Characteristic chest CT findings for progressive cavities in Mycobacterium avium complex pulmonary disease: a retrospective cohort study

Background Although cavities are an important finding in Mycobacterium avium complex pulmonary disease (MAC-PD), there is little information regarding the types of cavities that indicate disease progression. This study was performed to identify cavity characteristics that were associated with disease progression in patients with MAC-PD. Methods This retrospective cohort study included 97 patients presenting with MAC-PD with cavities between December 2006 and June 2016. We compared initial and final computed tomography (CT) findings, classified 52 and 45 patients in the progressive and non-progressive cavity groups, respectively, and examined the progression-related imaging features in initial CT images. A progressive cavity was defined by more than two-fold increase in internal diameter or emergence of a new cavity around the initial cavity. Results Patients in the progressive group were older ( p < 0.001), had a lower body mass index ( p = 0.043), and showed higher diabetes complication rates ( p = 0.005). The initial CT in the progressive group showed a longer maximum internal diameter of the cavity ( p < 0.001) and higher rates of cavities close to the chest wall ( p < 0.001), multiple cavities ( p = 0.023), consolidation around the cavity ( p < 0.001), atelectasis ( p = 0.011), and pleural thickening ( p < 0.001). Multivariable logistic regression analysis revealed that the maximum internal diameter of the cavity (odds ratio [OR]: 1.11, 95% confidence interval [CI]: 1.02–1.21; p =0.012) and consolidation around the cavity (OR: 16.15, 95% CI: 4.05–64.46; p < 0.001) were significantly associated with progressive cavities. In cavities with a maximum internal diameter of ≥10 mm and simultaneous consolidation, the probability of progression was as high as 96.2%. The 10-year mortality rates in the progressive and non-progressive cavity groups were 46.7 and 9.8% ( p < 0.001), respectively, while the 10-year respiratory failure rates were 28.1 and 0%, respectively ( p < 0.001). Conclusions Large cavity size and consolidation on CT showed strong relationships with disease progression, which led to respiratory failure and high mortality rate.