Complex lung segmentectomies: current state of art

Introduction

Lobectomy has been standard surgical treatment for non-small cell lung cancer (NSCLC), even for early-stage diseases, after a clinical randomized trial demonstrating 75% increase in recurrence and 30% increase in mortality from segmentectomy or wedge resection compared to lobectomy (1,2). Later on, low-dose computed tomographic screening was shown to reduce lung cancer mortality (3). As a result, lung cancer screening programs were established for high-risk patients (50 to 80 years old current smokers with 20 pack-year history of smoking, or former smokers with 20 pack-year history of smoking who quit smoking within the last 15 years) (4-6). With more and more small sized lung cancer detected, segmentectomy has regained popularity and been increasing in the US (7-10). The widely adopted minimal invasive surgery also promotes segmentectomy. Minimal invasive surgery has been shown to be associated with better perioperative outcomes (shorter length of stay and lower short-term mortality) compared to open approach (10,11). Currently, more than 80% of segmentectomy were performed through minimal invasive surgery (10). Compared to lobectomy, segmentectomy has equivalent survival for stage I NSCLC (12-14). In addition, most recent clinical trials also demonstrated non-inferior outcomes from segmentectomy for small (tumor size ≤2 cm) stage IA NSCLC, compared to lobectomy (15,16). Hence, current clinical guideline considers segmentectomy as appropriate oncologic resection for peripheral nodule ≤2 cm with very low risk features (17).

Definition of complex segmentectomy

Not all segmentectomies are the same. It can be simple or complex. Simple segmentectomy could be defined as a segmentectomy which requires only one linear intersegmental plane dissection, e.g., lower lobe superior segment with lower lobe basal segment, or left upper division with left lingular segment. Complex segmentectomy is defined as a segmentectomy which requires at least two intersegmental plane dissection. Due to additional intersegmental plane dissection, complex segmentectomy has theoretically higher risk of postoperative air leak. Anatomic variations also bring technical challenge for complex segmentectomy with risk of missing targeted segment and positive surgical margin (18,19). Hence, complex segmentectomy, according to our judgement, technically differs from simple segmentectomy significantly.

To perform precise complex segmentectomy, it is critical to identify bronchovascular structures of the targeted segment. Anatomic variations would further challenges and create confusion. Preoperative imaging during NSCLC work up, such as computed tomography scan and positron emission tomography, usually provides sufficient information on anatomy for surgeons to be prepared. We also routinely perform bronchoscopy intraoperatively to confirm the anatomy. Additionally, complex segmentectomy has more intersegmental planes, and intersegmental plane dissection has to be accurate to complete precise complex segmentectomy. When intersegmental plane is uncertain, clamping bronchus of the targeted segment while inflating the lung would show clear intersegmental plane on the parenchyma with and without aeration. When real-time near-infrared imaging system is available, indocyanine green can facilitate visualize the intersegmental plane. We generally use this technique in our robotic segmentectomy procedures.

Simple vs. complex segmentectomy

Nevertheless, studies investigating complex segmentectomy and simple segmentectomy did not show inferior outcomes associated with complex segmentectomy (Table 1). Study populations enrolled in these studies with similar age and gender distributions. Different from the other studies, Bédat et al. included patients with metastasis and benign lesions, and also those who cannot tolerate lobectomy (20). Okubo et al. and Handa et al. only enrolled patients with lung cancer and excluded those who cannot tolerate lobectomy (21,22). As a result, Okubo et al. and Handa et al. have study population more similar to the focus of this commentary. These studies showed comparable overall survival between complex segmentectomy and simple segmentectomy (20,21). Interestingly, Okubo et al. further demonstrated that complex segmentectomy had statistically significantly lower postoperative complications (2% vs. 7%), including less prolonged air leak (0.8% vs. 3.5%) (22), and Bédat et al. demonstrated statistically significantly shorter length of stay associated with complex segmentectomy (5 vs. 7) (20). Handa et al. further compared complex segmentectomy to lobectomy and showed similar prolonged air leak (0% vs. 0%), overall complication (26.3% vs. 21.3%), 5-year survival (93.5% vs. 96.4%), and recurrence-free survival (92.3% vs. 88.5%) (23). One important note for the unexpected high success rate of complex segmentectomy could be, mostly, that the most experienced surgeons from experienced centers would perform complex segmentectomy. This indicates that complex segmentectomy is a safe operation with acceptable outcomes in selected patients.

However, selection bias cannot be ignored in interpretation of these studies. It is important to note that these studies did not include patients who were planned to have complex segmentectomy but converted to lobectomy. In practice, thoracic surgeons would convert to lobectomy when identifying targeted segmental bronchovascular structures is challenging, intraoperative frozen section shows positive surgical margin, a positive lymph node or tumor involvement is more than what is expected before the surgery. These situations are associated with worse surgical outcomes but not included in the comparison of the studies. Further studies accounting for conversion from complex segmentectomy to lobectomy are still needed.

Furthermore, complex segmentectomy and simple segmentectomy might have differential impact on post-operative pulmonary function. Even though clinical trial JCOG0802/WJOG4607L did not show clinical significant difference as much as expected in pulmonary function reserve after segmentectomy versus lobectomy (16), there is evidence that pulmonary function reserve after segmentectomy was associated with the number of intersegmental plane dissection and the presence of an adjacent non-operated lobe for re-expansion (24). Dai et al. showed that superior segmentectomy preserved pulmonary function significantly comparing to the corresponding lobectomy, while basal or left upper anterior segmentectomy did not preserve more pulmonary function than the corresponding lobectomy (24). Nowadays, intersegmental plane dissection is achieved using staplers. Staple line might prevent residual lung parenchyma to re-expand to fill in the pleural space after pulmonary resection (25). As a result, complex segmentectomy with more intersegmental plane dissection would be more difficult to re-expand. Tane et al. also showed that the pleural space after resection was mainly filled with ipsilateral non-operated lobes (25). Hence, pulmonary function reserve after complex segmentectomy is also complex, depending on location of targeted segments and adjacent non-operated lobe.

Conclusions

With more and more segmentectomy performed through widely adopted minimal invasive surgery, thoracic surgeons are facing challenges from preoperative assessment, intraoperative decision making, and post-operative management regarding segmentectomy. Comparing to simple segmentectomy or lobectomy, complex segmentectomy with at least two intersegmental plane dissection is complicated surgery that needs accurate identification of anatomic bronchovascular structures, oncologic principles and special postoperative care. Complex segmentectomy remains an art requiring surgical techniques, clinical caution, and further research.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Journal of Visualized Surgery. The article has undergone external peer review.

Peer Review File: Available at https://jovs.amegroups.com/article/view/10.21037/jovs-24-21/prf

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://jovs.amegroups.com/article/view/10.21037/jovs-24-21/coif). A.T. serves as an unpaid editorial board member of Journal of Visualized Surgery from June 2023 to May 2025. The other author has no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

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