Circulating tumour DNA assays in focus: highlights from ASCO 2025 for clinicians

Circulating tumour DNA (ctDNA) assays are rapidly developing a strong evidence base for use in patients with cancer [1]. At the American Society of Clinical Oncology (ASCO) Annual Meeting, 2025 a large number of clinical studies involving the use of ctDNA assays were presented, and notably these included analysis of large real-world databases [2, 3] reflecting the high utilisation of ctDNA assays already in clinical practice outside of clinical trials. With a view to providing an update to practicing clinicians who may consider utilising ctDNA assays in routine clinical practice, here we review selected key clinical studies in the use of ctDNA assays in solid tumour malignancy in the settings of early detection, early disease, and advanced disease presented at the ASCO Annual Meeting, 2025 (Fig. 1).

Fig. 1. Graphical Abstract.

Summary of key clinical research settings and remaining challenges for ctDNA assays post ASCO Annual meeting 2025 including detection and screening, early disease and advanced disease settings.

ctDNA assays in early detection of cancer

ctDNA assays hold great promise as a non-invasive approach to screen at-risk populations for malignancy. Blood based methylation multicancer detection ctDNA assays continue to be of great interest, but although these assays have high specificity, the key limitation highlighted again at ASCO 2025 is limited sensitivity in detection of early stage cancers [4], reflecting the difficulty in detecting very low levels of ctDNA found in early stage disease with non-tumour informed ctDNA assays. Interestingly, data presented from Memorial Sloane Kettering Cancer Centre demonstrated that pap-derived cell free tumour DNA was more effective in detecting tumour mutations compared to plasma ctDNA in patients with endometrial cancer [5], suggesting liquid biopsy approaches beyond blood based ctDNA assays, where feasible, may aid detection of larger numbers of cancers in high risk populations.

ctDNA assays in early-stage disease

Detection of ctDNA after curative intent therapy, termed molecular or minimal residual disease (MRD), is associated with a high risk of clinical relapse [6]. There were presentations confirming that detection of ctDNA, and ctDNA dynamics post operatively are strongly prognostic for patient outcomes (e.g. DARE clinical trial [7]), alongside evidence that ctDNA assays after neo-adjuvant therapy may be more prognostic than pathological response at surgery (e.g. PREDICT-DNA clinical trial [8]). However, the pertinent question requiring prospective clinical trials, is if ctDNA assays in early disease are ready to be utilised to predict response to treatment and better select patients for escalated or de-escalated adjuvant treatment strategies.

Key study: DYNAMIC-III clinical trial is the first prospective randomised study of ctDNA informed management in resected stage III colon cancer, with patients assigned to ctDNA-informed or standard of care management. The primary analysis for ctDNA positive patients was presented and demonstrated that treatment escalation strategies for ctDNA positive patients did not improve Recurrence Free Survival (RFS) (Table 1). The central question is if this negative outcome stemmed from the limitations of the available treatment strategies, or from the ctDNA assays’ ability to accurately select patients for escalation. Given the 3-year RFS was similar for ctDNA positive patients with FOLFOXIRI or doublet, and that ctDNA clearance rate, which was found to associate with favourable outcomes, did not differ by regimen, the limitations of current treatment modalities are likely to have played a strong role in these findings, and exploration of novel escalation treatment strategies is strongly recommended. Limitations of the study highlighted at discussion include the small sample size in each cohort and concerns that those randomised to ctDNA informed escalation represented patients of higher clinical risk [9].

Table 1.

Key clinical studies pertaining to ctDNA presented at ASCO Annual meeting 2025.

Clinical Trial	Design	ctDNA assay	Outcomes
DYNAMIC-III; Primary analysis of the ctDNA positive cohort	• Randomised phase II • 1:1 ctDNA-informed or standard of care management • Standard of Care (selected pre-randomisation) and accompanying treatment escalation strategies: A. Single agent fluoropyrimidine to (oxaliplatin-based) doublet, B. 3 months doublet to 6 months doublet/FOLFOXIRI or, C. 6 months doublet to FOLFOXIRI	Tumour informed SaferSeqS targeted Colorectal panel MRD assay. (Central research laboratory, John Hopkins)	2-year RFS ctDNA positive patients: ctDNA informed treatment escalation arm 52% versus 61% with Standard of Care (HR 1.11, 90% CI 0.83–1.48, p = 0.57) 3-year RFS ctDNA positive patients with FOLFOXIRI versus doublet similar (HR 1.09, 90% CI 0.78–1.53, p = 0.662)
SERENA-6; Interim analysis	• Randomised phase III • 1:1 ESR1 mutation-guided, double-blind CDK4/6i + camizestrant + placebo for AI or CDK4/6i + AI + placebo for camizestrant	Guardant360™	Median PFS: 16.0 months in the camizestrant group and 9.2 months in the aromatase-inhibitor group (HR 0.44; 95% CI, 0.31 to 0.60; p < 0.0001). Median Time to deterioration in the patient-reported global health status and QoL: 21.0 months with camizestrant and 6.4 months with an aromatase inhibitor (HR 0.54; 95% CI 0.34–0.84).

FOLFOXIRI is triplet chemotherapy including fluorouracil, oxaliplatin and irinotecan, MRD Molecular Residual Disease, RFS recurrence free survival, PFS progression free survival, HR hazard ratiol, CI confidence interval, CDK4/6i CDK4/6 inhibitor, QoL quality of life.

ctDNA assays in advanced disease

Molecular profiling through ctDNA is quickly being adopted in advanced disease across multiple different tumour types. There were many presentations at this ASCO 2025 Annual Meeting for different ctDNA assays showing potential utility for clinical practice in the advanced disease setting, with notable studies in advanced breast cancer.

Key study: The first interim analysis from the SERENA-6 clinical trial was presented at the plenary session. This is the first registrational study to demonstrate that switching therapies upon ctDNA findings has clinical utility. SERENA-6 is a prospective randomised double-blind study that enroled patients with advanced Hormone Receptor (HR) positive HER2 negative breast cancer following 6 months or longer of first-line CDK4/6 inhibitor (CDKi) and Aromatase Inhibition. Patients had ctDNA testing every 2-3 months for detectable ESR1 mutations and those patients with an ESR1 mutation detected without concomitant clinical or radiological progression were randomised to a switch to camizestrant, an oral Selective Estrogen Receptor Degrader (SERD), or to continue to receive an aromatase inhibitor, with both arms maintaining CDK4/6i [10]. The study demonstrated an improvement in Progression Free Survival (PFS) and Quality of Life (QoL) for those patients switching upon molecular progression. Potential limitations highlighted in the discussion included the potential lead-time bias introduced by anticipating a second hormonal therapy and the uncertainties around how much of the PFS improvement could be “rescued” if camizestrant were given after clinical progression, in particular as there was a lack of crossover in the study design. Further follow-up is required to assess potential Overall Survival (OS) impact of the strategy, but the QoL improvement shown may be sufficient to deem the switch clinically useful (Table 1).

Furthermore, the VERITAC-2 study [11] presented at the meeting added to the growing body of evidence that there is clinical value in interrogating ctDNA for treatment decisions. VERITAC-2 confirmed a clinical benefit of vepdegestrant, a PROTAC protein degrader, over fulvestrant for patients with advanced HR positive HER2 negative breast cancer but the benefit was restricted to the population testing positive for ESR1 mutations on pretreatment ctDNA [7], which is in accordance with results of prior phase 3 studies for different oral SERDs.

In addition, a large retrospective study led by Memorial Sloane Kettering, analysed a real-world cohort of patients with advanced breast cancer who underwent ctDNA testing with the Signatera ctDNA assay (n = 2362 HR positive HER2 negative, n = 1943 HER2 positive, n = 605 Triple Negative Breast Cancer) and found that early on treatment ctDNA dynamics were associated with time to next treatment, adding to the evidence that ctDNA dynamics may have a potential clinical utility for treatment decision making in the advanced disease setting [2].

Conclusion: In summary, at the ASCO Annual Meeting, 2025 there were exciting developments investigating the clinical utility of ctDNA testing in solid tumour malignancies. Although clinicians may be keen to integrate ctDNA assays into their routine clinical practice, these studies highlight that limitations still exist in early detection of cancers, and in the early disease setting, where ctDNA is prognostic, but not yet predictive of response to escalated adjuvant therapies currently available. In the advanced disease setting there is exciting emerging data that changing treatment on the basis of ctDNA findings improves PFS and QOL but further follow up is needed to assess longer term outcomes with this treatment strategy.

Author contributions

MC and JP wrote the main manuscript and text. MC prepared the figure. All authors reviewed and revised the manuscript.

Data availability

No datasets were generated or analysed during the current study.

Competing interests

MC reports travel and conference support from Novartis and Daiichi-Sankyo. JP reports institutional research grants from AstraZeneca and Roche. He also reports advisory board honoraria from AstraZeneca, MSD, Novartis and Stemline Therapeutics Inc, speakers’ honoraria from AstraZeneca, Gilead, Lilly, Novartis, Pfizer, and Pierre Fabre Pharmaceuticals, and travel from AstraZeneca, Gilead, Novartis and Pfizer. SOR is deputy editor at BJC Reports and had no role in peer review process. He has no other relevant conflicts of interest.