Risk prediction of pneumothorax in lung malignancy patients treated with percutaneous microwave ablation: development of nomogram model.

OBJECTIVES To develop effective nomograms for predicting pneumothorax and delayed pneumothorax after microwave ablation (MWA) in lung malignancy (LM) patients. METHODS LM patients treated with MWA were randomly allocated to a training or validation cohort at a ratio of 7:3. The predictors of pneumothorax identified by univariate and multivariate analyses in the training cohort were used to develop a predictive nomogram. The C-statistic was used to evaluate predictive accuracy in both cohorts. A second nomogram for predicting delayed pneumothorax was developed and validated using identical methods. RESULTS A total of 552 patients (training cohort: n = 402; validation cohort: n = 150) were included; of these patients, 27.9% (154/552) developed pneumothorax, with immediate and delayed pneumothorax occurring in 18.8% (104/552) and 9.1% (50/552), respectively. The predictors selected for the nomogram of pneumothorax were emphysema (hazard ratio [HR], 6.543; p < .001), history of lung ablation (HR, 7.841; p= .025), number of pleural punctures (HR, 1.416; p < .050), ablation zone encompassing pleura (HR, 10.225; p < .001) and pulmonary fissure traversed by needle (HR, 10.776; p < .001). The C-statistics showed good predictive performance in the training and validation cohorts (0.792 and 0.832, respectively). Another nomogram for delayed pneumothorax was developed based on emphysema (HR, 2.952; p= .005), ablation zone encompassing pleura (HR, 4.915; p < .001) and pulmonary fissure traversed by needle (HR, 4.348; p = .015). The C-statistics showed good predictive performance in the training cohort, and it had efficacy for prediction in the validation cohort (0.719 and 0.689, respectively). CONCLUSIONS The nomograms could effectively predict the risk of pneumothorax and delayed pneumothorax after MWA.