Nutritional + Usual Corticosteroids Randomized Trial for Immune-Related pneumoniA - Therapeutic Utilization Evaluation

Inclusion Criteria:

1. Voluntary participation with full understanding of the study and signed informed consent form.
2. Age 18 to 75 years (inclusive) on the day of informed consent signing.
3. Histologically or cytologically confirmed malignancy.
4. Received at least one cycle of immune checkpoint inhibitor therapy.
5. Grade 3-4 immune-related pneumonitis (per CTCAE v5.0 and radiologic grading).
6. ECOG performance status 0-2, with expected survival of more than 3 months.
7. Adequate organ function based on laboratory results (without transfusion, apheresis, erythropoietin, or granulocyte colony-stimulating factor support within 14 days before the first dose). Women of childbearing potential must have a negative serum pregnancy test within 7 days before first dose.

Exclusion Criteria:

1. Severe cardiac, cerebrovascular, renal, hematologic, or other serious systemic disease, including: NYHA Class III-IV heart failure; acute myocardial infarction or unstable angina within 6 months; severe post-stroke functional impairment (mRS greater than or equal to 3); progressive neurodegenerative disease; Child-Pugh Class B or C liver disease or acute liver failure; CKD stage 4-5 (eGFR less than 30 mL/min/1.73 m2) or requiring dialysis; absolute neutrophil count less than 1.5 x 10\^9/L, platelet count less than 50 x 10\^9/L, or Grade 3 or higher anemia (Hb less than 8 g/dL).
2. Severe allergic constitution or contraindications to the study treatment.
3. Significant psychiatric or psychological disorder, or doubts about the treatment plan.
4. Investigator judgment that the patient is unsuitable for the trial (e.g., poor follow-up adherence, refusal of supportive care).
5. Use of anti-tumor traditional Chinese medicine within 14 days before first dose.
6. History of or active inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis).
7. Severe acute or chronic infection.
8. Known alcohol or drug abuse history.
9. Pregnancy or breastfeeding.
10. Use of antibiotics, probiotic food, or microecological preparations within 2 weeks before enrollment.
11. Prior treatment-related lung injury: (a) targeted-therapy-related pulmonary toxicity (prior EGFR-TKI, ALK inhibitor, VEGF inhibitor, or antibody-drug conjugate causing interstitial lung disease or pneumonitis that has not fully resolved, with radiologic fibrosis or persistent functional impairment); (b) thoracic radiation-related lung injury (radiation pneumonitis or radiation fibrosis with irreversible CT findings).
12. Use of another investigational drug within 28 days before first dose that, per investigator judgment, would interfere with evaluation of study treatment.
13. Gastrointestinal disorder precluding oral administration.