Characteristics, prognosis, and risk factors for relapse in patients with cryptogenic organizing pneumonia: A prospective cohort study in China.

Abstract

Background: Cryptogenic organizing pneumonia (COP) is classified as a subtype of idiopathic interstitial pneumonia (IIP), which has a good prognosis. Relapse remains one of the most challenging and intriguing aspects of COP. This study aimed to characterize the clinical features, prognosis, and relapse patterns of COP.

Methods: In this prospective cohort study, patients diagnosed with COP between March 1, 2004 and June 30, 2022 at China-Japan Friendship Hospital and Beijing Chao-Yang Hospital were enrolled after a comprehensive multidisciplinary review. Patients were followed up through regular clinical visits every 3-6 months until October 30, 2023. Data collected included demographic characteristics, clinical presentation, laboratory findings, radiologic features, and prognostic outcomes. The primary outcome measure was relapse. Cox regression analyses were performed to explore factors related to the presence of relapse.

Results: This study included 268 patients with a final diagnosis of COP based on multidisciplinary discussion. After diagnosis, the one-year survival rate was 99.6%, decreasing to 97.7% at 3 years, 94.5% at 5 years, and 81.7% at 10 years. Relapses occurred in 20.9% (56/268) of patients, with a median time to relapse of 12 months. Of these relapses, 28.6% (16/56) occurred when prednisone was tapered to below 10 mg/day, and 62.5% (35/56) occurred after discontinuation of prednisone therapy; fewer than 10% of relapses occurred at prednisone doses above 15 mg/day. Ground-glass opacities (GGOs) (225/268, 84.0%) and consolidations (212/268, 79.1%), predominantly with bilateral lung distribution, were the most common computed tomography (CT) features at diagnosis. No patient developed residual lung fibrosis on high-resolution CT, regardless of relapse status. Furthermore, no deaths were attributable to COP progression or relapse, and all-cause mortality was unrelated to COP itself.

Conclusion: This study indicated that patients with COP had a good prognosis with favorable survival outcomes. However, relapse was relatively common, occurring in more than 20% of patients. Therefore, close follow-up is essential for early detection of relapses, particularly during corticosteroid tapering or after treatment discontinuation.