Forceps biopsies of airway lesions have variable yields. The yield increases when combining techniques in order to collect more material. With the use of cryotherapy probes (cryobiopsy) larger specimens can be obtained, resulting in an increase in the diagnostic yield. However, the utility and safety of cryobiopsy with all types of lesions, including flat mucosal lesions, is not established.
The traditional approach to the diagnosis of visible endobronchial disease has been through forceps biopsy (FB) via a flexible bronchoscope with a diagnostic yield of 65% [
The use of the cryotherapy probe allows sampling of endobronchial tumors, producing well-preserved tissue, which tends to be of superior quality to that obtained by flexible FB. Recent studies demonstrate that cryobiopsy (CB) samples are devoid of the crush artifact commonly seen in biopsies obtained with traditional forceps [
The putative advantages of performing CB of endobronchial lesions are improved diagnostic yields, reduced operative time, and potentially decreased complications. Additionally, the cryotherapy probe may facilitate the sampling of airway lesions positioned tangentially to the bronchoscope. Such lesions, especially if flat, are difficult to sample with the endobronchial forceps.
Though there is a paucity of data on the subject, a recent study in Europe suggests that the use of cryotherapy probes to sample endobronchial exophytic visible lesions is safe and yields well preserved tissue samples [
An institutional retrospective analysis was performed to all patients that underwent bronchoscopic CB from August of 2008 until August of 2010, either singly or in combination with FB. The study was approved by the “Carilion Clinic Institutional Review Board,” approval number N/A with approval filed by name (safety and benefits of endobronchial cryobiopsy). Only patients (inpatients and outpatients) that received care by a newly established interventional pulmonary service were included, regardless of lesion location, appearance (exophytic versus flat lesions), and diagnoses, including both benign and malignant disease. Both flexible and rigid bronchoscopic procedures were included. All biopsy procedures were performed either directly or supervised by three pulmonologists, two of which were specifically trained and experienced in interventional pulmonology. Both FB and CB were performed in many cases as part of the training of staff and pulmonary fellows in both techniques. The decision to perform CB was at the discretion of the interventional pulmonologist.
CB was performed using the ERBOKRYO CA system (ERBE USA Incorporated Surgical Systems). Two probes were utilized, one of 2.4 mm in diameter and one of a smaller 1.9 mm diameter, the latter allowing its use through the smaller diagnostic bronchoscope. Endobronchial FB was obtained using a Boston Scientific Radial Jaw 3, 2.0 mm single use needleless forceps (Boston Scientific Corporation).
Endobronchial CB is performed in our institution with the following protocol; the cryotherapy probe is placed in direct contact with the lesion that is being sampled, and when approaching exophytic lesions, the probe is frozen for 3 seconds (or until the initiation of the frosting at the tip of the probe is visible). With flat lesions a freezing time of 2 seconds is used (to minimize freezing and remove normal mucosa adjacent to the lesion), and at times the freezing time is extended to 3 seconds based on the observation of the operator. After this short period of freezing, the bronchoscope is removed en bloc with the cryotherapy probe. The sample obtained is placed in 0.9% sodium chloride solution through passive thawing and then placed in 10% formalin. FBs were performed by passing the forceps into the bronchoscope working channel or via the rigid bronchoscope barrel, opening the forceps, advancing the bronchoscope or forceps onto the lesion, closing the forceps thus grasping, gently tugging as to tear the tissue while retrieving the forceps through the working channel or barrel, and then placing in 10% formalin. In the patients that were studied, a minimum of 3 endobronchial forceps biopsies were performed initially, and subsequently 2 cryobiopsies were obtained in each case. As noted, in all cases the number of FB exceeded the number of CB.
All samples were fixed in 10% formalin for at least 24 hours. Pathological analysis was routinely performed by staff pathologists. Using centimeters (cm), biopsies were measured in three dimensions (length, width, and depth) prior to sectioning for microscopic evaluation. When tissues were limited and volumetric measurements could not be reasonably performed (a total of only 3 cases), specimen slides were retrospectively reviewed by a pathologist, who measured the length and width of material on each slide. Each dimensional measurement was divided by the total number of slides for each specimen to establish an average length (example: FB length on slide 1 was 0.02 cm; FB length on slide 2 was 0.01. Therefore, the average FB length of this specimen was 0.02 + 0.01/2 = 0.015 cm). Tissue depth on the slides was standardized to 0.01 cm. Pathological interpretation was reported in the patients’ electronic medical record.
All results were classified as malignant or nonmalignant based on histology. A diagnosis of malignancy was confirmed with the clinical findings. A nonmalignant diagnosis was established by close clinical and radiological followup to monitor stability. This followup extended to a mean duration of 22.9 months (range, 14 to 36 months) until the submission of data.
Charts were reviewed looking for potential complications to include bleeding, bronchospasm, or respiratory distress. Bleeding severity was defined as minimal if
In patients where both CB and FB were performed, the Wilcoxon signed-rank test was utilized to analyze the volumes of biopsies obtained by each method.
Over a two-year period, 166 bronchoscopies were performed at our institution by the interventional pulmonary service. With three pulmonologists routinely performing CB, 31 patients were identified as undergoing CB either singly or in combination with FB. Patient characteristics (sampling technique utilized, pathological diagnosis, location of lesion, volume of material obtained, complications, and type of lesion—exophytic or flat) are summarized in Tables
Patient diagnosis (
Cryobiopsy diagnosis | Forceps diagnosis | Location of lesion | Vol. (cm3) cryobiopsy | Vol. (cm3) forceps | Type of lesion |
---|---|---|---|---|---|
Squamous cell carcinoma | Squamous cell carcinoma | BI | 0.4 | 0.2 | Exophytic |
Benign inflammation | Benign inflammation | RUL | 0.06 | 0.018 | Flat |
Necroinflammation | Necroinflammation | RUL | 0.048 | 0.001 | Flat |
Necroinflammation | Necroinflammation | Carina | 0.018 | 0.002 | Flat |
Papillary squamous cell carcinoma | Papillary squamous cell carcinoma | RMS | 0.702 | 0.004 | Exophytic |
Adenocarcinoma | Adenocarcinoma | RMS | 0.02 | 0.00025 | Exophytic |
Adenosquamous | Adenosquamous | RLL | 0.004 | 0.004 | Flat |
Squamous cell carcinoma | Squamous cell carcinoma | RUL | 0.032 | 0.144 | Exophytic |
Small cell | Small cell | LMS | 0.027 | 0.021 | Exophytic |
Benign | Benign | RMS | 0.018 | 0.009 | Flat |
Squamous cell carcinoma | Squamous cell carcinoma | LLL | 0.112 | 0.006 | Exophytic |
Poorly differentiated NSCLC | Poorly differentiated NSCLC | LLL | 0.024 | 0.04 | Exophytic |
Small cell | Small cell | RUL | 0.03 | 0.016 | Exophytic |
Squamous cell carcinoma | Squamous cell carcinoma | RMS | 0.96 | 0.009 | Exophytic |
Adenocarcinoma | Adenocarcinoma | LLL | 0.045 | 0.032 | Flat |
Carcinoid | Carcinoid | RLL | 0.39 | 0.234 | Exophytic |
Adenocarcinoma | Adenocarcinoma | RLL | 0.024 | 0.006 | Flat |
Benign | Benign | LUL | 0.05 | 0.032 | Flat |
Squamous cell carcinoma | Squamous cell carcinoma | RMS | 0.042 | 0.006 | Flat |
Squamous cell carcinoma | Squamous cell carcinoma | RUL | 0.04 | 0.001 | Flat |
Squamous cell carcinoma | Squamous cell carcinoma | LMS | 0.016 | 0.003 | Flat |
Adenocarcinoma | Atypical | RMS | 12.25 | 0.032 | Exophytic |
NSCLC: Nonsmall cell lung cancer; BI: bronchus intermedius; RUL: right upper lobe; RLL: right lower lobe; LUL: left upper lobe; LLL: left lower lobe; RMS: right main stem; LMS: left main stem.
Patient diagnosis (
Cryobiopsy diagnosis | Location of lesion | Vol. (cm3) cryobiopsy | Type of lesion |
---|---|---|---|
In situ squamous cell carcinoma | RUL | 0.39 | Flat |
Acid fast bacilli | LMS | 0.147 | Exophytic |
Necrotic debris | RLL | 0.36 | Exophytic |
Small cell* | RUL | 0.027 | Exophytic |
Small cell | LMS | 2.0 | Exophytic |
Small cell | LLL | 0.45 | Exophytic |
Squamous papillomata | Trachea | 0.12 | Exophytic |
Adenocarcinoma | Carina | 0.21 | Flat |
Small cell | LLL | 0.168 | Exophytic |
RUL: right upper lobe; RLL: right lower lobe; LLL: left lower lobe; LMS: left main stem.
Comparison of cryobiopsy versus forceps biopsy (
CB can be performed using both the flexible and rigid bronchoscope. The use of the cryotherapy flexible probe guided by a flexible bronchoscope allowed endobronchial cryobiopsies of central airways, as well as more distal airways, provided that the lesion is visible on bronchoscopic evaluation. Though all lesions were deemed approachable at the outset, one operator noted that it was difficult to flex the bronchoscope in order to biopsy a lesion in the right upper lobe even with the use of the smaller diameter cryotherapy probe (although this was eventually accomplished). Thus, one potential limitation is that lesions located in airways requiring significant flexure of the bronchoscope may not be reached with the current cryotherapy probes. Operators found that sampling lesions lying parallel to the axis of the bronchoscope (rigid and flexible) was much easier with the cryotherapy probe than with the endobronchial forceps.
A disadvantage of CB via a flexible bronchoscope is that the frozen probe with the attached biopsy material cannot be removed through the working channel. In order to remove the specimen from the airway, it is necessary to remove both the bronchoscope with the cryoprobe and the attached specimen en block. The procedure is repeated by reinserting the bronchoscope and the cryoprobe. Endotracheal intubation could be utilized to minimize the possibility of vocal cord and airway trauma. In this regard, Hetzel and colleagues in their recent study of CB actually indicated that a disadvantage of CB was that it is recommended to intubate all patients, either with a flexible endotracheal tube or through rigid bronchoscopy [
Our data demonstrates that the diagnostic yield and accuracy of CB is comparable and possibly superior to traditional endobronchial FB. This has also been suggested by our colleagues in Europe. The diagnostic yield of FB is generally accepted to be below 80%, though it can improve with the performance of additional sampling techniques [
While others have examined the importance of biopsy tissue area, we analyzed volume [
Biopsies performed with the cryotherapy probe proved extremely safe. One minor complication was reported, related to a small bleed that resolved spontaneously, following instillation of cold saline. This patient was on clopidogrel bisulfate therapy but presumably had stopped this a week earlier. While in general we do not perform biopsies in patients on this therapy, the pressing need to start treatment on some of these patients may indicate the need to proceed with the biopsy even while actively taking such drug. Additionally, one could argue that the vasoconstrictive properties of the cryobiopsy may ameliorate excessive bleeding. Of interest in this regard, it must be noted that the study by Hetzel et al. included 5 patients on Clopidogrel Bisulfate, but they do not report specifically on any associated bleeding in these patients. Additionally, they report a comparable rate of severe bleeding of 17.8% and 18.2% for FB and CB, respectively, although the overall bleeding rate was significantly higher with CB [
It is necessary to point out that the CB will be enduring over time. If multiple sampling techniques could be avoided, it is foreseeable that the operative time would be decreased when utilizing CB, as this single technique would achieve adequate tissue samples to secure a diagnosis. Additionally, the fact that the cryotherapy probe is reusable may also translate in cost savings (the same two flexible cryoprobes were used in all the cases, with no breakages during any of the procedures). An additional consideration is that if CB is able to provide improved yields, perhaps this can also be accomplished with a single sample versus two or more. Considering this to be true, then procedure times and cost could be minimized, though given the fact that the same probe is being used and time needed for each additional CB is short (estimated at less than 1 minute) the potential benefits would likely be negligible. In any case, our study was not designed to evaluate this question, as all patients had 2 CB which were submitted in a single preparation tube and analyzed in toto. It is nevertheless suggested that the operator, as she/he becomes more experienced, could accurately make the decision to obtain a simple specimen if that is visually of large enough volume and does not appear clearly necrotic. It is our hope that in future studies, we will be able to better address some of these considerations.
While our study has limitations due to the small numbers, it adds to a slowly growing body of the literature supporting the use of cryobiopsy as an important tool in the diagnosis of endobronchial disease. Additionally, our study provides further insight in how to safely perform the procedure in order to limit complications. We also demonstrate that this technique is useful to sample both exophytic, as well as visible flat irregular mucosal lesions. This technique is safe and appears to provide equivalent or superior diagnostic yields when sampling malignant lesions, as suggested by others, with our study also highlighting its utility to diagnose benign airway lesions. Additionally, as cancer targeted therapies evolve, tissue biopsy volume may be crucial to obtain adequate DNA quantities for proper genotyping and patient management, and as noted we have demonstrated a significant advantage for CB in this regard.
Finally, our study demonstrates that this procedure can be safely performed without the need to intubate patients, by using an anesthesia driven protocol with the placement of a supraglottic airway mask.
We encourage further evaluation of this technique and hope that our study will help promote awareness of this emerging approach to endobronchial biopsies. We hope to continue to study the many advantages that CB has to offer, by increasing the number of patients in the studies. We would also welcome the development of smaller diameter probes, which may overcome any potential limitations of this approach to sampling lesions within upper lobe segments.
The authors declare that they have no conflict of interests.
Dr. Rubio was responsible for Concepts, Design, Definition of intellectual content, Clinical studies, Experimental studies, and Data acquisition. Dr. Boyd was responsible for Concepts, Design, Data acquisition, Data analysis, Statistical analysis, and Guarantor. Dr. le was responsible for Literature search, paper preparation, paper editing, and paper review. Dr. Whatley was responsible for Literature search, paper preparation, paper editing, and paper review.
The authors thank American College of Chest Physicians 2010, Vancouver, Canada.