Continuing Education Activity

Segmental lung resection is the removal of the sublobar anatomic portion of pulmonary parenchyma. The current guidelines for lung cancer are for lobar resection, but certain patients may benefit from the removal of less tissue. There is increasing interest and investigation into the efficacy of segmental lung resection in early-stage lung cancer treatment. This activity reviews the indications and approaches to segmental lung resection and highlights the role of the interprofessional team in performing this operation and caring for patients.

Objectives:

• Identify the indications for segmental lung resection.
• Describe the technique in regards to segmental lung resection.
• Review the potential complications of segmental lung resection.
• Summarize interprofessional team strategies that can lead to improved outcomes for patients who require segmental lung resection.

Introduction

Lung cancer is the second most common cancer in men and women in the United States and the leading cause of cancer death. One of the primary treatment approaches for lung cancer is removing all or part of the diseased lung. The earliest lung surgery approaches were limited by the complexity of operating on the lungs without general anesthesia as we know it today. This often resulted in the resection of more healthy tissue than may be necessary. The initial approach involved the removal of an entire lung, the pneumonectomy. As the morbidity and mortality of pneumonectomies became clear, the research ended in less radical procedures.[1] In 1962 Shimkin showed that lobectomy, or removing a single lobe of the lung, was equal to pneumonectomy in survival and carried lower morbidity.[2] This led to the current paradigm wherein lobectomy is the gold standard for lung cancer resection.

The North American Lung Cancer Study Group (LCSG) released a prospective randomized study in 1995 that demonstrated increased recurrence and worse outcomes with sublobar resection than lobectomy in lung cancer.[3] Due to this result, segmentectomy is currently limited to patients that cannot undergo lobectomy. Multiple studies have been conducted to compare lobectomy and segmentectomy, incorporating thoracic surgery advancement since the LCSG study. Jensik first described resection of the anatomic lung segment in 1973.[4] There is ongoing interest in sublobar resection for lung cancer, although currently, indications remain limited.

Anatomy and Physiology

Lung segments are defined by the segmental bronchi and associated vascular supply. The right lung is composed of 3 lobes: the upper lobe, the middle lobe, and the lower lobe. The left lung is composed of 2 lobes: the upper lobe and the lower lobe. Parenchymal segments are labeled with S#. Bronchial anatomy is correlated with segmental anatomy and is labeled with B#. Pulmonary arterial anatomy correlates with segmental anatomy and is labeled with A#. Pulmonary venous anatomy correlates with segmental anatomy and is labeled with V#. Each lung has 10 anatomic segments.

Right Lung

Upper Lobe – The apical segment (S1) is the most superior aspect of the lung. It is defined by B1, A1, and V1. The posterior segment (S2) incorporated the inferior posterior aspect of the upper lobe. It is defined by B2, A2, and V2. The anterior segment (S3) encompasses the inferior anterior aspect of the upper lobe. It is defined by B3, A4, and V4. These segments might be resected individually or together.

Middle Lobe – The lateral segment (S4) is at the middle lobe's posterior and lateral aspect. It is defined by B4, A4, and V4. The medial segment (S5) is at the anterior and medial aspect of the middle lobe. It is defined by B5, A5, and V5. Individual middle lobe segmentectomies are not commonly performed.

Lower Lobe – The right lower lobe comprises two segments, with the basilar segment containing 4 subsegments. The superior segment (S6) is at the superior posterior aspect of the lobe. It is defined by B6, A6, and V6. The basilar segment encompasses the remainder of the inferior aspect of the lobe. It has four subsegments. The medial basal segment (S7) is at the medal base of the lobe. It is defined by B7, A7, and V7. The anterior basal segment (S8) composes the anterior aspect of the lobe. It is defined by B8, A8, and V8. The lateral basal segment (S9) is at the lower lobe's lateral aspect between the anterior and posterior basal segments. It is defined by B9, A9, and V9. The posterior basal segment (S10) composes the posterior aspect of the lobe. It is defined by B10, A10, and V10. Individual basilar subsegmental resections are technically difficult and not commonly performed. Removal of the entire basilar segment is more commonly performed.

Left Lung

Upper Lobe – The left upper lobe has two segments and four subsegments. The upper segment is divided into the apicoposterior and anterior segments. The lingular segment, correlating to the right middle lobe, is divided into superior and inferior segments. The apicoposterior segment (S1+2) forms the superior and posterior aspects of the upper lobe. It is defined by B1+2, A1+2, and V1+2. The anterior segment (S3) forms the anterior and inferior aspects of the upper segment down to the lingula. It is defined by B3, A3, and V3. The superior segment (S4) forms the superior aspect of the lingula. It is defined by B4, A4, and V4. The inferior segment (S5) encompasses the remaining inferior aspect of the lingula. It is defined by B5, A5, and V5. Left upper lobe segmentectomies are most commonly performed by removing the entire segment, upper segment, or lingular segment, and not at the individual subsegmental level.

Lower Lobe – The left lower lobe comprises two segments, but the basilar segment only has 3 subsegments. The superior segment of the lower lobe (S6) forms the superior aspect of the lobe. It is defined by B6, A6, and V6. The basilar segment has three subsegments. The anteromedial basal segment (S8) forms the anterior aspect of the lobe. It is defined by B8, A8, and V8. The lateral basal segment (S9) forms the lobe between the anteromedial and posterior basal segments. It is defined by B9, A9, and V9. The posterior basal segment (S10) forms the posterior aspect of the lobe. It is defined by B10, A10, and V10. Left lower lobe segmentectomies are also commonly performed at the larger segment level, superior and basilar segments, rather than at the subsegmental level.[5]

Lymph Node Stations: The mediastinum consists of 14 lymph node stations described and numbered by Mountain and Dresler in 1997. N2 nodes are within the mediastinal pleural envelope. N2 nodes are within the visceral pleura.[6]

Superior Mediastinum – Station 1 consists of the highest mediastinal nodes. These are found at the level of the left brachiocephalic vein crossing the trachea in the midline. Station 2 consists of the upper paratracheal nodes. These are found at the level of the aortic arch. Station 3 consists of the retrotracheal nodes. Station 4 consists of the lower paratracheal nodes. These are found between the aortic arch and the right main bronchus on the right and between the aortic arch and the left main bronchus.

Aortic Nodes – Station 5 consists of the subaortic nodes. These are found lateral to the ligamentum arteriosum along the pulmonary artery. Station 6 consists of the para-aortic nodes. These are found anterior to the aortic arch.

Inferior Mediastinum – Station 7 consists of subcarinal nodes. These are found inferior to the tracheal carina. Station 8 consists of paraesophageal nodes. These are found inferior to the subcarinal nodes along the esophagus. Station 9 consists of pulmonary ligament nodes. These are found within the inferior pulmonary ligament bilaterally.

N1 Nodes – Station 10 consists of hilar nodes. These are found at the mainstem bronchi. Station 11 consists of interlobar nodes. These are found at the level of proximal lobar bronchi. Station 12 consists of lobar nodes. These are found at the level of distal lobar bronchi. Station 13 consists of segmental nodes. These are found at the level of segmental bronchi. Station 14 consists of subsegmental nodes. These are found at the level of subsegmental bronchi.

Indications

Many disease processes are amenable to anatomic segmental resection: malignant, metastatic, and nonmalignant.

Malignant - Segmental resection is appropriate in select patients with non-small cell lung cancer defined by NCCN:[7][8][9][10]

• Poor pulmonary reserve or other contraindication for lobectomy
• Peripheral nodule with equal or less than 2cm size with pure adenocarcinoma in situ (AIS) histology, greater than 50% ground-glass appearance on CT, or long doubling time confirmed on radiologic surveillance. Segmentectomy should achieve parenchymal margins of equal or greater than 2cm and sample appropriate N1 and N2 lymph node stations.
• Metastatic - Resection of pulmonary metastases has been shown to improve survival in colon cancer. This may involve resection of isolated lesions or multiple lesions to minimize loss of pulmonary reserve.[11][12][13]
• Nonmalignant - Segmentectomy has been documented in congenital malformations (bronchial atresia, bronchiectasis, pulmonary arteriovenous malformation, and pulmonary sequestration), infectious processes (aspergilloma and nontuberculous mycobacterium), and other pulmonary pathology (bronchiectasis and inflammatory pseudotumors).[14][15][16][17][18][19][20]

Contraindications

Currently, segmental sublobar resection is not considered an adequate resection in patients that can tolerate lobectomy. It has also not been studied in patients with small-cell lung cancer. Other relative contraindications are severe emphysema, interstitial pneumonia, and extensive adhesive burden due to previous surgeries, as these may make the operation technically unfeasible.[21]

Equipment

Equipment requirements will depend on the selected surgical approach.

Open approach: double-lumen endotracheal intubation, airplane splint for ipsilateral arm extension, rib spreader, electrocautery, and appropriate staples.

Video-assisted thoracoscopic surgery (VATS) approach double-lumen endotracheal intubation, airplane splint for ipsilateral arm extension, a video system with screens for surgeon and assistant, thoracoscope, electrocautery, and appropriate endoscopic instruments.[22]

Robotic approach: similar to the VATS approach with the addition of the robotic system and instruments.[23]

Personnel

Lung segmental resection should be performed by a trained thoracic surgeon specializing in surgical therapy of lung cancer. All cases should be discussed at a multidisciplinary tumor board to determine appropriate multimodality therapy. This should include oncology, pathology, pulmonology, radiation therapy, and thoracic surgery.

In the operating room, the thoracic surgeon will be joined by an assistant surgeon, an anesthesiologist experienced in single lung ventilation, a scrub nurse familiar with thoracic surgical procedures, and a circulating nurse familiar with commonly used thoracic surgery equipment.

Preparation

A significant number of patients will be identified via lung cancer screening programs. These programs are a valuable tool for identifying and monitoring patients at high risk for lung cancer to diagnose it at a stage that remains amenable to curative therapy. The US preventive services task force (USPSTF) currently recommends annual screening with low-dose CT in adults aged 55 to 80 that have a cumulative 30-pack-year smoking history and currently smoke or have quit within the past 15 years. This topic is currently under discussion, considering decreasing the smoking history to 20-pack-years and starting the age of screening at 50.

All patients with suspected or biopsy-proven lung cancer should undergo appropriate staging workup. Standard assessments include CT chest and abdomen with contrast, smoking cessation counseling, pulmonary function testing, bronchoscopy (may be performed intraoperatively), fluorodeoxyglucose (FDG) positron emission tomography PET-CT scan, and consideration of lymph node evaluation.

Once the decision has been made to proceed with lung resection, all patients need to undergo respiratory testing to determine their ability to tolerate the procedure. The mainstay is pulmonary function testing, V/Q scan, and cardiac stress testing, as indicated.

Technique or Treatment

Open Thoracotomy Approach[24]

The patient is placed in the lateral decubitus position with hyperextension of the chest cavity. Posterolateral thoracotomy is the classic approach. Rib-spreaders are placed for visualization. Single lung ventilation is typically employed. Dissection of the target anatomy is carried out, and resections are performed with appropriate staplers. 

Video-Assisted Thoracoscopic Approach[25]

Typical segmentectomy [segment 6 bilaterally, lingulectomy (left S4 + S5), left upper segment (S1+2 + S3), left basilar segment (S8 + S9 + S10), right basilar segment (S7 + S8 + S9 + S10)] involves dissection in two planes. Standard VATS approach with the patient in lateral decubitus position with hyperextension of the thorax. Make a 3 to 4 cm incision at the 4 or 5 interspace anterior to the latissimus dorsi. Insert the thoracoscope and inspect the pleural cavity. More instruments can be inserted via this single incision, and adhesions should be divided.

For the segmentectomy, identify the pulmonary artery and follow the branching of the upper segments. This is divided by a vascular load stapler. Then the venous supply is identified. With the left upper segmentectomy is must be ensured that the venous drainage from the lingula is not compromised. Finally, the bronchus is identified and stapled off. Then a leak test should be performed. The plane of the parenchyma can then be dissected and the segment removed. Following lung reexpansion, a thoracostomy drain is typically left in place, and closure is performed.

Atypical segmentectomy [individual segmentectomies on the bilateral basilar segments] involve dissection in three planes and are more technically challenging. The appropriate surgical approach must be determined via preoperative imaging and accommodate individual surgeons' skills.

Robotic-Assisted VATS Approach[26]

Positioning is similar to the VATS approach with port-placement determined by the targeted segment. Two common approaches differ on the number of ports, 3 versus 4.[27][28]

Complications

Early postoperative complications from lung resection are pulmonary edema, pneumonia, adult respiratory distress syndrome, bronchial dehiscence, bronchopleural fistula, lobar torsion, hemothorax, chylothorax.

Later postoperative complications from lung resection are bronchial stenosis, empyema, postpneumonectomy syndrome, stump thrombus, and esophagopleural fistula.

Segmentectomy is associated with a higher rate of cancer recurrence and inadequate lymph node sampling, which must be discussed with any patient considering sublobar resection for malignant disease.[29]

Clinical Significance

Lung cancer is the second most common cancer in men and women in the United States and the leading cause of cancer death. The current surgical guidelines for lung cancer call for lobectomy as the minimal resection for most stages. However, certain patients cannot tolerate that level of lung volume reduction and may undergo segmental lung resection. There is also ongoing interest and investigation into segmental lung resection as the first-line surgical approach to early-stage non-small cell lung cancer.

Enhancing Healthcare Team Outcomes

Segmental lung resection is an important component of the lung cancer treatment apparatus. Interprofessional communication is imperative for maximizing the number of patients reached and receiving appropriate care. This begins with primary care providers encouraging healthy lifestyle choices and following screening guidelines. Once identified, a system must be in place to quickly mobilize the workup or follow-up concerning screening findings.

Following the identification of likely lung cancer, the patient should be brought before a multidisciplinary lung cancer board to discuss the course of treatment. Perioperative care will include a thoracic surgeon team, anesthesia, nursing staff, physical therapy, occupational therapy, respiratory therapy, and social workers. Creating a system that follows screening guidelines and quickly moves patients through the workup will, in conjunction with appropriate surgical planning and execution, lead to improved results via identification and treatment of earlier-stage disease.