The eighth edition of the TNM classification for staging lung cancer was derived from a retrospective analysis of 94,708 patients with diagnosed lung cancer (1). A study conducted by Asamura et al. that analysed 26,326 patients with any T staging category and no metastasis (M0), showed a difference in prognosis in neighbouring pathological N (pN) categories. The 5-year survival rate according to pN status was 75% for N0, 49% for N1, 36% for N2, and 20% for N3 (2). The N stage is the most significant prognosticator in lung cancer surgery. A robust lymph node evaluation is therefore imperative to optimise oncological outcomes for curative intent lung surgery.

The International Association for the Study of Lung Cancer (IASLC) guidelines consider adequate dissection of lymph nodes as stations 2R, 4R, 7, 10R, and 11R for right-sided tumours and 5, 6, 7, 10L, and 11L for left-sided tumour. Additionally, they recommend that station 9 be dissected in patients undergoing a lung cancer resection involving the lower lobe.

The efficacy of lymph node dissection with a VATS approach has been shown to have equivalent outcomes with an open thoracotomy approach (3, 4). A meta-analysis by Zhang and colleagues comparing VATS and open lung resections for stage 1 lung cancer found fewer total lymph nodes were dissected in the VATS group compared to the open group (5). Comparisons between VATS and RATS have demonstrated non-inferior lymph node dissection in RATS (6, 7). Toker and colleagues having compared open, VATS and RATS reported greater N1 dissection with RATS approach (8). Robot-assisted thoracic surgery has gained wider adoption in this timeframe and the evaluation of optimal lymph node dissection remains (6–8); hence we aim to add to the literature by comparing lymph node dissection in RATS, and VATS lung resection for NSCLC patients.

We analysed the database using Excel software (Microsoft Corp, Seattle, WA). Between-group differences were evaluated using the Chi-test for categorical variables and the Wilcoxon-Mann-Whitney test for continuous variables. All statistical tests were two-tailed, and p values < 0.05 were considered statistically significant. All analyses were carried out using GraphPad Prism version 9.5.1 (528).

The total number of operations in the database was 717. The RATS group accounted for 375 (52.3%) operations (223 right-sided and 152 left-sided), the VATS group accounted for 342 (47.7%) operations (205 right-sided and 137 left-sided).

Out of the 717 operations, 570 (79.5%) of the operations were lobectomies. This was followed by 117 (16.3%) segmentectomies and 30 (4.1%) wedge resections. The RATS group accounted for 313 of the lobectomies, this was measured 257 times via VATS approach. There were 58 RATS segmentectomies compared to 59 VATS segmentectomies.

Lymph node dissection remains a topic of investigation in the era of robot-assisted minimally invasive thoracic surgery. The ACOSOG Z0030 trial showed that mediastinal lymph node dissection provides the patient with the most accurate staging and opportunity for adjuvant therapy if occult metastatic disease is present (9).

The N component of the TNM staging is useful for physicians assessing malignancies that have significantly different prognoses. The importance of cancer staging has been compounded with recent trials suggesting the addition of neoadjuvant or adjuvant immunotherapy may improve event-free survival or disease-free survival of lung cancer (10). The FDA has approved the use of nivolumab and atezolizumab as neoadjuvant and adjuvant treatment for stages II and IIIA NSCLC respectively based on the CheckMate 816 and Impower010 trials (11, 12). Staging the patients correctly will enable the identification enabling increasingly effective treatment options.

In our study, we have shown a higher degree of lymph node dissection in RATS operations compared to VATS operations in patients undergoing lung resection for early-stage NSCLC lung cancer. The ROMAN study demonstrated superior lymph node dissection in RATS. The results showed a median number of seven hilar nodes dissected with RATS compared to four with VATS. In addition, there was a median of seven mediastinal nodes dissected by RATS compared to five by VATS. Both findings in the trial were statistically significant (13). The RVLob trial, a randomised control trial comparing robot-assisted lobectomy to video-assisted lobectomy demonstrated a higher degree of lymph node dissection in robot robot-assisted approach (14). Conversely, a meta-analysis by Hu et al. looking at twenty retrospective cohort studies argued that there was no statistically significant advantage between VATS and RATS (15). The risk stratification of the TNM staging relies on proper application, the prognostic value of pN depends on the thoroughness of the assessment (16). In this context, improving surgical nodal staging must be prioritised for optimal oncological outcomes.

A possible explanation for the increased level of dissection in robotic operations is the enhanced range of motion with articulated extensions when dissecting lymph nodes compared to video-assisted operations. Palande et al. reasoned that difficulties with VATS lymph node dissection were mostly due to suboptimal exposure, especially for subcarinal nodes (17). In addition to the broadened range of motion, a three-dimensional view of the operative field in robot-assisted operations equips the operating surgeon with an enhanced visualisation of the lymph node. The different surgical modalities have been compared in the literature. Toker et al. comparing open, VATS and RATS lymph node dissection reported superior N1 lymph node dissection in RATS operations when compared to VATS. The group speculated that the sharp dissection of the vascular sheath around the pulmonary vessels in RATS procedures compared to a blunt dissection in VATS procedures could explain the higher degree of N1 lymph nodes obtained in RATS (8). From a technical perspective, it is feasible to dissect each mediastinal and hilar lymph node station with a VATS approach however a RATS approach provides the surgeon with better imaging and retraction opportunities when compared to VATS.

Nodal upstaging occurs when the patient is found to have more advanced disease compared to the clinical assessment in the preoperative period. A study by Kneuertz et al. comparing 1,053 patients with clinical stage N0/N1 NSCLC undergoing RATS, VATS and open lung resection found that the overall rate of LN upstaging was highest in open thoracotomies (21.8%) followed by RATS (16.2%) and VATS (12.3%) (18). Open procedures have been demonstrated to have a significantly higher rate of upstaging than VATS procedures (19–21). This could be due to the patient selection for open procedures as opposed to minimally invasive procedures. Between VATS and RATS, nodal upstaging from N0 to N1 was seen in 21 out of 342 (6.1%) of VATS operations and 26 out of 375 (6.9%) RATS operations. The difference between the two groups was negligible and not significant. One possible explanation is that a lot of the VATS data is more historic, and performed during a time when mediastinal staging techniques were less developed. Nodal upstaging acts as a surrogate for the extent of lymph node sampling and subsequently effective oncological staging, as such correlation with survival remains a key area of study in the future.

Cost effectivity is a controversial point of discussion, one of the outcomes of the RVLob trial was the higher hospitalisation cost of the robot-assisted approach (14). A detailed micro-cost analysis by Shanahan et al. showed that the increased cost of RATS was primarily driven by the higher cost of consumable equipment and the secondary reason was higher staff expenses (22). The RAVAL trial studying if robot-assisted lobectomy is cost-effective and offers improved patient-reported health utility in early NSCLC when compared to video-assisted lobectomy is ongoing. Early results released in 2023 suggest that robot-assisted lobectomy is cost-effective with similar patient-reported health utility (23).

There are certain limitations to our study these include being a retrospective study with a relatively small sample size of 717 patients. This study was conducted at a single tertiary centre by two surgeons limiting the generalisability of the study and introducing operator dependency to the data presented. The study does not include long-term data on outcomes such as survival or recurrence.

In this study, we compare lymph node dissection obtained from RATS approach and VATS approach for lung resection of NSCLC. We analysed data on N1/N2 lymph node dissection and nodal upstaging. We conclude that there is a higher rate of overall lymph node dissection in RATS approach when compared to VATS. These findings suggest that RATS may be a more effective approach for achieving adequate lymph node dissection in patients with early NSCLC, however it is important to appreciate that this can be attributed to other factors including the skill of the surgeon and complexity of the procedure, not solely the employed technique.