Purpose: Breast-conserving surgery and postoperative radiotherapy have played important roles in the treatment of early breast cancer. Bronchiolitis obliterans organizing pneumonia (BOOP) syndrome has recently been reported to be one of the complications of adjuvant radiotherapy. The purpose of this study was to determine the incidence of and risk factors for BOOP syndrome in breast cancer patients.
Methods and materials: Between January 1996 and December 1998, 157 patients with breast cancer underwent radiotherapy after breast-conserving surgery. The criteria used for the diagnosis of BOOP syndrome were as follows: 1) radiation therapy to the breast within 12 months, 2) general and/or respiratory symptoms lasting for at least 2 weeks, 3) radiographic lung infiltrates outside the radiation port, and 4) no evidence of a specific cause.
Results: BOOP syndrome developed in 4 (2.5%) patients, who had fever and nonproductive cough, with patchy infiltrative shadows on chest roentgenograms which emerged between 5 and 6 months after radiotherapy. The symptoms and pulmonary infiltrates were rapidly improved by treatment with prednisone (40 mg/day), which was tapered over 2- to 5-month periods. However, BOOP syndrome relapsed in all cases during the tapering period or after withdrawal of prednisone. The eosinophil and neutrophil counts were increased and the ratios of CD4+ to CD8+ lymphocytes were elevated in bronchoalveolar lavage fluid in all four cases. There were no differences in proportions of patients by age, irradiated breast site, use of tamoxifen and/or chemotherapy, or radiation dose between those with and without BOOP syndrome.
Conclusions: BOOP syndrome is considered an intractable form of lung toxicity after radiotherapy to the breast. An immunologic reaction mediated by eosinophils, neutrophils, and lymphocytes may be responsible for the development of this syndrome. Methods of prevention of BOOP syndrome should be established.