High-Resolution CT Findings in Fibrotic Idiopathic Interstitial Pneumonias With Little Honeycombing: Serial Changes and Prognostic Implications

OBJECTIVE. This retrospective study evaluates serial changes of lung abnormalities on high-resolution CT (HRCT) and clarifies prognostic determinants among CT findings in fibrotic idiopathic interstitial pneumonias (IIPs) with little honeycombing. MATERIALS AND METHODS. We enrolled 154 patients with a histologic diagnosis of a fibrotic IIP (< 5% honeycombing on CT) who were followed clinically for at least 2 years. One hundred one patients had usual interstitial pneumonia (UIP) and 53 had fibrotic nonspecific interstitial pneumonia (NSIP). On baseline CT, the extent and distribution of lung abnormalities were visually assessed, and serial CT scans were evaluated with a follow-up period of at least 6 months (n = 132). RESULTS. Significant differences were noted in the extent of reticulation and ground-glass opacification (GGO) between the UIP and fibrotic NSIP groups (p < 0.001). On serial scans, honeycombing (5% in UIP and 3% in fibrotic NSIP; p = 0.08) and reticulation (3% in UIP and 8% in fibrotic NSIP; p = 0.03) progressed in extent and GGO (-2% in UIP and -10% in fibrotic NSIP; p = 0.009) decreased in extent. Overall extent of lesions increased in UIP (6%) and decreased in NSIP (-4%) (p = 0.04). On univariate and multivariate Cox proportional hazards analysis, the overall extent of parenchymal abnormalities was a prognostic factor predictive of poor survival duration. CONCLUSION. Even in cases of fibrotic IIP with little honeycombing, serial CT reveals an increase in the extent of honeycombing and reticulation and a decrease in extent of GGO. Overall extent of lung fibrosis on the baseline CT examination appears predictive of survival in fibrotic IIP with little honeycombing.