The concept of broad exposure facilitates uniportal video-assisted thoracoscopic mediastinal lymph nodes dissection

At present, lung cancer is the malignant tumor with the highest morbidity and mortality [1]. Surgery is the best treatment for early stage lung cancer. Video-assisted thoracoscopic surgery (VATS) for radical resection of lung cancer has been becoming the mainstream method of lung cancer surgery in recent years. The development of uniportal VATS technology brings a more minimally invasive treatment method for lung cancer patients. Systematic lymph node dissection, an important part of radical resection of lung cancer is one of the main factors affecting the long-term prognosis [2]. Some studies believe that uniportal VATS for radical resection of lung cancer can achieve similar surgical results as traditional triportal VATS [3, 4].

However, the fluency of the uniportal VATS is seriously affected by the mutual interference of instruments used by the operator and the assistant. The limited exposure of the surgical field seriously affects the safety of operation and the integrity of mediastinal lymph nodes dissection (MLND). MLND is challenging for uniportal VATS radical resection of lung cancer, the key lies in how to effectively expose the mediastinal lymph nodes (MLNs). Insufficient incision of the mediastinal pleura results in a tapered or tunnel-like operation surface, which increases the difficulty of uniportal video-assisted thoracoscopic mediastinal lymph node dissection. We summarized the experience of uniportal video-assisted thoracoscopic MLND in recent years and proposed the concept of broad exposure. The objective of this study was to report the concept of broad exposure and investigate the efficacy and safety of this concept in 204 patients who underwent uniportal video-assisted thoracoscopic MLND.

All operations were successfully completed under uniportal VATS following the concept of broad exposure, including 193 cases of lobectomy, 8 cases of bilobectomy, 3 cases of pneumonectomy. The perioperative results were shown in Table 2. The median surgery time was 102 min (range, 76–285 min), and the median blood loss was 50 ml (range, 20–900 ml). The median chest tube duration time was 2 days (range, 1–6 days), and the median postoperative hospital duration time was 5 days (range, 4–10 days). The final pathological examination revealed that all patients had radical resection with negative margins, 121 cases of adenocarcinoma, 64 cases of squamous cell carcinoma, and 19 cases of other types of non-small cell lung cancer. The median number of dissected lymph node stations was 8(6–9), the median number of dissected lymph nodes was 15(12–19), the median number of dissected MLNs stations was 5(3–6), the median number of dissected MLNs was 11(10–15). The up-staging rate of N staging was 6.86%(3 patients upgraded from cN0 to pN1, 7 patients upgraded from cN1 to pN2a, 4 patients upgraded from cN2a to pN2b). The postoperative complication rate was 10.29% (21/204, including 1 patient with chylothorax, 2 patients with arrhythmia, 1 patient with hoarse voice, 6 patients with atelectasis, 9 patients with lung infection and 2 patients with others). All patients had no obvious symptoms when they left hospital, and there was no perioperative death. No recurrence or death was observed within 13 months of the median follow-up (range, 1–30 months), and the last follow-up was until March 2020.

Since 2004, uniportal VATS was first reported for biopsy of pulmonary nodules, its application scope has been gradually expanded for lobectomy, segmentectomy, vascular reconstruction and bronchoplasty with the improvement of endoscopic instruments and surgical techniques [5‐7]. Some studies believed that uniportal VATS for lung cancer radical surgery had advantages in controlling postoperative pain, reducing postoperative chest tube duration, shortening postoperative hospital duration, and had the same effect of lymph node dissection compared with triportal VATS [8]. Because MLND is an important part of radical resection for lung cancer, the integrity of MLND under uniportal VATS is a key factor in determining whether radical resection of tumor can be achieved. Some limitations of uniportal VATS, such as mutual interference between instruments, insufficient exposure, and high coordination requirements between surgeon and assistant [9], these all increase the difficulty and surgical risk of uniportal video-assisted thoracoscopic MLND.

In our study, uniportal video-assisted thoracoscopic MLND was performed following the concept of broad exposure. A wide range of incision of the mediastinal pleura relieves the mediastinum pleura from covering the MLNs, and increases the mobility of the lung and hilar tissue. The assistant pushes the lung lobe in a certain direction away from the MLNs, so that the deeper MLNs become superficial. The sufficient isolation for the target area of the operation with suction device and energy equipment, and the appropriate skeletalization of the surrounding structure makes it easier to achieve complete dissection of the MLNs. Our results showed that the total number of dissected lymph nodes and dissected lymph nodes stations were 15(12–19) and 8(6–9), respectively; the number of dissected MLNs and dissected MLNs stations were 11(10–15) and 5(3–6), respectively. We strictly followed the principle of complete lymph node resection,lymph node fragmentation was inevitable, the reported number of lymph nodes was based on post-operative pathology reports. The uniportal video-assisted thoracoscopic MLND following the concept of broad exposure meets the requirements of radical resection of lung cancer [10], at least three stations of MLNs be dissected, subcarinal lymph nodes must be included, and the number of dissected MLNs must not be less than 10.

The uniportal video-assisted thoracoscopic MLND following the concept of broad exposure reduces the instruments in the surgical operation area, avoids the mutual interference between instruments to the greatest extent, reduces the surgeon’s dependence on assistants, and increases the cooperation between the surgeon and the assistant. According to our results, there were no perioperative deaths, the median operation time (102 min)and the median intraoperative blood loss (50 ml) were comparable to the data reported in another study [11]. The safety of video-assisted thoracoscopic MLND following the concept of broad exposure was confirmed by our results. When exposure is insufficient, it is easy to cause damage to the lymphatic vessels and vagus nerve branches. The risk of conventional tunneling lymph node dissection was reduced by exposure to large planes.

It’s difficult to expose the operating area during the process of uniportal video-assisted thoracoscopic MLND, especially the subcarinal lymph node located in the posterior mediastinum. There are many important organs around the carina and the operation space is narrow. At present, most surgeons use the method of pulling the lung forward to expose the subcarinal area [12], which may cause lung damage. The concept of broad exposure emphasizes the protection of important organizational structures while exposure to large planes. Use sponge forceps to push lung tissue instead of directly clamping and pulling to reduce lung tissue damage. The device should be used to block the nerve to the side or lift the fascia near it, rather than directly pull the nerve to move it away from the operation area. Our results showed that the incidence of postoperative complications, median postoperative drainage duration and median postoperative hospital duration were 10.29%, 2 days and 5 days, respectively. There was no increase in tissue damage due to broad exposure compared with the data reported by Cai et al. [13]. So broad exposure requires not only adequate exposure, but also the protection of important organs.

This study has some limitations. First, this is a single-center retrospective study that may have a selection bias; second, there is a lack of long-term follow-up of the included patients. However, broad exposure is a novel concept proposed by our center for uniportal video-assisted thoracoscopic MLND, it may provide new surgical ideas for thoracic surgeons. We plan to conduct a prospective comparative study within multiple centers in the future, and observe the long-term effects of the patients, to further investigate the advantages of uniportal video-assisted thoracoscopic MLND following the concept of broad exposure.

According to our results, it’s effective and safe to perform uniportal video-assisted thoracoscopic MLND following the concept of broad exposure. This new concept emphasizes sufficient exposure, which makes it easier to achieve complete dissection of MLNs, while focuses on protection of important tissues. Its long-term efficacy needs to be confirmed by further follow-up.