A 61-year-old man with carcinoma of the lung presented with a 1-week history of worsening dyspnea, nonproductive cough, and fever (ie, temperature of up to 39°C), while still receiving radiotherapy. Six months earlier, he had received a diagnosis of stage IV non-small cell carcinoma. He had received six courses of chemotherapy, which included cisplatin and etoposide, with partial response. Chemotherapy was followed by radiotherapy to the mediastinum and right middle lobe. The total dose was 5,400 cGy, consisting of 4,140 cGy in 23 fractions, and a boost to the tumor bed of 1,260 cGy in 7 fractions. Toward the end of his radiotherapy, the patient began experiencing worsening dyspnea associated with fever and dry cough. His medications included oral dexamethasone, 2 mg daily, which was started in preparation for radiotherapy to the brain.