Description

Background. Postoperative recurrence is frequent in resected early-stage and locally advanced NSCLC (stage I-IIIA), most often within 2-3 years after surgery. Standard surveillance relies on chest CT and serum tumor markers such as CEA, which cannot detect molecular recurrence at the MRD stage before it appears on imaging. ctDNA-based MRD assessment is being actively investigated in several solid tumors. In early-stage lung cancer, however, plasma ctDNA levels after surgery are very low, which may limit detection sensitivity. Bronchial washing fluid reflects the local tumor environment of the lung, and prior studies suggest it may detect tumor-derived mutations with higher sensitivity than plasma. This study builds a patient-specific, tumor-informed MRD panel for each participant, instead of relying on a fixed generic gene panel, and evaluates plasma and BWF MRD in parallel.

Hypotheses. (1) A patient-specific MRD panel built from resected tumor tissue and normal control specimens can detect postoperative recurrence earlier than conventional imaging-based diagnosis. (2) BWF ctDNA, which reflects the local tumor environment, may show higher MRD detection sensitivity than plasma ctDNA.

Objectives. The primary objective is to evaluate whether MRD positivity in plasma and BWF is associated with subsequent clinical or radiologic recurrence in resected NSCLC. The secondary objectives are (a) to compare MRD detection rates and quantitative values between plasma and BWF and determine which specimen is more sensitive for detecting recurrence, and (b) to explore the lead time of MRD detection relative to recurrence confirmation and compare it with CT and CEA.

Design and procedures. At baseline (first outpatient visit within 1 month after surgery), unstained (10) and stained (1) slides of the surgical pathology specimen are obtained, together with blood for normal control and cfDNA. WES is performed on tumor tissue and buffy coat, and a patient-specific mutation panel is designed. At 6, 12, 18 and 24 months after surgery, 20 mL of blood and 20 mL of BWF (collected by bronchoscopy from the lobe or segment of the original lesion, using saline) are obtained for MRD analysis. Additional blood/BWF MRD assessments may be performed at unscheduled visits when recurrence is clinically suspected. MRD follow-up ends at 24 months, recurrence or death. After 24 months, participants are followed under standard practice (CT and CEA every 3 months) without additional MRD testing. All specimens are shipped under anonymized serial codes to an external laboratory (IMBDx) for analysis and are handled according to the participant's consent regarding retention and secondary use.

Statistical analysis. The main analysis set includes enrolled participants whose patient-specific panel was successfully built and who have at least one evaluable postoperative MRD result. Recurrence-free survival (RFS) of MRD-positive and MRD-negative groups is estimated by the Kaplan-Meier method and compared with the log-rank test. Hazard ratios with 95% confidence intervals are estimated by Cox regression as exploratory analyses. Paired plasma-BWF detection rates are compared with McNemar's test, and paired quantitative values (variant allele frequency) with the paired t-test or Wilcoxon signed-rank test. Sensitivity, specificity, PPV, NPV, ROC curve and AUC are computed exploratorily. Lead time is summarized descriptively. Missing data are not imputed. Because this is a pilot study of 40 participants, results are interpreted by effect sizes and confidence intervals rather than formal significance testing.

Safety and monitoring. MRD results are not used alone to confirm recurrence or change adjuvant therapy. Adverse events related to blood sampling and bronchoscopy are recorded. An independent safety monitor, who is not a member of the study team, will perform two monitoring visits. Serious adverse events are reported according to each institution's IRB requirements. Data from all sites are de-identified, coded, and managed centrally.