Genomic Testing for Breast Cancer

Advancements in breast cancer research have led to more personalized treatment approaches, allowing oncologists to tailor therapies to each patient’s unique genetic profile. One of the most significant developments in this field is genomic testing. 

Genomic testing analyzes specific genes within a cancer tumor to assess their activity levels and identify any mutations that cause breast cancer to develop. 

Dr. Sarah Robinson, a medical oncologist at Rocky Mountain Breast Specialists, emphasizes the importance of genomic testing in modern cancer care. She explains that before these tests were available, many women with early-stage breast cancer were routinely recommended for chemotherapy. However, genomic testing has revealed that some patients can safely avoid chemotherapy, sparing them from unnecessary side effects without increasing their risk of recurrence.

What is Genomic Testing for Breast Cancer?

Genomic testing analyzes the genes in a breast cancer tumor to assess how they influence the tumor’s growth and behavior. These tests help oncologists determine:

• The risk of recurrence after initial treatment.
• The likelihood that chemotherapy will be beneficial alongside hormone therapy.
• How aggressive the tumor is and its potential to spread.

It’s important to differentiate genomic testing from genetic testing:

• Genomic testing examines the genes in a tumor, noting any mutations that are causing cancer to grow.  
• Genetic testing evaluates inherited mutations (such as BRCA1 and BRCA2) to determine an individual’s risk of developing cancer from a hereditary gene mutation.

Who Should Consider Genomic Testing?

Dr. Robinson highlights that genomic testing is primarily used for patients diagnosed with early-stage, HR-positive, HER2-negative breast cancer. Historically, oncologists based treatment recommendations on tumor size and whether cancer had spread to the lymph nodes. However, genomic testing now allows for treatment decisions based on the biology of the tumor rather than its anatomical stage.

• Patients with smaller tumors (under 1 cm) may not need genomic testing, as the risk of recurrence is already low.
• For larger tumors or lymph node-positive cases, genomic testing helps determine whether chemotherapy is necessary.
• Triple-negative and HER2-positive breast cancers are typically not candidates for genomic testing, as treatment decisions for these subtypes are based on different molecular markers.

According to Dr. Robinson, genomic testing has transformed breast cancer treatment by reducing overtreatment and ensuring that chemotherapy is only used when truly beneficial.

Types of Genomic Tests for Breast Cancer

Several genomic tests are available to analyze a tumor’s genetic expression. The most commonly used tests in the U.S. include:

1. Oncotype DX®

• Analyzes 21 genes to determine a Recurrence Score® (0–100).
• Low scores (0–17) indicate a low risk of recurrence, meaning chemotherapy is likely unnecessary.
• High scores (31 and above) suggest a higher risk of recurrence, where chemotherapy may be beneficial.
• Intermediate scores (18–30) require careful evaluation, particularly in pre-versus postmenopausal women, as premenopausal women may still benefit from chemotherapy.
• The TAILORx trial confirmed that women with low-risk scores can safely skip chemotherapy without affecting survival rates.

2. MammaPrint®

• Examines 70 genes to categorize tumors as low risk or high risk for recurrence.
• Particularly useful for high clinical-risk patients (larger tumors or node-positive cases) to determine if chemotherapy is necessary.
• The MINDACT trial found that 40% of women classified as high-risk based on clinical factors could avoid chemotherapy based on MammaPrint results.

3. EndoPredict®

• Analyzes 12 genes to assess the risk of late recurrence (beyond five years).
• Helps determine if extended hormone therapy (beyond five years) is necessary.
• Faster turnaround time than other tests (often within a week).

4. Prosigna (PAM50)®

• Evaluates 50 genes and classifies tumors into molecular subtypes.
• Provides a Risk of Recurrence (ROR) score, particularly useful for postmenopausal women.

Each of these tests provides oncologists with additional data to personalize treatment recommendations, helping ensure that patients receive the most effective therapies with the fewest unnecessary side effects.

How Genomic Testing Influences Treatment Decisions

One of the most significant benefits of genomic testing is its ability to prevent overtreatment. In the past, chemotherapy was often prescribed broadly, but genomic tests now help identify which patients can safely avoid chemotherapy without compromising their long-term survival.

Benefits of Genomic Testing:

• Reduces unnecessary chemotherapy for low-risk patients.
• Provides precise treatment guidance, improving confidence in decisions.
• Minimizes side effects and long-term health risks associated with chemotherapy.
• Identifies patients who will truly benefit from chemotherapy, ensuring optimal outcomes.

Dr. Robinson explains that chemotherapy is not a one-size-fits-all solution. Avoiding chemotherapy when possible reduces risks such as:

• Heart damage – some chemotherapy drugs can cause long-term heart issues.
• Neuropathy – nerve damage that may lead to lasting pain or numbness.
• Bone loss – chemotherapy can contribute to osteoporosis.
• Increased risk of secondary cancers such as treatment-related leukemia.
• Emotional and psychological distress, including anxiety and depression.

For many patients, genomic testing provides reassurance that hormone therapy alone after surgery is enough to effectively manage their breast cancer.

What to Expect During Genomic Testing

The process of genomic testing involves several steps:

1. Tissue collection – A tumor sample is obtained during a biopsy or surgery.
2. Lab analysis – The sample is sent to a specialized lab for genetic evaluation.
3. Results interpretation – Your oncologist reviews the results and discusses treatment options.

Turnaround Time:

• Oncotype DX and MammaPrint results take about two weeks.
• EndoPredict results are often available within a week.

While waiting for results can be stressful, Dr. Robinson emphasizes that taking time to get the right answer is better than rushing into unnecessary treatment.

Is Genomic Testing Covered by Insurance?

Most insurance plans, including Medicare, cover genomic testing for eligible patients with early-stage HR-positive, HER2-negative breast cancer. However, coverage may vary depending on the test and the individual’s insurance policy. Your healthcare team can help determine eligibility and assist with insurance verification.

Discuss Genomic Testing with Your Breast Oncologist

Genomic testing has transformed breast cancer treatment, making it more personalized and precise than ever before. If you have been diagnosed with early-stage HR-positive, HER2-negative breast cancer, talk to your doctor about whether genomic testing is right for you.

By understanding your tumor’s unique genetic activity, you and your oncologist can make informed, confident treatment decisions that optimize your outcomes while minimizing unnecessary treatments.

Talk more about this with one of our breast cancer specialists.