Our patient was on long term moderate doses of prednisone and azathioprine throughout the radiation treatment. Despite being on two immunosuppressive medications, both BOOP and classic radiation pneumonitis developed with clinical deterioration. Both prednisone and azathioprine have been used as treatment for radiation pneumonitis , but there are no published studies assessing the effectiveness of corticosteroids or azathioprine as prophylaxis against radiation-induced pneumonitis.Rats treated with steroids after radiotherapy show suppression of alveolitis provided steroids are used throughout the period of radiation; tissue mast cell response to radiation is also delayed, but the development of fibrosis is not altered . In humans, however, as our case demonstrates that moderate doses of corticosteri-ods and azathiorprine are not effective as prophylaxis against either BOOP or classic radiation pneumonitis.

Despite the failure of prednisone and azathioprine to prevent radiation pneumonitis and BOOP, a higher dosage of prednisone at 1 mg/kg/day did result in significant clinical improvement and resolution of chest x-ray abnormalities. This suggests that BOOP resulting from radiation therapy is comparable with BOOP caused by other etiologies and that it can be treated with high dose corticosteroids. Prompt recognition and correct diagnosis is, therefore, crucial for early treatment and prevention of disease progression.