• Aged 18 years or older (including 18 years) and less than 75 years (including 75 years).

• Subjects with histologically or cytologically confirmed unresectable NSCLC and stage IIIB-IV tumours (as determined by the International Association for the Study of Lung Cancer (IASLC) Manual of Thoracic Tumour Staging, 8th edition). Oligometastatic lesions (≤5) in the brain on head-enhanced MRI were eligible for enrolment, and at least 1 lesion in the brain could be accurately measured at baseline, with the longest diameter at baseline ≥5 mm. Measurements were made by MRI (layer thickness 1.5 mm).

• Have not received any systemic therapy after diagnosis of NSCLC or have not progressed with 1-2 cycles of chemotherapy.

• Tumour tissue samples or blood samples diagnosed with NSCLC are tested and confirmed to have an EGFR-sensitive mutation (including exon 19 deletion or L858R, either alone or coexisting with mutations in other EGFR loci). Tumour tissue is recommended if the tumour tissue is accessible; if the tumour tissue is inaccessible or the patient is not amenable to tissue biopsy, blood samples will be sent to test EGFR mutation.

• Patients with an Eastern Cooperative Oncology Group (ECOG) physical status score of 0 or 1 and no deterioration in the previous 2 weeks, with a minimum expected survival of 12 weeks.

• At least 1 tumour lesion in the patient's lungs can be accurately measured at baseline with a longest diameter of ≥10 mm at baseline (in the case of lymph nodes, a short diameter of ≥15 mm is required). The measurement method of choice is suitable for accurate repeat measurements, either computed tomography (CT) or magnetic resonance imaging (MRI). Only 1 measurable lesion is accepted as a target lesion if it is present, subject to baseline evaluation of the tumour lesion at least 14 days after diagnostic biopsy. And the primary residual lung lesion is suitable for SBRT after targeted therapy.

• Women of childbearing potential are required to use adequate contraception and should not be breastfeeding from screening until 3 months after discontinuation of study treatment. Negative pregnancy test prior to initiation of dosing or no risk of pregnancy as evidenced by meeting one of the following criteria:

‣ Postmenopausal defined as amenorrhoea for at least 12 months after age greater than 50 years and cessation of all exogenous hormone replacement therapy;

⁃ Women younger than 50 years of age may also be considered postmenopausal if they have had amenorrhoea for 12 months or more after cessation of all exogenous hormone therapy and have luteinising hormone (LH) and follicle-stimulating hormone (FSH) levels in the range of laboratory postmenopausal reference values.

⁃ Previous irreversible sterilisation including hysterectomy, bilateral oophorectomy or bilateral salpingo-oophorectomy, with the exception of bilateral tubal ligation.

• Barrier contraception (i.e., condoms) should be used by male patients from screening until 3 months after discontinuation of study treatment.

• Subjects participate voluntarily and sign a written informed consent form.