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To date, precision oncology has largely focused on selecting therapies based on tumor genomics. One of the most persistent challenges in clinical practice remains knowing what to do next. After surgery, during systemic therapy or in surveillance, clinicians are often navigating uncertainty, balancing overtreatment against the risk of recurrence.
Reshaping patient management
Circulating tumor DNA (ctDNA)–based minimal residual disease (MRD) assessment with tumor-informed Signatera
is reshaping this paradigm by providing a dynamic, patient-specific signal that can illuminate next steps across the continuum of care. Unlike conventional imaging or clinicopathologic risk factors, ctDNA offers a real-time measure of tumor burden at the molecular level. Signatera is designed using the patient’s tumor, enabling highly sensitive and specific detection of residual disease at levels far below radiographic visibility. This creates a new layer of clinical intelligence that is actionable across neoadjuvant, adjuvant, surveillance, metastatic, and treatment response settings.
Neoadjuvant setting: early readouts to adapt therapy
In the neoadjuvant setting, clinicians often need to wait until the time of surgery to determine whether therapy was effective. Assessing ctDNA dynamics during neoadjuvant therapy can provide an early indication of treatment response; ctDNA clearance has been associated with improved outcomes while conversely, persistent ctDNA may signal resistance, prompting consideration of treatment escalation, clinical trial enrollment, or alternative regimens.1 This creates an opportunity to move beyond static endpoints toward adaptive treatment strategies. Clinicians can watch ctDNA trends to refine therapy in real time. This is especially relevant in aggressive tumor types where early response assessment is critical.
Adjuvant setting: refining who may benefit from additional therapy
MRD testing may provide immediate clinical impact in the adjuvant setting. Current decision-making relies heavily on population-level risk factors, often leading to overtreatment in some patients and undertreatment in others. Postoperative ctDNA positivity is a strong, independent predictor of recurrence across multiple tumor types. Signatera data demonstrates that ctDNA-positive patients after surgery can have dramatically higher recurrence risk compared with ctDNA-negative patients.2 More importantly, Signatera ctDNA status can help predict who benefits from adjuvant therapy. Evidence suggests that ctDNA-positive patients derive meaningful benefit from additional systemic treatment, while ctDNA-negative patients may not.3

Surveillance: detecting recurrence earlier
Surveillance after curative-intent therapy remains a gray zone as imaging can often be intermittent and insensitive to early recurrence. While many biomarkers like CEA, CA-19-9, CA-125 generally have limitations in both sensitivity and specificity, Signatera ctDNA testing offers a more sensitive approach to detect molecular relapse earlier than imaging and other blood biomarkers. Studies have shown that Signatera can identify recurrence months before it becomes radiographically apparent with high sensitivity and specificity and substantial lead times.4 Earlier detection opens the door to intervention at a lower disease burden, when therapies may be more effective. It also enables more tailored surveillance strategies to intensify monitoring or imaging when ctDNA becomes positive, provides reassurance, and potentially reduces imaging frequency in persistently negative patients. Rather than a fixed surveillance schedule, ctDNA enables a response-guided follow-up strategy.
Treatment on MRD (TOMR)
TOMR is a new paradigm in precision oncology that is used to guide earlier, more proactive therapy decisions to escalate treatment in MRD-positive patients at high risk of relapse and de-escalate or avoid unnecessary toxicity in MRD-negative patients. For clinicians, this moves decision-making from prognostic to personalized, anchored by the presence of residual disease at an earlier and potentially curable stage.
Metastatic setting: real-time disease monitoring
In metastatic disease, treatment decisions are often based on imaging intervals that may lag behind molecular changes in disease burden. A newer technology like ctDNA introduces a more immediate and dynamic tool. Because ctDNA reflects tumor burden and molecular activity, it can be used to monitor treatment response earlier than imaging and identify emerging resistance to inform timely switches in therapy. In practice, this allows clinicians to avoid prolonged exposure to ineffective therapies and pivot more quickly. Additionally, Signatera is being used to monitor response to immunotherapy across tumor types, providing a pan-cancer application in advanced disease.
Treatment response monitoring: a continuous feedback Loop
Across all stages, one of the most powerful aspects of ctDNA is its ability to create a longitudinal feedback loop. Serial testing enables clinicians to track ctDNA trends over time:
- Clearance means favorable response and improved prognosis
- ctDNA dynamics have been shown to correlate strongly with outcomes. Patients who remain ctDNA negative demonstrate significantly better survival than those who become or remain ctDNA positive which could mean there is a higher risk of disease progression
This transforms monitoring from episodic snapshots into a continuous signal, providing actionable insight at each decision point.
A pan-cancer framework for clinical decision-making
What makes Signatera particularly compelling is its pan-cancer applicability. Its tumor-informed design allows it to be used across multiple solid tumors, including colorectal, breast, lung, bladder, ovarian, and melanoma. This consistency enables a unified framework for integrating MRD into clinical workflows:
- At diagnosis or pre-treatment—establish baseline and design assay
- During neoadjuvant therapy—assess early response
- Post-surgery—evaluate MRD and guide adjuvant decisions
- During surveillance—detect molecular relapse early
- In advanced disease—monitor response and resistance
Rather than being confined to a single decision point, ctDNA becomes a longitudinal biomarker embedded throughout the care pathway.
From uncertainty to actionability
Signatera ctDNA testing bridges the gap from uncertainty to actionability by answering clinically meaningful questions at each stage of the patient’s journey: Is there still disease present, and is it changing? By doing so, ctDNA doesn’t just add another biomarker. It redefines how clinicians navigate the care pathway, moving from reactive to proactive care.
References
- Chakrabarti S, Cohen S, Tin A, et al. Utility of Circulating Tumor DNA to Assess Tumor Response in Patients with Locally Advanced Rectal Cancer Undergoing Neoadjuvant Therapy. Cancers. 2026; 18(4):589.
- Reinert T, Henriksen TV, Christensen E, et al. Analysis of Plasma Cell-Free DNA by Ultradeep Sequencing in Patients With Stages I to III Colorectal Cancer. JAMA Oncol. 2019.
- Nakamura Y, Watanabe J, et al. ctDNA-based molecular residual disease and survival in resectable colorectal cancer. Nature Medicine. 2024. doi: 10.1038/s41591-024-03254-6.
For additional information: www.natera.com.
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