With the development of SV-VATS, the safety, feasibility, and advantages of this new surgical mode have been recognized by more and more thoracic surgeons. Although it remains a new and challenging surgical technique, the intraoperative bleeding in SV-VATS is less than MV-VATS, while the operating time is not significantly different between SV-VATS and MV-VATS.[6] Patients showed satisfaction to SV-VATS for its advantages in reducing postoperative complications and accelerating postoperative recovery compared to MV-VATS. One possible reason may be that SV-VATS attenuate the inflammatory responses caused by surgery and stimulate cellular immune function.[6] SV-VATS reduced patient subjective discomfort after surgery.[23, 24] Without tracheal intubation, SV-VATS reduces the adverse effects such as intubation-related airway trauma, residual neuromuscular blockade and irritable, and postoperative cough.[25] Besides, SV-VATS reduces the risk of moderate or more thoracic effusion and is associated with shorter extubating time.[6, 26] Shorter extubating time is associated with less postoperative pain and shorter hospital stays as well.[27] Finally, SV-VATS is associated with reduced risk of short-term postoperative complications and financial burden of patients.
Although the obvious advantages of SV-VATS have been recognized, SV-VATS imposes higher requirements on careful patient selection, appropriately experienced anesthetic, and surgical teams, which restrict the more extensive application and further development of SV-VATS to some extent. Currently, SV-VATS can only be performed on selected patients in a few centers. For institution applying this technique, it is important for surgeons and anesthesiologists to select the proper patients in the early phase of learning curve. This is necessary and the first step to decrease the risk of conversion to intubated general anesthesia and complications.[28]
Currently, consensus for SV-VATS has been published. Surgeons and anesthesiologists can select patients according to the inclusion and exclusion criteria in consensus. However, such consensus is not just for patients with NSCLC, but also other thoracic diseases. Besides, the consensus was based on a larger population of patients, which cannot quantitively predict the risk in an individual patient. For example, patients older than 60 years old are not suggested to undergo SV-VATS in the consensus. However, evidence has showed that patients over 65 years old can still undergo SV-VATS and have a comparable effect with MV-VATS.[10, 23] Besides, BMI > 30 kg/m2 is an exclusion criterium of SV-VATS in the consensus. However, research has reported that it was safe and feasible for patients with BMI > 30 kg/m2 to undergo SV-VATS and the effect was comparable to MV-VATS.
In fact, while making a surgery plan for each patient, clinicians will consciously or subconsciously assign point to each potential risk factors based on the published literature and experience. Plan for treatment will be formed based on the total score in mind. However, such skill is highly subjective and difficult to disseminated to less-experienced surgeons and anesthesiologists. Besides, even expert may make mistakes sometimes. Therefore, a more robust and customized surgery decision model is urgently needed to identify the optimal candidates for SV-VATS among patients with NSCLC.
Nomogram, which has been proven to be capable of assisting the preoperative assessment and surgical planning, is readily used, and interpreted by clinical workers owing to its intuitive features. In this study, we built an SDS model in the form of nomogram with several clinically and statistically significant predictors via univariate and multivariate logistic regression analysis. Many common and readily accessible information like age, BMI, smoking status, Fev1/FVC, TMN stage, ASA grade and surgical technique are included. Only when the factor is significant in both univariate and multivariate logistic regression analysis can be included in the model and be assigned certain points. Finally, based on the demographic characteristics, oncological information, and operation information from the patient with NSCLC, a total points and probability to perform SV-VATS will be generated from the surgery decision model. Exceptionally, Fev1/FVC was maintained in the model even though it did not reach statistical significance in the multivariate analysis, because it is an important factor that needs to be considered in clinical surgical plan. Besides, the concordance index was 0.738 and 0.739 before and after the inclusion of FEV1/FVC respectively, which indicated that the inclusion of FEV1/FVC improved the overall performance of the model. The computed AUC values of the training set and the test set were 0.725 and 0.772 respectively, which indicated a high precision in the prediction of the model.
The model is promising in clinical applications, especially in the centers that are new to the technique of SV-VATS. Three major elements are needed for a successful SV-VATS: careful patient selection, appropriately experienced anesthetic, and surgical teams. Although SV-VATS is still a new and challenging technique with a steep learning curve, the latter two elements can be improved by systemic training. Currently, there have been many lobectomy video tutorials based on single-hole the SV-VATS.[29] Besides, the advances in image recognition techniques and artificial intelligence-assisted identification of anatomic sites can also help building a better understanding of a new surgical technique.[30] Our center has also made similar attempts in SV-VATS. the follow-up results are in progress. As for the first element, selecting optimal patients is not just about repeated practice and experience, but it needs a more objective basis. Therefore, with the model we developed, professional and systematic training, and technical improvement, SV-VATS can be developed better and applied more widely in patients with NSCLC.
Nevertheless, there are still some limitations. First, the SV-VATS is a relatively new technique and only practicable in a few hospitals by some experienced anesthetists. External validation has not been scheduled, which may reduce the reliability of the SDS model. Second, there might be potential selection bias due to the limited sample size. Third, whether the other surgical procedures applied to our model remains to be seen and further improvement is needed in future research.