The incidence and clinical characteristics of bronchiolitis obliterans organizing pneumonia syndrome after radiation therapy for breast cancer

STUDY OBJECTIVE: Bronchiolitis obliterans organizing pneumonia (BOOP) syndrome after adjuvant radiation therapy for breast cancer has been recently recognized. However, the precise incidence of this syndrome remains to be determined. The aim of this study was to clarify the incidence and clinical characteristics of radiation-induced BOOP syndrome. METHODS: We conducted a retrospective analysis of 206 consecutive patients wit breast cancer undergoing tangential-field radiation therapy at our institution from 1992 to 2002. RESULTS: Among the patients, five (2.4%) developed BOOP syndrome. These five patients began with flu-like symptoms 2-7 months after the completion of radiation therapy. Four of them had received tamoxifen, an estrogen receptor antagonist, and the other one underwent cytotoxic chemotherapy. Their chest radiographs revealed peripheral alveolar opacities with migration outside the irradiated fields. Increased lymphocyte counts and elevated CD4/CD8 ratios were observed in the bronchoalveolar lavage fluid. Transbronchial biopsy revealed organizing pneumonia. The serum levels of KL-6, a marker of interstitial pneumonia, did not increase in any patients. Treatment with corticosteroids resulted in a rapid improvement, but two patients relapsed after the cessation of corticosteroids. CONCLUSIONS: These results suggest that BOOP syndrome after tangential-field radiation therapy for breast cancer is not rare and more attention should be directed to this condition as a radiation-induced pulmonary toxicity.