Feasibility of Radial Endobronchial Ultrasound-Guided Bronchoscopic Cryobiopsy without Fluoroscopy for Lung Parenchymal Lesions

Background Cryobiopsy is used to biopsy peripheral lung lesions through flexible bronchoscopy with fluoroscopic guidance. However, fluoroscopy is not available at some institutions. This study evaluated the feasibility of radial endobronchial ultrasound-guided bronchoscopic cryobiopsy without fluoroscopy. Methods This retrospective study was conducted at Chang Gung Memorial Hospital, Linkou branch, in Taiwan. This study enrolled patients who received bronchoscopy examinations with cryotechnology between July 2014 and June 2016. The data were collected through medical chart review. Results During the study period, 101 patients underwent bronchoscopy examinations with cryotechnology. Ninety patients with endobronchial tumors were excluded from this study. Eleven patients who underwent radial endobronchial ultrasound-guided bronchoscopic cryobiopsy for lung parenchymal lesions were enrolled into this study. The mean age was 61.1 ± 13.8 years. Five patients were men, and the other six were women. The number of cryobiopsies ranged from 1 to 3. In the histological biopsies, the mean specimen diameter was 0.53 ± 0.23 cm, and the mean biopsy area was 0.20 ± 0.19 cm2. Nine of 11 patients had pathological diagnoses. No complications, including pneumothorax, respiratory failure, or major bleeding, were recorded after the procedure. Conclusions Endobronchial ultrasound is used to ensure biopsy location, and endobronchial ultrasound-guided cryobiopsy is a feasible technique to biopsy peripheral lung lesions in selected cases at institutions without fluoroscopy equipment. This study provided some rationale for further studies examining the impact of fluoroscopy.


Introduction
Cryotherapy is an evolving therapeutic and diagnostic tool used in bronchoscopy [1]. Conventional forceps transbronchial biopsy (TBB) obtains a relatively small amount of alveolar tissue, and the specimen has more artifacts in the alveolar part [2]. Cryobiopsy has been recommended for diagnosing parenchymal lung diseases, including di use and peripheral lung lesions, because of its safety and high diagnostic yield rate [3,4]. Studies have demonstrated that cryoprobe biopsy is an acceptable and useful technique for endobronchial mass diagnosis [5,6]. Two recent systematic reviews have shown that cryotechnology in bronchoscopy is useful for the diagnosis of lung diseases, including interstitial lung diseases and lung tumors [7,8]. A recent prospective, randomized, controlled, multicenter trial revealed a higher diagnostic yield for endobronchial cryobiopsy than for forceps biopsy [9]. For pulmonologists, the cryoprobe is a useful tool during exible bronchoscopy examination. e literature review revealed that uoroscopic guidance was used in bronchoscopic cryobiopsy [3,[10][11][12][13][14][15][16]. However, the uoroscopy equipment for bronchoscopy examination is not available at some institutions. During bronchoscopy examination, radial endobronchial ultrasonography (EBUS) is used to localize peripheral lung lesions, and the echoic feature can o er additional information on the structure of the lung lesions [17,18]. To the best of our knowledge, the reports of cryobiopsy for peripheral lung lesions during exible bronchoscopy are few. is retrospective study evaluated the feasibility of endobronchial ultrasound-guided cryobiopsy without uoroscopy.

Patients.
is retrospective study was performed at Chang Gung Memorial Hospital, Linkou branch, a tertiary referral medical center in Taiwan. is study enrolled patients aged more than 20 years who received bronchoscopy examinations with cryotechnology between July 2014 and June 2016, and their data were collected through medical chart review. Patients with endobronchial mass who received cryotherapy through exible bronchoscope were excluded. e clinical data of the study patients, including age, sex, pathological diagnosis, specimen size, procedurerelated complications (i.e., pneumothorax, major bleeding, or respiratory failure), and outcomes, were retrospectively reviewed and analyzed.

Procedure and Equipment.
Bronchoscopy was performed using a exible bronchoscope (BF-P240 or BF-40; Olympus, Tokyo, Japan), and during the procedure, patients received local anesthesia with 2% xylocaine. A 20 MHz miniature radial probe (UM-S20-S20R; Olympus) and an ultrasound unit (Endoscopic Ultrasound System, Olympus) were also used. All patients underwent chest computed tomography (CT) before the bronchoscopy procedure, and the radial EBUS probe was inserted into the target segmental bronchus determined by the bronchoscopists. e echoic features of the peripheral parenchymal lesions were recorded [19]. Patients received conscious sedation with midazolam or propofol infusion under bispectral index for consciousness monitoring [20]. e heart rate, blood pressure, and oxygen saturation were continuously monitored during the bronchoscopy procedure.

Cryobiopsy Procedure.
Cryobiopsy was performed using a 1.9 mm exible cryoprobe (Erbokryo CA, Erbe, Germany) with carbon dioxide as the cryogen. A temperature of approximately −70°C was achieved at the probe tip. e biopsy sites were determined by the bronchoscopists according to the CT and EBUS ndings. e probe cooling time was approximately 4-6 seconds. After cooling, the cryoprobe was immediately retracted using the bronchoscope. e frozen biopsy specimens were then thawed in normal saline and xed in formalin. e bronchoscope was reintroduced to con rm airway status [5]. e size and diagnosis of the specimens were assessed by adequately experienced pathologists.

Statistical Analyses.
Continuous variables are expressed as the mean ± standard deviation and categorical variables as the frequency and percentage. All statistical analyses were performed using MedCalc, version 12.5 (MedCalc Software, Ostend, Belgium). Two-tailed p values less than 0.05 were considered statistically signi cant.

Results
During the study period, 101 patients underwent bronchoscopy examinations with cryotechnology. Ninety patients with endobronchial tumors were excluded from this study. us, this study included 11 patients with a mean age of 61.1 ± 13.8 years (Table 1). Five (45%) patients were men, and the other 6 were women. Six patients received bronchoscopy examination for di use interstitial lung disease, and the other ve were for peripheral parenchymal lesions, respectively (Figures 1 and 2). Forceps biopsies were not applied simultaneously during the procedure. e six patients with di use interstitial lung disease received bronchoalveolar lavage. e other ve patients with peripheral parenchymal lesions also received bronchial washing, and malignant cytology results were found in two cases. All the eleven patients did not receive endotracheal tube intubation during and after the procedure. e number of cryobiopsies ranged from 1 to 3. In the histological biopsies, the mean specimen diameter was 0.53 ± 0.23 cm, and the mean biopsy area was 0.20 ± 0.19 cm 2 . Two patients had no histopathological diagnosis (negative for malignancy), and the other nine patients had pathological diagnoses. e biopsy sites and pathological diagnoses are provided in Table 2. e two patients with negative for malignancy had lung tissue described in the histology report. But the patient with chronic in ammation had only bronchial mucosa with lymphocytic in ltrates in the histology report. No major complications, including pneumothorax, respiratory failure, admission to the intensive care unit, or major bleeding with the need for further e nal diagnosis of interstitial lung disease was made by the clinical physicians individually according to the clinical data, radiologic study, biopsy results, and follow-up data. e nal diagnoses of the six patients with interstitial lung disease were two idiopathic pulmonary brosis, two nonspeci c interstitial pneumonia, one sarcoidosis, and one undiagnosed. One of the two patients with pathological negative for malignancy was diagnosed with non-small cell lung cancer by CT-guided biopsy, and the other one remained undiagnosed because the patient did not receive a further examination and did not return to our hospital for follow-up.

Discussion
Few studies have used radial EBUS-guided cryobiopsy without uoroscopy for peripheral lesions. An important nding of our study is that radial EBUS-guided cryobiopsy is useful to biopsy peripheral lung lesions at institutions without uoroscopy equipment. e biopsy specimen retrieved was adequate, and no major complications were noted.
Cryotechnology is useful and safe for diagnosing and treating central airway lesions [21]. Fluoroscopy is useful for identifying peripheral lung lesions during the bronchoscopy procedure [22]. Fluoroscopy also ensures that the bronchoscope does not contact the visceral pleura, thus preventing the development of iatrogenic pneumothorax. In   [23]. Fluoroscopy is recommended to reduce the complications. However, uoroscopy is not always available at many institutions. erefore, radial EBUS is useful to biopsy peripheral lesions, instead of uoroscopic guidance [24]. Although radial EBUS-guided transbronchial forceps biopsy without radiographic uoroscopy is e ective for the diagnosis of peripheral lung lesions [25], bronchoscopists are concerned about the complications of cryobiopsies, because of the large size of the specimen retrieved. To prevent pneumothorax development, some researchers have suggested that the cryoprobe should be withdrawn approximately 1 cm during cryobiopsy for di use lung disease. In our study, radial EBUS was used to localize peripheral lung lesions. If the radial probe reached the distal lung lesion, we could use the echoic feature to decide the optimal biopsy site. In di use lung disease, we could also avoid biopsy when the EBUS echoic feature showed prominent vessels. To select biopsy site by bronchoscopists is relatively subjective. Kropski and his colleagues suggested taking biopsies from the dependent part of the lungs in concern of bleeding risk [12]. e procedure of cryobiopsy through a exible bronchoscope varies across studies, and the cooling time and the cryoprobe size have not been standardized [26]. In this study, a 1.9 mm cryoprobe was used, and the specimen size is similar to that described in the literature but is larger than the forceps biopsy specimen size [3]. A previous study suggested that two cryobiopsies are optimal for endobronchial tumors [27], but the optimal number of cryobiopsies for peripheral lesions has not been determined. Recently, important issues regarding safety and standardization of transbronchial cryobiopsies were addressed [23,28]. e complications, including serious bleeding, iatrogenic pneumothorax, and respiratory failure, were reported. DiBardino et al. reported major bleeding in three patients, all of whom had undergone cryobiopsy without uoroscopy [23]. ere were no severe or life-threatening complications in our study. e possible explanations may be that our procedure was relatively conservative (using a 1.9 mm cryoprobe, taking biopsies in single lobe with few number of biopsies). Besides, all the patients had radial EBUS guided. Safety remains the major concern of the cryobiopsy procedure, and bronchoscopists should do a complete preprocedural evaluation, perform the procedure meticulously, and use all the available facilities, including uoroscopy, at their hospitals. To optimize and standardize the transbronchial cryobiopsy procedure is also important for further studies. e diagnostic yield rate of transbronchial biopsy is in uenced by several factors, including lesion size, lesion location, bronchus sign, rapid on-site evaluation, prevalence of disease in the patient cohort, or navigation systems [25,[29][30][31]. e radial EBUS probe can easily access lesions close to the bronchial wall. In this study, patients did not receive surgical biopsy nally, and a multidisciplinary team did not decide the diagnosis of interstitial lung disease. e nal diagnosis and treatment were decided by clinical physicians individually according to the imaging study and biopsy results. A systematic review showed a high diagnostic yield for transbronchial lung cryobiopsy when histopathology was combined with multidisciplinary discussion [32]. Recent studies have also shown that cryobiopsy is useful when interstitial lung disease is diagnosed through multidisciplinary discussion [33,34].
Our study has several limitations. First, this study was conducted in a single tertiary referral medical center; thus, the generalizability of the ndings may be limited. Bronchoscopists have a high level of experience for interventional bronchoscopy, including cryotechnology and transbronchial biopsy. Second, the study was retrospective, and the inclusion of patients receiving bronchoscopic cryobiopsy might be highly selective. We had no standard procedure protocol for patient selection. ird, the sample size was small, because transbronchial cryobiopsy was an alternative method to surgical biopsy for diagnosis of interstitial lung disease.

Conclusion
EBUS-guided cryobiopsy is a feasible technique to biopsy peripheral lung parenchymal lesions in selected cases to obtain a large specimen at institutions without uoroscopy equipment. is study provided some rationale for further studies examining the impact of uoroscopy.

Ethical Approval
is study was conducted in accordance with the amended Declaration of Helsinki.
is study was approved by the institutional review boards at Chang Gung Medical Foundation (IRB no. 201600902B0). All individual information was delinked.

Conflicts of Interest
e authors declare that they have no con icts of interest.