ctDNA Testing in Breast Cancer

Some oncologists are using liquid biopsy as part of their monitoring approach for various cancers. Providing an additional approach to imaging, such as CT and PET scans, this emerging technology measures cancer at a molecular level.

Signatera uses the patient’s tumor and its unique genetic signature to customize a blood test. Able to detect tumor DNA fragments, called circulating tumor DNA or ctDNA, that shed into the bloodstream, this technology is being tested in clinical trials and used by some oncologists to provide additional information about different cancers, including early-stage breast cancer.

Establishing a Pretreatment Baseline

Before the patient starts cancer treatment, a baseline blood test is conducted using a sample of tumor tissue. Because every tumor possesses a distinct DNA sequence, this initial step identifies tumor-specific mutations and maps a unique “DNA fingerprint” of the cancer. Subsequent blood tests then look for these specific molecular markers, allowing clinicians to track ctDNA levels in the blood over time.

Monitoring Treatment Response

For patients undergoing neoadjuvant therapy, which refers to treatment before surgery, routine blood draws can measure rising or falling concentrations of ctDNA. Some studies in early-stage breast cancer show reduced ctDNA levels during treatment are associated with a favorable treatment response.

Evaluating Postsurgical Residual Disease

Following the surgical removal of a tumor, ctDNA testing can reveal microscopic traces of cancer cells—referred to as molecular residual disease (MRD). Research shows the presence of MRD after surgery in breast cancer is associated with a higher risk of recurrence. This knowledge about increased risk can help oncologists when evaluating additional treatments or monitoring strategies.

Long-term Surveillance

After treatment for breast cancer, patients often worry about the cancer coming back. Studies continue to explore how serial ctDNA monitoring could provide additional clinical insights. For example, a 2024 study that assessed 156 people who had completed treatment for breast cancer found Signatera was able to detect molecular signs of metastatic recurrence a median of 10.5 months before traditional imaging scans or clinical symptoms. In an interim analysis of the DARE trial, approximately 99% of patients with stage II or III breast cancer who had serially negative ctDNA results were alive without cancer recurrence after a median follow-up of 27.4 months.

Signatera is a laboratory-developed test performed in a CLIA-certified laboratory. This test recently gained Food and Drug Administration (FDA) approval as a companion diagnostic in muscle-invasive bladder cancer. Signatera has not been cleared or approved by the FDA for use in breast cancer. Patients who are interested in ctDNA monitoring should discuss the option with their oncology team to help determine whether it is appropriate and available for their specific situation.

About Natera

Natera is a diagnostics company dedicated to providing highly personalized cancer monitoring and specialized testing to help patients and their care teams manage cancer with clarity and confidence. For more information about Signatera, visit Natera.com.

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