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Background: Sublobar resection is increasingly recognized as an effective treatment for early-stage NSCLC. However, no studies to date have investigated the potential role of preoperative ctDNA detection in guiding surgical decisions, such as opting for sublobar resection, in stage I NSCLC., Methods: Patients with solid-dominant (CTR>0.5), clinical stage I NSCLC were prospectively recruited between March 2014 and December 2020. Pre-surgical plasma samples were analyzed using a tumor-naïve, methylation-based cell-free DNA assay. The impact of sublobar resection versus lobectomy on recurrence-free survival (RFS) was assessed according to pre-surgical ctDNA status. Associations between pre-surgical ctDNA detection and clinicopathologic factors were also investigated., Results: The analysis included 544 patients (178 women [33 %]; median age 66 [IQR, 60-71] years). Pre-surgical ctDNA was detected in 188 (35 %) patients. In patients without presurgical ctDNA, sublobar resection did not significantly increase the risk of relapse (adjusted HR, 1.01, p = 0.98). However, among ctDNA-positive patients, sublobar resection was associated with an increased risk of relapse (adjusted HR, 2.25; 95 % CI, 1.12-4.54; p = 0.024). Patients with presurgical ctDNA had higher rates of nodal upstaging (OR, 3.58; p < 0.001) and exhibited higher pathologic grade (p = 0.021), perineural invasion (p < 0.001), and lymphovascular invasion (p < 0.001)., Conclusions: Pre-surgical tumor-naïve ctDNA analysis holds promise in identifying patients with aggressive tumors that may not be sufficiently managed with sublobar resection. This approach can help personalize treatment strategies, potentially improving outcomes for patients with early-stage NSCLC., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Chris Abbosh is a full-time employee of and owns stock in SAGA Diagnostics and holds patents/patent applications in MRD detection (PCT/GB2017/053289, PCT/US2017/028013 and PCT/EP2022/077987). Abhijit Dasgupta is a full-time employee of and owns stock in AstraZeneca. Tiffany Hung is a full-time employee of GRAIL, LLC and owns stock in Illumina, Inc. Jörg Bredno is a full-time employee of GRAIL, LLC and owns stock in Illumina, Inc, and holds IP from Philips Medical Systems (with remuneration) and Roche (no remuneration). Darren Hodgson is a full-time employee of and owns stock in AstraZeneca. Myung-Ju Ahn reports advisory board participation for AstraZeneca, Yuhan, Arcus, Takeda, Amgen, MSD, Merck, Daiichi-Sankyo, Alpha Pharmaceuticals, Pfizer, Voronoi, and Eutilex and advisory roles for AstraZenceca, Yuhan, Arcus, Takeda, Amgen, MSD, Merck, Daiichi-Sankyo, Alpha Pharmaceuticals, and Pfizer. Other authors have no conflicts of interest to declare., (Copyright © 2025 Elsevier Ltd. All rights reserved.)

Objectives: The use of tumor-informed circulating tumor DNA (ctDNA) testing in patients with early-stage disease before surgery is limited, mainly owing to restricted tissue access and extended turnaround times. This study aimed to evaluate the clinical value of a tumor-naïve, methylation-based cell-free DNA assay in a large cohort of patients with resected NSCLC., Method: We analyzed presurgical plasma samples from 895 patients with EGFR and anaplastic lymphoma kinase-wild-type, clinical stage I or II NSCLC. The ctDNA status was evaluated for its prognostic significance in relation to tumor volume, metabolic activity, histologic diagnosis, histologic subtypes, and clinical-to-pathologic TNM upstaging., Results: Presurgical ctDNA detection was observed in 55 of 414 patients (13%) with clinical stage I lung adenocarcinoma (LUAD) and was associated with poor recurrence-free survival (2-year recurrence-free survival 69% versus 91%; log-rank p < 0.001), approaching that of clinical stage II LUAD. Presurgical ctDNA detection was not prognostic in patients with clinical stage II LUAD or non-LUAD. Within LUAD, tumor volume and positron emission tomography avidity interacted to predict presurgical ctDNA detection. Moreover, presurgical ctDNA detection was predictive of the postsurgical discovery of International Association for the Study of Lung Cancer grade 3 tumors (p < 0.001) and pathologic TNM upstaging (p < 0.001). Notably, presurgical ctDNA detection strongly correlated with higher programmed death-ligand 1 expression in tumors (positive rates 28% versus 55%, p < 0.001), identifying a subgroup likely to benefit from anti-programmed death-ligand 1 therapies., Conclusion: These findings support the integration of ctDNA testing into routine diagnostic workflows in early-stage NSCLC without the need for tumor tissue profiling. Furthermore, it is clinically useful in identifying patients at high risk who might benefit from innovative treatments, including neoadjuvant immune checkpoint inhibitors., Competing Interests: Disclosure Dr. Dasgupta is a full-time employee of and owns stock in AstraZeneca. Dr. Abbosh is a full-time employee of and owns stock in SAGA Diagnostics and holds patents/patent applications in minimal residual disease detection (PCT/GB2017/053289, PCT/US2017/028013 and PCT/EP2022/077987). Dr. Hung is a full-time employee of GRAIL, LLC and owns stock in Illumina, Inc. Dr. Bredno is a full-time employee of GRAIL, LLC and owns stock in Illumina, Inc, and holds IP from Philips Medical Systems (with remuneration) and Roche (no remuneration). Dr. Walker is a full-time employee of and owns stock in AstraZeneca. Dr. Shi is a full-time employee of and owns stock in AstraZeneca. Dr. Milenkova is a full-time employee of and owns stock in AstraZeneca. Dr. Horn is a full-time employee of and owns stock in AstraZeneca. Dr. Chai is a full-time employee of GRAIL, LLC and owns stock in Illumina, Inc. Rhodes is a full-time employee of GRAIL, LLC and owns stock in Illumina, Inc. Dr. Roychowdhury-Saha is a full-time employee of GRAIL, LLC and owns stock in Illumina, Inc. Dr. Hodgson is a full-time employee of and owns stock in AstraZeneca. Dr. Ahn reports advisory board participation for AstraZeneca, Yuhan, Arcus, Takeda, Amgen, MSD, Merck, Daiichi-Sankyo, Alpha Pharmaceuticals, Pfizer, Voronoi, and Eutilex and advisory roles for AstraZenceca, Yuhan, Arcus, Takeda, Amgen, MSD, Merck, Daiichi-Sankyo, Alpha Pharmaceuticals, and Pfizer. The remaining authors declare no conflict of interest., (Copyright © 2024 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.)

Background: Circulating tumor DNA (ctDNA) positivity at diagnosis, which is associated with worse outcomes in multiple solid tumors including stage I-III non-small cell lung cancer (NSCLC), may have utility to guide (neo)adjuvant therapy., Methods: In this retrospective study, 260 patients with clinical stage I NSCLC (180 adenocarcinoma, 80 squamous cell carcinoma) were allocated (2:1) to high- and low-risk groups based on relapse versus disease-free status ≤5 years post-surgery. We evaluated the association of preoperative ctDNA detection by a plasma-only targeted methylation-based multi-cancer early detection (MCED) test with NSCLC relapse ≤5 years post-surgery in the overall population, followed by histology-specific subgroup analyses., Results: Across clinical stage I patients, preoperative ctDNA detection did not associate with relapse within 5 years post-surgery. Sub-analyses confined to lung adenocarcinoma suggested a histology-specific association between ctDNA detection and outcome. In this group, ctDNA positivity tended to associate with relapse within 2 years, suggesting prognostic implications of MCED test positivity may be histology- and time-dependent in stage I NSCLC. Preoperative ctDNA detection was associated with upstaging of clinical stage I to pathological stage II-III NSCLC., Conclusions: Our findings suggest preoperative ctDNA detection in patients with resectable clinical stage I NSCLC using MCED, a pan-cancer screening test developed for use in an asymptomatic population, has no detectable prognostic value for relapse ≤5 years post-surgery. MCED detection may be associated with early adenocarcinoma relapse and increased pathological upstaging rates in stage I NSCLC. However, given the exploratory nature of these findings, independent validation is required., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Y. Bossé has received grants (paid to institution) from AstraZeneca and the IUCPQ foundation. A. Dasgupta is a full-time employee of and owns stock in AstraZeneca. M. Abadier is a full-time employee of and owns stock in Moderna Therapeutics. V. Guthrie is a full-time employee of and owns stock in Exact Sciences. F. Song is a full-time employee of and owns stock in AstraZeneca. F.C. Lamaze has a patent pending related to cancer diagnosis (U.S. Application No. 17/612,695; filed November 19, 2021). C. Melton is a full-time employee of GRAIL, LLC and owns stock in Illumina, Inc. T. Nance is a full-time employee of GRAIL, LLC. T. Hung is a full-time employee of GRAIL, LLC and owns stock in Illumina, Inc. D. Hodgson is a full-time employee of and owns stock in AstraZeneca. C. Abbosh is a full-time employee of and owns stock in AstraZeneca, and holds patents in MRD detection (ES2913468T3 and US20200248266A1). P. Joubert has received honoraria and research grants from AstraZeneca. The remaining authors declare no conflict of interest., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Systemic treatment of resectable non-small cell lung cancer (NSCLC) is evolving with emerging neoadjuvant, perioperative, and adjuvant immunotherapy approaches. Circulating tumor DNA (ctDNA) detection at clinical diagnosis, during neoadjuvant therapy, or after resection may discern high-risk patients who might benefit from therapy escalation or switch. This Review summarizes translational implications of data supporting ctDNA-based risk determination in NSCLC and outstanding questions regarding ctDNA validity/utility as a prognostic biomarker. We discuss emerging ctDNA capabilities to refine clinical tumor-node-metastasis (TNM) staging in lung adenocarcinoma, ctDNA dynamics during neoadjuvant therapy for identifying patients deriving suboptimal benefit, and postoperative molecular residual disease (MRD) detection to escalate systemic therapy. Considering differential relapse characteristics in landmark MRD-negative/MRD-positive patients, we propose how ctDNA might integrate with pathological response data for optimal postoperative risk stratification., Competing Interests: Declaration of interests C.A. was formerly an employee of, and held stocks/shares in, AstraZeneca, and is currently an employee of SAGA Diagnostics. D.H., G.J.D., D.G., L.H., and J.S.R.-F. are employees of, and hold stocks/shares in, AstraZeneca. J.R.M.B. has no conflicts of interest to disclose. D.G. is the cofounder of Inivata, acquired by NeoGenomics in 2021, and holds shares in AstraZeneca and GSK. C.S. is the co-founder of, a Scientific Advisory Board (SAB) member for, and has stock options in Achilles Therapeutics; has stock options in Epic Bioscience, Relay Therapeutics, and Bicycle Therapeutics; held stock options in Apogen Biotechnologies and GRAIL until June 2021; was a member of the American Association for Cancer Research (AACR) Board of Directors until April 2022; is chief investigator of AstraZeneca's MeRmaiD I and II clinical trials and co-chief investigator of the NHS Galleri Trial funded by GRAIL; has received honoraria from Amgen, AstraZeneca, Boehringer Ingelheim, Bristol-Myers Squibb, GlaxoSmithKline, Illumina, MSD, Novartis, Pfizer, and Roche; has received consulting fees from Genentech, Sarah Canon Research Institute, GRAIL (SAB), Medicxi, Bicycle Therapeutics (SAB), Metabomed – until June 2021, China Innovation Centre of Roche (CICor) – (formerly Roche Innovation Centre-Shanghai), Relay Therapeutics (SAB), and Saga Diagnostics (SAB); has received grants or funds from AstraZeneca, Boehringer Ingelheim, Bristol-Myers Squibb, Invitae (formerly Archer Dx), Ono Pharmaceuticals, Personalis, and Pfizer; and holds the following patents – US20190106751A1 – Methods for lung cancer detection; PCT/EP2016/071471 – 'immune checkpoint intervention' in cancer; PCT/EP2016/059401 – Method for treating cancer; PCT/US2017/028013 – Methods for lung cancer detection; PCT/GB2018/051912 – Method for identifying responders to cancer treatment; PCT/GB2018/052004 – Analysis of HLA alleles in tumors and the uses thereof; PCT/GB2020/050221 – Method of predicting survival rates of patients with cancer; PCT/GB2017/053289 – Method of detecting tumor recurrence; PCT/EP2021/059989 – Modulation of T cell cytotoxicity and related therapy; and PCT/EP2022/077987 – Methods and systems for tumor monitoring; PCT/EP2023/059039 – Analysis of HLA alleles transcriptional deregulation., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Lung adenocarcinomas (LUADs) display a broad histological spectrum from low-grade lepidic tumors through to mid-grade acinar and papillary and high-grade solid, cribriform and micropapillary tumors. How morphology reflects tumor evolution and disease progression is poorly understood. Whole-exome sequencing data generated from 805 primary tumor regions and 121 paired metastatic samples across 248 LUADs from the TRACERx 421 cohort, together with RNA-sequencing data from 463 primary tumor regions, were integrated with detailed whole-tumor and regional histopathological analysis. Tumors with predominantly high-grade patterns showed increased chromosomal complexity, with higher burden of loss of heterozygosity and subclonal somatic copy number alterations. Individual regions in predominantly high-grade pattern tumors exhibited higher proliferation and lower clonal diversity, potentially reflecting large recent subclonal expansions. Co-occurrence of truncal loss of chromosomes 3p and 3q was enriched in predominantly low-/mid-grade tumors, while purely undifferentiated solid-pattern tumors had a higher frequency of truncal arm or focal 3q gains and SMARCA4 gene alterations compared with mixed-pattern tumors with a solid component, suggesting distinct evolutionary trajectories. Clonal evolution analysis revealed that tumors tend to evolve toward higher-grade patterns. The presence of micropapillary pattern and 'tumor spread through air spaces' were associated with intrathoracic recurrence, in contrast to the presence of solid/cribriform patterns, necrosis and preoperative circulating tumor DNA detection, which were associated with extra-thoracic recurrence. These data provide insights into the relationship between LUAD morphology, the underlying evolutionary genomic landscape, and clinical and anatomical relapse risk., (© 2023. The Author(s) under exclusive license to Springer Nature America, Inc.)

A complete understanding of how exposure to environmental substances promotes cancer formation is lacking. More than 70 years ago, tumorigenesis was proposed to occur in a two-step process: an initiating step that induces mutations in healthy cells, followed by a promoter step that triggers cancer development 1 . Here we propose that environmental particulate matter measuring ≤2.5 μm (PM 2.5 ), known to be associated with lung cancer risk, promotes lung cancer by acting on cells that harbour pre-existing oncogenic mutations in healthy lung tissue. Focusing on EGFR-driven lung cancer, which is more common in never-smokers or light smokers, we found a significant association between PM 2.5 levels and the incidence of lung cancer for 32,957 EGFR-driven lung cancer cases in four within-country cohorts. Functional mouse models revealed that air pollutants cause an influx of macrophages into the lung and release of interleukin-1β. This process results in a progenitor-like cell state within EGFR mutant lung alveolar type II epithelial cells that fuels tumorigenesis. Ultradeep mutational profiling of histologically normal lung tissue from 295 individuals across 3 clinical cohorts revealed oncogenic EGFR and KRAS driver mutations in 18% and 53% of healthy tissue samples, respectively. These findings collectively support a tumour-promoting role for  PM 2.5 air pollutants  and provide impetus for public health policy initiatives to address air pollution to reduce disease burden., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Lung cancer is the leading cause of cancer-associated mortality worldwide 1 . Here we analysed 1,644 tumour regions sampled at surgery or during follow-up from the first 421 patients with non-small cell lung cancer prospectively enrolled into the TRACERx study. This project aims to decipher lung cancer evolution and address the primary study endpoint: determining the relationship between intratumour heterogeneity and clinical outcome. In lung adenocarcinoma, mutations in 22 out of 40 common cancer genes were under significant subclonal selection, including classical tumour initiators such as TP53 and KRAS. We defined evolutionary dependencies between drivers, mutational processes and whole genome doubling (WGD) events. Despite patients having a history of smoking, 8% of lung adenocarcinomas lacked evidence of tobacco-induced mutagenesis. These tumours also had similar detection rates for EGFR mutations and for RET, ROS1, ALK and MET oncogenic isoforms compared with tumours in never-smokers, which suggests that they have a similar aetiology and pathogenesis. Large subclonal expansions were associated with positive subclonal selection. Patients with tumours harbouring recent subclonal expansions, on the terminus of a phylogenetic branch, had significantly shorter disease-free survival. Subclonal WGD was detected in 19% of tumours, and 10% of tumours harboured multiple subclonal WGDs in parallel. Subclonal, but not truncal, WGD was associated with shorter disease-free survival. Copy number heterogeneity was associated with extrathoracic relapse within 1 year after surgery. These data demonstrate the importance of clonal expansion, WGD and copy number instability in determining the timing and patterns of relapse in non-small cell lung cancer and provide a comprehensive clinical cancer evolutionary data resource., (© 2023. The Author(s).)

Circulating tumour DNA (ctDNA) can be used to detect and profile residual tumour cells persisting after curative intent therapy 1 . The study of large patient cohorts incorporating longitudinal plasma sampling and extended follow-up is required to determine the role of ctDNA as a phylogenetic biomarker of relapse in early-stage non-small-cell lung cancer (NSCLC). Here we developed ctDNA methods tracking a median of 200 mutations identified in resected NSCLC tissue across 1,069 plasma samples collected from 197 patients enrolled in the TRACERx study 2 . A lack of preoperative ctDNA detection distinguished biologically indolent lung adenocarcinoma with good clinical outcome. Postoperative plasma analyses were interpreted within the context of standard-of-care radiological surveillance and administration of cytotoxic adjuvant therapy. Landmark analyses of plasma samples collected within 120 days after surgery revealed ctDNA detection in 25% of patients, including 49% of all patients who experienced clinical relapse; 3 to 6 monthly ctDNA surveillance identified impending disease relapse in an additional 20% of landmark-negative patients. We developed a bioinformatic tool (ECLIPSE) for non-invasive tracking of subclonal architecture at low ctDNA levels. ECLIPSE identified patients with polyclonal metastatic dissemination, which was associated with a poor clinical outcome. By measuring subclone cancer cell fractions in preoperative plasma, we found that subclones seeding future metastases were significantly more expanded compared with non-metastatic subclones. Our findings will support (neo)adjuvant trial advances and provide insights into the process of metastatic dissemination using low-ctDNA-level liquid biopsy., (© 2023. The Author(s).)

Metastatic disease is responsible for the majority of cancer-related deaths 1 . We report the longitudinal evolutionary analysis of 126 non-small cell lung cancer (NSCLC) tumours from 421 prospectively recruited patients in TRACERx who developed metastatic disease, compared with a control cohort of 144 non-metastatic tumours. In 25% of cases, metastases diverged early, before the last clonal sweep in the primary tumour, and early divergence was enriched for patients who were smokers at the time of initial diagnosis. Simulations suggested that early metastatic divergence more frequently occurred at smaller tumour diameters (less than 8 mm). Single-region primary tumour sampling resulted in 83% of late divergence cases being misclassified as early, highlighting the importance of extensive primary tumour sampling. Polyclonal dissemination, which was associated with extrathoracic disease recurrence, was found in 32% of cases. Primary lymph node disease contributed to metastatic relapse in less than 20% of cases, representing a hallmark of metastatic potential rather than a route to subsequent recurrences/disease progression. Metastasis-seeding subclones exhibited subclonal expansions within primary tumours, probably reflecting positive selection. Our findings highlight the importance of selection in metastatic clone evolution within untreated primary tumours, the distinction between monoclonal versus polyclonal seeding in dictating site of recurrence, the limitations of current radiological screening approaches for early diverging tumours and the need to develop strategies to target metastasis-seeding subclones before relapse., (© 2023. The Author(s).)

Although precision medicine has had a mixed impact on the clinical management of patients with advanced-stage cancer overall, for NSCLC, and more specifically for lung adenocarcinoma, the advances have been dramatic, largely owing to the genomic complexity and growing number of druggable oncogene drivers. Furthermore, although tumor tissue is historically the "accepted standard" biospecimen for these molecular analyses, there are considerable innate limitations. Thus, liquid biopsy represents a practical alternative source for investigating tumor-derived somatic alterations. Although data are most robust in NSCLC, patients with other cancer types may also benefit from this minimally invasive approach to facilitate selection of targeted therapies. The liquid biopsy approach includes a variety of methodologies for circulating analytes. From a clinical point of view, plasma circulating tumor DNA is the most extensively studied and widely adopted alternative to tissue tumor genotyping in solid tumors, including NSCLC, first entering clinical practice for detection of EGFR mutations in NSCLC. Since the publication of the first International Association for the Study of Lung Cancer (IASLC) liquid biopsy statement in 2018, several additional advances have been made in this field, leading to changes in the therapeutic decision-making algorithm for advanced NSCLC and prompting this 2021 update. In view of the novel and impressive technological advances made in the past few years, the growing clinical application of plasma-based, next-generation sequencing, and the recent Food and Drug and Administration approval in the United States of two different assays for circulating tumor DNA analysis, IASLC revisited the role of liquid biopsy in therapeutic decision-making in a recent workshop in October 2020 and the question of "plasma first" versus "tissue first" approach toward molecular testing for advanced NSCLC. Moreover, evidence-based recommendations from IASLC provide an international perspective on when to order which test and how to interpret the results. Here, we present updates and additional considerations to the previous statement article as a consensus from a multidisciplinary and international team of experts selected by IASLC., (Copyright © 2021. Published by Elsevier Inc.)

An aim of molecular biomarkers is to stratify patients with cancer into disease subtypes predictive of outcome, improving diagnostic precision beyond clinical descriptors such as tumor stage 1 . Transcriptomic intratumor heterogeneity (RNA-ITH) has been shown to confound existing expression-based biomarkers across multiple cancer types 2-6 . Here, we analyze multi-region whole-exome and RNA sequencing data for 156 tumor regions from 48 patients enrolled in the TRACERx study to explore and control for RNA-ITH in non-small cell lung cancer. We find that chromosomal instability is a major driver of RNA-ITH, and existing prognostic gene expression signatures are vulnerable to tumor sampling bias. To address this, we identify genes expressed homogeneously within individual tumors that encode expression modules of cancer cell proliferation and are often driven by DNA copy-number gains selected early in tumor evolution. Clonal transcriptomic biomarkers overcome tumor sampling bias, associate with survival independent of clinicopathological risk factors, and may provide a general strategy to refine biomarker design across cancer types.

Background: Among patients with non-small-cell lung cancer (NSCLC), data on intratumor heterogeneity and cancer genome evolution have been limited to small retrospective cohorts. We wanted to prospectively investigate intratumor heterogeneity in relation to clinical outcome and to determine the clonal nature of driver events and evolutionary processes in early-stage NSCLC., Methods: In this prospective cohort study, we performed multiregion whole-exome sequencing on 100 early-stage NSCLC tumors that had been resected before systemic therapy. We sequenced and analyzed 327 tumor regions to define evolutionary histories, obtain a census of clonal and subclonal events, and assess the relationship between intratumor heterogeneity and recurrence-free survival., Results: We observed widespread intratumor heterogeneity for both somatic copy-number alterations and mutations. Driver mutations in EGFR, MET, BRAF, and TP53 were almost always clonal. However, heterogeneous driver alterations that occurred later in evolution were found in more than 75% of the tumors and were common in PIK3CA and NF1 and in genes that are involved in chromatin modification and DNA damage response and repair. Genome doubling and ongoing dynamic chromosomal instability were associated with intratumor heterogeneity and resulted in parallel evolution of driver somatic copy-number alterations, including amplifications in CDK4, FOXA1, and BCL11A. Elevated copy-number heterogeneity was associated with an increased risk of recurrence or death (hazard ratio, 4.9; P=4.4×10 -4 ), which remained significant in multivariate analysis., Conclusions: Intratumor heterogeneity mediated through chromosome instability was associated with an increased risk of recurrence or death, a finding that supports the potential value of chromosome instability as a prognostic predictor. (Funded by Cancer Research UK and others; TRACERx ClinicalTrials.gov number, NCT01888601 .).

The early detection of relapse following primary surgery for non-small-cell lung cancer and the characterization of emerging subclones, which seed metastatic sites, might offer new therapeutic approaches for limiting tumour recurrence. The ability to track the evolutionary dynamics of early-stage lung cancer non-invasively in circulating tumour DNA (ctDNA) has not yet been demonstrated. Here we use a tumour-specific phylogenetic approach to profile the ctDNA of the first 100 TRACERx (Tracking Non-Small-Cell Lung Cancer Evolution Through Therapy (Rx)) study participants, including one patient who was also recruited to the PEACE (Posthumous Evaluation of Advanced Cancer Environment) post-mortem study. We identify independent predictors of ctDNA release and analyse the tumour-volume detection limit. Through blinded profiling of postoperative plasma, we observe evidence of adjuvant chemotherapy resistance and identify patients who are very likely to experience recurrence of their lung cancer. Finally, we show that phylogenetic ctDNA profiling tracks the subclonal nature of lung cancer relapse and metastasis, providing a new approach for ctDNA-driven therapeutic studies.