Efficacy and safety of oral versus intravenous cyclophosphamide in treatment of connective tissue disease‐related interstitial lung disease

Abstract Objective Interstitial lung disease (ILD) resulting from connective tissue disease (CTD) greatly undermines people's health. Cyclophosphamide (CYC) is a widely used agent in treating CTD‐ILD. We compared the efficacy and safety of oral and intravenous CYC in CTD‐ILD treatment. Methods The retrospectively enrolled CTD‐ILD patients were divided into the oral and intravenous CYC groups. The chest high‐resolution computed tomography examination, forced vital capacity (FVC), lung carbon monoxide diffusion capacity (Dlco) determinations, and 6 min walk test (6MWT) were performed pre‐treatment and at the 3rd, 6th, and 12th months posttreatment. Radiographic ILD severity was assessed using the Warrick score. Krebs Von den Lungen‐6, surfactant protein A (SP‐A), SP‐D, and erythrocyte sedimentation rate (ESR) before and at the 12th month post‐treatment were determined. CYC cumulative dose and occurrence of adverse reactions during treatment were recorded. Results CYC cumulative dose in the intravenous CYC group was reduced. Compared with oral CYC treatment, intravenous CYC caused decreased Warrick score and increased FVC and 6MWT at the 6th month, and elevated DLco at the 3rd and 6th months posttreatment. SP‐A, SP‐D and ESR levels in both groups were reduced 12 months posttreatment, with a more evident decrease in the intravenous CYC group. Intravenous CYC had lower total adverse reaction incidence. Conclusion Compared with oral CYC, intravenous CYC decreases Warrick score and increases FVC and 6MWT at 6 months posttreatment, and reduces SP‐A, SP‐D, and ESR levels after 12 months of treatment, which shows low CYC cumulative dose and adverse reaction incidence in treating CTD‐ILD.