Standardized anesthetic and ventilation protocol to prevent atelectasis during robotic-assisted bronchoscopy: retrospective observational study

Abstract

Background

Robotic-assisted bronchoscopy (RAB) relies on stable intrathoracic geometry during cone-beam CT (CBCT) acquisition to ensure accurate navigation and lesion targeting. However, anesthesia-induced atelectasis develops rapidly after induction and can distort airway anatomy, critically impacting the stable intrathoracic geometry required for accurate RAB navigation and lesion targeting. This study evaluated an standardized anesthetic and ventilation protocol designed to prevent atelectasis and maintain physiologic stability during RAB.

Methods

This single-center retrospective observational study included 20 adult patients who underwent RAB between August and November 2025. All patients received an standardized anesthetic and ventilation protocol integrating a balanced strategy of preoxygenation, ventilation, and hemodynamic management tailored for RAB. The primary outcomes were radiologic atelectasis on intraprocedural CBCT and intraoperative stability. Secondary outcomes included ventilatory mechanics, apnea performance, hemodynamic trends, and procedure-related adverse events.

Results

Among the 17 patients who underwent intraprocedural CBCT, no radiologic atelectasis was observed (0/17, 0%). No disruptive patient movements occurred in the entire cohort (0/20, 0%). The mean tidal volume was 9.0 ± 0.5 mL/kg ideal body weight and the mean PEEP was 12.2 ± 0.7 cmH₂O. Breath-hold maneuvers supported prolonged apnea (mean 123.6 s) with preserved oxygenation. 30% of the patients required rescue vasopressors, but no episodes of refractory hypotension occurred. Procedure-related complications included pneumothorax requiring chest drainage in two patients and minor airway bleeding in one patient, with no serious anesthesia-related events.

Conclusions

A structured anesthetic and ventilation protocol emphasizing low-to-moderate FiO₂, moderate tidal volume, elevated PEEP, and anticipatory hemodynamic management was associated with the prevention of anesthesia-induced atelectasis while maintaining physiologic stability during RAB. These findings support the potential role of anesthesia in maintaining imaging fidelity for advanced bronchoscopic procedures and provide a physiology-based framework that may guide anesthetic practice for RAB and other image-dependent thoracic interventions.

Background

Atelectasis develops rapidly after the induction of general anesthesia and is reported in up to 90% of patients, contributing to reduced functional residual capacity, impaired oxygenation, and ventilation–perfusion mismatch [1–3]. In procedures that depend on stable intrathoracic geometry, such as robotic-assisted bronchoscopy (RAB), even small degrees of anesthesia-induced atelectasis can distort bronchial alignment, increase CT-to-body divergence, and compromise the accuracy of image-guided navigation [4, 5].

Several ventilatory strategies have been explored to mitigate anesthesia-related atelectasis during advanced bronchoscopic procedures, including high tidal volume ventilation, elevated positive end-expiratory pressure (PEEP), and breath-hold maneuvers [6, 7]. However, these protocols often rely on extreme ventilatory settings. High tidal volumes (≥ 10–12 mL/kg ideal body weight) may improve aeration but increase the risk of volutrauma and elevated plateau pressure [8]. Likewise, preoxygenation with 100% FiO₂ accelerates nitrogen washout and promotes rapid absorption atelectasis even before the procedure begins [1–3]. These limitations highlight the need for a more balanced, physiology-based anesthetic and ventilation strategy tailored specifically to the requirements of RAB.

Given the critical need for stable intrathoracic geometry in RAB for accurate navigation, the procedure uniquely demands a static end-inspiratory state during intraoperative cone-beam CT (CBCT) acquisition to ensure accurate target confirmation [4, 5]. Achieving this state demands prolonged apnea, consistent airway pressure, and a sealed airway system, which impose unique physiological and mechanical challenges for anesthetic management. Despite these strict requirements, standardized anesthetic protocols specifically tailored for RAB remain undefined. Consequently, current clinical practice often relies on strategies adapted from conventional bronchoscopy or general thoracic surgery, which may not fully address the specific demands of robotic navigation.

To address this gap, we implemented an standardized anesthetic and ventilation protocol designed to minimize anesthesia-induced atelectasis while maintaining the physiological stability required for accurate CBCT imaging. This protocol integrates low-FiO₂ preoxygenation to reduce absorption atelectasis, moderate tidal volume ventilation to avoid excessive mechanical strain, elevated PEEP to sustain alveolar recruitment, and proactive hemodynamic support to counterbalance PEEP-related cardiovascular effects.

In this study, we describe our initial institutional experience with a physiology-based anesthetic protocol during RAB implementation. We aimed to assess the feasibility and safety of this protocol, specifically focusing on its ability to maintain lung aeration and hemodynamic stability, without evaluating a control group during the adoption phase.

Materials and methods

Study design and ethical approval

This single-center, retrospective observational study included consecutive adult patients who underwent robotic-assisted bronchoscopy (RAB) using a standardized anesthetic and ventilation protocol between August and November 2025. In this context, ‘protocol’ refers to an institutional clinical management pathway. The anesthetic and ventilatory protocol had been implemented as the institutional standard of care for all RAB procedures prior to this retrospective analysis and was uniformly applied to all eligible patients. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. Approval was obtained from the Institutional Review Board, and the requirement for informed consent was waived due to the retrospective design.

Patient population

Eligible patients were adults (≥ 18 years) scheduled for RAB using the Ion endoluminal platform (Intuitive Surgical, Sunnyvale, CA, USA) for the evaluation of peripheral pulmonary lesions. Patients were excluded if their automatic anesthesia record data were incomplete or if the procedure was converted to another diagnostic modality. Demographic data, comorbidities, lesion characteristics, intraoperative ventilatory parameters, hemodynamic data, and perioperative outcomes were obtained from electronic medical records.

Anesthetic management

An overview of the standardized anesthetic and ventilation workflow used in this study is shown in Fig. 1.

Fig. 1.

Schematic Flowchart of the Standardized Anesthetic and Ventilation Protocol. APL, Adjustable Pressure Limiting valve; CBCT, Cone-Beam Computed Tomography; IBW, Ideal Body Weight; PCV-VG, Pressure-Controlled Volume-Guaranteed; PEEP, Positive End-Expiratory Pressure

Induction and maintenance

General anesthesia was induced using intravenous propofol and remifentanil, followed by neuromuscular blockade using rocuronium. Neuromuscular blockade was maintained with a continuous infusion of rocuronium throughout the procedure. An 8.5-mm internal diameter endotracheal tube was used in all cases to minimize airway resistance during robotic bronchoscope advancement. Preoxygenation was performed with FiO₂ 60% oxygen to reduce absorption atelectasis. Immediately after induction, a prophylactic norepinephrine infusion (0.02 µg/kg/min) was initiated. The infusion rate was titrated to maintain a mean arterial pressure ≥ 65 mmHg, with rescue vasopressor boluses administered only for hypotension refractory to infusion adjustment. To reduce airway inflammation and postoperative nausea and vomiting (PONV), patients received dexamethasone (5 mg) and palonosetron (0.075 mg) at the time of anesthesia induction.

Ventilation protocol

Mechanical ventilation was delivered using the pressure-controlled volume-guaranteed (PCV-VG) mode. The standardized protocol was designed to prevent anesthesia-induced atelectasis while preserving a stable inspiratory state for CBCT acquisition. Tidal volume was set to 8–10 mL/kg of ideal body weight (IBW). PEEP was maintained between 12 and 15 cmH₂O to prevent alveolar collapse. The fraction of inspired oxygen (FiO₂) was maintained at 50% to minimize absorption atelectasis while preserving oxygen reserves. Regarding alveolar recruitment, a single manual inflation to 30 cmH₂O for 20 s was performed immediately after robotic docking to ensure a sealed airway. For the breath-hold technique, the APL valve was set to match the inspiratory plateau pressure identified during PCV-VG ventilation. The switch to manual mode was executed specifically at the end of the inspiratory phase. To compensate for the transient pressure drop associated with the breathing circuit during this transition, the fresh gas flow was immediately increased to 10 L/min.

Outcomes

The primary outcomes focused on anesthetic and ventilation performance: (1) absence of radiologic atelectasis, strictly defined as no new segmental or lobar opacity greater than 1 cm on intraprocedural CBCT compared with pre-procedural imaging; and (2) absence of disruptive patient movement, defined as no involuntary movements requiring interruption of imaging or additional neuromuscular blockade. To ensure an objective assessment, the CBCT images were independently reviewed by two board-certified radiologists who were blinded to the clinical details, and discrepancies were resolved by consensus. Atelectasis was evaluated in a subgroup of patients who underwent intraprocedural CBCT, while the absence of movement was assessed in the entire study cohort.

The secondary outcomes evaluated physiological performance and procedure-related safety. Ventilatory and apnea performance were assessed using tidal volume, plateau pressure, respiratory rate, apnea duration, and oxygen saturation nadir during the breath-hold maneuver. Hemodynamic stability was characterized by the incidence of hypotension that required rescue vasopressors. Safety outcomes included complications such as pneumothorax requiring intervention, clinically significant bleeding, post-procedure sore throat, and PONV.

Statistical analysis

Due to the exploratory nature and small sample size, only descriptive statistics were performed. Continuous variables were reported as mean ± standard deviation, and categorical variables as frequency and percentage. No imputation for missing data or inferential statistical tests was applied.

Results

Twenty patients were included in the analysis. The mean age was 60.9 years, and 65% of the patients were female. Most patients were classified as ASA physical status II (85%). The mean body mass index was 24.1 kg/m². A total of 28 peripheral pulmonary lesions were targeted, with a mean diameter of 16 mm; 96% were < 30 mm. The baseline characteristics are summarized in Table 1.

Table 1.

Baseline Characteristics of Patients and Lung Lesions

Characteristics	Value (N = 20)
Patient Characteristics
Total no. of patients	20
Age, years	60.9 ± 9.4
Sex, male	7 (35%)
BMI, kg/m²	24.1 ± 4.4
ASA physical status
I	2 (10%)
II	17 (85%)
III	1 (5%)
Comorbidities
Hypertension	7 (35%)
Diabetes Mellitus	7 (35%)
COPD	0 (0%)
Lung Lesion Characteristics
Total no. of lung lesions	28
Lesion size, mm	16.0 ± 7.2
Lesion size < 30 mm	27 (96%)
Location
Right upper and middle lobe	11 (39%)
Left upper lobe	9 (32%)
Right lower lobe	7 (25%)
Left lower lobe	1 (4%)

Values are presented as mean ± SD or number (%). ASA American Society of Anesthesiologists, BMI Body Mass Index

All patients were managed using an standardized anesthetic and ventilation protocol. The mean tidal volume was 9 mL/kg ideal body weight, and the mean PEEP was 12.2 cmH₂O. The mean peak inspiratory pressure was 21.5 cmH₂O and the mean respiratory rate was 9.3 breaths/min. Breath-hold maneuvers were required for cone-beam CT imaging or biopsy. The mean apnea time was 123.6 s, and the mean oxygen saturation nadir was 97.9%, with no patient experiencing oxygen desaturation of < 90%.

Intraprocedural CBCT was performed in 17 of the 20 patients. In two patients, CBCT was not performed because the target lesions were successfully visualized via radial EBUS, rendering additional imaging unnecessary. One patient was excluded from the analysis due to a technical error in image data transmission. No visible atelectasis was observed in any of the 17 intraprocedural CBCT scans (0/17, 0%). No new dependent opacities or segmental/lobar collapse greater than 1 cm were detected by radiologists. Representative images are presented in Fig. 2. Additionally, no patient exhibited disruptive movements that required interruption of imaging or additional neuromuscular blockade.

Fig. 2.

Absence of atelectasis during robotic-assisted bronchoscopy under the Protocol. (A) Pre-procedural CT image showing the peripheral target lesion (arrow). (B) Intraprocedural cone-beam CT demonstrates no new dependent opacity or segmental collapse, confirming effective atelectasis prevention

Despite continuous prophylactic norepinephrine infusion, six of the 20 patients (30%) required additional vasopressor support for hypotension. Specifically, the maximum infusion rate of norepinephrine was 0.07 µg/kg/min, and the primary rescue vasopressors used were phenylephrine and ephedrine. Among patients receiving rescue support, the maximum cumulative dose of phenylephrine administered to a single patient was 400 µg. No episodes of severe or refractory hemodynamic instability were observed. The mean blood pressure was maintained above 65 mmHg in all remaining patients with titration of the baseline norepinephrine infusion.

Pneumothorax requiring chest tube placement occurred in two patients (10%), both involving lesions adjacent to the pleura. No pneumothorax was identified while the patients remained on mechanical ventilation; all were detected on postoperative imaging during spontaneous breathing. One patient (5%) required postoperative bronchoscopy for minor clot removal. No significant intraoperative bleeding was noted. Postoperative sore throat occurred in four patients (20%) and was self-limited. No postoperative nausea or vomiting was observed. Furthermore, there were no emergency department visits or unplanned readmissions related to procedural complications within 30 days of discharge. A detailed summary of the intraoperative parameters and clinical outcomes is provided in Table 2.

Table 2.

Intraoperative Management and Clinical Outcomes

Variables	Value
Intraoperative Management (N = 20)
Time Metrics
Total anesthesia time, min	95.5 ± 29.0
Total procedure time, min	73.8 ± 28.4
Ventilation Strategy
Tidal volume, ml/kg IBW	9.0 ± 0.5
PEEP, cmH₂O	12.2 ± 0.7
Respiratory Rate, breaths/min	9.3 ± 1.1
Peak Inspiratory Pressure, cmH₂O	21.5 ± 1.3
Breath-hold (Apnea)
Apnea duration, sec	123.6 ± 79.1
SpO₂ nadir, %	97.9 ± 2.9
Clinical Outcomes
Primary Outcome
Visible atelectasis (N = 17)	0 (0%)
Disruptive movement (N = 20)	0 (0%)
Secondary Outcomes (N = 20)
Hypotension requiring rescue vasopressors	6 (30%)
Pneumothorax requiring intervention	2 (10%)
Significant bleeding	1 (5%)*
PONV	0 (0%)
Postoperative sore throat	4 (20%)

Values are presented as mean ± SD or number (%). PEEP Positive End-Expiratory Pressure, PONV Postoperative Nausea and Vomiting. *Refers to a postoperative bronchoscopy to evacuate retained minor blood clots; no significant intraoperative bleeding occurred

Discussion

This study describes the initial institutional experience with an standardized anesthetic and ventilation protocol specifically tailored for robotic-assisted bronchoscopy (RAB). Our results demonstrate that this standardized protocol consistently provided a stable procedural environment, associated with a complete absence of visible atelectasis in all patients, as assessed by cone-beam CT (CBCT). This finding suggests the potential value of implementing a structured, evidence-based protocol to ensure patient safety and procedural quality when introducing new technology.

This protocol builds upon established frameworks, such as the Lung Navigation Ventilation Protocol (LNVP) [6]. Although both protocols share the primary goal of preventing atelectasis, our protocol introduces specific modifications to better balance procedural conditions with patient safety. Instead of maximizing oxygen and tidal volume, we utilized a lower FiO₂ to minimize absorption atelectasis and employed intermediate tidal volumes to avoid the risks of high-volume ventilation while maintaining lung expansion. The key methodological differences between this protocol and the LNVP are compared in Table 3.

Table 3.

Comparison of Key Methodological Differences Between Standardized Approach and LNVP

Parameter	Standardized Approach (This Study)	LNVP (Bhadra et al. )	Significance of Standarized Approach
Preoxygenation (FiO2)	60%	100%	Mitigates the risk of absorption atelectasis
Tidal Volume (ml/kg IBW)	8–10	10–12	Balances atelectasis prevention with lung protection
PEEP Strategy (cmH₂O)	12–15	10–15 (Upper/Middle) 15–20 (Lower)	Simplifies the protocol while maintaining effective alveolar recruitment.
Breath-hold Mechanism	APL valve set to Inspiratory Plateau Pressure	APL valve set to PEEP level	Replicates inspiratory lung expansion for optimal target stability.
Post-op Prophylaxis	Standardized (dexamethasone and palonosetron)	Not standardized (Dexamethasone 70%, Zofran 84%)	Enhances patient recovery by standardizing PONV/sore throat prophylaxis

IBW Ideal Body Weight, APL Adjustable Pressure Limiting valve, PEEP Positive End-Expiratory Pressure, PONV Postoperative Nausea and Vomiting

A key component is a balanced ventilation strategy tailored for bronchoscopy. Although high tidal volumes are often advocated in RAB to minimize atelectasis, they pose a risk of lung overdistension and ventilator-induced lung injury (VILI) through barotrauma or volutrauma, even in non-ARDS patients [8]. To mitigate this risk without compromising image quality, we employed an intermediate tidal volume (8–10 mL/kg of IBW) in our study. This range represents a strategic compromise that aims to provide sufficient alveolar inflation to prevent atelectasis while avoiding unnecessary mechanical strain associated with excessive tidal volumes.

The preoxygenation strategy was designed to balance atelectasis prevention with other considerations. Preoxygenation was limited to FiO₂ 60%, a deliberate modification from the conventional 100% approach to mitigate the risk of absorption atelectasis. Previous studies have shown that high inspired oxygen fractions promote absorption atelectasis, whereas moderate FiO₂ levels maintain oxygenation while reducing atelectatic lung volume [1–3]. To compensate for the reduced oxygen reserve associated with a lower FiO₂, a higher induction dose of rocuronium (≥ 1 mg/kg) was used to achieve a rapid and complete neuromuscular blockade, thereby facilitating prompt tracheal intubation and minimizing the risk of desaturation.

The breath-hold technique was designed to maintain a stable inspiratory state during both the CBCT acquisition and biopsy. To achieve this, the APL valve was set according to the plateau pressure (Pplat) measured during the PCV-VG mode, aiming to replicate the lung inflation state of the peak inspiratory phase. Crucially, upon switching to manual mode, the fresh gas flow was temporarily increased to 10 L/min to compensate for the transient circuit volume loss and ensure rapid equilibration of the airway pressure. The APL valve setting was meticulously titrated using real-time feedback from the ventilator monitoring parameters to strictly match the target Pplat (Fig. 3). This approach ensured a consistent inspiratory plateau throughout the procedure, contributing to enhanced image quality and target-site stability.

Fig. 3.

Pressure–Time Waveform During the Breath-Hold Maneuver. Pplat, Inspiratory Plateau Pressure; PEEP, Positive End-Expiratory Pressure

Although high PEEP is essential for alveolar recruitment, it imposes predictable hemodynamic consequences [9]. Approximately one-third of patients required additional vasopressor boluses despite prophylactic norepinephrine infusion, reflecting the expected reduction in venous return under elevated intrathoracic pressure. Crucially, however, the prophylactic infusion provided a hemodynamic safety margin; all hypotensive episodes were transient and easily managed with modest titration or intermittent boluses, with no cases of refractory hypotension. This proactive strategy aligns with recent evidence suggesting that prophylactic norepinephrine effectively reduces post-induction hypotension in high-risk surgical populations [10–12]. However, the combination of high PEEP and prolonged breath-holds should be applied with caution in high-risk populations, such as those with ASA physical status III/IV, advanced coronary artery disease, or morbid obesity. These patients may be more susceptible to significant decreases in venous return and refractory hypotension.

An endotracheal tube (ETT) with an internal diameter of 8.5 mm, which is larger than conventional sizes, was selected to accommodate the robotic bronchoscope and reduce airway resistance. Although manufacturer guidelines permit an 8.0 mm ETT, we strongly advocate the use of an 8.5 mm tube to minimize the significant airflow resistance created by the robotic catheter. Additionally, to address friction and restricted scope maneuverability, we established a protocol for shortening the ETT to 30–32 cm based on patient height, and strict midline fixation was applied to prevent torque-induced circuit leaks at the airway adapter.

To mitigate the potential risk of post-procedure sore throat from the larger ETT, prophylactic dexamethasone was administered for its anti-inflammatory and antiemetic effects, in alignment with the protocol’s goal of enhancing patient recovery [13, 14]. Despite the use of a large-bore ETT, which is a known risk factor for airway mucosal injury, the observed incidence of sore throat (20%) was considered acceptable and comparable to the reported rates in conventional bronchoscopy. All reported cases were minor and self-limiting.

All patients received prophylactic antiemetics. Although PONV is generally uncommon after bronchoscopy, it poses specific risks for airway procedures, including coughing and aspiration [15]. Previous studies have supported the benefits of antiemetic prophylaxis for bronchoscopy performed under general anesthesia [16, 17]. Consequently, we incorporated routine antiemetic therapy into our protocol. No PONV incidents were observed in this cohort.

Regarding apnea management, our protocol—despite its use of FiO₂ 50%—supported prolonged breath-holds, including one case exceeding 8 min without desaturation. However, to maximize the oxygen reserve and further prolong the safe duration of apnea, ‘apneic oxygenation’—increasing FiO₂ to 100% for pre-oxygenation and maintaining it throughout the breath-hold—can be an effective solution. Styrvoky et al. achieved a median apnea duration of 23 min by utilizing a 100% oxygen [18]. Although not implemented in this cohort, this strategy could be adopted for prolonged procedures in the future. Tools such as the Oxygen Reserve Index (ORi) would be useful for visually assessing the patient’s oxygen reserve [19]. Close collaboration with the pulmonology team to minimize the duration of apnea is crucial.

Pneumothorax occurred in two patients (10%). Given that both patients had peripheral lesions adjacent to the pleura, a known risk factor for RAB complications [20], these events were likely primarily procedure-related. However, considering the physiological effects of our protocol, the potential contribution of the high-PEEP strategy to the development or exacerbation of pneumothorax cannot be entirely excluded. Neither pneumothorax was apparent immediately post-procedure while the patients remained on mechanical ventilation, but both cases were identified on chest radiographs obtained in the post-anesthesia care unit. This suggests that pneumothorax, previously masked by positive pressure ventilation, became apparent only after negative intrathoracic pressure was re-established during spontaneous breathing [21]. Anticipating this risk, we prearranged collaboration with the thoracic surgery and interventional radiology teams, enabling prompt intervention when these events were detected.

No significant bleeding occurred intraoperatively. Only one patient (5%) required a toilet bronchoscopy on postoperative day 1 to evacuate minor retained blood clots generated during the procedure.

This study had several important limitations that must be considered. First, the retrospective, single-center design with a small sample size (N = 20) and the absence of a control group preclude definite conclusions regarding the superiority of our protocol over conventional anesthetic methods. The findings primarily demonstrate the protocol’s feasibility and initial safety profile rather than its comparative efficacy. Consequently, the observed absence of visible atelectasis in this cohort and the 10% incidence of pneumothorax should be interpreted with caution.

Second, while our cohort included some high-risk patients the majority consisted of non-obese individuals with favorable ASA physical status (I–II). Furthermore, a significant majority of the target lesions (71%) were located in the upper and middle lobes, where the risk of gravity-dependent atelectasis is inherently lower. The safety and efficacy of our high-PEEP strategy have not been fully validated in more challenging scenarios, such as morbidly obese patients or lesions located in dependent lung regions.

Future prospective randomized trials are essential to directly compare our protocol with other anesthetic strategies. It is also crucial to validate its efficacy and safety in diverse and high-risk patient populations. Furthermore, subsequent studies should investigate whether lower tidal volumes and PEEP settings can maintain optimal conditions, which would further enhance the overall safety profile of the protocol.

Conclusion

In conclusion, our initial experience suggests that this structured, physiology-based anesthetic and ventilation protocol is a feasible approach for robotic bronchoscopy. This strategy was associated with stable, atelectasis-free conditions suitable for high-fidelity imaging. While further comparative studies are needed, this framework offers a practical guide for institutions adopting this technology and provides a foundation for future research aimed at optimizing anesthetic management for advanced image-guided thoracic interventions.

Abbreviations

APL

Adjustable pressure-limiting

ASA

American Society of Anesthesiologists

CBCT

Cone-beam computed tomography

ETT

Endotracheal tube

FiO₂

Fraction of inspired oxygen

IBW

Ideal body weight

LNVP

Lung Navigation Ventilation Protocol

ORi

Oxygen Reserve Index

PCV-VG

Pressure-controlled ventilation volume-guaranteed

PEEP

Positive end-expiratory pressure

PONV

Postoperative nausea and vomiting

RAB

Robotic-assisted bronchoscopy

STROBE

Strengthening the Reporting of Observational Studies in Epidemiology

VILI

Ventilator-induced lung injury

Authors’ contributions

JL contributed to the study conceptualization, methodology, formal analysis, writing of the original draft, and supervision. HC, GHH, and JYP contributed to data curation, investigation, and review and editing of the manuscript. All authors read and approved of the final manuscript.

Funding

This research received no specific grant from any funding agency.

Data availability

The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Institutional Review Board of the National Cancer Center (Approval No. NCC2025-0362; December 2025). The requirement for informed consent was waived by the Institutional Review Board of the National Cancer Center due to the retrospective design of the study.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.