Intrathoracic Tumors: Current Status and Classification

Introduction

Thoracic oncology encompasses a large spectrum of diseases. Between the various anatomic spaces and the different organ systems, there are a large variety of benign and malignant tumors that can develop within the chest. This chapter will focus primarily on the surgical management of the most commonly encountered thoracic malignancies.

General Diagnostic Principles

Aside from a thorough history and examination, certain radiographic studies are essential tools for the thoracic surgeon. A standard chest x-ray provides a good overview—it can show larger lesions and may even show sequelae of smaller lesions such as effusions or postobstructive atelectasis. Different projections can offer additional information. Computed tomography (CT) enables visualization of smaller lesions and helps determine size, location, depth, and relation to other structures. Magnetic resonance imaging (MRI) is limited to assessing neural involvement or differentiating mediastinal structures; it does not usually offer more information than a CT. It is more often used for the evaluation of brain metastases. Positron emission tomography (PET) has become the standard for staging thoracic malignancies because it is more accurate than conventional imaging in detecting metastatic disease.

Lung Cancer

Tumors within the lung parenchyma may arise from primary lung etiologies or because of metastatic disease. The focus of this section will remain on primary lung cancers, for which nonsmall cell and small cell cancers account for over 90%. Smoking remains the single most important risk factor for the development of lung cancer, increasing risk 20-fold compared with nonsmokers. Other risk factors include radiation, other environmental toxins, and pulmonary fibrosis that have synergistic effects.

Most patients are asymptomatic and develop symptoms once locally advanced or metastatic disease is present. Typicalsymptoms can include cough, hemoptysis, chest pain, or dyspnea. Involvement of local structures can result in specific symptoms, such as hoarseness (because of recurrent laryngeal nerve invasion), superior vena cava (SVC) syndrome (facial and upper extremity swelling because of SVC obstruction), and Pancoast syndrome (shoulder pain and Horner syndrome because of superior sulcus tumor invasion).

CT imaging has revolutionized the detection of lung cancer, allowing the discovery of smaller tumors and, consequently, enabling the treatment of earlier stage disease. The International Early Lung Cancer Action Program showed that 85% of patients diagnosed with lung cancer during screening were clinical stage I disease, and that those patients who underwent surgical resection within 1 month of diagnosis had an estimated 10-year survival of 92%. As a result, lung cancer screening has been deemed essential in the diagnosis and treatment of lung cancers such that it is recommended for patients aged 55 to 80 years with a 30-pack-year smoking history by the U.S. Preventive Services Task Force.

Diagnosis can only be confirmed with a tissue biopsy. Surgical biopsy has historically been performed, but, in more recent times, an initial biopsy is performed less invasively with a needle via either a transbronchial or transthoracic approach. Once a malignant diagnosis is obtained, decision on appropriate therapy is driven by the clinical stage. Lung cancer staging is based on the tumor node metastasis (TNM) classification ( Table 4.1 ). In addition to PET imaging and MRI when clinically indicated to evaluate the presence of tumor spread, mediastinal staging may be necessary. This has classically been achieved with mediastinoscopy, but endobronchial ultrasound has seen increased utilization because of its less invasiveness and its ability to assess N1 nodes as well.

Surgery offers the best chance for cure in patients with resectable nonsmall cell lung cancer. For patients who are not surgical candidates or who refuse surgery, local therapy such as stereotactic body radiation therapy can be offered. It is important to differentiate between operability and resectability. Operability refers to the patient’s comorbidities and ability to undergo surgery. Resectability refers to the extent of parenchymal resection required and the patient’s ability to tolerate it in light of their pulmonary functional status. For example, the patient may have a relatively small cancer centrally located such that a pneumonectomy would be required, but the patient would only be able to tolerate a lobectomy.

Clinical stage 1 and stage 2 cancers should proceed directly to surgery. Stage 3 cancers encompass a wide spectrum. N3 disease stage 3 cancers are not surgical candidates. A multidisciplinary approach is the best strategy for non-N3 disease stage 3 cancers and treatment can range from prompt surgery to induction therapy, followed by surgery to definitive chemotherapy with or without radiation therapy. Induction therapy may consist of either chemotherapy alone or chemoradiation therapy and is usually determined by institutional or surgeon practices. There are currently investigations in the role of immunotherapy into the neoadjuvant setting. Pembrolizumab (KEYTRUDA) recently approved by the FDA, is a sample of a drug that presumably stimulates the immune system to attack the cancer cells. Stage 4 cancers are referred for systemic therapy, and surgery is reserved for palliation of symptoms.

Once the decision to proceed with surgery has been made, the extent of resection and surgical approach must be considered. Lobectomy has been considered the gold standard technique for resection. The Lung Cancer Study Group reported increased locoregional recurrence rate and a trend toward decreased survival with limited resection versus lobectomy in 1995 ( Fig. 4.1 ). However, with the advent of lung cancer screening and the discovery of smaller cancers, this is being challenged, as more recent studies suggest no significant differences in recurrence rates and overall survival. The authors consider performing a sublobar resections in patients with small (<2 cm), anatomically feasible cancers with low standardized uptake value ( Fig. 4.2 ). Extended resections may be required in the setting of locally advanced disease, such as chest wall invasion ( Fig. 4.3 ) or invasion of the great vessels.

Thoracotomy is the standard approach for lung resection. However, minimally invasive techniques such as video-assisted thoracoscopic surgery (VATS) and robotic surgery are increasingly being used. Minimally invasive surgery offers short-term benefits, such as less pain, shorter hospital stays, and fewer complications. ^, VATS also appears to offer improved long-term outcomes.

Morbidity after lung cancer surgery is approximately 35%, ^, with the risk of major adverse events 9.1%. Cardiac and pulmonary events are the predominant complications seen. Several risk models have been developed to try to predict perioperative risk for patients. Perioperative mortality is 1.5% to 2.5%.

Esophageal Cancer

Esophageal cancer is the most common primary esophageal malignancy. Squamous cell carcinoma is more prevalent worldwide, with its strong association with smoking and alcohol, but adenocarcinoma is more common in the United States, with the rise of obesity, gastroesophageal reflux disease, and Barrett metaplasia. Because the esophagus traverses through three anatomic domains—the neck, chest, and abdomen—determining the location of the cancer is essential in guiding treatment. Cervical esophageal cancers are primarily treated with chemotherapy and radiation. Middle and lower esophageal cancers are offered multimodality therapy consisting of surgery, chemotherapy, and radiation.

Patients commonly present with dysphagia and weight loss. Diagnosis is obtained with endoscopy. Direct visualization provides information, such as size and location of the mass, and tissue diagnosis is obtained with biopsy forceps. Once the diagnosis is confirmed, clinical stage must be determined ( Table 4.2 ). In esophageal cancer, depth of radial invasion is more important than size in staging. Therefore determining T and N staging is best achieved with endoscopic ultrasound (EUS). Tissue biopsy via ultrasound-guided fine needle aspiration (FNA) can also be performed on suspicious lymph nodes. EUS and EUS-FNA have high sensitivity and specificity in accurately diagnosing T stage and N stage, respectively. However, T2 lesions remain notoriously challenging with an accuracy of approximately 30% because both tumor upstaging and downstaging can occur ( Fig. 4.4 ). Bronchoscopy may be necessary to rule out airway invasion.

Small cancers limited to the mucosa (T1a) can be treated with endomucosal resection, but surgical resection remains the standard therapy for early stage esophageal cancer. Patients with clinical T1 cancers should proceed directly to surgery. Given the level of uncertainty regarding T2 lesions on EUS, it is reasonable to proceed with either surgery or induction therapy for clinical T2 cancers. The authors prefer to proceed directly to surgery. More locally advanced resectable cancers should undergo neoadjuvant chemoradiotherapy with carboplatin and paclitaxel and 41 Gy of radiation, as the Dutch ChemoRadiotherapy for Oesophageal cancer followed by Surgery Study (CROSS) trial showed improved complete resection rates and overall survival with induction therapy. The authors randomly assigned patients with resectable tumors to receive surgery alone or weekly administration of carboplatin and paclitaxel for 5 weeks, followed by surgery. They prospectively enrolled a total of 366 patients, 178 were randomly assigned to chemoradiotherapy followed by surgery, and 188 to surgery alone. Complete resection with no tumor within 1 mm of the resection margins (R0) was achieved in 92% of patients in the chemoradiotherapy-surgery group versus 69% in the surgery group ( P < .001). Overall survival was significantly better in the chemoradiotherapy-surgery group.

Surgical oncologic principles dictate R0 resection with adequate margins over 10 cm and locoregional clearance of metastatic lymph nodes. Surgeon preference, tumor location, patient factors, and ability to adhere to oncologic principles determine the type of approach. Mid- and distal esophageal cancers can be resected via total thoracic esophagectomy with the creation of a neck anastomosis. This is achieved with either a triincisional (McKeown) approach or a transhiatal approach. Distal esophageal cancers can be resected via partial thoracic esophagectomy with the creation of an intrathoracic anastomosis. The neoesophagus is typically recreated using the stomach as the first choice for the conduit but the colon or jejunum may also be used if the stomach is unusable.

McKeown esophagectomy begins in the left lateral decubitus position. A thoractomy is performed, and the right chest is entered in the fifth intercostal space. The inferior pulmonary ligament and the azygos vein are divided. The esophagus is then mobilized from the thoracic inlet down to the hiatus with all periesophageal tissue. A regional thoracic lymphadenectomy is performed. The chest is closed, and the patient placed supine. A midline laparotomy is performed and the stomach is mobilized in its entirety, taking care to preserve the gastroepiploic vessels. A regional abdominal lymphadenectomy is performed. The authors routinely perform a pyloroplasty as a gastric drainage procedure, and the stomach is tubularized into a conduit. A feeding jejeunostomy tube is placed for nutrition. A left cervical incision is then made and dissected down to the esophagus. Once the cervical esophagus is mobilized, the thoracic esophagus and the tubularized stomach is pulled up into the neck. The esophagus is resected and a hand-sewn anastomosis is performed between the cervical esophagus and the stomach.

Transhiatal esophagectomy allows for the resection of the thoracic esophagus without the morbidity of a thoracotomy. This is achieved by performing a laparotomy and a left cervical neck incision and mobilizing the esophagus bluntly by finger dissection from the neck and abdomen. Therefore this may be more advantageous for surgical candidates who are frailer and less likely to tolerate single lung ventilation. However, the main disadvantage of this technique is the inability to perform regional lymphadenectomy, which may be of some prognostic value.

The conventional less invasive Ivor Lewis esophagectomy consists of a laparotomy and a right thoracotomy for esophageal resection, followed by an intrathoracic anastomosis of the gastric conduit, with the proximal esophagus at the level of the proximal mediastinum.

Ivor-Lewis esophagectomy begins in the supine position. A laparotomy is performed, and the stomach is mobilized as earlier. The authors do not tubularize the stomach in the abdomen or place a feeding jejunostomy tube when performing an Ivor-Lewis esophagectomy. The patient is then turned to the left lateral decubitus position, and a right thoracotomy is performed. The chest is entered through the fifth intercostal space, and the thoracic esophagus is mobilized up to the level of the azygos vein. The stomach is brought up in its entirety into the chest, and it is anastomosed to the esophagus.

Perioperative 30-day morbidity and mortality of esophagectomy is 33.1% and 3.1% respectively. Pulmonary complications are most commonly encountered, but the most dreaded complications are anastomotic leak and conduit ischemia. Anastomotic leaks have been reported as high as 30% and are likely related to anastomotic tension and a poorly perfused conduit. Therefore it is not surprising that cervical anastomoses have a higher rate of anastomotic leaks compared with thoracic anastomoses (12.9% vs. 9.3%). However, cervical leaks are easily managed by draining the neck wound and providing local wound control. Thoracic leaks, in contrast, require more invasive interventions with either reoperation for local control or placement of an esophageal stent. Conduit ischemia occurs in 9% of patients and can present as an anastomotic leak or total ischemia. Patients with total ischemia are extremely ill with signs of septic shock. A high degree of suspicion is necessary, and a prompt endoscopy confirms the diagnosis. Emergent surgical removal of the conduit and proximal esophageal diversion is necessary.