If you’ve been diagnosed with metastatic breast cancer (MBC), it can feel overwhelming to navigate the many tests and results that follow. Metastatic breast cancer, also called stage IV breast cancer, is when the cancer spreads beyond the breast and nearby lymph nodes to other parts of the body. Understanding your test results is crucial in helping your healthcare team choose the best treatment for your specific situation.
Testing for Metastases
Your doctor will likely use a combination of metastases imaging tests, such as bone scans, X-rays, MRIs, PET scans, and CT scans, to determine where and how far the cancer has spread. These tests provide a clear picture of which areas of the body are affected and guide treatment planning.
For more information on these diagnostic tools, you can visit Breastcancer.org’s imaging section.
Understanding Your MBC Subtype
Not all breast cancers are the same, and identifying your MBC subtype is essential. Doctors typically test for three key receptors:
- Estrogen receptor (ER)
- Progesterone receptor (PR)
- Human epidermal growth factor receptor-2 (HER2)
Hormone receptor-positive (HR-positive) cancers are fueled by estrogen or progesterone. Subtypes include:
- HR-positive/HER2-negative
- Triple-positive (HR-positive/HER2-positive)
HER2-positive tumors have higher-than-normal levels of the HER2 protein, which promotes cell growth. Triple-negative breast cancer (TNBC) lacks all three receptors (ER, PR, HER2) and accounts for about 10–15% of cases, according to the American Cancer Society.
Triple-positive breast cancer, on the other hand, tests positive for all three receptors and represents roughly 10% of breast cancer cases.
Molecular Testing of Metastases
Your doctor may also recommend molecular testing to analyze tumor samples for gene mutations and proteins that can influence treatment decisions. Key markers include:
- PD-1 and PD-L1: These proteins regulate the immune system. Patients with TNBC and PD-L1 expression may benefit from immunotherapy combined with chemotherapy.
- PIK3CA gene mutations: Found in up to 40% of HR-positive, HER2-negative cancers, these mutations can be targeted with specific drugs.
- BRCA1 and BRCA2 mutations: Involved in DNA repair, tumors with these mutations may respond well to PARP inhibitors, which prevent cancer cells from repairing damaged DNA.
For further insights on targeted therapy options, visit National Cancer Institute.
Next Steps After Testing
Once your receptor status and molecular features are known, your doctor can recommend a treatment plan tailored to your cancer subtype. Preparing questions ahead of appointments can help you make informed decisions, such as:
- What are the possible side effects of treatment?
- How will the treatment impact my daily life?
- Are there alternative options, including clinical trials?
- What happens if treatment is delayed?
Treatment Options for MBC
While metastatic breast cancer currently has no cure, several treatment options can help manage symptoms, slow progression, and improve quality of life:
- Hormone Therapy: Drugs like tamoxifen, aromatase inhibitors, or fulvestrant are effective for HR-positive cancers by reducing hormone-driven tumor growth.
- Chemotherapy: Often recommended for triple-negative tumors or when hormone therapy is ineffective.
- Targeted Therapy: Drugs such as trastuzumab or pertuzumab target HER2-positive tumors. Other targeted therapies may address BRCA mutations or PIK3CA gene changes.
- Radiation Therapy: Helps shrink tumors and relieve pain in affected areas.
- Surgery: Sometimes used for symptom relief but rarely removes all metastatic tumors.
- Immunotherapy: Treatments like pembrolizumab (Keytruda) help the immune system recognize and destroy cancer cells, particularly in PD-L1 positive TNBC.
Learn more about treatment approaches at Cancer Research UK.
The Takeaway
Understanding your MBC subtype and the results of imaging and molecular tests is key to choosing the most effective treatment. Although metastatic breast cancer is not curable, modern therapies—especially targeted treatments—can significantly improve outcomes and quality of life.
Open communication with your healthcare team about your options, side effects, and goals will help ensure that your treatment aligns with your personal needs. Knowledge is power, and the more you understand your cancer, the better you can navigate the journey ahead.
