An Explorative Analysis on Cryo-passes and Freezing Time in Endobronchial Ultrasound-Guided Transbronchial Mediastinal Cryobiopsy

<bold>Introduction</bold> EBUS guided-transbronchial mediastinal cryobiopsy (TBMC) has emerged as a promising biopsy tool in uncommon malignancies and benign disorders. Nevertheless, several fundamental technical aspects of TBMC remain unexplored and unstandardized. <bold>Methods:</bold> This multicentre retrospective review aimed to explore the number of cryo-passes and the optimal freezing time of TBMC. <bold>Results:</bold> During the study period, EBUS-TBMC approach was attempted in 137 patients, eventually completed in 129, demonstrating an overall technical feasibility of 94.2% (129/137 cases). The overall diagnostic yield was higher for TBMC at 88.4%, compared to 53% for TBNA. TBMC is more sensitive than TBNA in identifying uncommon tumours and benign disorders (82.9% vs. 48.8%, p<0.01). The overall median total aggregate specimen diameter of TBMC was 7.0 (IQR 5.0-9.5) mm, showing a positive correlation to diagnostic yield that plateaued at 4.1-6.0 mm. The median number of TBMC cryo-passes correlated positively with diagnostic yield which plateaued after 2-3 passes. No significant correlation or difference was observed concerning various freezing time thresholds. The safety profile of TBMC was favourable, with 1 case (0.8%) of pneumothorax and 9 cases (7%) of self-limiting bleeding. <bold>Conclusion:</bold> Optimizing TBMC performance with 2-3 cryo-passes and a 4-second freezing time to achieve a total aggregate specimen size of 6mm or more seems to be sufficient in our cohort. Further prospective studies are needed to validate these findings.