Tissue-Free ctDNA Detects Molecular Residual Disease Months Before TNBC Recurrence

A blood-based circulating tumor DNA (搜索)搜索该靶点 (ctDNA) assay that does not require sequencing of the primary tumor identified molecular residual disease (MRD) months before clinical recurrence in patients with early triple-negative breast cancer (搜索)搜索该疾病 (TNBC), while achieving lead times similar to a highly sensitive tumor-informed approach, according to a prognostic analysis published in JAMA Oncology.

In the analysis, researchers evaluated 1,026 plasma samples from 159 patients with moderate- to high-risk triple-negative breast cancer (搜索)搜索该疾病 who had completed curative-intent treatment and entered ctDNA surveillance in the c-TRAK TN study. The tissue-free assay detected circulating tumor DNA (搜索)搜索该靶点 in 34.0% of patients, and detection was strongly associated with subsequent recurrence (HR 27.2; 95% CI, 13.7–54.2; P < .001).

Among patients in whom ctDNA was detected before recurrence, the median lead time between molecular detection and clinical relapse was 7.9 months (Cunningham et al., 2026). Importantly, the assay did not require sequencing of each patient's original tumor. Instead, it used cancer-associated DNA methylation patterns in circulating cell-free DNA.

Why Molecular Residual Disease Matters in Early Breast Cancer

After apparently successful treatment for early breast cancer (搜索)搜索该疾病, conventional imaging and clinical assessment may show no evidence of disease while microscopic cancer persists. Detection of tumor-derived DNA in plasma after definitive treatment is commonly described as molecular residual disease, or MRD.

Previous breast cancer (搜索)搜索该疾病 studies have shown that ctDNA detection after treatment is strongly associated with subsequent relapse and can precede clinically apparent recurrence by months (Garcia-Murillas et al., 2015; Garcia-Murillas et al., 2019). This creates a potential therapeutic window: if molecular recurrence can be identified before metastatic disease becomes clinically visible, treatment might theoretically be introduced at an earlier stage.

However, an important distinction remains. Detecting recurrence earlier is not the same as proving that treating at the moment of ctDNA detection improves survival. That clinical utility remains under investigation.

Tissue-Free Versus Tumor-Informed Testing

Most highly sensitive MRD assays have historically been tumor-informed. With this approach, tissue from the patient's primary tumor is sequenced first, and specific genomic variants are incorporated into a personalized assay designed to search for those same variants in plasma. This can provide extremely high analytical sensitivity, but the approach has practical limitations: tumor tissue may be unavailable or contain insufficient cancer cells, sequencing can fail, and personalized assay development requires additional time and resources.

A tissue-free assay attempts to avoid this step. Rather than requiring sequencing of the original tumor, the assay used in the present study identifies patterns of differential DNA methylation associated with cancer directly from plasma. That potentially allows MRD testing even when an adequate archival tumor sample does not exist.

Study Design and Population

The analysis used samples collected during the ctDNA surveillance component of c-TRAK TN, a multicenter Phase II study of patients with triple-negative breast cancer (搜索)搜索该疾病 at moderate to high risk of recurrence. Patients entered surveillance after completing adjuvant treatment, with blood samples collected every 3 months for up to 2 years.

The investigators retrospectively analyzed plasma using the tissue-free Guardant Reveal (搜索)搜索该药品 assay on the Infinity targeted next-generation sequencing platform. Results were compared with two tumor-informed approaches: personalized digital polymerase chain reaction (dPCR) tracking one or two tumor-specific variants, and a more sensitive whole-exome sequencing-powered multivariant tumor-informed assay capable of tracking multiple tumor-specific variants.

The analysis included 159 patients and 1,026 plasma samples. Patients had a mean age of 51.4 years, with an age range from 25 to 78 years. Median follow-up from the start of ctDNA surveillance was 33.9 months. The tissue-free approach successfully generated results from 98.6% of plasma samples (1,012 of 1,026), with most unsuccessful samples associated with insufficient cell-free DNA yield. At the patient level, ctDNA was detected at least once in 54 of 159 patients (34.0%).

Prognostic Performance

The association between ctDNA detection and recurrence was substantial. Patients with ctDNA detected during serial tissue-free surveillance had a markedly higher risk of recurrence than patients whose ctDNA remained undetected (HR 27.2; 95% CI, 13.7–54.2; P < .001). Median recurrence-free survival from the beginning of surveillance was 5.9 months among patients with ctDNA detected, versus not reached among patients without ctDNA detection.

Among patients whose ctDNA became detectable before clinical relapse, the median interval from molecular detection to recurrence was 7.9 months (95% CI, 6.1–10.5 months). Most ctDNA detections occurred within the first year of surveillance, consistent with the recurrence biology of higher-risk TNBC described by the investigators.

At 24 months, the assay demonstrated sensitivity of 84.4%, specificity of 87.8%, positive predictive value of 79.2%, and negative predictive value of 91.1%. Among patients who developed a distant recurrence within 24 months, sensitivity was 85.7%, with ctDNA detected in 24 of 28 patients who subsequently developed distant recurrence.

Comparative Performance Against Tumor-Informed Assays

The study compared the tissue-free assay and personalized dPCR across 1,005 paired time points from 159 patients. Overall agreement was 94.5%, and patient-level agreement was 89.9%. Both assays detected ctDNA in 42 patients; among these, 28 of 42 (66.7%) were detected at the same surveillance time point, while 14 of 42 (33.3%) were detected earlier by the tissue-free assay. There were no patients in whom dPCR detected ctDNA earlier than the tissue-free assay among those positive by both approaches.

Median lead time from ctDNA detection to recurrence was 7.9 months with the tissue-free assay versus 5.8 months with dPCR, a difference favoring the tissue-free approach (HR 0.57; 95% CI, 0.34–0.95; P = .03).

The comparison against the multivariant tumor-informed assay produced a more nuanced result. Both tissue-free and multivariant tumor-informed results were available for 133 patients across 809 paired time points, with overall sample-level agreement of 95.2% and patient-level agreement of 92.5%. Among 41 patients in whom both assays detected ctDNA, 28 (68.3%) were detected at the same time point, 12 (29.3%) were detected earlier by the multivariant tumor-informed assay, and only 1 patient (2.4%) was detected earlier by the tissue-free assay.

Despite this greater analytical sensitivity, the tumor-informed approach did not translate into a significantly longer clinical lead time. Median time between ctDNA detection and clinical recurrence was 7.6 months with tissue-free testing versus 7.1 months with the multivariant tumor-informed assay (HR 1.46; 95% CI, 0.87–2.44; P = .15).

Among 10 patients with discordant results, four had ctDNA detected only by the tissue-free assay and six only by the multivariant tumor-informed assay. Five of the six patients identified only by the tumor-informed assay subsequently experienced clinical recurrence, whereas none of the four patients detected only by the tissue-free assay had experienced relapse during available follow-up. The authors therefore caution that the multivariant tumor-informed approach appears to have greater analytical sensitivity, which becomes particularly important when considering treatment de-escalation.

The Practical Case for Tissue-Free Testing

The major advantage of tissue-free testing is logistical. Tumor-informed testing requires adequate tumor tissue. In this study, 26 of 159 patients (16.4%) did not have multivariant tumor-informed results available. For 21 of those 26 patients, the reason was absence of adequate whole-exome sequencing data from archival tumor material because of insufficient tumor content, inadequate DNA, inability to identify appropriate variants, or sample contamination.

A tissue-free approach bypasses this requirement, potentially allowing MRD testing when archival tumor tissue is unavailable, tumor DNA quantity or quality is inadequate, personalized assay construction fails, or rapid testing is needed without waiting for tumor sequencing. The study therefore positions tissue-free testing primarily as a practical alternative, rather than demonstrating that it is analytically superior to the most sensitive tumor-informed platforms.

Clinical Utility Remains Unproven

The original c-TRAK TN study was an important early attempt to move ctDNA from prognosis toward intervention, with patients monitored using personalized dPCR assays and eligible patients with detected ctDNA receiving pembrolizumab查看药品详情. However, the present JAMA Oncology analysis was not designed to demonstrate that treatment initiated according to tissue-free ctDNA improves outcomes. Instead, it establishes prognostic validity and assay comparability.

The authors explicitly state that the clinical benefit of early MRD detection and intervention remains uncertain. Tissue-free ctDNA identified patients at very high risk of recurrence and created a median molecular lead time approaching eight months, but the study does not establish which treatment should be given during that interval, or whether treatment at molecular recurrence improves recurrence-free or overall survival compared with waiting until conventional recurrence.

The investigators recommend particular caution regarding treatment de-escalation. Using a negative ctDNA result to withhold or reduce therapy requires exceptionally high sensitivity because missed microscopic disease could result in undertreatment. The multivariant tumor-informed assay detected some very-low-level ctDNA signals missed by the tissue-free assay, including in patients who later experienced relapse. For that reason, the authors suggest caution in applying tissue-free testing to de-escalation trials when a tumor-informed assay can be generated.

Unresolved Questions and Limitations

Six patients had repeated ctDNA detection by both tissue-free and multivariant tumor-informed assays but had not developed clinical relapse by the data cutoff. The investigators discuss several possible explanations, including longer-than-observed lead times, more indolent biology, or possible immune control of microscopic disease. Additionally, four patients had positive results only with the tissue-free assay and had not relapsed during follow-up. The study could not determine whether these represented true molecular disease that later cleared, another cancer signal, very long lead times, or false-positive results.

The authors identify several limitations. The tissue-free approach was not compared directly with the newest whole-genome sequencing-powered tumor-informed assays, which may achieve even greater analytical sensitivity. Routine surveillance imaging was also not performed in asymptomatic patients, consistent with standard clinical follow-up, so some patients with positive ctDNA may already have had radiographically occult metastatic disease at the time of molecular detection. The analysis also remains fundamentally prognostic and exploratory.

Implications for TNBC Surveillance

The study shifts part of the MRD discussion away from whether ctDNA can predict recurrence — the evidence for that association is increasingly strong — and toward how MRD testing can be implemented practically. A future surveillance model could involve blood collection after curative-intent treatment, molecular assessment every several months, and identification of patients whose cancers are beginning to recur molecularly before conventional clinical relapse.

But the next step cannot simply be earlier detection. The decisive question is whether clinicians can successfully intervene during that molecular window. Until prospective intervention studies answer that question, tissue-free ctDNA should be viewed as a highly promising prognostic and clinical-trial tool rather than an established standard for directing adjuvant treatment.