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A ctDNA MRD test looks for the tumour's own mutations in blood after surgery. Detection predicts relapse months before scans, and in 2026 the FDA approved Signatera as the companion test selecting bladder cancer patients for adjuvant atezolizumab.
Tumour-informed assays (Signatera, RaDaR, NeXT Personal) sequence the tumour first and track a personalised set of variants in plasma; tumour-naive assays (Guardant Reveal) use mutations and methylation without a tumour sample. A positive result is any detection above the assay's calling threshold, reported as detected or not detected with a level. IMvigor011 showed a survival benefit for atezolizumab over placebo in ctDNA-positive muscle-invasive bladder cancer after cystectomy, and the FDA list carries Signatera CDx as the companion diagnostic for Tecentriq in that setting (P260004, 15 May 2026); the Tecentriq label read on 20 May 2026 predates the indication text in the openFDA copy, so the threshold here is quoted from the FDA list. In colorectal cancer the DYNAMIC trial and the ongoing CIRCULATE trials use ctDNA to guide adjuvant chemotherapy. As a genome-wide readout it sits under no target.
A positive ctDNA test after surgery means traces of the cancer's DNA are still in your blood and relapse is likely without more treatment. In muscle-invasive bladder cancer a positive Signatera result now selects a year of atezolizumab; in bowel cancer it is used in trials and by some teams to decide on chemotherapy. A negative result is reassuring but not a guarantee, and testing is usually repeated over time.
Written only from the label or guideline text cited on this page. Not medical advice; your own report and the reading your team gives it come first.
Detection of tumour-derived DNA in plasma above the assay's validated calling threshold after curative treatment (Signatera: two or more of 16 patient-specific variants detected), reported as MRD-positive with a mean tumour molecules per millilitre level.
“Circulating tumor DNA (ctDNA) molecular residual disease (MRD): Signatera CDx (Natera, Inc.) Muscle Invasive Bladder Cancer (MIBC) - Plasma TECENTRIQ (atezolizumab), TECENTRIQ HYBREZA BLA 761347 P260004 (05/15/2026)”
FDA: List of FDA-Authorized Companion Diagnostic Devices| Threshold | Drug | Cancer | Regulator | Source |
|---|---|---|---|---|
| ctDNA MRD-positive by Signatera CDx after cystectomy FDA companion diagnostic row P260004 (15 May 2026) for Tecentriq in muscle-invasive bladder cancer; the atezolizumab label copy read on DailyMed on 23 Sept 2026 (effective 20 May 2026) is the label version to check for the indication text. | Atezolizumab | Bladder & urothelial cancer | FDA | label |
| Device | Maker | Indication and sample | Drug | PMA / 510(k) |
|---|---|---|---|---|
| Signatera CDx | Natera | Muscle Invasive Bladder Cancer (MIBC) - Plasma | Atezolizumab | P260004 (05/15/2026) |
Matched on the name and aliases of the readout in the title, setting and summary of each trial; a match is a mention, not proof the readout was an entry criterion.
ctDNA and RCB measure different things and both should stratify post-neoadjuvant TNBC trials; an RCB-II patient with negative ctDNA has an 87% three-year event-free survival.
The blood test stratifies risk far better than stage or pathology. It supports treating ctDNA-positive patients and suggests ctDNA-negative patients gain little from chemotherapy, but because treatment was not randomised the de-escalation claim needs the randomised trials that are now under way.
The first prospective test of acting on ctDNA in triple-negative disease, and a negative one: with a quarterly, single-mutation assay the window between detectable DNA and visible metastasis was too short to intervene. Later designs use tumour-informed assays, earlier sampling and drugs with more single-agent activity.
It reframes the blood test from a yes-or-no residual disease result into a measure of how well chemotherapy is working and how fast a relapse is coming, which is what an escalation trial would need.
For stage II colon cancer, where most patients are cured by surgery alone, a blood test can identify the minority who benefit from chemotherapy and spare everyone else its side effects. It does not yet prove that treating ctDNA-positive patients improves survival compared with not treating them.
ctDNA clearance may refine pCR as a surrogate: a patient with residual disease but no ctDNA may not need escalation, the hypothesis behind ctDNA-guided post-neoadjuvant trials.
It is the proof that plasma genotyping can enrol patients for a targeted colorectal trial, which matters most for a 2 to 3% alteration where archival tissue is often exhausted or out of date.
The proof that a blood test can split residual-disease patients into those likely to relapse and those likely cured, the premise of the ctDNA-guided adjuvant idea; no completed trial has yet acted on the result.
Shares Early triple-negative breast cancer, Triple-negative breast cancer (TNBC), Pancreatic ductal adenocarcinoma and the tags biomarker, genome-wide.
Shares Circulating tumor DNA as a potential marker of adjuvant chemotherapy benefit following surgery for localized pancreatic cancer, Circulating tumor DNA analysis detects minimal residual disease and predicts recurrence in patients with stage II colon cancer, GALAXY: tumour DNA in blood four weeks after bowel cancer surgery predicts relapse tenfold, DYNAMIC: a blood test safely halved chemotherapy use after surgery for stage II colon cancer and the tag ctdna.
Shares Circulating tumour DNA (ctDNA), Hodgkin lymphoma, Non-Hodgkin lymphoma (all types) and the tag biomarker.
Shares RaDaR, Guardant Reveal, Association of Circulating Tumor DNA and Circulating Tumor Cells After Neoadjuvant Chemotherapy With Disease Recurrence in Patients With Triple-Negative Breast Cancer: Preplanned Secondary Analysis of the BRE12-158 Randomized Clinical Trial, Results of the c-TRAK TN trial: a clinical trial utilising ctDNA mutation tracking to detect molecular residual disease and trigger intervention in patients with moderate- and high-risk early-stage triple-negative breast cancer and the tag ctdna.
Shares ESR1 mutation (ligand-binding domain, usually in ctDNA), Triple-negative breast cancer (TNBC), Colorectal cancer, Non-small-cell lung cancer and the tag biomarker.
Shares Atezolizumab, Bladder & urothelial cancer, Triple-negative breast cancer (TNBC), Non-small-cell lung cancer and the tag biomarker.
Shares Minimal / molecular residual disease (MRD), Diffuse large B-cell lymphoma, Non-Hodgkin lymphoma (all types) and the tag biomarker.
Shares TMB-high (tumour mutational burden >= 10 mutations per megabase), Triple-negative breast cancer (TNBC), Pancreatic ductal adenocarcinoma, Colorectal cancer and the tag biomarker.