Introduction
Mediastinal tumours represent a variety of tumours, such as thymomas, teratomas, thyroid diseases, bronchogenic cysts, and neurogenic tumours [
1,
2]. Currently, surgery with curative intent is the primary choice for most mediastinal tumours [
3]. Traditional surgical approaches include median sternotomy or lateral thoracotomy; however, patients experience extensive trauma and slow recovery from surgery [
3]. With the development of minimally invasive surgery (MIS), video-assisted thoracic surgery (VATS) has been accepted for the treatment of mediastinal tumours in selected cases [
4]. However, VATS requires a deep learning curve for mediastinal tumour resection and has only been performed in experienced centres with large volumes, which has hindered its use and expansion [
5].
In recent years, robot-assisted thoracoscopic surgery (RATS) has raised the interest of surgeons in the treatment of mediastinal tumours with the advantages of three-dimensional visualisation and small-wristed instruments, making fine operations possible as a minimally invasive approach [
6‐
8]. However, the results of the previous studies on robotic mediastinal tumour resection were retrospective [
6,
9]. Moreover, studies on robotic mediastinal tumour resection differ significantly in terms of surgical technique and different mediastinal tumour types [
10,
11]. Therefore, we believe that more studies are essential to define robotic surgical techniques, their feasibility, and outcomes in mediastinal tumour resection, especially when using prospectively collected data. Our previous studies demonstrated that the robotic portal approach using CO
2 insufflation could flatten the learning curves and have satisfactory short-term outcomes in lung resections for lung cancer patients [
12‐
15], and was feasible in resection of the challenging mediastinal tumour in technique point of view from a case report [
16]. Herein, we designed a prospective observational study that included a series of consecutive patients with mediastinal tumours who underwent robotic portal resections (RPRs) by a single surgical team, with the purpose of further determine the effectiveness and feasibility of the robotic portal approach for minimally invasive resection of a variety of mediastinal tumours in a real-world practice by a single robotic surgical team, and to provide a comprehensive overview of its utility across different mediastinal regions. The prospective nature and the variety of tumour types may be valuable to clinical practice.
Discussion
Since the first report of robotic thymectomy in 2001 [
4], RATS has been used to treat mediastinal tumours in some large-volume medical centres [
25,
26]. However, previous studies were retrospective [
6,
9], and the surgical approach and technique varied among different centres from a technical perspective. Therefore, further studies are warranted to define the robotic surgical technique and its feasibility and outcomes in mediastinal tumour resection using prospectively collected data. We prospectively included 73 consecutive patients with mediastinal tumours who underwent RPRs, in which a complete robotic portal procedure with CO
2 insufflation was used as the preferred approach. The outcomes demonstrated that this procedure is safe and feasible for mediastinal tumour resection, even for selected complicated tumours. The findings of this study may help to flatten the learning curve and broaden the application of a minimally invasive approach for the surgical treatment of mediastinal tumours and benefit patients by avoiding extensive trauma. The prospective nature of this study lends itself to its reliability and makes it meaningful for clinical practice.
Since Cerfolio et al. introduced the complete portal robotic surgical technique through a lobectomy series in 2011, it has been rapidly promoted and applied in thoracic surgery [
27]. In this study, all operations were performed by one surgical team and initiated with complete portal robotic surgery with CO
2 insufflation, except for one case in which a small utility incision was adopted because of the extensive pleural adhesion that hindered the port setting. We made a small utility incision to facilitate adhesion release and enabled the completion of the port setting. The complete-portal robotic surgical technique provides many advantages over traditional robotic thoracic surgery with a utility incision. First, CO
2 insufflation provides a better view of the surgical field, extending the endoscopic field by lowering the diaphragm and compressing the lung [
13,
15,
28]. This is particularly important for mediastinal tumour resection in remote and narrow spaces. Second, the complete portal robotic procedure described in this study can help avoid interference between surgical instruments and reduce the difficulty of surgery, thereby reducing the requirement for surgical assistance. Only one junior doctor was qualified to perfectly coordinate with the surgeon to complete the operation. In addition, for some small tumours, the specimen can be removed directly from the assistant port without extending the incision, which is conducive to postoperative pain management and rapid recovery. We believe that these advantages in favour of generalisation can help facilitate the widespread use of this technique in clinical practice.
Short-term outcomes, such as perioperative complications, are essential parameters to evaluate the safety and feasibility of the surgical technique [
17,
29]. In this study, only two patients underwent sternotomy, both of which were converted intentionally because of suspected invasion of the innominate veins during intraoperative exploration; however, no operative deaths occurred, indicating the safety and feasibility of our procedures. Similar outcomes were also reported in other studies [
6,
9,
25]. Currently, resection of mediastinal tumours involving major vessels using MIS is challenging, and median sternotomy remains the primary choice for patients with these tumours [
30]. One advantage of RATS is the quick and safe discontinuation of intraoperative bleeding to avoid conversion to open surgery [
30]. Using the fenestrated forceps of the robot, surgeons can directly grab the crevasses of blood vessels to temporarily stop bleeding. Subsequently, surgeons could deal with injured vessels by suturing or other management techniques, which could avoid conversion to sternotomy or thoracotomy in some cases [
30]. In our study period, only one patient had intraoperative bleeding caused by a left innominate vein injury; however, the bleeding point was successfully sutured without conversion owing to the articulated wrist for suturing. Although there was no control group, the fact that there were no emergency conversion in this study indicates that the robotic procedure was superior to the previously reported VATS procedure which showed a much higher unplanned conversion rate [
31].
Previous studies have suggested that it is time-consuming to dock a robot and exchange instruments during surgery [
17,
32,
33]. The proficiency of the assistant and the perfect cooperation of the scrub nurse could effectively reduce these time expenses. With the application of the complete portal robotic surgical technique and perfect cooperation between the assistant and operator, both the docking time and total operation time in this study were much shorter than those in previous studies [
6,
8]. The console time is an essential index that reflects the complexity of the surgery and intraoperative conditions. However, many cohort studies lack such data because of their retrospective nature [
6,
9]. However, our experience revealed that the console time could be reduced compared to VATS. The results of this study are important for the application and expansion of this technique. During the study period, we also performed other robotic procedures, such as robotic lobectomies and oesophagectomies, which may have also contributed to shortening the docking and console times in this study [
13‐
15]. Compared to previous studies, the rest of the perioperative outcomes in our study were comparable or even better, including intraoperative blood loss, postoperative complications, chest tube, drainage, and duration and length of hospital stay [
6,
9]. The results of our study confirm the safety and reliability of RPR for mediastinal tumours.
There are various types of mediastinal tumours [
34]. The pathology in the anterior and superior mediastinum was mainly originated from the thymus, whereas that of the posterior mediastinum was mainly neurogenic. Owing to the different anatomic structures around the tumours and different oncological characteristics, a large difference may exist in terms of surgical outcomes between these tumours. In addition, the selection of suitable patients has traditionally been the critical factor to the success of robotic surgery, especially those with large sizes and complex anatomical positions has always been considered as a contraindication for robotic surgery[
18,
35]. To analyzed the effect of tumour size on perioperative outcomes, all enrolled patients were divided into two groups according to tumour size, with a cutoff of 4 cm. The data suggested that Group B (tumours over 4 cm) had longer operative time, more intraoperative blood loss, longer chest tube drainage, more cost, and longer hospital stay. Moreover, Group B had more perioperative complications, and both the cases that were converted to sternotomy were from Group B. These outcomes are not surprising given the malignant nature of thymoma, with a larger tumour diameter indicating a higher degree of malignancy and invasiveness, more likely to invade adjacent important structures, such as pericardium and innominate vein [
19]. The traditional view is that when the tumour is larger than 4 cm, it is not suitable for minimally invasive robotic surgery, and open surgery should be employed [
17,
36]. In this study, however, with the assistance of a robot, most patients in Group B (tumours over 4 cm) were able to avoid thoracotomy, thereby reducing surgical trauma and accelerating postoperative recovery. These results showed that with the help of robots, the indications for minimally invasive surgery could be expanded. But we should keep in mind that the size of the tumour is not the sole factor to consider in the surgical approach, but the tumour’s relationship with surrounding tissues, such as vascular structures is also crucial to determine if MIS is feasible. For example, some large malignant tumours invade the surrounding vital structures and require neoadjuvant therapy, and the subsequent treatment depends on the response of tumours to the neoadjuvant therapy, the relationship of the tumours with vital structures, and the patients’ physical performance.
Limitations also need to be considered when interpreting our data. First, the sample size was not large enough to conduct subgroup analyses based on different pathological diagnoses, and we will continue to collect additional cases from the prospective database. Second, this was an observational study that focused on the technical point of view but lacked control over other surgical techniques.
In conclusion, our results demonstrated that RPR was safe and effective in the surgical treatment of mediastinal tumours and may help expand the indications of MIS and benefit selected complicated patients by avoiding extensive trauma due to large incisions.
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