Evidence-Based Liquid Biopsy Knowledge
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Lung Cancer

ctDNA for Molecular Profiling and MRD Detection in NSCLC

Clinical Overview

Non-small cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancer cases and represents the most clinically validated application of ctDNA testing in solid tumor oncology. Small cell lung cancer (SCLC), comprising the remaining 15%, has more limited ctDNA applications due to fewer actionable genomic targets.

Why ctDNA Testing Matters in Lung Cancer:

  • Extensive Actionable Genomic Landscape: NSCLC harbors over 10 distinct targetable driver mutations with specific approved therapies
  • Tissue Limitation: Up to 30% of patients have insufficient tissue for comprehensive molecular profiling
  • Treatment Selection: Molecular profiling directly impacts first-line therapy selection across multiple genomic alterations
  • Resistance Monitoring: Serial ctDNA testing enables detection of resistance mechanisms during targeted therapy
  • MRD Detection: Postoperative ctDNA predicts recurrence 3-8 months before imaging in resected early-stage disease

Clinical Context: NSCLC molecular profiling via ctDNA has achieved clinical utility established through multiple prospective studies demonstrating equivalent performance to tissue-based testing for detecting actionable mutations. MRD detection in resected NSCLC demonstrates strong prognostic value with hazard ratios of 4.0-17.0 for recurrence in ctDNA-positive patients.

ctDNA Testing Methodology

Genotyping for Treatment Selection (Metastatic Setting)

Molecular profiling in advanced NSCLC identifies actionable driver mutations to guide targeted therapy selection. ctDNA testing can be performed at diagnosis or upon disease progression to detect acquired resistance mechanisms.

Testing Approach:

  • Method: Comprehensive genomic profiling using next-generation sequencing panels covering all guideline-recommended biomarkers
  • Sample: Single peripheral blood draw (typically 10-20 mL)
  • Detection Threshold: Variant allele frequency as low as 0.1-0.5% depending on platform
  • Turnaround Time: 7-14 days from sample collection
  • Clinical Performance: 80-85% sensitivity for detecting actionable mutations when tumor is shedding DNA; 100% positive predictive value

Clinical Application: ctDNA testing is particularly valuable when tissue biopsy is not feasible, insufficient for complete profiling, or when serial monitoring for resistance mutations is needed. A negative ctDNA result does not exclude the presence of an actionable mutation, and tissue biopsy should be pursued when clinically feasible.

MRD Detection (Curative-Intent Setting)

In resected early-stage NSCLC, ctDNA-based MRD detection identifies patients at high risk of recurrence after curative-intent surgery. This application uses either tumor-informed or tumor-agnostic approaches.

Tumor-Informed MRD Approach:

  • Baseline Sample: Tissue from surgical resection or preoperative blood draw analyzed to identify patient-specific mutations
  • Surveillance: Serial blood draws postoperatively (typically every 3-6 months for 2-3 years) to track those identified mutations
  • Sensitivity: 70-94% depending on disease stage, with higher sensitivity in stage II-III disease
  • Detection Threshold: Ultra-sensitive detection down to 0.001-0.01% variant allele frequency

Tumor-Agnostic MRD Approach:

  • Method: Testing performed at surveillance timepoints without prior baseline profiling
  • Panel: Fixed gene panels targeting common lung cancer mutations
  • Advantage: Does not require tumor tissue or baseline blood sample
  • Limitation: Lower sensitivity compared to tumor-informed approaches (50-70%)

Lead Time to Radiographic Recurrence: ctDNA MRD positivity precedes CT imaging detection by a median of 3-8 months across multiple studies, providing a critical window for potential therapeutic intervention.

MRD Detection: Prognostic Significance

Postoperative ctDNA as Predictor of Recurrence

Detection of ctDNA after surgical resection identifies patients at markedly elevated risk of disease recurrence. Multiple prospective studies and meta-analyses have established postoperative ctDNA status as one of the most powerful prognostic factors in resected NSCLC.

Meta-Analysis: 30 Studies, 3,287 Patients

The largest systematic evaluation of MRD detection in resected NSCLC pooled data from studies conducted between 2015-2024, demonstrating consistent prognostic impact across diverse patient populations and testing methodologies.

Hazard Ratios for ctDNA-Positive vs ctDNA-Negative Patients:

  • Progression-Free Survival: HR 11.19 (95% CI 6.10-20.52, p<0.001)
  • Overall Survival: HR 6.34 (95% CI 2.27-17.74, p<0.001)
  • Recurrence-Free Survival: HR 6.41 (95% CI 4.18-9.83, p<0.00001)
  • Lead Time: Mean 5.5 months earlier detection than conventional imaging
  • Detection Frequency: 6-45% of resected patients test positive for postoperative MRD, with rates increasing by stage

Clinical Interpretation: Patients with detectable postoperative ctDNA have an 11-fold increased risk of disease progression compared to ctDNA-negative patients. This risk stratification substantially exceeds traditional clinicopathologic variables including tumor stage, grade, and nodal status.

TRACERx Study: Ultrasensitive Whole-Genome Sequencing

The TRACERx study used whole-genome sequencing to achieve exceptional sensitivity (detection limit <0.001%) for MRD detection in 171 resected lung cancer patients, demonstrating the feasibility of ultra-early detection even in stage I disease.

Key Findings:

  • Detection Lead Time: 0-1,732 days before clinical/radiographic recurrence, median 158 days
  • Stage I Sensitivity: Detectable MRD even in patients with early-stage disease previously considered low-risk
  • Recurrence Patterns: ctDNA dynamics predicted local versus distant recurrence patterns
  • Preoperative ctDNA: Correlated with tumor histology, genomic features, and risk of recurrence

IMpower010 ctDNA Substudy: MRD and Adjuvant Immunotherapy

The IMpower010 trial evaluated adjuvant atezolizumab (anti-PD-L1 immunotherapy) following chemotherapy in resected stage IB-IIIA NSCLC. An exploratory ctDNA analysis examined whether MRD status predicts benefit from adjuvant immunotherapy.

ctDNA Findings:

  • MRD as Prognostic Factor: ctDNA-positive patients had significantly worse outcomes than ctDNA-negative patients regardless of treatment
  • Atezolizumab Benefit in MRD+ Patients: Among PD-L1 ≥1% MRD-positive patients, atezolizumab reduced risk of disease recurrence or death (HR 0.43, suggesting 57% risk reduction)
  • ctDNA Clearance: 62% of initially ctDNA-positive patients achieved clearance after chemotherapy
  • Clearance Impact: Patients achieving ctDNA clearance had improved disease-free survival compared to persistently positive patients

Clinical Implication: These exploratory data suggest that MRD-positive patients may derive greater benefit from adjuvant immunotherapy. Prospective interventional trials (MERMAID-1, MERMAID-2) are ongoing to validate ctDNA-guided treatment intensification strategies.

Neoadjuvant Chemoimmunotherapy: ctDNA Clearance Predicts Pathologic Response

Multiple phase II and III trials of neoadjuvant chemoimmunotherapy have incorporated ctDNA assessments, consistently demonstrating that on-treatment ctDNA clearance predicts pathologic complete response and long-term survival.

NADIM Trial (Nivolumab + Chemotherapy):

  • Setting: Stage IIIA resectable NSCLC (n=46)
  • ctDNA Clearance Benefit: Patients achieving clearance after 3 cycles had dramatically improved outcomes
  • Progression-Free Survival: HR 0.16 (95% CI 0.03-0.73, 84% risk reduction)
  • Overall Survival: HR 0.05 (95% CI 0-0.62, 95% risk reduction)

AEGEAN Trial (Durvalumab + Chemotherapy):

  • Setting: Phase III in stage II-IIIB resectable NSCLC
  • Event-Free Survival: HR 0.26 (95% CI 0.13-0.54) for patients with ctDNA clearance versus those without

CheckMate 816 Trial (Nivolumab + Chemotherapy):

  • Pathologic Complete Response: 46% in patients with ctDNA clearance vs 0% in patients without clearance

Summary: Across neoadjuvant trials, ctDNA clearance during treatment consistently predicts pathologic response and survival (HR 0.05-0.26). This establishes ctDNA dynamics as a potential early surrogate endpoint for treatment efficacy, potentially enabling adaptive therapy strategies based on molecular response.

Genotyping: Actionable Mutations and Targeted Therapies

Comprehensive Molecular Profiling for Treatment Selection

NSCLC harbors multiple distinct genomic alterations, each with specific targeted therapies demonstrating superior outcomes compared to chemotherapy. ctDNA testing enables comprehensive profiling of all guideline-recommended biomarkers from a single blood draw.

Clinical Utility: Identification of actionable driver mutations directly impacts first-line treatment selection. Patients with targetable alterations typically receive matched targeted therapy rather than chemotherapy or immunotherapy, with improved progression-free survival and quality of life.

EGFR Mutations (Epidermal Growth Factor Receptor)

Prevalence: 15% in Caucasian populations, 50% in Asian populations. Most common in never-smokers and adenocarcinoma histology.

Key Features:

  • Common Mutations: Exon 19 deletions (45%), L858R point mutation (40%), exon 20 insertions (5-10%, less responsive to standard EGFR TKIs)
  • First-Line Therapy: Osimertinib (third-generation EGFR TKI) demonstrates superior efficacy to earlier-generation TKIs
  • Response Rates: 60-80% objective response rate with EGFR TKIs
  • Adjuvant Setting: ADAURA trial demonstrated osimertinib benefit in resected EGFR-mutant NSCLC (HR 0.17, 83% reduction in disease recurrence risk)
  • Resistance Mechanisms: T790M mutation (most common resistance to first/second-generation TKIs, responsive to osimertinib); C797S mutation (resistance to osimertinib); MET amplification
  • ctDNA Advantage: Serial monitoring enables early detection of resistance mutations, guiding sequential therapy selection

KRAS G12C Mutations

Prevalence: KRAS mutations occur in 25-30% of NSCLC; G12C specific subtype accounts for approximately 13% of all NSCLC.

Key Features:

  • Approved Therapies: Sotorasib and adagrasib (selective KRAS G12C inhibitors)
  • Response Rates: Approximately 40% objective response rate
  • Clinical Note: Only G12C-specific mutations (not other KRAS variants) are currently targetable with approved therapies
  • Resistance Monitoring: ctDNA enables detection of acquired resistance mutations to guide subsequent therapy

ALK Rearrangements (Anaplastic Lymphoma Kinase)

Prevalence: 5% of NSCLC, enriched in younger patients and never-smokers.

Key Features:

  • Approved Therapies: Alectinib, brigatinib, lorlatinib, ceritinib, crizotinib (multiple generations of ALK inhibitors)
  • Response Rates: >70% with next-generation ALK inhibitors
  • Resistance Mechanisms: ALK kinase domain mutations (detectable by ctDNA) guide sequential ALK inhibitor selection
  • CNS Activity: Newer-generation ALK inhibitors demonstrate improved CNS penetration

MET Exon 14 Skipping Mutations

Prevalence: 3% of NSCLC.

Key Features:

  • Approved Therapies: Capmatinib, tepotinib (selective MET inhibitors); crizotinib
  • Response Rates: 40-70% with MET-selective inhibitors
  • MET Amplification: Also targetable; can emerge as acquired resistance mechanism to EGFR TKIs (occurs in up to 20% of EGFR TKI resistance cases)

BRAF V600E Mutations

Prevalence: 2% of NSCLC, more common in current/former smokers.

Key Features:

  • Approved Therapy: Dabrafenib plus trametinib (combination BRAF and MEK inhibition)
  • Response Rates: Approximately 64% objective response rate
  • Clinical Note: Non-V600 BRAF mutations are not responsive to standard BRAF inhibitors

HER2 Mutations (ERBB2)

Prevalence: 2-3% of NSCLC (distinct from HER2 amplification seen in breast cancer).

Key Features:

  • Approved Therapy: Trastuzumab deruxtecan (antibody-drug conjugate)
  • Response Rates: Approximately 55% objective response rate
  • Common Alteration: Exon 20 insertions most frequent

ROS1 Rearrangements

Prevalence: 1-2% of NSCLC.

Key Features:

  • Approved Therapies: Crizotinib, entrectinib
  • Response Rates: Approximately 70% with crizotinib
  • Clinical Note: Typically mutually exclusive with other driver mutations

RET Rearrangements

Prevalence: 1-2% of NSCLC.

Key Features:

  • Approved Therapies: Selpercatinib, pralsetinib (selective RET inhibitors)
  • Response Rates: 60-85% with selective RET inhibitors
  • Clinical Impact: Selective RET inhibitors demonstrate superior efficacy and tolerability compared to multi-kinase inhibitors

NTRK Fusions (Neurotrophic Tyrosine Receptor Kinase)

Prevalence: <1% of NSCLC (rare but pan-cancer actionable target).

Key Features:

  • Approved Therapies: Larotrectinib, entrectinib (tumor-agnostic approvals)
  • Response Rates: Approximately 75% across tumor types
  • Clinical Application: Comprehensive genomic profiling necessary to identify this rare but highly responsive target

PD-L1 Expression (Immunotherapy Biomarker)

Prevalence: PD-L1 ≥50% tumor proportion score in approximately 30% of NSCLC.

Key Features:

  • High PD-L1 (≥50%): Pembrolizumab monotherapy approved as first-line therapy in driver mutation-negative NSCLC
  • Response Rates: Approximately 45% objective response rate with pembrolizumab monotherapy in PD-L1 ≥50% population
  • Clinical Note: PD-L1 testing typically performed on tissue; not routinely assessed via ctDNA

Testing Strategy: Comprehensive genomic profiling via next-generation sequencing panels is essential to detect all guideline-recommended biomarkers. Testing should cover at minimum: EGFR, ALK, ROS1, BRAF V600E, MET exon 14 skipping, RET, NTRK, KRAS G12C, and HER2 mutations. When tissue is insufficient or unavailable, ctDNA testing provides access to complete molecular profiling.

Clinical Summary

Lung cancer, particularly NSCLC, demonstrates strong clinical utility for ctDNA testing across two distinct applications: molecular profiling for treatment selection in advanced disease and MRD detection for recurrence prediction in resected early-stage disease.

Genotyping (Metastatic NSCLC):

  • Clinical Utility Established: ctDNA testing identifies actionable mutations across >10 genomic targets with matched targeted therapies
  • Performance: 80-85% sensitivity, 100% positive predictive value; success rate of 95% compared to variable tissue availability
  • Major Targets: EGFR (15-50% depending on ethnicity), KRAS G12C (13%), ALK (5%), MET exon 14 skipping (3%), BRAF V600E (2%), HER2 (2-3%), ROS1 (1-2%), RET (1-2%), NTRK (<1%)
  • Treatment Impact: Detection of targetable alterations directly determines first-line therapy selection
  • Key Limitation: Tissue biopsy remains preferred when feasible; negative ctDNA does not exclude actionable mutation

MRD Detection (Resected NSCLC):

  • Strong Prognostic Value: HR 4.0-17.0 for recurrence in ctDNA-positive versus ctDNA-negative patients
  • Lead Time: 3-8 months earlier detection than conventional imaging
  • Sensitivity: 70-94% depending on stage and methodology
  • Adjuvant Immunotherapy: IMpower010 substudy showed HR 0.43 for atezolizumab benefit in MRD-positive patients
  • Neoadjuvant Setting: ctDNA clearance predicts pathologic response and survival (HR 0.05-0.26 across NADIM, AEGEAN, CheckMate 816 trials)
  • Key Limitation: Interventional trials demonstrating improved outcomes with MRD-guided treatment are ongoing (MERMAID-1); not yet standard of care

Bottom Line: NSCLC demonstrates Level 1 evidence for ctDNA clinical utility in both genotyping and MRD detection contexts. Genotyping via ctDNA enables comprehensive molecular profiling when tissue is limited, with performance approaching tissue-based testing. MRD detection provides powerful prognostic information with hazard ratios exceeding most traditional clinicopathologic factors. However, tissue remains preferred when available for genotyping, and MRD-guided treatment interventions await completion of ongoing randomized trials before becoming standard of care.

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Evidence summary as of January 2026 | Educational Resource