Liquid nitrogen spray cryotherapy (SCT) in central airway disease: a multicenter prospective registry

Spray cryotherapy (SCT) has been used as a bronchoscopic tool within the large airways for over a decade. SCT is unique in its non-contact method of flash freezing (up to -196 ℃) tissue versus a contact cryoprobe (up to -50 ℃). Techniques for venting nitrogen gas formed from liquid nitrogen during SCT are essential for safe use. Prospective data on SCT in bronchoscopy are lacking. The objective of this study was to evaluate the safety, dosimetry, and clinical outcomes of the trūFreeze SCT system in a prospective multicenter registry of patients with benign and malignant central airway disease.

This was a prospective observational registry of patients undergoing SCT enrolled at 4 participating institutions for up to 5-year follow-up (2013-2021). Data focusing on patient safety, diseases treated, dosimetry and selected efficacy measures were collected in a standardized electronic report form and central database.

A total of 64 patients (47 with malignant disease and 17 with benign disease) were enrolled in the registry. A total of 114 SCT procedures were performed and 472 SCT freeze/thaw cycles delivered. The median observed follow-up for the malignant cohort was 520 days [interquartile range (IQR), 153-1,818 days]. The median observed follow-up for the benign cohort was 1,803 days (IQR, 1,769-1,832 days). Malignant disease included 14 different cancer types. Subglottic stenosis was the most common benign disease treated and only 3 patients needed more than 2 serial SCT treatments. SCT was used to treat endobronchial bleeding in 30% of cases, with complete success reported in 91%. Adverse events included one death which was unrelated to SCT and one small asymptomatic pneumothorax which did not require a chest tube.

SCT can be safely used within the central airways, adding the unique capability of delivering flash-freezing temperatures to tissue. This approach shows potential utility in treatment strategies for a wide range of benign and malignant conditions, though further controlled studies would better define these roles.