Case Presentation: A 50 year old woman with history of left breast cancer, treated with lumpectomy and eight weeks of radiation therapy completed four months ago, presented with one month of dyspnea, dry cough, and low grade fevers. Prior to admission, the patient was treated for both community acquired pneumonia and healthcare-acquired pneumonia with three courses of oral and intravenous antibiotics for a total of 21 days. One week after her latest antibiotic course, the patient was admitted for recurrent symptoms. She had no history of lung disease, smoking history, recent travel, pets, or known environmental exposures. Her only home medication was Tamoxifen. Exam revealed bilateral expiratory wheezing. Laboratory data was unremarkable. Chest X-ray and CT showed bilateral upper lobe consolidations, unchanged from prior imaging. Infectious disease and pulmonary teams were consulted, and the patient was placed on Vancomycin, Imipenem, and Azithromycin, to initiate a prolonged course of HCAP treatment. Blood, respiratory, and AFB sputum cultures were negative. Suspicions then turned to non-infectious etiologies. Given her recent radiation therapy, and her CT findings, the patient was started on Prednisone for suspected radiation-induced organizing pneumonia. Bronchial washings were positive for macrophages and acute inflammatory cells, while transbronchial biopsy showed interstitial inflammation. Antibiotics were stopped and the patient improved on steroids alone. She was discharged home on a Prednisone taper with pulmonology follow up.

Discussion: Radiation-induced organizing pneumonia (OP) is a rare complication of radiation therapy, with an incidence up to 2.3% in women undergoing radiation for breast cancer. Unlike radiation pneumonitis, a more common form of radiation-induced lung injury, OP can occur regardless of radiation dose and outside the irradiated field. Symptom onset ranges from 0 to 23 months after radiation treatment, with symptoms including low-grade fevers, dry cough, and dyspnea. These symptoms persist following a trial of antibiotics, and warrant further workup after treatment failure. Imaging findings include areas of ground glass opacities with or without air bronchograms. OP can be definitively diagnosed with a transbronchial biopsy showing plugs of granulation tissue within alveoli, as well as chronic inflammation in the surrounding areas. Washings may show alveolar macrophages, as seen in our patient. Treatment consists of corticosteroids, which are gradually tapered. Relapses occur in up to a third of cases, requiring additional corticosteroid courses or secondary agents like cyclophosphamide and azathioprine.

Conclusions: Our case highlights that for patients presenting with recurrent pneumonia-like symptoms after radiation therapy, radiation-induced organizing pneumonia should be high on the list of possible diagnoses. Treatment consists of corticosteroids, as antibiotics will be ineffective in relieving symptoms.