Purpose: Bronchiolitis obliterans with pneumonic organization, or organizing pneumonia (OP), is an inflammatory disorder of the lungs, which can be triggered following pulmonary attacks of infectious or non-infectious origin. The non-infectious origins of OP include various entities including connective tissue diseases, exposure to toxic substances, medications, autoimmune diseases, and thoracic radiotherapy. The objective of this article is to summarize the literature on post-radiotherapy organized pneumonia, its etiologies, its clinical and radiological characteristics, as well as its treatment.

Materials and methods: A systematic review was performed in Medline database using the search engine PubMed. Keywords for the search included cryptogenic organizing pneumonia, bronchiolitis obliterans organizing pneumonia (BOOP), idiopathic organizing pneumonia and radiation, radiotherapy, breast cancer. The selected articles had to study the link between bronchiolitis obliterans with pneumonic organization and radiotherapy.

Results: A total of 96 articles were identified. Of these 96 articles, 49 fulfilled the defined selection criteria. Fourteen epidemiological studies were found in the literature. These epidemiological studies have published incidences of post-radiotherapy organizing pneumonia of less than 2.9% for patients treated for breast cancer. The predictive risk factors for bronchiolitis obliterans with pneumonic organization syndrome were age, smoking and the volume of irradiated lung. In a post-radiation context, bronchiolitis obliterans with pneumonic organization could be diagnosed several months, or even up to a year, after the end of irradiation. Treatment was based on the prescription of long-term corticosteroid therapy. Bronchiolitis obliterans with pneumonic organization should not be confused with post-radiation pulmonary fibrosis, which is inflammatory, dose-dependent, non-immunological, and localized in the irradiation area.

Conclusion: Organized pneumonia secondary to radiotherapy is a syndrome affecting approximately 1.4 to 3% of patients treated with radiotherapy for breast cancer. The main risk factors found are age, smoking and the volume of lung irradiated. Post-radiotherapy organized pneumonia needs to be known to all radiotherapists to improve patient care.