Although corticosteroid and cytotoxic agent such as cyclophosphamide have been used for the treatment of idiopathic interstitial pneumonia (IIP), efficacy of these toxic drugs are unclear because previous reports included the patients who did not undergo surgical lung biopsy and none evaluated the response according to histopathologic entities of IIP. To answer this, we retrospectively analyzed the treatment response and side effects of corticosteroids and cyclophosphamide therapy in patients with idiopathic UIP and NSIP.

Among 61 patients with UIP and 26 patients with NSIP diagnosed by surgical lung biopsy at Samsung Medical Center from July 1996 to June 2002, those who received corticosteroid or cyclophosphamide therapy for at least 6 months and were followed for at least one year after the initiation of treatment were enrolled (32 UIP, 23 NSIP). Treatment response of 55 patients was assessed by ATS response criteria (clinical symptoms, pulmonary function test and radiological findings).Adverse reactions to either agent (42 cases of cyclophosphamide±low-dose prednisolone, 49 cases of prednisolone alone) were also analyzed.

Irrespective of treatment regimen, NSIP showed more favorable response than UIP (6 months: 78.3% vs. 9.4%, 12 months: 69.6% vs. 9.4%, p<0.001). Cyclophosphamide showed comparable response to corticosteroid in NSIP while its efficacy was as poor as those of corticosteroid therapy in UIP. Significant adverse reaction to drug more frequently occurred in corticosteroid group (35.7%) than cyclophosphamide group (14.3%) (p=0.017).

Cyclophosphamide is effective and more tolerable than corticosteroids in the treatment of idiopathic nonspecific interstitial pneumonia.