ctDNA Assay Precise MRD Expands to Breast, Colorectal, Renal Cancer

Myriad Genetics has expanded the clinical availability of its tumor-informed minimal residual disease (MRD) assay, Precise MRD (Precise™ MRD Test), to patients undergoing treatment and surveillance for breast, colorectal, and renal cancers.¹ The expansion is accompanied by publication of the MONITOR-Breast study in Future Oncology, which evaluated serial circulating tumor DNA (ctDNA) monitoring during neoadjuvant therapy in early-stage breast cancer.²

Precise MRD is a whole-genome sequencing–based, tumor-informed assay that builds a personalized panel of up to 1,000 patient-specific variants to track ctDNA across the treatment continuum, from neoadjuvant therapy through post-surgical assessment and long-term surveillance. According to the manufacturer, the assay's design is intended to maintain analytic sensitivity in low-shedding tumor types, including breast and renal cell carcinoma, where ctDNA detection has historically been more limited than in colorectal cancer.

More than 6 million people in the United States are living with breast, colorectal, or renal cancer, based on National Cancer Institute surveillance data, representing the population now eligible for broader access to the test.³

“Frequent monitoring of tumor DNA in the blood may provide an accurate and timely assessment of treatment response. This could help identify patients who are responding well and may benefit from less intensive therapy, as well as those who may require different treatment. While additional studies are needed, these findings support the potential role of blood-based monitoring to guide more personalized treatment decisions…” wrote Foldi et al in the Future Oncology publication.²

Study Design and Population

MONITOR-Breast is a prospective, multi-center study that enrolled 154 patients with stage I to III breast cancer spanning all molecular subtypes. Investigators collected 949 plasma samples longitudinally across the treatment course—at baseline, during neoadjuvant therapy, after neoadjuvant therapy, and after surgery—to assess ctDNA status using Precise MRD.

Key Findings

ctDNA was detectable at baseline in 93% of patients, including 20% at ultrasensitive concentrations below 100 parts per million—levels that are typically missed by earlier-generation MRD assays. Precise MRD predicted pathologic complete response with 100% specificity, meaning no patient who achieved a pathologic complete response had been ctDNA-positive at the relevant assessment point.

Persistence of ctDNA after neoadjuvant therapy carried strong prognostic weight: patients who remained ctDNA positive at the end of neoadjuvant therapy were 47 times more likely to also be ctDNA positive after surgery, compared with patients who had cleared ctDNA.

Longitudinal sampling also revealed two distinct response patterns. Most patients (78%) showed sustained ctDNA clearance over the treatment course and were significantly more likely to achieve a pathologic complete response. The remaining 22% showed persistent or intermittent ctDNA positivity, identifying a subgroup at elevated risk for residual disease and worse outcomes. Notably, serial testing throughout treatment identified 44% more at-risk patients than a single post neoadjuvant assessment alone would have captured—suggesting that timing and frequency of ctDNA testing may materially affect risk stratification.

Clinical Context, Interpretations, and Limitations

"MONITOR-Breast highlights the strength of a whole-genome, tumor-informed approach to MRD detection," said Dale Muzzey, PhD, chief scientific officer at Myriad Genetics, in a news release.¹ He noted that identifying additional at-risk patients through frequent sampling, rather than relying on a single timepoint, underscores the potential role of molecular monitoring in risk stratification and treatment decision-making.

The findings add to a growing evidence base supporting serial, rather than single-timepoint, ctDNA monitoring during neoadjuvant treatment for breast cancer. However, MONITOR-Breast is an observational, company-supported study without a comparator arm testing whether acting on ctDNA results—for example, escalating or de-escalating systemic therapy based on MRD status—improves outcomes such as disease-free or overall survival. Prospective, interventional trials designed to test ctDNA-guided treatment decisions will be needed before serial MRD testing can be incorporated into routine practice guidelines. Clinicians considering Precise MRD or comparable assays should weigh current evidence as prognostic and risk-stratifying rather than as a validated basis for altering standard-of-care treatment.

REFERENCES

1. Myriad Genetics Expands Availability of Precise MRD™ for Colorectal, Renal and Breast Cancers, Supported by New Publication. News release. Myriad Genetics. June 23, 2026. Accessed June 25, 2026. https://tinyurl.com/ynkpm56p

2. Foldi J, Hogan G, Johansen Taber K, et al. Personalized whole-genome-based ctDNA dynamics during neoadjuvant therapy across breast cancer subtypes: results from MONITOR-Breast. Future Oncol. 2026 Jun 21:1-12. doi: 10.1080/14796694.2026.2690165. Epub ahead of print. PMID: 42324681.

3. National Cancer Institute. Cancer Stat Facts. Surveillance, Epidemiology, and End Results (SEER) Program. Accessed June 18, 2026. https://seer.cancer.gov/statfacts/