By Dr. Rick Baehner, Chief Medical Officer, Precision Oncology, Abbott’s cancer diagnostics business
I’ve spent much of my career thinking about one central question in oncology: how do we give patients clearer answers about their cancer?
In the clinic, those questions are often simple but profound.
Is my treatment working?
Is the cancer gone?
And perhaps most difficult of all — will it come back?
Those questions are deeply human, but they require scientific answers. For clinicians, they demand accurate, individualized insight into a patient’s cancer — how it is responding to therapy and what the risk of recurrence might be. The better those insights become, the better the decisions doctors and patients can make together.
Over the past two decades, breast cancer care has become increasingly personalized. I witnessed one of the earliest shifts firsthand when genomic testing began informing treatment decisions. As a founding member of the team who developed the Oncotype DX Breast Recurrence Score® test, I saw how partnering with thought leaders and conducting rigorous clinical trials drove strong clinical validation, broad adoption, and a fundamental improvement in breast oncology practice. The Oncotype DX® test result helps physicians identify whether a patient with HR+, HER2- breast cancer is likely to benefit from chemotherapy. This test helped establish a new global standard of care, and its predictive utility has enabled an estimated 1.6 million patients1 to safely avoid potentially unnecessary chemotherapy.2
Today, another transformation may be underway.
A new lens on residual disease
Recent data presented at the American Association for Cancer Research (AACR) Annual Meeting — building on results first shared at the San Antonio Breast Cancer Symposium (SABCS) in December — highlight the potential role of tumor-informed Molecular Residual Disease (MRD) testing in triple-negative breast cancer (TNBC).
The findings come from a substudy of the NSABP-B-59/GBG-96-GeparDouze trial, the largest TNBC MRD dataset reported to date.3 Investigators evaluated the presence of circulating tumor DNA (ctDNA) at key timepoints during treatment using the Oncodetect® MRD test.
The results were striking.
Patients who were ctDNA-negative after neoadjuvant therapy were far more likely to achieve pathologic complete response at the time of surgery, suggesting that therapy had been effective.4 Patients who remained ctDNA-positive before surgery had roughly a 10-fold higher risk of distant recurrence.4 Additionally, those who remained ctDNA-positive after surgery faced a 30-fold higher risk of distant recurrence compared with patients who were ctDNA-negative.5
Patients who were ctDNA-negative after surgery experienced very low recurrence rates over a median of three years of follow-up.5
For diseases like TNBC, one of the most aggressive breast cancer subtypes,4,5 these findings represent an important step forward. Historically, clinicians have had limited biomarkers to assess treatment response and recurrence risk after therapy. Imaging and pathology remain essential tools, but they cannot always detect microscopic disease that may remain after treatment. MRD testing offers another layer of biological insight.
From prognostic signal to clinical insight
The promise of MRD lies in its ability to deliver actionable information at pivotal moments in care. In the NSABP B-59 substudy, ctDNA status provided meaningful signals at multiple timepoints — post neoadjuvant therapy and both before and after surgery — offering clinicians a potential way to evaluate treatment response and stratify recurrence risk.
In practice, this kind of information could help guide conversations between physicians and patients as they consider next steps — whether that means continuing therapy, intensifying treatment, or transitioning to surveillance.
The goal is not simply to generate more data; it is to provide clearer insight into an individual’s risk of recurrence, supporting better decision-making.
MRD testing in breast cancer is still an evolving field. Continued research will be essential to determine how best to integrate this tool into routine clinical care. Studies such as the ongoing EXActDNA-003 /NSABP B-64 study, which is enrolling patients with high-risk, early breast cancer across subtypes, will help expand the evidence base.
But the direction is clear: we are moving toward a future where molecular information increasingly influences how we monitor and treat cancer.
A new chapter in precision oncology
Precision oncology began with the idea that every tumor has a unique molecular signature and that treatment should be tailored to the patient. Today, we are entering the next phase, where timely data on therapy response and recurrence risk can further individualize patient care.
MRD testing could play a central role in that evolution.
In the years ahead, I believe these tests will become an important clinical tool for oncologists, offering dynamic information about how cancers respond to treatment and whether molecular disease persists. Used thoughtfully, they have the potential to guide more individualized care, helping some patients avoid unnecessary treatment while ensuring that others receive needed therapies.
For now, the NSABP B-59 substudy provides an important signal of what may be possible. For patients facing TNBC, that signal offers something we are always striving to provide in oncology: better answers for patients when they matter most.
Sources
- This estimate was calculated using the total global lifetime volume of patients that had an Absolute Chemotherapy Benefit result of <1% using the Oncotype DX Breast Recurrence Score test, as this value is defined for each nodal and menopausal (or assumed by age) status.
- DOF. Exact Sciences Corporation; Madison, WI. 1.6 million patients [REF-01276]. 2026.
- Data source on file. Accessed November 25, 2025.
- Balic, Marija, et. al. Whole-exome sequencing tumor-informed circulating tumor DNA detection after completion of neoadjuvant treatment predicts non-pCR and distant recurrence in patients with early triple-negative breast cancer (TNBC) — Results from a sub-study of the NSABP-B-59/GBG-96-GeparDouze Trial. Presented at: American Association for Cancer Research (AACR) Annual Meeting: April 18, 2026; San Diego, CA.
- Balic, Marija, Geyer, Charles Jr. et. al. Evaluation of a whole-exome sequencing tumor-informed circulating tumor DNA MRD assay in patients with early triple-negative breast cancer receiving neoadjuvant chemotherapy with or without atezolizumab: A substudy of the NSABP-B-59/GBG-96-GeparDouze Trial. Presented at: San Antonio Breast Cancer Symposium (SABCS): December 11, 2025; San Antonio, TX.