Radiation pneumonitis

• Typically presents 1-2 months after Y90, after high acute or cumulative dose to lungs (>30Gy for single treatment, >50 gy overall).
• Symptoms: nonproductive cough, dyspnea, fever, and bronchoalveolar lymphocytosis and eosinophilia. Mild restrictive process on initial pulmonary testing.
• Imaging: RP presents 1–2 months after Y90 with ill-defined patchy opacities and ground-glass nodularity in a symmetric (ie, “bat-wing”) pattern with relative peripheral/hilar sparing. Can resemble an organizing or chronic eosinophilic pneumonia. Findings may resolve or evolve into localized fibrosis, traction bronchiectasis, and focal honeycombing.
• Late complications include pneumothorax and superinfections.
• Prior or concurrent chemotherapy might potentiate risk of RP.
• Transbronchial biopsy should be rarely needed, but histopathologic findings may include hemorrhage, interstitial edema, and fibrinous exudates with fibrotic changes. Microspheres deposition can confirm RP but not necessary for diagnosis, in which case is diagnosis of exclusion based on clinical, functional, and radiographic findings without other infectious/inflammatory/cytotoxic etiologies.
• Prior or current chemo may increase risk

Treatment of radiation pneumonitis (PMID: 22525023):

• Acutely high pulse dose steroids: Intravenous methylprednisone (500 mg twice per day for 3 d) (typically with rapid resolution)
• then discharge with pentoxifylline (400mg tid), home oxygen, and high-dose oral prednisone (60 mg/d) with slow taper over a period of 2 months.