October is Breast Cancer Awareness Month, a time dedicated to spreading knowledge, supporting research, and empowering patients and healthcare providers alike. Throughout the month, we’ll explore various critical aspects of breast cancer care. In this post, we focus on the current role of immunotherapy in treatment and encourage both patients and providers to consider clinical trials when appropriate, to access cutting-edge options for care.
Breast cancer remains the most common cancer among women, with an estimated 300,000 new cases diagnosed annually. Historically, the treatment of breast cancer has involved surgery, radiation, chemotherapy, and hormonal therapy, depending on the cancer subtype. However, immunotherapy has emerged as a powerful tool, especially for certain types of breast cancer. In this post, we’ll explore the role of immunotherapy in breast cancer care today and encourage patients to explore clinical trials that offer these therapies as part of their treatment.
Understanding Immunotherapy in Breast Cancer
Immunotherapy harnesses the body’s immune system to recognize and attack cancer cells, providing a more targeted approach than traditional treatments like chemotherapy. In breast cancer, immunotherapy has shown the most promise in treating triple-negative breast cancer (TNBC), an aggressive form of the disease that lacks hormone receptors and HER2 expression. Because of its lack of targeted receptors, TNBC historically has had fewer treatment options, making immunotherapy a significant breakthrough for these patients.
Recent advances have led to the approval of immunotherapies that target the PD-1/PD-L1 pathway. Drugs like pembrolizumab (Keytruda) have been used in combination with chemotherapy to treat patients with advanced or metastatic TNBC that expresses PD-L1 at high levels. Specifically, PD-L1 expression greater than 10% is an important threshold, as these tumors tend to respond better to immunotherapy.
What Is PD-L1, TMB, and MSI?
To better understand how immunotherapy works, it’s essential to clarify some of the medical terminology that determines who can benefit from these treatments.
- PD-L1 (Programmed Death-Ligand 1): PD-L1 is a protein found on the surface of some cancer cells. When it binds to its receptor (PD-1) on immune cells, it effectively turns off the immune response, allowing cancer cells to evade detection. By blocking the interaction between PD-1 and PD-L1, immunotherapy drugs help reactivate the immune system to target and destroy cancer cells. For breast cancer, immunotherapy is often used when tumors show high PD-L1 expression (greater than 10%), indicating that these drugs may be more effective.
- TMB (Tumor Mutational Burden): Tumor Mutational Burden refers to the total number of mutations present within a tumor’s DNA. A high TMB means that the cancer has many mutations, which can make the tumor cells appear more “foreign” to the immune system, enhancing the effectiveness of immunotherapy. In metastatic breast cancer, immunotherapy may be an option for patients with high TMB, as these tumors are more likely to respond to immune-based treatments.
- MSI (Microsatellite Instability): Microsatellite Instability is a condition where cancer cells have genetic hypermutability, often due to defective DNA repair mechanisms. High MSI (MSI-H) indicates a higher level of genetic instability, making these tumors more likely to be recognized and attacked by the immune system. Immunotherapy is an option for breast cancer patients whose tumors demonstrate MSI-H, as it can improve the immune system’s ability to target the unstable cells.
Current Applications of Immunotherapy in Breast Cancer
Immunotherapy is currently approved for advanced or metastatic breast cancer in specific situations, particularly when tumors express high PD-L1, have high TMB, or demonstrate MSI-H. It has shown the incremental promise in treating triple-negative breast cancer, especially when combined with chemotherapy. The combination of immunotherapy and chemotherapy works synergistically to help the immune system better recognize and fight the cancer cells.
Clinical Trials and Immunotherapy
While this therapy is making strides in breast cancer treatment, it is still not universally available for most breast cancer patients. However, clinical trials provide an opportunity for patients to access existing or newer classes of immunotherapy, even if it’s not part of the standard care for their specific subtype. Clinical trials explore new combinations of immunotherapy with other treatments, aiming to make these therapies more effective across various breast cancer subtypes.
Why Consider Immunotherapy?
For patients with advanced breast cancer, especially TNBC, immunotherapy represents an important option that can potentially improve outcomes. While not suitable for every breast cancer subtype at this time, clinical trials may offer access to innovative treatments that combine immunotherapy with standard therapies. Exploring these trials at your treatment institution is an important step in expanding your care options.
Final Thoughts: Stay Informed and Explore Clinical Trials
If you’re managing breast cancer, it’s important to explore all available treatment options, including the possibility of immunotherapy. By working closely with your oncology team and exploring clinical trials at your institution, you can potentially access cutting-edge treatments that combine immunotherapy with standard care approaches. Talk to your oncologist about the role immunotherapy might play in your treatment plan, and don’t hesitate to explore trials that could offer additional options in your care journey.
About the Author
Dr. Thomas is a distinguished medical professional and a compassionate guide in the field of oncology. With over a decade of dedicated experience as a board-certified medical oncologist/internal medicine specialist, Dr. Thomas has become a trusted expert in the treatment of melanoma, sarcoma, and gastrointestinal conditions. With his many years of experience, he brings a wealth of expertise to the complex and challenging world of oncology. About Dr Thomas – MedOncMD