Adding immune checkpoint inhibitors or molecularly targeted drugs as adjuvant therapy to curative treatments-such as surgery or chemoradiotherapy-for stage I-III non-small cell lung cancer (NSCLC) has been established as a standard of care and has improved treatment outcomes. However, there is currently no adequate method to determine which patients should receive these adjuvant therapies. Identifying those with a good prognosis without adjuvant therapy could reduce the risk of adverse events, lessen the burden of clinic visits, and reduce healthcare costs.

Among various approaches, ctDNA-based MRD (minimal residual disease) analysis is highly anticipated and has already been introduced into clinical practice for hematologic malignancies. However, solid tumors' development as a companion diagnostic has been limited, and regulatory approval is mainly being considered based on performance evaluation data. In this study, we will conduct a performance evaluation of MRD analysis using Signatera™ in patients with stage I-III NSCLC while also collecting other prognostic factors based on clinicopathological information and survival data.

Inclusion Criteria:

1. A histopathologically confirmed diagnosis of non-small cell lung cancer (NSCLC)

   The diagnosis (by cytology or biopsy) must be one of the following: "adenocarcinoma," "squamous cell carcinoma," "non-small cell carcinoma consistent with adenocarcinoma," "non-small cell carcinoma consistent with squamous cell carcinoma," or "non-small cell carcinoma not otherwise specified (NOS)." If the histological subtype differs between cytology and biopsy specimens, the subtype determined by the biopsy specimen shall be used.

   At the time of enrollment, diagnoses of "squamous cell carcinoma" or "non-small cell carcinoma consistent with squamous cell carcinoma" are classified as squamous cell carcinoma, whereas "adenocarcinoma," "non-small cell carcinoma consistent with adenocarcinoma," and "non-small cell carcinoma NOS" are classified as non-squamous cell carcinoma.

2. Meets one of the following criteria (1-3):

1. Stage IB-III (preoperative clinical stage) deemed resectable, with no planned neoadjuvant therapy.

2. Stage III disease deemed amenable to curative-intent chemoradiotherapy. 3. Stage II-III (preoperative clinical stage) deemed resectable, with planned neoadjuvant therapy.

3) Age ≥ 18 years at the time of enrollment. 4) The attending physician has determined that tissue and blood samples can be provided.

5) Written informed consent has been obtained from the patient.

Exclusion Criteria:

• Presence of active multiple primary malignancies (defined as synchronous multiple cancers/tumors or metachronous multiple cancers/tumors with a disease-free interval of 3 years or less). However, even if the disease-free interval is less than 3 years, a history of clinical stage I prostate cancer or a completely resected cancer with any of the pathological stages specified below is not considered "active multiple primary malignancies.

non-small cell lung cancer (NSCLC)