If breast cancer spreads beyond its original location, it’s known as metastatic breast cancer (MBC). Your doctor will classify the cancer based on three key receptors to help determine the best treatment. While there are many treatment options, their effectiveness depends on the specific type of MBC.
What Makes MBC Different?
Not all breast cancers are the same. After an MBC diagnosis, doctors often run more tests to understand the tumor’s characteristics. These tests help identify the best treatment options since some treatments work better for specific subtypes or genetic mutations.
Testing for Metastases
To find out how far the cancer has spread, your doctor will use diagnostic imaging tests like bone scans, X-rays, MRIs, PET scans, and CT scans. These tests show the location and extent of the metastases, or areas where the cancer has spread.
Understanding MBC Subtypes
Doctors test for three important receptors:
- Estrogen receptor (ER)
- Progesterone receptor (PR)
- Human epidermal growth factor receptor-2 (HER2)
These receptors are proteins that attach to substances in the blood. If the cancer tests positive for ER or PR, it’s called hormone receptor-positive (HR-positive). Based on the test results, MBC is further classified into subtypes:
Common Subtypes:
- HR-Positive/HER2-Negative
- Triple-Positive (HR-Positive/HER2-Positive)
- Triple-Negative
Hormone receptors, like ER and PR, allow hormones to feed cancer cells. If your tumor has these receptors, it’s considered HR-positive. According to Breastcancer.org, about 80% of breast cancers are ER-positive, and about 65% of those are also PR-positive.
HER2 Status
HER2 is a protein that helps cells grow. If your tumor has too much HER2, it’s classified as HER2-positive. Tumors without this overexpression are HER2-negative.
Triple-Negative Breast Cancer
Triple-negative breast cancer means the tumor is negative for HER2, ER, and PR. It’s more aggressive and makes up about 10-15% of all breast cancers.
Triple-Positive Breast Cancer
This type of breast cancer tests positive for HER2, ER, and PR. In a 2019 study of over 1,200 people with breast cancer, around 10% had triple-positive breast cancer.
Molecular Testing of Metastases
Doctors may run additional lab tests on your tumor to find genetic mutations or unique proteins. This information helps them choose the most effective treatment.
Key Genetic Mutations:
- PD-1 and PD-L1 Proteins: These proteins help cancer hide from your immune system. If you have triple-negative breast cancer and test positive for these proteins, adding immunotherapy to your treatment may help.
- PIK3CA Mutations: These mutations are found in up to 40% of HR-positive, HER2-negative breast cancers. If you have this mutation, your doctor might prescribe a targeted therapy.
- BRCA1 or BRCA2 Mutations: Mutations in these genes increase the risk of breast cancer. Tumors with these mutations may respond well to PARP inhibitors, which block cancer cells from repairing damaged DNA.
Next Steps
After receiving your test results, your doctor will use the information to recommend treatment options. These options will depend on your cancer’s subtype. It’s important to discuss your treatment choices with your doctor and make a decision together.
Questions to Ask Your Doctor:
- What side effects can I expect from treatment?
- How will treatment affect my daily life?
- Are there other treatments available?
- What happens if I delay treatment?
- Are there any clinical trials I can join?
Treatment Options
While MBC can’t be cured, many treatments can help manage symptoms and slow the spread of cancer.
Common Treatments:
- Hormone Therapy: Used to treat HR-positive cancers. Drugs like tamoxifen, fulvestrant, or aromatase inhibitors stop hormones from feeding the cancer.
- Chemotherapy: Often used for triple-negative cancers. It destroys cancer cells throughout the body.
- Targeted Therapy: These treatments target specific proteins or mutations. For example, trastuzumab is often used for HER2-positive cancers.
- Radiation Therapy: Used to shrink tumors and relieve symptoms.
- Surgery: Sometimes used to remove tumors, though it’s not always possible with metastatic cancer.
- Immunotherapy: Helps your immune system recognize and attack cancer cells. Drugs like pembrolizumab (Keytruda) are used for triple-negative breast cancer.
Mental Health and Support
Coping with MBC can be emotionally challenging. It’s important to seek mental health support, such as counseling or joining support groups. These resources can help you manage stress, anxiety, and depression that may come with your diagnosis and treatment journey.
The Takeaway
Genetic and molecular testing can help guide your treatment plan. Knowing your cancer’s subtype allows you and your doctor to choose the best treatments. While MBC treatments won’t cure the disease, they can improve your quality of life and help you manage symptoms.
Be sure to discuss all treatment options, possible side effects, and other concerns with your healthcare team. Remember, you’re not alone—there are many resources and support groups to help you through your journey.
Future Research Directions
Ongoing research is focused on developing new treatments for MBC. Scientists are working on better ways to target specific gene mutations and improve immunotherapy options. Clinical trials may provide access to new therapies that could become the future standard of care.
Staying informed about new research and clinical trials can offer hope and additional options. Talk to your healthcare provider about whether participating in a clinical trial might be right for you.
