Radiation-induced pneumonitis in the "nonirradiated" lung

Objective: To describe six cases of radiation-induced organizing pneumoniti s occurring outside the direct radiation field and to review clinical, radi ologic, and histologic aspects of this entity. Material and Methods: We present detailed case reports of six women, with a mean age of 62.8 years (range, 50 to 75), who had received radiation thera py (mean dose, 6,560 cGy) for breast cancer. Results: From 6 to 17 months (mean, 8.8) after the completion of radiothera py, recurrent and migrating lung infiltrates were detected outside the radi ation field in the six study patients. Three patients had pronounced respir atory symptoms, whereas the rest were minimally symptomatic or asymptomatic . Thoracic computed tomography showed dense alveolar infiltrates. Bronchoal veolar lavage in two patients revealed lymphocytosis (25% and 19%), and lun g biopsy in five patients demonstrated a histologic pattern consistent with bronchiolitis obliterans organizing pneumonia. Even though the symptomatic patients showed prompt resolution of their symptoms and roentgenographic a bnormalities after systemic corticosteroid therapy, the lung infiltrates re curred after corticosteroid therapy was discontinued. Conclusion: These six cases, including their prompt response to corticoster oid therapy, provide additional evidence that irradiation damages lung tiss ue outside of the direct treatment field and suggest that an immunologicall y mediated lymphocytic alveolitis may be responsible for the recurrent migr atory organizing pneumonitis.