Abstract
This retrospective single-center study evaluated and compared the short-term outcomes of robot-assisted thoracic surgery (RATS) segmentectomy with those of conventional segmentectomy performed via thoracotomy or video-assisted thoracic surgery (VATS). The primary objective was to assess the safety of RATS segmentectomy. Our findings demonstrated that RATS segmentectomy was found to be as safe as conventional segmentectomy, with shorter operation times and hospital stays. No significant differences were observed in intraoperative blood loss and rates of surgical complications. However, prolonged postoperative air leaks are a potential concern. Among simple segmentectomy cases, RATS still showed shorter operation time and hospital stay. The longer experience of the surgeons in the RATS group may be a reason for the shorter operation time in this group. Additionally, the use of preoperative transbronchial marking with indocyanine green dye and barium, and intraoperative identification of intersegmental boundaries using intravenously administered indocyanine green dye may contribute to shorter operation time. Further studies are warranted to clarify the long-term oncological outcomes.
Introduction
Video-assisted thoracic surgery (VATS) lung resection was introduced in the 1990s and rapidly gained worldwide acceptance, as it exhibited better 5-year survival outcomes than open thoracotomy in patients with stage I non-small cell lung cancer1). In 2022, 73% of surgeries for primary lung malignancy in Japan were VATS procedures2). Today, robot-assisted thoracic surgery (RATS) segmentectomy for primary lung malignancy is on the rise3-5). The number of RATS procedures performed in Japan has rapidly increased since RATS became covered by the national health insurance system in April 2018. In 2022, 5,497 cases were performed, accounting for 12% of all primary lung malignancy surgeries2). Because recent studies have demonstrated favorable long-term outcomes for sublobar resection of small non-small cell lung cancers (≤20 mm)6,7), segmentectomy is being performed in a higher proportion of patients. In Japan, segmentectomy was performed in 11% of primary lung malignancy cases in 20178);this increased to 17% in 20222), and it is expected to continue to increase in the future. However, most segmentectomy studies involve VATS6,7). In a meta-analysis comparing VATS and RATS lobectomy/segmentectomy, short-term outcomes and number of lymph nodes removed did not differ between the groups9). The outcomes of RATS segmentectomy have not yet been sufficiently evaluated.
In a retrospective analysis comparing RATS segmentectomy with open/VATS segmentectomy, operation time, blood loss, and duration of chest tube drainage were shorter/lower in the RATS group. Additionally, the incidence of postoperative complications was similar between the groups, suggesting that RATS segmentectomy is useful10). Another report found no differences between RATS and VATS segmentectomy in terms of short-term outcomes11). Thus, short-term outcomes for RATS segmentectomy appear to be favorable. However, more evidence is warranted.
This single-center study retrospectively compared short-term outcomes of RATS segmentectomy with those of conventional (VATS or open) segmentectomy to determine the safety of RATS segmentectomy. The primary objective was to assess the safety of RATS segmentectomy. We began performing lung resection using the da Vinci Si system (Intuitive Surgical, Sunnyvale, CA, USA) in 2019;the Xi and X systems (Intuitive Surgical) were introduced in 2021. RATS segmentectomy was first initiated using the Xi system in 2022. We perform the procedure in accordance with previously reported methods4,12), which enables the surgeon to use the bipolar energy device and stapler from either the left or right arm. Since we have been performing VATS segmentectomy using three ports under an upward view, we anticipated that the performance of surgery under the same field of view would be relatively smooth for both the surgeon and assistant. Additionally, we thought that the ability for the surgeon to control energy devices and staplers from both sides could expand the surgeon’s discretion.
Materials and Methods
Patient selection
A study flow chart is shown in Figure 1. We reviewed 88 patients who underwent lung segmentectomy at Fukushima Medical University Hospital from January 2017 to December 2024. Patients who underwent preoperative treatment and those whose operation was converted from segmentectomy to lobectomy were excluded from study eligibility. To compare short-term outcomes, we excluded 12 patients who underwent both lobectomy and segmentectomy simultaneously and one in whom resection of distant segments was performed simultaneously. Among the 75 patients included for analysis, 43 underwent conventional surgery, and 32 underwent RATS. In the conventional surgery group, 37 underwent VATS and 6 underwent open thoracotomy. VATS was generally performed for patients with clinical stage IA lung cancer. Those with clinical stage IB or higher underwent VATS if they were unable to tolerate lobectomy due to respiratory function or other factors and it was technically feasible. VATS was actively considered for diseases other than lung cancer. However, RATS was limited to treatment of lung cancer owing to insurance coverage considerations, including clinical stage IA, stage IB, and higher stages. Clinical and pathological staging was performed according to the eighth edition of the TNM Classification. RATS operation time was analyzed as total operating time rather than console time. Postoperative complications were graded using the Clavien–Dindo classification system. This study was conducted according to the guidelines of the Declaration of Helsinki and was approved (approval no. REC2024-174;February 25, 2025) by the institutional Ethics Committee of Fukushima Medical University.
Surgical procedure
All surgeries were performed under general anesthesia with the patient in the lateral decubitus position. The lungs were ventilated separately using a double-lumen endotracheal tube. Open thoracotomy was performed using a skin incision of 8 cm or more and a rib spreader. VATS was performed entirely under thoracoscopy through three skin incisions of less than 4 cm (Figure 2A). The operator performs the surgical procedure from the patient’s abdominal side, while the assistant performs the procedure from the back side. In both open thoracotomy and VATS, the intersegmental plane was dissected using both staplers and an electric cautery. We began performing RATS segmentectomy in our hospital using the da Vinci Xi system through five ports in January 2022. Skin incisions are shown in Figure 2B. The axillary wound is an access port for the assistant. Patient cart rolls in from the oblique head of the patient’s surgical side. In RATS, the intersegmental plane was divided using da Vinci SureForm staplers. Hilar and mediastinal lymph node dissection was not mandatory in any of the operations performed.
Preoperative transbronchial marking of the lesion
Preoperative marking of the lesion is commonly performed13) because intraoperative identification of the lesion (typically a ground-glass nodule in early-stage non-small cell lung cancers) can be difficult. The conventional transbronchial barium marking method was used14). Briefly, 0.2 to 0.5 mL of barium was injected near the target lesion using a bronchoscope with virtual bronchoscopic navigation 2 days before surgery. Computed tomography (CT) was performed the day before surgery to confirm the location of the barium in relation to the lesion. During the operation, the injected barium was found using x-ray fluoroscopy. In cases required for preoperative marking in RATS, 0.1 mL of indocyanine green (ICG) dye was injected immediately before the barium for preoperative transbronchial marking two days prior to surgery. This was because X-ray fluoroscopy cannot be used during RATS owing to interference between the machines. The ICG dye was identified during surgery using a near-infrared camera. Barium was continued to be used to confirm the location of the lesion and the marking site in preoperative CT. The ICG dye/barium method was also used for preoperative marking in some VATS cases since 2022.
Identification of intersegmental lines
To identify the intersegmental line during surgery, the conventional inflation-deflation method was used. The bronchoscope was wedged into the bronchus of the lesional segment and air was injected using jet ventilation. In January 2022, we began to also use systemic administration of ICG. Five mg of ICG was administered after dividing the pulmonary artery of the lesional segment and a near-infrared scope was used15).
Classification of segmentectomy
Segmentectomy was classified as simple or complex. In simple segmentectomy, there is only one plane between the segments to be resected and those to be preserved. Simple segmentectomy includes left upper segmentectomy (S1+2 and S3), left lingular segmentectomy (S4 and S5), S6 segmentectomy, right basal segmentectomy (S7-S10), and left basal segmentectomy (S8-S10). In contrast, in complex segmentectomy, there are two or more planes between the segments to be divided. Complex segmentectomy includes any segmentectomy other than simple segmentectomy.
Statistical analysis
Continuous and categorial variables were compared using the Mann–Whitney U test and Fisher’s exact test, respectively. Statistical analyses were performed using Prism software version 10.4.2 (GraphPad Software, Inc., La Jolla, CA, USA). All statistical tests were two-sided. P <0.05 was considered significant.
Results
Clinicopathological characteristics
Figure 3 shows the annual number of cases of lung segmentectomy performed at our hospital stratified by surgical approach. The total number has been increasing since 2017. RATS segmentectomy was approved by Japan’s health insurance system in 2020, and we began performing it in January 2022. The proportion of segmentectomies performed via RATS increased rapidly from 44% in 2022 to 94% in 2024. Conversely, the proportion of VATS procedures is decreasing. We have not performed an open thoracotomy for lung segmentectomy since 2022.
Patient and surgical characteristics of the conventional and RATS groups are shown in Table 1. The proportion of simple segmentectomies was significantly higher in the RATS group (97% vs. 74%;p = 0.0101). The two groups did not significantly differ in terms of age, sex, smoking history, clinical diagnosis (lung cancer, metastatic tumor, and other), c-stage (in patients with lung cancer), or laterality of surgery. The prevalence of pulmonary emphysema and interstitial pneumonia was not different between the two groups. No patients experienced acute exacerbation of interstitial pneumonia after surgery. Among the seven patients with metastatic lung tumor in the conventional group, the primary disease was as follows:colorectal cancer in five, renal cancer in one, and liposarcoma in one;in the two RATS group patients, the primaries were renal cancer and malignant melanoma, respectively. In the conventional surgery group, the four patients with a diagnosis classified as other included two with benign lung tumors, one with a solitary fibrous tumor, and one with intralobar pulmonary sequestration. The surgeon’s years of experience were significantly longer in the RATS group (17 vs 13 years;p < 0.0001).
Surgical outcomes
Short-term surgical outcomes are shown in Table 2. Operation time was significantly shorter in the RATS group (184 vs. 219 min;p = 0.0029). Intraoperative blood loss volume and duration of chest tube drainage did not differ between the groups. Length of hospital stay was significantly shorter in the RATS group (5.5 vs. 7 days;p = 0.0473). In each group, one patient experienced intraoperative injury of the pulmonary artery. The overall incidence of surgical complications during the three months after surgery did not significantly differ between the groups. The incidence of prolonged air leak was significantly higher in the RATS group (19% vs. 2%;p = 0.0376). No other type of complication occurred in the RATS group. In the conventional group, other surgical complications included pneumonia (two cases), pleural effusion (one case), cardiac arrhythmia (one case), and hypoxemia (one case). Since the proportion of simple segmentectomies was significantly higher in the RATS group, we performed the same analysis within the patients who underwent simple segmentectomy (Table 3). The operation time (185 vs 221 min;p = 0.0056) and length of hospital stay (6 vs 7 days;p = 0.0379) were significantly shorter in the RATS group. Although there was a tendency toward more prolonged air leakage in the RATS group, there was no significant difference.
Preoperative marking and intraoperative identification of intersegmental boundaries
Figure 4 shows CT and operative findings of a patient with early-stage lung cancer who underwent preoperative transbronchial marking using both ICG dye and barium. Table 4 shows the number of cases in which preoperative marking was performed and the intraoperative method used to identify segment boundaries. In the conventional group, preoperative marking was performed in only one patient (using barium alone). In the RATS group, barium alone was not used in any patient, ICG dye combined with barium was used in seven, and no marking was performed in 25. The distribution in frequency and method of preoperative marking significantly differed between the groups (p = 0.017). The intraoperative method used to identify segment boundaries significantly differed between the groups (p <0.0001):systemically administered ICG dye was used in 25 RATS group patients (78%), whereas the inflation-deflation method was used in 31 conventional group patients (72%).
Discussion
Lung segmentectomy has been increasing in our hospital in recent years, and the proportion of RATS has also been increasing. This trend has been accelerating in recent years because of the increase in diagnosis of tumors <20 mm in size16) and the favorable results of randomized controlled trials6,7). The adoption of RATS has also progressed rapidly worldwide2,17).
Compared with lobectomy, segmentectomy requires a deeper understanding of anatomy and more precise surgical maneuvers18). The results of our study show that RATS segmentectomy appears to be safe and feasible. Our short-term RATS segmentectomy outcomes were comparable to those of the conventional procedure. The absence of non-malignant tumors in the RATS group is due to insurance coverage reasons. We considered that the high proportion of simple segmentectomies in the RATS group might explain the shorter operation time in this group, but even when limited to patients who underwent simple segmentectomy, the operation time was shorter in the RATS group. The longer experience of the surgeons in the RATS group may be a reason for the shorter operation time in this group. We attempted to avoid complex segmentectomy as much as possible when introducing RATS segmentectomy in our hospital. In a 2019 study comparing complex and simple segmentectomy for stage I non-small lung cancer, although operation time was significantly longer for complex segmentectomy, 30-day mortality, overall complications, and prolonged air leakage were nearly equivalent19). Nonetheless, when introducing RATS segmentectomy, avoiding complex segmentectomy seems to be prudent.
Our results support previous reports of early RATS segmentectomy outcomes10,11). RATS using the da Vinci Xi system enhances the surgeon’s dexterity through high-resolution three-dimensional visualization. The system provides precise wrist-like instruments (EndoWrist Technology), making it suitable for segmentectomy, as it facilitates surgery in more complex procedures and in challenging anatomical conditions20). However, the robotic joints outside the field of view may cause lung injury and air leak, so special care is required. Additionally, it is thought that CO2 insufflation into the thoracic cavity during RATS is effective for expanding the surgical field and suppressing minor bleeding21).
The following three factors are considered to have affected the results of our study:the minimally invasiveness of RATS, preoperative marking with ICG dye and barium, and intraoperative identification of the intersegmental plane using intravenous administration of ICG dye.
Regarding the minimally invasiveness of RATS, the fixation of the equipment at the remote center may reduce intraoperative intercostal nerve compression20). This may contribute to reduced postoperative pain and shorter hospital stays.
Next, preoperative marking using ICG dye and barium is considered useful for improving short-term surgical outcomes. It is particularly thought to assist in decreasing operation time. Additionally, compared with marking using barium alone, it can prevent intraoperative radiation exposure. The high frequency of preoperative marking with ICG dye and barium in the RATS group was influenced by the increase in sublobar resection. Furthermore, since the tumor is not palpable, preoperative marking is considered more important in RATS than in conventional surgery. We inform our pathologists when these preoperative marking methods are used, and it does not appear to have affected pathological diagnosis. Although pneumothorax caused by transbronchial ICG dye marking has been reported22), we did not experience any such adverse events in this series. Compared with percutaneous marking, the risk of bleeding or air embolism is significantly lower, making the transbronchial approach a safer option13). Although virtual-assisted lung mapping22) injects ICG dye at multiple sites on the intersegmental plane, our method targets only the lesion, so it is simpler. In our method, we consider it desirable to inject barium with ICG dye when confirming the spatial relationship between the lesion and the site marked before surgery on CT. This is because, in virtual-assisted lung mapping, where ICG is injected at the intersegmental plane, the ICG is separated from the lesion, making it easy to identify the marked site in the lung field on CT. However, in our method, which directly marks the lesion, it is difficult to identify the marked site on CT if using ICG alone because the lesion and marking are overlapped.
Finally, for intraoperative identification of the intersegmental line, systemic administration of ICG dye is simpler and more useful than the inflation-deflation method. Blood flow evaluations using ICG dye have been covered by health insurance in Japan since 2018. In the inflation-deflation method, the segment to be resected is selectively inflated with jet ventilation using the bronchoscope. It can confirm the targeted bronchus not only in the surgical field, but also under bronchoscopy. However, bronchoscopy during surgery is time-consuming and requires a thorough understanding of the patient’s bronchial anatomy. Chest surgeons sometimes need to perform the bronchoscopy by themselves. In contrast, systemic administration of ICG dye allows identification of blood flow defects within approximately 15 seconds after intravenous injection using a near-infrared camera23). Therefore, it contributes to shortening operation time. In a meta-analysis of VATS segmentectomy, systemic administration of ICG dye was associated with shorter operation time, shorter hospital stay, and lower incidence of postoperative complications than the inflation-deflation method24). Compared with the inflation-deflation method, the resection margin is approximately 13 mm closer to the resection side;however, the success rate of identifying the intersegmental line was higher with systemic ICG dye administration23). In patients with emphysema, identification using the inflation-deflation method is difficult. Furthermore, intravenously administered ICG dye rapidly binds to plasma proteins, is transported to the liver, and is excreted into bile. It is also safe, although a few instances of anaphylaxis have been reported25). Our preoperative transbronchial marking is performed in the planned resection area, and the systemically administered ICG dye causes fluorescence of the area to be preserved, so the fluorescence does not overlap.
This study has several limitations. It was retrospective in design and did not use patient background adjustment methods such as propensity score matching. The conversion rate to lobectomy is an important indicator of short-term results in segmentectomy. However, it was difficult to accurately identify conversion cases retrospectively. Therefore, we were unable to analyze conversion rate to lobectomy. In addition, we did not compare long-term outcomes between RATS and conventional segmentectomy. Although a previous report showed no difference in long-term outcomes26), we would like to conduct additional studies at our hospital by following up on recurrence-free survival and overall survival.
In conclusion, we found RATS segmentectomy to be as safe as conventional segmentectomy, with shorter operation times and hospital stays; moreover, intraoperative blood loss and rates of surgical complications did not significantly differ. Our five-port access RATS lung segmentectomy may be considered safe. However, prolonged air leaks are a potential problem. Preoperative transbronchial marking using ICG dye and barium, and intraoperative identification of intersegmental boundaries using intravenously administered ICG dye contributed to reducing operation time. Long-term treatment outcomes require further investigation.
Conflict of Interest Disclosure
The authors have no conflicts of interest to disclose.
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