (triple-positive) cancers (ER/PR-positive and HER2-positive) involve some of the same treatments as hormone receptor-positive cancers, such as a hormone blockade. Targeted therapy delivered through a monoclonal antibody, trastuzumab, attacks the HER2 protein in this cancer. Pertuzumab may also be added to treatment. These two agents are given with chemotherapy as well. If the cancer progresses, your team may focus primarily on the HER2 and discontinue the hormone therapy.
• HER2+ (HER2-positive) cancers can be aggressive in nature, but there are many effective therapies, Dr. Gil noted. In the past, chemotherapy was the main option, but today targeted monoclonal antibody treatments, such as trastuzumab or pertuzumab, are paired with chemotherapy agents through an intravenous treatment that is delivered every three weeks.

Stage IV treatment options are palliative, not curative, in nature, Dr. Gil said. But with advances in treatment options, she says many patients are seeing their prognosis outlooks described in years, not months.

“There’s been an explosion in treatment options,” she said, adding that controlling the cancer and its symptoms helps improve a patient’s quality of life. “There is better supportive medicine and better supportive care for patients.”

“Communicating with your care team about your health and any side effects you are experiencing is key,” said Dr. Gil. “Be sure to let your physician know of any problems or concerns you have.”

Advances in treatment for metastatic breast cancer — including targeted therapies for specific mutations and immunotherapies, as well as genomic profiling to personalize care — continue to improve outcomes for patients. There are also several clinical trials underway for metastatic breast cancer that are showing promising results and providing more options.