This is a clinical retrospective study that will collect and analyze clinical data from all patients treated with fumeitinib mesylate in the Oncology Department of Tiantan Hospital between January 1, 2020 and May 31, 2025. The data collection will include general demographic characteristics (gender, age, family history, smoking history, etc.), clinicopathological features, NGS test reports, fumeitinib initiation time and dosage, concomitant medications, local treatments (surgery, radiotherapy, etc.), and baseline and follow-up imaging examinations related to efficacy and safety. The study will conduct: 1) clinical data analysis; and 2) exploration of resistance-related clinical characteristics and influencing factors.

Inclusion Criteria:

1. Histologically or cytologically confirmed stage IIIb-IVb NSCLC or postoperative recurrent NSCLC;
2. Positive EGFR test result, which can be determined by methods such as RT-PCR/FISH/IHC/NGS from hospital laboratories or testing institutions;
3. Patients aged ≥18 years;
4. Patients have clinically received Firmonertinib treatment, with recorded objective efficacy evaluation and adverse reactions;
5. Sign the Beijing Tiantan Hospital broad informed consent form.

Exclusion Criteria:

- Patients who cannot provide follow-up data for at least one cycle.

All patients who have received at least one treatment cycle of Firmonertinib are defined as the Full Analysis Set (FAS). Except for specially specified study endpoints (such as DOR which is evaluated only in the population achieving objective response), the primary endpoints, secondary endpoints, and safety endpoints of the study are evaluated in the FAS.