Take Home Messages
  • A growing number of clinical applications of ctDNA are being explored for the management of advanced non-small cell lung cancer (NSCLC), such as non-invasive diagnosis, monitoring, and recurrence detection.

  • The detection of MRD using ctDNA has significant advantages in estimating lung cancer recurrence, metastasis, and drug sensitivity. If this is incorporated into the staging system as a new indicator, it could help guide precision medicine for patients with NSCLC.

  • The role of EGFR (Epidermal Growth Factor Receptor) tyrosine kinase inhibitors (TKIs) in the first-line treatment of patients with NSCLC with EGFR mutations is well-established and has significantly influenced treatment guidelines.

  • Landmark clinical trials, such as the IPASS trial, and FLAURA trial have played a pivotal role in establishing the efficacy of various EGFR TKIs in the first line setting for metastatic patients with EGFR mutations.

  • Understanding the dynamic nature of resistance mechanisms and staying abreast of evolving treatment strategies is essential in the management of patients with EGFR-mutated NSCLC.

Translational Science Update in Lung Cancer

Historically, lung cancer treatment was viewed as a ‘one-size-fits-all’ approach. It is now evident that non-small cell lung cancer (NSCLC) is a molecularly complex amalgam of diseases resulting in vastly different outcomes.1 Consequently, treatment paradigms have shifted towards increasingly personalized approaches, giving rise to circulating tumor DNA (ctDNA) as a tool for making informed treatment decisions. Plasma-derived ctDNA is the most extensively studied analyte to provide sampling of the molecular content within tumor cells.2 ctDNA refers to small fragments of DNA that are released by cancer cells into the bloodstream. Analyzing ctDNA can provide valuable information about the genetic makeup of a tumor and can be particularly useful in the context of non-small cell lung cancer (NSCLC). As such, the assessment of oncogenic driver alterations by ctDNA has become an accepted companion diagnostic for advanced NSCLC.

A. Clinical applications of ctDNA

There is a growing list of DNA sequencing methods that are useful in the clinical management of NSCLC including:

  • Tumor Genetic Profiling: DNA analysis allows for the profiling of genetic alterations from the tumor. This includes mutations, rearrangements, and other genomic changes that may be driving the cancer and expedite the effective initiation of therapy. It can also be applied to plasma blood specimens to find circulating tumor DNA (ctDNA)

  • Liquid Biopsy: ctDNA analysis is often part of what is known as a “liquid biopsy.” Unlike traditional tissue biopsies, which involve removing a piece of the tumor, a liquid biopsy involves a simple blood draw. This can be particularly useful in situations where obtaining a tissue biopsy is challenging.3–5

  • Guiding Treatment Decisions: Understanding the genetic profile of the tumor, as revealed by plasma ctDNA analysis, can expedite treatment decisions as ctDNA is usually faster to analyze (1–2-week turnaround) than tumor (2-4 week turnaround). For example, identifying specific mutations may indicate eligibility for targeted therapies.

  • Detection and Monitoring: ctDNA can be used for the early detection of NSCLC and for monitoring disease progression. Changes in the levels or types of genetic alterations in ctDNA over time can provide insights into the tumor’s response to treatment or the emergence of resistance.

  • Minimal Residual Disease (MRD) Detection: ctDNA can be used to detect minimal residual disease, which refers to the presence of small amounts of cancer cells secreting a DNA signature that remain after treatment. Detecting MRD can be important for early identification of likely disease recurrence.

B. Challenges of ctDNA

While ctDNA analysis has shown great promise in NSCLC, there are important challenges including:

  • Sensitivity and Specificity: Detection of ctDNA requires highly sensitive and specific techniques. The low abundance of ctDNA in the bloodstream, especially in early-stage disease, can make it challenging to distinguish tumor-derived DNA from normal DNA. For instance, the presence of clonal hematopoiesis, which involves mutations in blood cells that can be mistakenly identified as tumor-derived mutations can results in false positives and negatives.

  • Tumor Heterogeneity: NSCLC tumors may have distinct genetic profiles, therefore ctDNA analysis might not capture the full spectrum of genetic alterations present in the tumor, leading to incomplete information.

  • Dynamic Nature of ctDNA: The levels and composition of ctDNA can change over time due to factors such as tumor growth, treatment response, and the development of resistance. Monitoring these changes requires frequent and longitudinal sampling, which may not always be practical.

  • Technical Issues: Sample contamination, degradation, and variations in extraction methods can impact the reliability of results. Moreover, standardization of ctDNA analysis methods is crucial for ensuring consistency and comparability of results across different laboratories and studies. Currently, there is ongoing work to establish standardized protocols and quality control measures.

  • Cost and accessibility: Implementing ctDNA analysis in routine clinical practice may be limited by cost considerations. High-tech equipment and specialized expertise are often required, and these resources may not be universally accessible.

Despite these challenges, technological advancements and ongoing research are addressing many of these issues. As ctDNA analysis continues to evolve, improvements will be made in sensitivity, specificity, and standardization, further increasing its clinical utility for NSCLC.

C. Detection of MRD by ctDNA

The detection of MRD using ctDNA is an area of active research and holds significant promise in NSCLC. MRD refers to cancer cells that remain after treatment but do not respond to or are resistant to treatment. Their secreted DNA can be detected by liquid biopsy, and they represent a highly likelihood of clinical recurrence in the next 6-12 months. The detection of MRD by ctDNA for patients with NSCLC after curative-intent treatment may serve as a prognostic and potentially predictive biomarker for recurrence and response to therapy.6 Among the various ctDNA detection technologies available, droplet digital PCR (ddPCR) and Next-Generation Sequencing (NGS) are two of the most common platforms for plasma ctDNA analysis. ctDNA MRD detection based on NGS platform is mainly divided into two strategies: tumor-naïve assays and tumor-informed assays. In tumor-naive assays, a large number of genes are tested at once without sequencing the entire genome or exons of patient tissues. As a result, it is easy to commercialize and takes a short time to develop. Assays that are tumor-informed must screen the mutation panel based on the sequencing results of the patient’s tumor tissue for high tumor association. Furthermore, either a tumor-naïve blood assay or specific ctDNA probes and primers can be designed that are tailored to the patient’s drug sensitivity and drug resistance gene mutations. As a result, it has high sensitivity and high correlation with tumor. Because of tumor heterogeneity and clonal variation during the treatment process, the initial tumor tissue genome may not represent the genomic variation of the entire tumor tissue.7 Researchers have continued to improve the ctDNA detection method to provide more sensitivity and accuracy in assessing ctDNA MRD, though MRD detection is not yet available as a standard of care assay.

Blood based ctDNA monitoring is a useful tool to personalize treatment throughout the treatment continuum: finding the molecular driver in the tumor, selecting, and optimizing treatment plans, and evaluating the efficacy of treatment. MRD’s excellent prognostic performance makes it a promising candidate for use in patients after treatment for early-stage disease, which should enable earlier detection of recurrence for high-risk patients.

Clinical Application of Precision Oncology in Lung Cancer

A. EGFR TKIs in the treatment of NSCLC

NSCLC has become a prominent example of precision medicine among solid tumor malignancies.8 To date, U.S. Food and Drug Administration (FDA)-approved therapies for oncogenic driver mutations are expanding. Here we review the latest updates of tyrosine kinase inhibitors (TKIs) in patients with NSCLC with activating epidermal growth factor receptor (EGFR) mutations. Several pivotal clinical trials have established the efficacy and safety of EGFR TKIs in the treatment of NSCLC with EGFR-activating mutations. These trials have shaped the standard of care and treatment guidelines for this subset of patients with NSCLC.9–11 Some key trials are:

  • IPASS trial: The IPASS trial (Iressa Pan-Asia Study) was a landmark phase III trial comparing gefitinib, an EGFR TKI, to chemotherapy as first-line treatment in Asian patients with advanced lung adenocarcinoma. The trial demonstrated that patients with EGFR mutations had a significantly better response to gefitinib compared to chemotherapy, leading to a shift in the standard of care. This was the first study to conclude that patients with EGFR mutations should be identified early on and receive an EGFR TKI upfront.9

  • NEJ002 Trial: The NEJ002 trial in Japan compared gefitinib to standard chemotherapy as first-line treatment in patients with advanced NSCLC harboring EGFR mutations. Gefitinib showed superior progression-free survival (PFS) compared to chemotherapy.10

  • FLAURA trial: The FLAURA trial (First-Line Treatment of Patients with EGFR Mutation-Positive Advanced Non-Small Cell Lung Cancer) is a landmark clinical trial that investigated the efficacy and safety of the third generation EGFR TKI, osimertinib, as a first-line treatment compared to the earlier generation EGFR TKIs for patients with advanced non-small cell lung cancer (NSCLC) with EGFR mutations. A total of 556 patients were randomized in a 1:1 ratio to receive either osimertinib or one of two other EGFR-TKIs (gefitinib or erlotinib, with patients receiving these drugs combined in a single comparator group). The median overall survival was 38.6 months (95% CI, 34.5-41.8) in the osimertinib group and 31.8 months (95% CI, 26.6-36.0) in the comparator group (HR for death, 0.80; 95.05% CI, 0.64-1.00; p=0.046).11 This study led to the FDA approval of osimertinib as a first-line treatment option for patients with metastatic NSCLC whose tumors harbor either an EGFR exon 19 deletion or exon 21 L858R mutation, as detected by an FDA-approved test.12

  • ADAURA trial: This was a randomized, double-blind, placebo-controlled trial in patients with EGFR exon 19 deletion or exon 21 L858R mutation-positive early stage NSCLC who had complete tumor resection, with or without prior adjuvant chemotherapy. A total of 682 patients were randomized (1:1) to receive osimertinib or placebo following recovery from surgery and after standard adjuvant chemotherapy if given. Osimertinib is a third-generation, irreversible EGFR TKI designed to inhibit both EGFR-sensitizing and EGFR T790M-resistance mutations, with clinical activity against central nervous system (CNS) metastases. Adjuvant osimertinib reduced the risk of disease or death in patients with stage II to IIIA disease by 83% (hazard ratio [HR], 0.17; 99.06% confidence interval [CI], 0.11-0.26; p<0.001) compared with the placebo group. Overall, 89% (95% CI, 85-92) of the participants in the study who received osimertinib and 52% (95% CI, 46-58) of patients in the placebo group were alive and disease-free at 24 months. The overall HR for disease recurrence or death was 0.20 for patients receiving osimertinib (99.12% CI, 0.14-0.30; p<0.001).13 These positive results of the study resulted in the FDA approval of osimertinib as an adjuvant treatment for early-stage resected EGFR-mutated NSCLC.14

These trials have been instrumental in establishing the role of EGFR TKIs in the first-line treatment of EGFR-mutant NSCLC. They have contributed to the evolution of treatment guidelines and have influenced the sequencing of different EGFR TKIs based on disease progression and the emergence of resistance mechanisms.

B. Resistance to TKIs in EGFR-Mutated NSCLC

Resistance to EGFR TKIs is a significant challenge in the treatment of EGFR-mutated NSCLC. While patients often initially respond well to EGFR TKIs, the development of resistance can occur, leading to disease progression. Understanding the mechanisms of resistance is crucial for developing strategies to overcome or delay it. Resistance to targeted therapy is inevitable, and resistance pathways are more challenging and complex with the use of later generation drugs. After an initial benefit with the use of the first-generation EGFR inhibitors, approximately 60% of the patients develop T790M mutation or other mechanism such as EGFR amplification concurrent with T790M, mesenchymal-epithelial transition (MET)/HER2 amplification, activation of the RAS-mitogen-activated protein kinase (MAPK), RAS-phosphatidylinositol 3-kinase (PI3K) pathways, and others.15

Addressing resistance to EGFR TKIs is an active area of research in the field of NSCLC. Third-generation EGFR TKIs, such as osimertinib, were developed to overcome the T790M resistance mutation. As a consequence, there are treatment strategies in development to delay or overcome EGFR TKI resistance. Combining different classes of drugs to target multiple signaling pathways simultaneously is an active area of investigation. For example, combining EGFR TKIs with MET inhibitors, anti-angiogenic agents, or other targeted therapies may enhance treatment efficacy and delay the onset of resistance.

C. Ongoing Trials Investigate Amivantamab Combinations for EGFR-Mutated NSCLC

The CHRYSALIS-2 study assesses the bispecific antibody targeting MET and EGFR amivantanab given in combination with the third generation EGFR TKI lazertinib for patients with disease progression after receiving osimertinib and platinum-based chemotherapy. As of November 6, 2021, 162 patients were enrolled in Cohort A. Of 50 efficacy-evaluable patients in the target population, the overall response rate (ORR) by blinded independent central review (BICR)-assessment was 36% (95% CI, 23-51), with 1 complete response and 17 partial responses. Median duration of response (DOR) was not reached based on BICR. At a median follow-up of 8.3 months, 7 responders (39%) have achieved a DOR lasting ≥ 6 months by BICR. Of 56 efficacy-evaluable patients in the heavily pretreated population (8.7-months median follow-up), ORR by investigator was 29% (95% CI, 17-42), with 1 complete response and 15 partial responses. mDOR was 8.6 months (95% CI, 4.2-not reached). Findings of CHRYSALIS-2 study showed encouraging antitumor activity with a manageable safety profile for pretreated patients with EGFR-mutant NSCLC.16 CHRYSALIS-2 trial continues investigating potential biomarker strategies and evaluating the amivantamab and lazertinib regimen in the post-osimertinib and chemotherapy-naïve setting.

The ongoing phase 3 MARIPOSA trial is also further investigating evaluating amivantamab, given with and without lazertinib, combined with chemotherapy (carboplatin and pemetrexed) compared with chemotherapy alone, in patients with locally advanced or metastatic EGFR exon 19 deletions (ex19del) or L858R substitution NSCLC after disease progression on or after osimertinib. In both experimental arms, the study demonstrated a statistically significant and clinically meaningful improvement in PFS compared with chemotherapy alone. Results also showed a favorable trend in overall survival for the combination of amivantamab and lazertinib in these patients compared to osimertinib (HR, 0.80, 95% CI, 0.61-1.05, p=0.11) at a first interim analysis.17

In summary, NSCLC is a complex disease with various genetic and molecular alterations, and identifying specific driver mutations has led to the development of targeted therapies tailored to the underlying biology of the tumor. An increasing understanding of the cellular biology of various driver alterations will lead to the development of therapies with higher selectivity and specificity. Importantly, applications of targeted therapies in the early setting may further transform the natural history of this malignancy.

Conflict of Interest

AstraZeneca, Genentech/Roche, Exelixis, Takeda Pharmaceuticals, Eli Lilly and Company, Amgen, Iovance Biotherapeutics, Blueprint Pharmaceuticals, Regeneron Pharmaceuticals, Natera, Sanofi/Regeneron, D2G Oncology, Surface Oncology, Turning Point Therapeutics, Mirati Therapeutics, Gilead Sciences, Abbvie, Summit Therapeutics, Novartis, Novocure, Janssen Oncology, Anheart Therapeutics; Research/Grants: Genentech/Roche, Merck, Novartis, Boehringer Ingelheim, Exelixis, Nektar Therapeutics, Takeda Pharmaceuticals, Adaptimmune, GSK, Janssen, AbbVie, Novocure.

Dr. Millie Das: Research Grant: Genentech, Merck, CellSight, Novartis, Varian; Consultant: Eurofins, Genentech (uncompensated); Advisor: Sanofi/Genzyme, Beigene, Regeneron, Astra Zeneca, Janssen, Gilead, Bristol Myer Squibb, Catalyst.

The other authors do not have a conflict of interest.

Funding Information


Ethical Statements



The authors thank the Binaytara Foundation for the opportunity to highlight this important topic.

Author Contributions

  • All authors: conception and design.

  • All authors: data collection and assembly.

  • HA and IA: data analysis and manuscript writing.

All authors have approved this manuscript.