Utility of ctDNA-molecular residual disease in predicting minimal residual disease in non-small cell lung cancer patients after radical resection

Minimal residual disease refers to a small number of cancer cells that may remain in the body after curative treatment and are below the detection threshold of conventional imaging. In non-small cell lung cancer (NSCLC), circulating tumor DNA (ctDNA)-based molecular residual disease (MRD) detection is emerging as a sensitive approach to identify molecular recurrence before radiological relapse. Zhang et al. reported that among 261 patients with stage I to III NSCLC who underwent radical resection, panel sequencing using next-generation sequencing (NGS) of blood samples to assess landmarks and longitudinal ctDNA-based MRD yielded positive predictive values of 91.3% and 92.8%, respectively, with a median lead time of 5.2 months. The corresponding negative predictive values (NPVs) were 76.5% and 93.2%, respectively (1). These results expand on those of the authors’ earlier study, in which the NPV of intermittent ctDNA-MRD monitoring was reported to be 96.8%. Over time, the NPV for landmark ctDNA-MRD declined from 86.6% to 76.5%, whereas that of longitudinal ctDNA-MRD decreased from 96.8% to 93.2% (2). Furthermore, patients who were ctDNA-MRD-negative at the landmark time point did not appear to benefit from adjuvant therapy during follow-up (P=0.53).

The ctDNA-MRD approach is highly valuable for two key reasons. First, the absence of ctDNA-MRD at the landmark time point suggests complete surgical resection and the absence of residual disease. This enables clinicians to avoid administering unnecessary adjuvant therapy to patients who are unlikely to benefit, thereby reducing their exposure to potential toxicities. Second, ctDNA-MRD facilitates the earlier detection of metastasis and recurrence, enabling timely intervention for high-risk patients. However, these advantages also raise fundamental questions regarding whether MRD can truly be eradicated by adjuvant therapy, and the interpretation of its clinical benefit remains open to debate. In comparison, conventional imaging modalities such as positron emission tomography-computed tomography (PET-CT) or magnetic resonance imaging (MRI) may miss microscopic residual disease, particularly in low-burden or central nervous system (CNS)-confined tumors. While imaging remains the standard tool for staging and response evaluation, its limited sensitivity to molecular recurrence underlines the complementary role of ctDNA-MRD.

A key limitation in interpreting MRD negativity is the possibility of false negative results, which may lead to missed opportunities for adjuvant therapy in patients with residual disease. Conversely, false positives may cause patients to undergo unnecessary treatment, exposing them to avoidable toxicities and psychological stress. These issues are especially impactful in early-stage NSCLC, where balancing treatment benefits against potential harms is critical. Therefore, understanding and minimizing false negative and false positive rates is essential for clinical decision-making and personalized treatment strategies. Patients who may benefit from adjuvant therapy may be overlooked if residual disease is not detected. False negatives typically arise because of the limited sensitivity of the current ctDNA detection technologies. A meta-analysis of 18 studies assessing the accuracy of ctDNA-based detection of driver mutations using NGS reported a pooled sensitivity of 0.69 and specificity of 0.99, with Guardant360^® being the most frequently used panel (3). In the TRACERx study, MRD was evaluated using a combination of ctDNA and RNA sequencing (4) as well as DNA panel sequencing (5), supported by the ECLIPSE informatics tool for subclone detection. Notably, relapse indicators were later identified in 20% of patients who initially tested negative for ctDNA when monitored at intervals of three to six months (6).

In comparison to these previous studies, the ctDNA-MRD assay used by Zhang et al. appears to have improved sensitivity and specificity (1). Zhang et al.’s platform differs by integrating exome and RNA sequencing of cell-free nucleic acids along with a sophisticated bioinformatics pipeline, ECLIPSE, which allows tracking of not only driver mutations but also subclonal evolution. This multi-dimensional approach enhances detection accuracy compared to prior studies like TRACERx, which primarily relied on DNA panel sequencing alone, thereby improving sensitivity particularly in tumors with low ctDNA shedding. Technological advances, such as exome and RNA sequencing of cell-free nucleic acids, and broader application of bioinformatics pipelines, such as ECLIPSE, which can track not only driver mutations but also subclonal evolution, may further improve detection accuracy, especially in tumors with low ctDNA shedding. Notably, 7 of the 13 patients (53.8%) with false-negative MRD results experienced CNS relapse. This observation supports the notion that solid tumors can behave in a systemic manner, similar to hematologic malignancies. Given that CNS involvement may prevent ctDNA detection in peripheral blood, preoperative assessment of cerebrospinal fluid (CSF) for MRD using our methodology may help mitigate false-negative findings. The blood-brain barrier may limit the release of ctDNA from CNS lesions into the systemic circulation, leading to false-negative results. As such, CSF analysis offers a direct method to detect CNS MRD, which has shown promise particularly in leptomeningeal metastasis and primary brain tumors. The implications of false negatives are particularly significant when adjuvant therapy involves immune checkpoint inhibitors (ICIs), which may offer curative potential, or tyrosine kinase inhibitors (TKIs) that can sustain MRD at near-CR levels. In such cases, failing to identify MRD could result in missed opportunities for effective intervention, underscoring the need for the judicious application of this platform. Another emerging biomarker for MRD evaluation is the detection of circulating tumor cells (CTCs), which, unlike ctDNA, provide intact cellular information. While technically more challenging to isolate, CTC analysis may offer additional insights into tumor phenotype and metastatic potential, particularly when combined with genomic analysis.

Conversely, the issue of false positives warrants further attention. Patients incorrectly identified as MRD-positive may receive unnecessary adjuvant therapy, exposing them to potential harm. In the present study, 5 of 69 MRD-positive patients (7.2%) were false positives. Their mutation profiles included common somatic alterations, such as KRAS, NRAS, and TP53, and these cases were not particularly biased toward higher-stage disease. As the authors suggested, sequencing artifacts or a predisposition to late relapse cannot be ruled out. Further investigations into whether similar mutational patterns are observed in relapsed patients may provide insights into this phenomenon.

In this study, ctDNA was extracted using the QIAamp^® Circulating Nucleic Acid Kit (1), whereas the TRACERx study utilized the MagMax Cell-Free DNA Isolation Kit (Thermo Fisher Scientific, Waltham, USA) (6). Although the current study did not discuss this aspect in detail, optimizing sample preparation remains a key area for improving assay performance. Other commercially available kits, such as the Cobas^® EGFR Mutation Test v2 (Roche Molecular Systems, Inc., Pleasanton, CA, USA) used in the FLAURA study (7) and the Maxwell RSC^® ccfDNA plasma kit (Promega, Madison, WI, USA), are also widely used. However, there is currently no consensus on the relative advantages of ctDNA over exosomal DNA (8). Although the sequencing platform and library preparation method have been validated (3), further enhancement in accuracy may be achieved through optimization of the pre-analytical process.

The concept that eradicating MRD may prevent relapses and serve as a surrogate marker of a cure is most compellingly supported by clinical experience with adjuvant therapy for completely resected NSCLC. Such a therapy is designed to eliminate microscopic diseases not addressed by surgery (9). Recent advances in perioperative treatment strategies have led to the approval of atezolizumab and osimertinib as postoperative adjuvant therapies, based on the IMpower010 (10) and ADAURA trials (11). Although the clinical significance of an MRD below the detection threshold remains uncertain, the shift from conventional chemotherapy to ICIs and TKIs has introduced new opportunities for durable disease control. As a result, the early and accurate identification of patients who may benefit from such therapies is becoming increasingly important. Moreover, the clinical utility of ctDNA extends beyond surgical candidates to patients undergoing adjuvant radiotherapy and chemotherapy. Given the growing recognition of radiation-induced lymphopenia as a negative prognostic factor—which may also impair the efficacy of systemic treatments including immunotherapy—ctDNA evaluation can be pivotal in stratifying patients who might benefit from treatment intensification or de-escalation, thus helping to minimize unnecessary toxicity. Recent evidence by Kuncman et al. demonstrated that early lymphocyte levels and low-dose lung radiation exposure are predictors of lymphopenia in lung cancer radiotherapy, underscoring the necessity for integrative biomarkers such as ctDNA to inform decision-making after surgery and radiotherapy (12).

The clinical interpretation of MRD results remains controversial. Deciding how to act upon MRD status (positive or negative) at a given postoperative time point is complicated by the limitations of the current assays. Three scenarios exemplify the challenges involved in clinical practice. Systemic therapy is likely to be considered in patients with moderately advanced NSCLC who are MRD-positive postoperatively. However, determining the appropriate intensity and duration of therapy is difficult in the absence of radiographically evident disease. Whether to discontinue therapy upon MRD clearance, escalate treatment if MRD persists, or incorporate MRD dynamics into response assessment frameworks, such as Response Evaluation Criteria in Solid Tumors (RECIST) (13) are all unresolved questions. Furthermore, the detected MRD variants may not necessarily originate from the primary tumor. Depending on the mutational profile, MRD could reflect malignancy in another organ, prompting consideration of further diagnostic workup, including cancers not readily detected by PET-CT. The cost-effectiveness of these strategies must also be considered.

The necessity of adjuvant therapy remains debatable for patients with similar disease stages who are MRD-negative after surgery. In this study, no significant difference in survival was observed based on the administration of adjuvant therapy in MRD-negative patients. However, treatment selection bias cannot be excluded, as some MRD-negative patients may have received adjuvant therapy based on pathological features such as high-grade histology, vascular invasion, or spread through air spaces are factors that may not have been included in the dataset or adequately adjusted for in propensity score analyses. Moreover, since a considerable number of MRD-negative patients still experience recurrence, some clinicians advocate adjuvant therapy in all stage II or III cases, regardless of MRD status. This underscores the urgent need for more definitive evidence. In early-stage lung cancer (stage I), in which adjuvant therapy is generally not recommended, postoperative MRD positivity may prompt clinicians to consider interventions. Although conceptually similar to the first scenario, early-stage disease carries a higher risk of MRD malignancy signals from another primary site. Therefore, careful clinical judgment is required to determine the intensity and duration of treatment, as well as whether further diagnostic testing is warranted. A recent review by Rossi et al. offers a comprehensive overview of emerging strategies for MRD detection in lung cancer, highlighting technical, clinical, and regulatory challenges in incorporating such biomarkers into routine care (14).

In summary, the integration of MRD assessments into standard clinical practice remains a complex and evolving issue. At present, no consensus exists, and decisions often depend on individual clinicians’ interpretations. A comprehensive approach that incorporates disease stage, pathological characteristics, and treatment history is essential. The accumulation of large-scale clinical datasets and the development of frameworks that incorporate MRD dynamics into response evaluation criteria are vital. Multicenter collaborative studies will be the key to validating and refining the clinical utility of MRD in NSCLC. Incorporating these perspectives strengthens the editorial’s relevance, highlighting ctDNA’s expanding role not only in surgical decision-making but also in optimizing adjuvant radiotherapy and chemotherapy strategies through integrated biomarker-driven personalized care. Future prospective trials may consider incorporating ctDNA-MRD status as a stratification factor or as a surrogate endpoint for recurrence, which could enhance trial efficiency and therapeutic targeting.

The ctDNA-MRD platform described in this study is a promising tool that offers important insights into several unresolved clinical questions. With further refinement, including a CSF analysis, broader panel coverage, and optimization of sample preparation, its utility is expected to significantly increase.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the Editorial Office, Translational Lung Cancer Research. The article has undergone external peer review.

Peer Review File: Available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-2025-470/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-2025-470/coif). The authors have no conflicts of interest to declare.

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