Abstract
Background/Aim: This study aimed to compare the efficacies of cryobiopsy and forceps biopsy for peripheral lung cancer detection. Patients and Methods: A retrospective review of peripheral lung cancer cases between December 2017 and April 2019 was conducted. Forceps biopsy was performed followed by cryobiopsy using a guide sheath (GS). Diagnostic yields were compared between cryobiopsy and forceps biopsy. Results: A total of 53 lung cancer lesions were evaluated. The diagnostic yields of forceps biopsy and cryobiopsy were 86.8% and 81.1%, respectively. Univariate and multivariate analyses indicated that cryobiopsy with a GS was significantly associated with increased diagnostic yield (odds ratio(OR)=11.6; p=0.044). Among the four patients who tested positive on cryobiopsy and negative on forceps biopsy, one had diffused pulmonary metastases and the others showed intratumoural air bronchograms. Conclusion: Cryobiopsy using a GS can significantly increase diagnostic yield and help identify lesions with intratumoural air bronchograms and external wall lesions.
Lung cancer is the leading cause of cancer-associated death worldwide. Peripheral lung lesions suspicious for lung cancer are diagnosed with a variety of techniques. According to the guidelines of the American College of Chest Physicians, radial endobronchial ultrasound (R-EBUS)-guided lung biopsy is recommended for increasing the diagnostic yield of peripheral lung nodules (1). For advanced non-small cell lung cancer, immunohistochemical and molecular tests are necessary for determining the appropriate treatment, and large specimens are required. However, the conventional technique of forceps biopsy yields relatively small samples.
Cryobiopsy has been useful for the diagnosis of interstitial lung diseases and endobronchial tumours (2-6), while the efficacy of cryobiopsy for the diagnosis of peripheral lung lesions has been recently reported (7-10), its efficacy compared with forceps biopsy remains unclear. Additionally, further investigation is needed to identify the subset of cases in which cryobiopsy would be the most suitable for detection. Therefore, we analysed the efficacy of cryobiopsy using R-EBUS for peripheral lung cancer, compared to that of forceps biopsy.
Materials and Methods
Study design. We retrospectively reviewed the patient medical records at our Institution using the database of bronchoscopies performed between December 2017 and April 2019. Peripheral pulmonary lesions (PPLs) were defined as bronchoscopically invisible lung lesions; from all patients with PPLs analysed by bronchoscopy during the study period, we included those with a final diagnosis of lung cancer who underwent both cryobiopsy and forceps biopsy. The study protocol was approved by the Medical Research Ethics Committee of Osaka Habikino Medical Center.
Patient selection. Prior to bronchoscopy, patient information and lesion characteristics were examined using the institutional database. Lesion characteristics, including target location, maximum diameter, and presence of the bronchus sign, were evaluated on thin-section (2 mm) chest computed tomography (CT) images by a team of doctors, including board-certified bronchoscopists, pulmonologists, and medical oncologists. When two or more targets were biopsied, the largest target was counted as the target location. Cryobiopsy was not performed in the following situations: 1) large blood vessels around the lesion identified by EBUS; 2) difficulty in cryoprobe approach (lung apex lesion); and 3) excessive bleeding after forceps biopsy. The final decision on whether to perform cryobiopsy was made by the operator.
Bronchoscopy procedure. All bronchoscopies were performed under local anaesthesia with intravenous midazolam and fentanyl for mild sedation. All patients were intubated with an endotracheal tube (8.5 mm Portex® Siliconised PVC, Oral/Nasal Uncuffed Tracheal Tube, Smiths Medical, Tokyo, Japan). A flexible fibre bronchoscope (BF-P290, BF-1TQ290, Olympus, Tokyo, Japan), R-EBUS probe (UM-S20-17S or UM-S20-20R, Olympus, Tokyo, Japan), a guide sheath (GS) kit (1.95 mm SG-200C or 2.55 mm SG-201C, Olympus), and a 1.9 mm cryoprobe (CRYO2; ERBE, Tuebingen, Germany) were used. A 1.95-mm SG-200C was used with BF-P290 (working channel diameter, 2.0 mm) and 2.55 mm SG-201C was used with BF-1TQ290 (working channel diameter, 3.0 mm). Before bronchoscopy, virtual bronchoscopic navigation (VBN; LungPoint, Bronchus China) was used when the target bronchus was small and difficult to trace. We advanced the scope as close as possible to the target lesion after confirming the position in advance with VBN. We inserted the EBUS-GS through the working channel and advanced under fluoroscopic guidance. After confirming the lesion with EBUS images, the probe was removed, keeping the GS in place. EBUS images were categorised into three types: ‘within’, the probe was introduced into a bronchus that was inside the lesion; ‘adjacent to’, the probe was introduced into a bronchus that ran alongside the lesion; and ‘invisible’, the probe was far from the lesion (11). The forceps were inserted into the GS and the biopsy was performed five or six times to obtain histological tissue. Subsequently, cryobiopsy was performed; the sample was frozen with CO2 for 3 seconds and retracted together with the GS and bronchoscope. The frozen biopsy specimen was thawed in saline and placed in formalin to obtain histological tissue. For cases in which the 1.95-mm SG-200C GS was used, the GS was withdrawn, and cryobiopsy was performed without the GS, as the 1.95-mm SG-200C GS was too narrow for insertion of the cryoprobe. Cryobiopsy with the GS was performed when the 2.55-mm SG-201C GS was used. Bleeding was prevented using a 2-scope technique (12). Briefly, after the cryobiopsy was performed, the cryoprobe and bronchoscope were withdrawn and handed to an assistant, and another bronchoscope was rapidly inserted into the airway and wedged at the targeted bronchus. The area of the histological specimen was measured using ImageJ software (National Institutes of Health, Bethesda, MD, USA).
Diagnostic criteria. The final diagnosis was determined based on histological findings. If a diagnosis could not be made by transbronchial biopsy, additional procedures, such as surgery, were performed for confirming the diagnosis. If the lesion revealed no clinical or pathologic findings and decreased in size on follow-up CT after at least 6 months, we regarded it as inflammation.
Statistical analysis. p-Values <0.05 were considered statistically significant. Univariate analyses were performed using the Fisher's exact test for categorical data. Multivariate logistic regression analyses were employed to determine the factors associated with increased cryobiopsy diagnostic yield. All statistical analyses were performed using R software (version 2.13.1; http://www.r-project.org/).
Results
Among 391 PPLs identified during the study period, 239 lesions (61.1%) were diagnosed as malignant. Fifty-three patients (13.6%; 34 male, 19 female) underwent forceps biopsy and cryobiopsy and were included in the study (Figure 1). Median patient age was 75 years (range=41-90 years), and median lesion size was 32 mm (Table I). Approximately half of the lesions were located in the lower lobe, with the other half located in the upper lobe. The positive bronchus sign was seen in the majority of cases (92%). ‘Within’ and ‘adjacent to’ EBUS images were seen in 43 and 9 cases, respectively (n=52). One patient showed a diffuse pulmonary nodule, and transbronchial lung biopsy was performed in the upper and lower lobes; EBUS was not used in this case. The other cases had only one target. In three cases, the transbronchial biopsy results were nondiagnostic, and surgeries were performed to confirm the diagnosis.
Study diagram. PPLs: Peripheral pulmonary lesions.
Baseline characteristics of patients.
Diagnostic yield and sample area. Histological diagnoses and diagnostic yields are shown in Table II. The diagnostic yields of forceps biopsy and cryobiopsy were 86.8% and 81.1%, respectively (p=0.60). The overall yield was 94.3%. Among ‘adjacent’ EBUS images, the diagnostic yields of forceps biopsy and cryobiopsy were 5/9 (55.6%) and 6/9 (66.7%), respectively, and there were no significant differences (p>0.99).
Histological diagnosis and diagnostic yields.
The sample size obtained by cryobiopsy [mean: 14.1 mm2 (range=3.67-40.7 mm2)] was significantly larger than that obtained by forceps biopsy [mean: 2.62 mm2 (range=0.737-10.0 mm2)] (p<0.001).
Factors affecting the diagnostic yield of cryobiopsy are shown in Table III. Univariate analysis indicated that cryobiopsy with GS had a significantly higher diagnostic yield than cryobiopsy without GS (95.8% vs. 69.0%, p=0.015). Multivariate analysis indicated that cryobiopsy with GS and positive bronchus sign were significantly associated with increased diagnostic yield of cryobiopsy (odds ratio (OR), 11.6; p=0.044 and OR, 21.5; p=0.034, respectively).
All seven patients who tested positive on forceps biopsy and negative on cryobiopsy were evaluated using a P290 fibre with the 1.95-mm SG-200C GS, and thus, cryobiopsy was performed without GS in these patients. In one of these seven cases, CT was performed because mild bleeding continued the day after bronchoscopy. This case was included in the ‘within’ category of EBUS images, and the forceps biopsy showed positive results. Cryobiopsy was performed at a site different from the lesion noted on CT, as the cryoprobe could not be inserted at the site where the forceps biopsy was performed (Figure 2). Among the four patients who tested positive on cryobiopsy and negative on forceps biopsy, one showed diffuse pulmonary metastases on CT (Figure 3a). The other patients showed intratumoural air bronchograms or bubble-like lucency (Figure 3b).
Complications. One patient (mentioned above) continued to experience mild bleeding after bronchoscopy, and a lobectomy was performed for the dual purposes of controlling bleeding and treating the underlying cancer. Severe bleeding was not observed in any other case. One patient developed pneumonia. Pneumothorax did not occur in any of the patients.
Factors affecting the diagnostic yield of cryobiopsy.
Discussion
In the present study, no significant differences in diagnostic yield were observed between forceps biopsy and cryobiopsy. However, the diagnostic yield increased significantly when cryobiopsy was performed with GS. Additionally, our study showed that the indication for cryobiopsy should be considered on a case-by-case basis. This is consistent with earlier findings, as a previous study has reported that there were no significant differences in diagnostic yields between forceps biopsy and cryobiopsy with GS (7); however, our study included cases in which cryobiopsy was performed without GS.
All cases that were positive on forceps biopsy and negative on cryobiopsy were performed using the P290 fibre with 1.95-mm SG-200C GS, and therefore, cryobiopsy was performed without GS. It is difficult to introduce the cryoprobe within the lesion when the airway contains multiple branches. As such, there was a possibility that the cryoprobe could not be inserted at the same site at which the forceps biopsy was performed, as observed in one patient (Figure 2).
Chest computed tomography (CT) of the patient (a) before and (b) after cryobiopsy. Forceps biopsy showed positive results and cryobiopsy showed negative results in this case, as the cryoprobe guide sheath (GS) could not be introduced at the site where the forceps biopsy with GS was performed. The cryoprobe was inserted into the right B9biα (black arrow), although the right B9biβ reached the lesion (white arrow). There was infiltration around the biopsy site because of bleeding.
Computed tomography showing a lesion with diffuse pulmonary metastases (a) and a lesion with an intratumoural air bronchogram (b). The forceps biopsy showed negative results and cryobiopsy showed positive results in these cases.
According to the results of the univariate and multivariate analyses, it is clearly preferable to perform cryobiopsy with GS, in terms of reproducibility, by cryoprobe. However, the currently used 1.9-mm cryoprobes cannot be inserted into a 1.95-mm SG-200C GS. If a 1.1-mm cryoprobe were to enter the market, it would allow easier access (13).
A case of diffuse pulmonary metastases was among those that tested positive on cryobiopsy and negative on forceps biopsy. Pulmonary metastasis is hematogenous, and this finding suggests that cryobiopsy is useful for identifying external wall lesions. However, cryobiopsy was not considered to be effective for all external wall lesions because the positive bronchus sign was significantly associated with increased diagnostic yield of cryobiopsy in our results. The other cases that were cryobiopsy-positive and forceps biopsy-negative involved intratumoral air bronchogram or bubble-like lucency, which usually indicate a well-differentiated tumour (14). In these cases, it was difficult to obtain tissue using forceps biopsy because of airspace dilatation due to alveolar collapse within the tumour, and cryobiopsy can be useful in such cases. Although cryobiopsy can also be reportedly useful in cases in the ‘adjacent to’ category of EBUS images (7), our study could not show significantly improved diagnostic yields for cryobiopsy compared to forceps biopsy due to the small sample size in this setting.
The volume of specimen obtained by cryobiopsy was significantly larger than that obtained by forceps biopsy, as in previous reports (7, 15). The sample size of cryobiopsy can provide a high quantity of good quality DNA for use in next-generation sequencing applications (8). Therefore, cryobiopsy is expected to be useful for the diagnosis of lung cancer and subsequent treatment selection. With respect to safety, no clinically significant complications were observed in our study, with the exception of one case involving mild bleeding after surgery. This illustrates that using EBUS to avoid large blood vessels can help decrease bleeding-related complications (16, 17).
Our study had some limitations. First, we retrospectively analysed data from a single institution with a relatively small sample size. Second, we selectively performed cryobiopsy after forceps biopsy, which may have skewed our data towards an increased diagnostic rate for cryobiopsy.
In conclusion, no significant differences in diagnostic yields between cryobiopsy and forceps biopsy were found. However, cryobiopsy with GS can significantly increase diagnostic yield, and cryobiopsy can be effective for identifying lesions with intratumoural air bronchograms and for identifying external wall lesions such as pulmonary metastases. Further prospective, randomised, comparative studies are warranted to expand upon our findings.
Footnotes
Authors' Contributions
Shingo Nasu designed the study, and wrote the initial draft of the manuscript. Shingo Nasu, Norio Okamoto, Hidekazu Suzuki and Takayuki Shiroyama contributed to analysis and interpretation of our data and assisted in the preparation of the manuscript. All other Authors have contributed to the data collection and interpretation and reviewed the manuscript. All Authors approved the version of the manuscript finally and agreed to be accountable for all aspects of the work.
Conflicts of Interest
The Authors have no conflicts of interest in regard to this study.
- Received July 23, 2019.
- Revision received August 5, 2019.
- Accepted August 7, 2019.
- Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved
