This is an observational, prospective, multicentre and nationwide study.

The study enroll resectable stage IIIA non-small cell lung cancer patients that are going to receive neoadjuvant treatment in real world.

The primary objective of this study is evaluating whether there is a significant association between ctDNA clearance (no detection of ctDNA) after neoadjuvant treatment and before surgery and progression free survival.

This is an observational, multicenter, one-arm, non-comparative, prospective study that will not under any circumstances interfere in the physician's normal clinical practice. Being limited to the collection of blood samples at five times and patient data, it does not entail any diagnostic or therapeutic procedure outside of normal clinical practice.

Approximately 100 resectable stage IIIA non-small cell lung cancer patients that are going to receive neoadjuvant treatment in real world will be recruited for this study in Spain. With this figure, it can be estimated whether ctDNA, both baseline and its negativization, has a role as a prognostic marker in the evolution of these patients in real-life conditions.

The primary objective of this study is evaluate whether there is a significant association between ctDNA clearance (no detection of ctDNA) after neoadjuvant treatment and before surgery and progression free survival.

The study is planned with the recruitment of patients over a year to a follow-up of 36 months post-surgery.

Inclusion Criteria:

• 1. Previously untreated patients with histologically- or cytologically- documented NSCLC who present stage IIIA disease (according to 8th version of the International Association for the Study of Lung Cancer Staging Manual in Thoracic Oncology) and also, potentially resectable locally advanced NSCLC patients' stage IIIB with T3N2 disease according to 8th edition can be included.
• 2. Tumor should be considered resectable before study entry by a multidisciplinary team
• 3. ECOG 0-1
• 4. Age ≥ 18 years at time of study entry
• 5. Patients that are going to be treated with neoadjuvant treatment before surgery
• 6. Patient capable of proper therapeutic compliance and accessible for correct follow-up
• 7. Patients must have signed, dated and IRB/EC-approved written informed consent form in accordance with regulatory and institutional guidelines. This must be obtained before the performance of any protocol-related procedures that are not part of normal subject care.

Exclusion Criteria:

• 1. Patients who refuse to sign and date an IRB/IEC-approved written informed consent form.
• 2. No possibility of venipuncture
• 3. Any medical, mental, or psychological condition which in the opinion of the investigator would not permit the patient to complete the study or understand the patient information.

Resectable stage IIIA non-small cell lung cancer patients that are going to receive neoadjuvant treatment in real world.