Treatment Options for When Chemo Stops Working With Metastatic Triple-Negative Breast Cancer

Even though chemotherapy is the standard treatment for metastatic triple-negative breast cancer (mTNBC), it’s not uncommon for these drugs to stop working eventually.

To understand why, it helps to keep in mind that breast cancer is made up of different types of cancerous cells — and while chemotherapy can be effective at destroying some kinds of cells, it may not be able to destroy other kinds, says Marisa Weiss, MD, chief medical officer and founder of BreastCancer.org, a patient-focused resource for people with breast cancer.

What’s more, breast cancer cells can also become resistant to chemotherapy over time, which makes the treatment less effective, says Mahmoud Charif, MD, an associate professor at the University of Cincinnati School of Medicine. This is especially the case for mTNBC, which tends to be a more aggressive form of cancer.

Chemotherapy isn’t your only option, though. If these drugs have stopped working, your doctor may recommend switching to a different type of breast cancer medication or adding other resources to your treatment plan. “There can be a whole list of other options besides chemotherapy,” says Dr. Weiss.

Treatment Options When mTNBC Becomes Unresponsive to Chemo

• Immunotherapy “Immunotherapy works by stimulating the body’s immune system to recognize and destroy cancer cells,” says Amy Tiersten, MD, a professor of hematology and medical oncology and the clinical director of breast medical oncology at Mount Sinai Medical Center in New York City. When used to treat mTNBC, immunotherapy medication targets a protein called PD-1, which is found on immune cells in the body called T cells. PD-1 proteins tell T cells not to attack other cells; therefore, by “turning off” the PD-1 protein, the immune system is better able to fight off cancer cells. Immunotherapy is most effective when used in combination with chemotherapy, says Dr. Tiersten.

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• PARP Inhibitors These medications can help prevent cancer cells from surviving in the body. They do so by blocking a particular enzyme called poly ADP-ribose polymerase (PARP), which helps repair DNA damage in both healthy cells and cancer cells. By inhibiting the PARP enzyme, the cancer cells can become less likely to repair themselves and survive. PARP inhibitors are only given to people who have a BRCA1 or BRCA2 mutation, though, in part because BRCA1- and BRCA2-related breast cancers seem to be particularly sensitive to PARP inhibitors. PARP inhibitors are available as a pill and taken by mouth.

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• Antibody-Drug Conjugates (ADCs) These drugs combine an antibody therapy and a chemotherapy drug, which work together to kill cancer cells. Here’s how it works: The antibody carries the chemotherapy molecules to the cancer cells; then the antibody binds to a certain receptor on the cancer cell and releases the chemotherapy, which enters the cell and kills the tumor, says Dr. Charif. When used to treat mTNBC, ADC is given through an IV.

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• Clinical Trials Ongoing clinical trials give people with metastatic breast cancer a chance to try new breast cancer treatments that may eventually become part of standard practice. If you are interested in joining clinical trials, talk to your oncologist to see if there’s one that will work for you.