What tests should I get after a HER2-Positive Breast Cancer diagnosis

Tests After a HER2-Positive Breast Cancer Diagnosis

After being diagnosed with HER2-positive breast cancer, your medical team will recommend several important tests to guide your treatment plan. Let me walk you through what you should expect and why these tests matter.

Core Biomarker Testing (Already Done or Confirmed)

HER2 Testing According to NCCN Guidelines, HER2 testing should be performed on all new primary breast cancers using validated methods. Your HER2 status was likely determined through:

• Immunohistochemistry (IHC): A staining test that measures HER2 receptors on cancer cells. A score of 3+ means HER2-positive.
• In Situ Hybridization (ISH): This test counts the actual number of HER2 gene copies if your IHC results were unclear (scored as 2+).

Hormone Receptor Status NCCN Guidelines recommend testing for estrogen (ER) and progesterone (PR) receptors on all new tumors. This is crucial because:

• If your cancer is ER+ and/or PR+ (hormone receptor-positive), you may benefit from hormone therapy in addition to HER2-targeted treatments
• If your cancer is ER- and PR- (hormone receptor-negative), your treatment approach will focus on HER2-targeted therapy and possibly chemotherapy

Staging and Spread Assessment Tests

Once your diagnosis is confirmed, your oncologist will order tests to determine if cancer has spread:

Imaging Studies:

• CT scan (chest, abdomen, pelvis) - to check for spread to organs
• Bone scan or PET scan - to detect spread to bones or other areas
• Brain MRI - sometimes recommended for HER2-positive cancers, as they can spread to the brain

Blood Tests:

• Complete blood count (CBC) - checks red blood cells, white blood cells, and platelets
• Comprehensive metabolic panel - evaluates kidney and liver function (important before starting treatment)
• Tumor markers (optional) - blood tests like CA 15-3 or CEA that may be elevated with cancer; these help track treatment response over time

Additional Biomarker Testing to Discuss

According to NCCN Guidelines, your doctor may recommend additional molecular testing depending on your specific situation:

Genetic/Mutation Testing:

• BRCA1/BRCA2 testing - if you have a family history of breast or ovarian cancer, or meet other criteria
• Other tumor mutations - tests like PIK3CA mutations may be relevant for treatment selection in some cases

Functional/Immune Profiling: If your cancer is metastatic (spread beyond the breast), your oncologist might discuss:

• Tumor microenvironment analysis
• PD-L1 testing (a protein that affects immune response)
• Circulating tumor DNA (ctDNA) from blood samples - can help monitor disease and detect early signs of progression

Questions to Ask Your Oncology Team

To ensure you get the right testing plan for YOUR specific situation:

1. "Have all my biomarkers been tested - HER2, hormone receptors, and any other relevant mutations?"

2. "What staging tests do you recommend for me, and why?" (This depends on your cancer stage and other factors)

3. "Are there additional biomarker tests that might help guide my treatment decisions?"

4. "How will you use these test results to create my treatment plan?"

5. "Will you retest my tumor if my cancer progresses or recurs?" (NCCN Guidelines note that retesting may be appropriate in certain situations)

Why This Matters

According to NCCN Guidelines for HER2-positive breast cancer, comprehensive testing helps your oncologist:

• Determine if you need HER2-targeted therapy (like trastuzumab/Herceptin or pertuzumab/Perjeta)
• Decide if hormone therapy should be added to your treatment
• Identify whether chemotherapy is needed
• Monitor your response to treatment over time
• Detect any changes in your cancer that might require treatment adjustments

The good news is that HER2-positive breast cancers have many effective treatment options available, and thorough testing helps ensure you get the most personalized approach for your specific cancer.

---

This information is for educational purposes only. Always consult your healthcare team for personalized medical advice and decisions.