This was a retrospective cohort study conducted at a single centre. This study included patients with suspected malignant peripheral lung lesions who underwent bronchoscopy at our hospital from October 2013 to March 2020.
Patients who had undergone multiple bronchoscopies were excluded from the study. In addition, patients who received diagnoses other than primary lung cancer were excluded.
Bronchoscopy and sedation
At our hospital, CT was performed at a thickness of 1.0 or 1.25 mm, and a VBN image was created on the basis of the CT data using LungPoint (Broncus Medical Inc., Mountain View, CA, USA) (6). All bronchoscopy procedures were performed using VBN by LungPoint and EBUS-GS. In all patients, we performed radial EBUS using an endoscopic ultrasound system (EU-ME1; Olympus, Tokyo, Japan) equipped with 20-MHz mechanical radial-type probes that were 1.4 (UM-S20-17S; Olympus) or 1.7 mm (UMS20-20R; Olympus) in diameter. A thin bronchoscope (channel diameter, 2.0 mm; BF-P290 or BF-P260; Olympus) and GS (external diameter, 1.95 mm; K-201; Olympus) were used for the 1.4-mm probe, whereas a thicker bronchoscope (channel diameter, 2.9 mm BF-1T290 or BF-1T260; Olympus) and GS (external diameter, 2.55 mm; K-203; Olympus) were used for the 1.7-mm probe. The appropriate probes and bronchoscopes were selected by the operator (a respiratory specialist).
After brushing cytology and transbronchial aspiration cytology (TBAC) of the lesion, one cytological specimen was evaluated by rapid onsite cytology. After cytology specimen collection, biopsies were taken with forceps under fluoroscopic guidance for histopathological examination. Biopsies were repeated until specimens of adequate number and size were collected. The procedures followed those of Kitamura et al. (7).
All procedures were performed under local anaesthesia and sedation with intravenous midazolam and pethidine.
At a different time than the actual bronchoscopy procedures, we compared the associations of the distance by VBN using VINCENT with the diagnosis rate of primary lung cancer and clinical factors. In addition, one observer (A.K., respiratory specialist) read the CT image and assessed the presence of the CT bronchus sign based on the location of the nearest branch and the lesion (2). Clinical factors included age, gender, lesion diameter, lesion structure, presence of the CT bronchus sign, EBUS-GS image (within, adjacent to, invisible) and pathological diagnosis. The lesion structure was classified as ground-glass nodule (GGN) or solid lesion, and solid lesions included cavities, consolidation and nodules.
Follow-up and statistical analysis
For lesions that could not be diagnosed by bronchoscopy, pathological specimens were obtained (to the extent possible) using other diagnostic methods such as surgery, EBUS-guided transbronchial needle aspiration or endoscopic ultrasound-fine needle aspiration. Cases for which pathological specimens could not be obtained were diagnosed after at least 1.5 years of follow-up by both a radiologist and respiratory specialist.
The chi-squared test was used for univariate analysis, and logistic regression analysis was used for multivariate analysis. P < 0.05 was regarded as statistically significant. All statistical analyses were conducted using R version 3.6.2, which was also used to draw the prediction graph. The prediction graph was created by randomly selecting 80% of the total patients for analysis. The area under the receiver operating characteristic curve (AUC) of the prediction graph was generated and evaluated in the remaining 20% of patients.
This study was approved by the Ethics Committee of St. Luke’s International Hospital (18-R177) on February 27, 2019.