Development and validation of a risk nomogram predicting pneumothorax requiring chest tube placement post-percutaneous CT-guided lung biopsy

Abstract

Background: Pneumothorax requiring chest tube after CT-guided transthoracic lung biopsy presents added clinical risk and costs to the healthcare system. Identifying high-risk patients can prompt alternative biopsy modes and/or better preparation for more focused post-procedural care. We aimed to develop and externally validate a risk nomogram for pneumothorax requiring chest tube placement following CT-guided lung biopsy, leveraging quantitative emphysema algorithm.

Methods: This two-center retrospective study included patients who underwent CT-guided lung biopsy from between 1994 and 2023. Data from one hospital was set aside for validation (n = 613). Emphysema severity was quantified and categorized to 3-point scale using a previously published algorithm based on 3×3×3 kernels and Hounsfield thresholding, and a risk calculator was developed using forward variable selection and logistic regression. The model was validated using bootstrapping and Harrell's C-index.

Results: 2,512 patients (mean age, 64.47 years ± 13.38 [standard deviation]; 1250 men) were evaluated, of whom 157 (6.7%) experienced pneumothorax complications requiring chest tube placement. After forward variable selection to reduce the covariates to maximize clinical usability, the risk score was developed using age over 60 (OR 1.80 [1.15-2.93]), non-prone patient position (OR 2.48 [1.63-3.75]), and severe emphysema (OR 1.99 [1.35-2.94]). The nomogram showed a mean absolute error of 0.5% in calibration and Harrell's C-index of 0.664 in discrimination in the internal cohort.

Conclusion: The developed nomogram predicts age over 60, non-prone position during biopsy, and severe emphysema to be most predictive of pneumothorax requiring chest tube placement following CT-guided lung biopsy.

Keywords: Image-guided biopsy; Lung neoplasms; Pneumothorax.

Fig. 1

Flow diagram shows patients who underwent CT-guided transthoracic lung biopsy procedures. AIC = Akaike information criterion

Fig. 2

ROC Analysis shows curves for both training and validation datasets, with the validation curve being higher than the training curve

Fig. 3

Screenshot from risk calculator website showing nomogram and risk calculator, with an example prediction. Website is publicly available at https://bit.ly/3n9Yu38

Fig. 4

Example cases. CT scans from CT-guided transthoracic lung biopsy in two patients. Biopsy needle (white arrow) and the nodule biopsied (black arrow) are shown. A) Patient is a male in their 40s presenting with no emphysema (as determined by quantitative emphysema algorithm), lying in the prone position, with a nodule in the left lower lobe. Our risk nomogram and calculator predicted this patient to have low risk of pneumothorax requiring chest tube (1.86% [1.13% - 3.13%]). The patient post biopsy had a tiny pneumothorax and did not need chest tube placement. B) Patient is a male in their 60s with severe emphysema (as determined by quantitative emphysema algorithm), lying in the supine position, and with a nodule in the right middle lobe. Our risk nomogram and calculator predicted this patient to have high risk (14.70% [10.90% - 19.50%]). The patient developed intraprocedural pneumothorax (red arrow) which grew into a large pneumothorax and chest pain necessitating a chest tube placement