RESULTS
Data from 19 patients who underwent semirigid pleuroscopy with conventional forceps and cryoprobe biopsies were analyzed. The baseline characteristics of the patients are shown in Table 1.
Table 1
Baseline characteristics.
Characteristics | Value |
|---|
Age (year) | 68 (63–789 |
Sex Female Male | 6 (31.6%) 13 (68.4%) |
Smoking status Current smoker Ex-smoker Non-smoker | 6 (31.6%) 7 (36.8%) 6 (31.6%) |
Smoking (pack-year) | 29 (0–40) |
ECOG ≥ 2 | 4 (21.1%) |
LDH < 1500 (UI/L) | 441,5 (242.2-885.2) |
NLR < 9 NLR (median) | 16 (84.2%) 4.4 (2.9–5.8) |
Etiology Lung cancer Lung adenocarcinoma Lung large cell carcinoma Others cancer Breast cancer Mesothelioma Ovarian Sarcoma | 14 13 (68.4%) 1 (5.3) 5 2 (10.5%) 1 (5.3%) 1 (5.3%) 1 (5.3%) |
Radiological characteristics Pleural effusion size chest radiograph Massive (˃2/3) Medium Small (≤ 2/3) Findings in CT Nodal thickening Circumferential thickening Pleural masses No pleural thickening | 9 (47.4%) 8 (42.1%) 2 (10.5%) 10 (52.6%) 2 (10.5%) 2 (10.5%) 5 (26.3%) |
| Definition of abbreviation = Eastern Cooperative Oncology Group (ECOG),High lactate dehydrogenase (LDH), Neutrophil-to-lymphocyte ratio (NLR), Computed tomography (CT) |
Regarding the procedural characteristics, the drainage amount (ml) was 1,900 ml (1,050 − 2,400).
The pleural abnormalities found during pleuroscopy were: plaques in 12 patients (63.2%), nodules in 2 patients (10.5%) and polyps in 5 patients (26.3%). The duration of subsequent chest drainage (days) was 3 (2–3) days and the length of stay after the procedure (days) was 6 (4–10) days.
The dose of sedative drugs used during the procedure was 6 (5–7) micrograms of midazolam and 100 (50–100) micrograms of fentanyl. The 30-day mortality was 2 cases (10.5%), and the overall survival was 4.5 (2-31.5) months.
There were no severe complications observed during the procedure, nor minor bleeding that required hemostatic control. Pain was reported in 2 patients (10.5%).
The patients with MPE due to NSCLC included in the study were 14 cases. The Table 2 presents some of their clinical, histological, and TNM characteristics.
Table 2
Clinical, histological, and prognostic characteristics of patients with malignant pleural effusion due to NSCLC
Patient | Age (years) | Sex | Histology | TNM |
|---|
1 | 69 | Male | ADC | T3N0 |
2 | 65 | Male | ADC | T3N1 |
3 | 65 | Male | ADC | TxN0 |
4 | 78 | Female | ADC | T3N2 |
5 | 79 | Male | ADC | TxN0 |
6 | 60 | Male | ADC | T4N3 |
7 | 63 | Male | ADC | TxN3 |
8 | 80 | Male | ADC | T4N3 |
9 | 73 | Male | ADC | T1N3 |
10 | 70 | Female | ADC | T2aN2 |
11 | 63 | Male | ADC | T4N0 |
12 | 68 | Male | ADC | TxN1 |
13 | 61 | Male | Large cell carcinoma | T1N2 |
14 | 60 | Male | ADC | TxN0 |
| Definition of abbreviation = Adenocarcinoma (ADC) |
In this group, the median biopsy size for conventional flexible forceps and cryoprobe was 2.5 mm (1.5–3.2 mm) and 5.5 mm (3.8–7.6 mm), respectively (p = 0.07). The number of biopsies also differed: flexible forceps: 5 (4-6.25) biopsies vs cryoprobe: 3 (3–4) biopsies(p = 0.01). The percentage of viable tumor in samples obtained by flexible forceps and cryoprobe was 55% (15–80%) and 55% (10–80%), respectively (p = 0.9). The tumor/non-tumor ratio in the conventional forceps sample was 2.4 (1.2–5.9), while in the cryoprobe sample, it was 3.6 (1.2–10) (p = 0.09).
In all patients, a morphological and immunohistochemical diagnosis was possible using both conventional forceps and cryoprobe biopsies. Only in one case, the samples obtained during semirigid pleuroscopy with both cryoprobe and forceps were insufficient for molecular diagnosis, requiring a surgical video-assisted thoracoscopic surgery. In this case, the pleuroscopy revealed plaque-like lesions.
DISCUSSION
Our study is the first published Spanish study to analyze the quality of cryoprobe obtained samples to optimize the molecular diagnosis of MPE due to NSCLC. When pleural biopsies were obtained using a cryoprobe, although there were no differences in the percentage of viable tumor cells, the sample size was significantly larger, as was the tumor/non-tumor ratio. Additionally, fewer biopsies were required when using the cryoprobe.
A limitation of semirigid pleuroscopy is its size and flexibility 1,2. Although the semirigid pleuroscope is more manageable than the rigid one, its smaller diameter limits the ability to obtain larger biopsies, potentially affecting the amount of tissue available for molecular studies. Furthermore, its lower rigidity can make biopsy collection more challenging.
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In a small study conducted by our group on the diagnostic performance of semirigid thoracoscopy for the molecular characterization of MPD due to NSCLC, molecular testing was performed in 14 adenocarcinomas. Sufficient and adequate material was obtained to determine EGFR mutation status in 100% of cases, but only in 90% of cases for ALK translocation15. EGFR mutations were identified in two patients, while no cases of ALK translocation were detected. EGFR mutation detection was possible in all cases, but the yield for ALK translocation analysis was lower 15. Many revolutionary advances have recently been made in the management of NSCLC. There have been a number of approvals of molecular-targeted therapy for subgroups of NSCLC patients with sensitizing EGFR, ALK, ROS1, RET, BRAF V600E, MET, or NTRK alterations 21. In addition to genetic examination, NSCLC are usually subjected to the analysis of PD-L1 protein expression in order to direct the use of immune checkpoint inhibitors 20,21.
Cryobiopsy, a relatively novel bronchoscopic technique, has gained prominence in recent years due to its ability to procure larger, higher-quality tissue samples with fewer crush artifacts compared to traditional forceps biopsies 3,4. This method has demonstrated promising diagnostic yields in lung cancer 3.
However, none of the published studies on MPE and lung cancer have primarily focused on analyzing the effectiveness of pleural cryobiopsies for mutation studies and other molecular alterations. In studies where this aspect was analyzed secondarily, only EGFR gene mutations had been investigated 8,10. In one study including 14 cases of MPE, four of which were lung adenocarcinomas, obtaining pleural biopsies with a cryoprobe allowed DNA isolation for EGFR mutation analysis in all samples using a commercially available kit8. In another study, samples were valid for EGFR mutation testing, but these results were not compared with the molecular diagnostic yield of biopsies obtained using conventional fórceps 10.
Another study conducted in an Asian population included six patients with NSCLC, all of whom underwent genetic panel testing to detect driver gene mutations. Sufficient specimens were obtained for appropriate genetic analysis in all cases 14. However, a limitation of this study was the lack of specification regarding which molecular alterations were analyzed. In our study, all the necessary molecular analyses, including PDL1 expression, were successfully performed.
There is ongoing debate regarding the ideal instrument for medical thoracoscopy. Bansal S et al. compared rigid mini-thoracoscopy with semirigid thoracoscopy and found that biopsy size was larger in the mini-thoracoscopy group (16.1 ± 4.5 mm vs. 8.3 ± 2.9 mm; P < 0.001)16. However, the diagnostic yield of pleural biopsy was similar between the two groups.
When comparing rigid versus semirigid thoracoscopy, differences have been observed. In 2016, Wurps H et al.
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conducted a prospective study with 80 patients to compare parietal pleural biopsies obtained using rigid forceps, flexible forceps, and a cryoprobe during medical thoracoscopy 17. Rigid biopsies were significantly larger than both cryobiopsies and flexible biopsies (P < 0.001), while cryobiopsies were significantly larger than flexible biopsies (P < 0.01). The diagnostic yield of cryobiopsies was lower than that of rigid biopsies but not inferior to flexible biopsies17. In our study, although the tumor percentage was similar in both biopsy types, cryobiopsies were larger, and fewer samples were required with cryobiopsy.
It is important to consider that tissue remains the standard material for NSCLC diagnosis, and there is a continuous search for new molecular markers in MPE, with the primary limiting factor being the availability of viable samples.
In this context, cryobiopsy of mediastinal lymph nodes (cryoEBUS) has been described as improving diagnostic accuracy. Although cryoEBUS did not significantly enhance lung cancer diagnosis compared to EBUS-TBNA, it appeared to provide superior samples for complete molecular characterization, including PDL1 studies, while requiring fewer passes per lymph node4.
Studies comparing the diagnostic yield of cryobiopsy by radial endobronchial ultrasound with that of conventional biopsy have shown that cryobiopsy improves diagnostic yield and obtains larger samples in patients with peripheral pulmonary lesions due to lung cancer 18,19.
As discussed earlier, the main limitation of semirigid pleuroscopy is the small sample size, which necessitates obtaining more biopsies. Additionally, when using flexible forceps, it can be difficult to biopsy lesions located tangentially to the instrument 1,2,5. However, a notable advantage of the semirigid pleuroscope is its ease of use compared to the rigid thoracoscope, making it a favorable option for Interventional Pulmonology Units. The incorporation of cryobiopsy into semirigid pleuroscopy could reduce the number of biopsies required, thereby shortening procedure time and facilitating tissue collection without increasing procedural risks.
Pleural cryobiopsy has been shown to be a technique with a low complication rate, as reported in recent systematic reviews on its efficacy and safety 4,5. In our study, despite performing biopsies with both a cryoprobe and conventional flexible forceps, no major complications were observed, nor were there increases in hospital stays or chest drainage duration. These findings are consistent with those reported in the literatura 22.
The primary limitation of this study is the small number of patients with MPE due to NSCLC, although it is the first study conducted in a Caucasian population for this purpose. Additionally, as previously mentioned, this is an innovative technique that will require further standardization and refinement for integration into clinical practice. Incorporating this technique into semirigid pleuroscopy could enhance procedural methodology, reduce procedure time by requiring fewer biopsies, and do so without increasing complication rates.
Pleural cryobiopsy has been demonstrated to be a safe and effective diagnostic tool during pleuroscopy semirigid, providing adequate samples for all molecular testing and for the histological characterization of patients with MPE due to lung cancer.
METHODS
Study population
Prospective study including all patients with a diagnosis or high suspicion of MPE due to NSCLC who underwent semirigid pleuroscopy with cryobiopsies between November 1, 2019, and November 30, 2024, at the Bronchopleural Techniques Unit of Hospital in Spain.
The inclusion criteria were: age > 18 years; caucasian population and patients with MPE due to NSCLC confirmed by cytology or histology
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Exclusion criteria included were: patients with benign pleural effusion; patients with paramalignant pleural effusion without evidence of malignant cells in the pleural cavity; other etiologies different from MPE and contraindication for pleural biopsy
Semirigid Pleuroscopy Procedure and Pleural Biopsy
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All procedures were performed according to clinical practice guideline recommendations 2,11. Pleuroscopy was conducted under aseptic conditions in the endoscopy suite, with the patient under spontaneous respiration, conscious sedation (midazolam ± fentanyl), and local anesthesia (2% mepivacaine). The semirigid pleuroscope (LTF-160 autoclave, Olympus, Tokyo, Japan) was used for the procedures. Ultrasound was performed on all patients before trocar insertion to determine the entry point. The pleural fluid was drained at the beginning, and the pleural cavity was inspected under direct visualization. All pleural biopsies were performed on parietal pleural lesions. Before biopsy collection, 5 ml of 2% lidocaine was applied under direct visualization through the working channel of the pleuroscope to the selected area. Initially, 4 to 8 pleural biopsies were taken using flexible conventional forceps. Subsequently, biopsies were collected using a flexible cryoprobe (ERBOCRYOCA, ERBE, Tübingen, Germany) with an external diameter of 1.7 mm (2 to 5 biopsies). The probe tip, which froze tissue using CO₂ gas, was placed on the lesion and frozen for 5–7 seconds. The adhered sample was then extracted.
Samples obtained by both conventional forceps and cryoprobe were placed in separate formalin containers and sent to the Pathology Department for histological analysis. Following the procedure, a 24Fr chest drain was placed
Study Variables:
The following variables were recorded: epidemiological characteristics of patient (age, sex, smoking history), functional characteristics (general health status using the ECOG performance scale), radiological characteristics (size of pleural effusion on chest radigraphic, and characteristics of pleural lesions and/or thickening on CT scan.
Others variables were also analyzed as tumor classification: Histological tumor type and TNM classification12 at the time of DPM diagnosis or at the time of primary tumor diagnosis in cases of disease progression.
The prognostic and survival variables were the predictive variables from the LENT prognostic scale13. We recorded the 30-day mortality rate and overall survival.
The procedure-related variables were: volume of pleural fluid drained, pleural findings during pleuroscopy, duration of chest drainage (days) and the length of hospital stay (days).
About the procedure safety, we classified bleeding complications as follows: mild (self-limiting), moderate (requiring topical vasoconstrictors such as adrenaline) and severe (requiring intervention with electrocautery or argon plasma). Other complications, including pain.
We analized the diagnostic yield and molecular analysis as follows: comparison of histological diagnostic yield between cryobiopsy and conventional forceps biopsies. The pathological findings in both biopsy samples, including: numer, sample size (mm). sample volume (mm²) and percentage of viable vs. non-viable tumor cells. The results of molecular studies were also analyzed (detection of genomic alterations EGFR, ROS1,BRAF, ALK, RET, MET, NTRK and PD-L1 expression)
Ethical aspects:
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The study was conducted following the Helsinki Declaration guidelines. The data were pseudonymized for biomedical research purposes.
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The study has been approved by the provincial research ethics committee of Galicia (Pontevedra-Vigo-Ourense code: 2019/293).
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All participants provided written informed consent to participate in this study and to allow the publication of their data and sample results.
Statistical analyses
Categorical variables were presented as counts and percentages, and continuous variables were presented as mean and standard derivation (SD). Statistical analyses were performed using SPSS Statistic 21 (IBM Corp., Armonk, NY). Pearson’s chi-square or Fisher exact test was used to compare proportions, as appropriate. For continuous data, differences between groups were determined using Students t-test or Mann-Whitney U test for parametric or non-parametric data, respectively. P < 0.05 was considered statistically significant.