The primary objective is to evaluate Progression Free Survival (PFS) of the group (160 mg group) in which dose reduction was performed for 12 weeks after the first administration of Lazertinib.

The Secondary objectives of this study are as follows.

1. To evaluate Progression-free survival (PFS) of the group maintaining the same dose (240mg group) and the group in which dose reduction was performed (160mg group) for 12 weeks after the first administration of Lazertinib
2. In the group maintaining the same dose (240mg group) and the group in which dose reduction was performed (160mg group) for 12 weeks after the first administration of Lazertinib, Time-to-Treatment Discontinuation(TTD), Objective Response Rate(ORR), Disease Control Rate(DCR), Tumor shrinkage and Overall Survival(OS) is evaluated.
3. In the group maintaining the same dose (240mg group) and the group in which dose reduction was performed (160mg group) for 12 weeks after the first administration of Lazertinib, specific reasons (adverse event name, grade, etc.) according to Lazertinib dose adjustment is evaluated.
4. To evaluate the treatment profile of Lazertinib including duration of treatment, dose adjustment, and reason for discontinuation of treatment.
5. To evaluate the safety of Lazertinib in the 240 mg and 160 mg groups

This study is a prospective multi-center observational study, and 11 institutions will participate to enroll 200 subjects competitively. We will evaluate the efficacy and safety of Lazertinib according to maintenance of the 240mg dose and reduction of the 160mg dose for 12 weeks after the first administration of Lazertinib in non-small cell lung cancer patients confirmed to be T790M mutation-positive after treatment failure with first- or second-generation EGFR-TKIs. The study period is up to 3 years from the date of IRB approval. Follow-up is 2 years from the last subject enrollment, and data will be collected through periodic medical record review during Lazertinib administration for enrolled subjects.

Inclusion Criteria:

1. Patients who agreed in writing to participate in this study
2. Adult men and women over 20 years of age
3. Patients with locally advanced or metastatic, recurrent non-small cell lung cancer with EGFR mutation (based on AJCC 8th edition)
4. Patients with confirmed disease progression after 1st or 2nd generation EGFR-TKI treatment
5. Patients scheduled to receive Lazertinib after T790M mutation was confirmed positive in tissue or plasma

Exclusion Criteria:

1. Patients who are receiving or have already completed Lazertinib
2. Patients whose life expectancy is less than 12 weeks

Patients who agreed to participate in this study among patients scheduled to receive Lazertinib after T790M mutation was confirmed positive after treatment with 1st or 2nd generation EGFR-TKIs