Patients with advanced lung cancer who have previously received immunocheckpoint inhibitor therapy, undergone chest radiation therapy again have developed radiation induced lung injury. Pirfenidone has anti-inflammatory and anti fibrosis effects. This study is intended to evaluate the effectiveness of pirfenidone combined with radiotherapy in the prevention of radiation pneumonitis.

Inclusion Criteria:

1. The patients joined the study voluntarily and signed an informed consent form (ICF). They had good compliance and cooperated with follow-up;
2. Patients with lung cancer who had received at least 2 cycles of immunomonotherapy or combination systemic therapy (including PD-1 or PD-L1 immunocheckpoint inhibitors) within 6 months;
3. Age ≥ 18 years, no gender limit;
4. ECOG PS score: 0～1;
5. The expected survival time ≥ 3 months;
6. Use appropriate methods of contraception or surgical sterilization during treatment and for 3 years after treatment for men and women of reproductive age；
7. Appropriate biochemical indicators and organ function.

Exclusion Criteria:

1. Currently participating in interventional clinical research and treatment, or receiving other research drugs or treatment with research equipment within 4 weeks before the first administration;
2. Accept solid organ or blood system transplantation;
3. Suffer from active autoimmune diseases that require hormone or immunomodulatory treatment, such as rheumatoid arthritis, ankylosing spondylitis, type I diabetes, psoriasis, vitiligo, immune-related thyroid dysfunction, etc. (hormone replacement Can be included after treatment is normal);
4. Suffer from acute or chronic infectious diseases, such as hepatitis B, hepatitis C, tuberculosis, and HIV;
5. Allergic to research drug ingredients;
6. Active infection or fever of unknown cause occurred during the screening period and before the first administration> 38.5℃ (according to the judgment of the investigator, the subject can be included in the group due to fever caused by the tumor);
7. Suffer from uncontrolled clinical symptoms or diseases of the heart, such as:(1) Heart failure above NYHA II; (2) Unstable angina pectoris; (3) Myocardial infarction occurred within 1 year; (4) Patients with clinically significant supraventricular or ventricular arrhythmia requiring clinical intervention;
8. Suffer from high blood pressure and cannot be well controlled by antihypertensive medication (systolic blood pressure ≥150 mmHg or diastolic blood pressure ≥100 mmHg);
9. Abnormal blood coagulation function (INR>2.0, PT>16s), have a bleeding tendency or are receiving thrombolytic therapy, and allow preventive use of low-dose aspirin and low-molecular-weight heparin;
10. Obvious coughing up blood or hemoptysis of 10ml or more per day in the 2 months before enrollment;
11. Have significant clinically significant bleeding symptoms or have a clear bleeding tendency within 3 months before enrollment;
12. Have received anti-tumor monoclonal antibodies (mAb) within 4 weeks before using the study drug for the first time, or the adverse events caused by the previously received drug have not recovered (ie ≤ grade 1 or reached the baseline level). Note: Except for subjects with ≤ Grade 2 neuropathy or ≤ Grade 2 hair loss, if the subject has undergone major surgery, the toxic reaction and/or complications caused by the surgical intervention must be fully recovered before starting treatment;
13. The investigator judged other situations not suitable for inclusion in this study.