Objective: To evaluate the efficacy and safety of prophylactic use of pegylated recombinant human granulocyte colony-stimulating factor (PEG-rhG-CSF) during definitive concurrent chemoradiotherapy (cCRT) in patients with inoperable stage II-III non-small cell lung cancer (NSCLC).

Methods: A prospective observational cohort study was conducted on patients receiving definitive cCRT. The radiation therapy technique uses intensity modulated radiation therapy (IMRT) and involves field irradiation. It protects more normal tissue from exposure.Chemotherapy regimens included platinum-based doublet combinations: etoposide plus cisplatin (every 28 days), pemetrexed plus platinum (every 21 days), or paclitaxel plus platinum (weekly, only for control group) .

Patients were followed up at one month post-treatment, then every three months for the two year, and every six months thereafter until disease progression.

In the study group, patients received subcutaneous injections of PEG-rhG-CSF (6 mg for patients weighing ≥45 kg, 3 mg for patients <45 kg) 48 hours after each chemotherapy cycle during cCRT. In the control group, patients received guideline-based supportive treatment. Radiotherapy was halted or chemotherapy was delayed when grade 3 or more (G3+) toxicities happened.

Endpoints:Primary endpoint was incidence of G3+ neutropenia during radiotherapy and one month post-radiotherapy. Complete blood counts were monitored weekly during cCRT and for one month post-treatment or as deemed necessary by the physician.

Following the completion of cCRT and the resolution of acute side effects, patients were followed up at one month post-treatment, then every three months for the first year, and every six months thereafter until disease progression.

Statistical Analysis:The inverse probability of treatment weighting (IPTW) algorithm was applied to balance differences between groups in terms of age, gender, smoking, clinical stage, KPS score, induction therapy received or not, ensuring the reliability of the study results. Statistical analysis was performed using R software (version 4.4.1). All tests were two-sided, with a P-value <0.05 considered statistically significant.

Inclusion Criteria:

1. Diagnosis

   • Histologically confirmed stage II-III non-small cell lung cancer (NSCLC)

2. Treatment Plan

   • Planned to receive concurrent platinum-based chemotherapy with radiotherapy (cCRT)

3. Demographics

   • Age 18-80 years

4. Performance Status

   • Karnofsky Performance Status (KPS) ≥70

5. Organ Function

   • Renal function: Creatinine clearance ≥60 mL/min
   • Hepatic function: Total bilirubin ≤1.5×ULN, AST/ALT ≤2.5×ULN
   • Absolute neutrophil count ≥2.0×10⁹/L
   • Platelets ≥100×10⁹/L
   • Hemoglobin ≥10 g/dL

Exclusion Criteria:

1. Active Malignancies

   • Concurrent diagnosis of active malignancies (excluding: non-melanoma skin cancer, carcinoma in situ, or malignancies in complete remission for ≥5 years)

2. Infectious/Immunological Conditions

   • Active systemic infection requiring intravenous antimicrobial therapy
   • Uncontrolled autoimmune diseases (defined as requiring systemic immunosuppressants at doses >10 mg/day prednisone equivalent within 30 days prior to screening)

3. Hypersensitivity Reactions

   • Allergy to PEG-rhG-CSF or other biological products derived from genetically engineered Escherichia coli

4. Neuropsychiatric Impairments

   • Severe psychiatric disorders (e.g., schizophrenia, major depressive disorder with suicidal ideation) requiring hospitalization within 6 months)

5. Prior Radiotherapy

   • History of thoracic radiotherapy involving >30% lung parenchyma or mean heart dose >20 Gy

Definitive Concurrent Chemoradiotherapy for Inoperable Stage II-III Non-Small Cell Lung Cancer，Patients received prophylactic PEG-rhG-CSF 48 hours after chemotherapy.