Cancer of the Lung

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Cancer of the Lung

Chapter Objectives

After reading this chapter, you will be able to:

• List the anatomic alterations of the lungs associated with cancer of the lung.

• Describe the causes of cancer of the lung.

• List the cardiopulmonary clinical manifestations associated with cancer of the lung.

• Describe the general management of cancer of the lung.

• Describe the clinical strategies and rationales of the SOAPs presented in the case study.

• Define key terms and complete self-assessment questions at the end of the chapter and on Evolve.

Key Terms

Anatomic Alterations of the Lungs

Cancer is a general term that refers to abnormal new tissue growth characterized by the progressive, uncontrolled multiplication of cells. This abnormal growth of new cells is called a neoplasm or tumor. A tumor may be localized or invasive, benign or malignant.

Benign tumors do not endanger life unless they interfere with the normal functions of other organs or affect a vital organ. They grow slowly and push aside normal tissue but do not invade it. They are usually encapsulated, well-demarcated growths. They are not invasive or metastatic; that is, tumor cells do not travel by way of the bloodstream or lymphatics and invade or form secondary tumors in other organs.

Malignant tumors are composed of embryonic, primitive, or poorly differentiated cells. They grow in a disorganized manner and so rapidly that nutrition of the cells becomes a problem. For this reason, necrosis, ulceration, and cavity formation are commonly associated with malignant tumors. They also invade surrounding tissues and may be metastatic. Although malignant changes may develop in any portion of the lung, they most commonly originate in the mucosa of the tracheobronchial tree.

Lung cancer arises from the epithelium of the tracheobronchial tree. Thus a tumor that originates in the bronchial mucosa is called bronchogenic carcinoma. The terms lung cancer and bronchogenic carcinoma are used interchangeably. As a tumor enlarges, the surrounding bronchial airways and alveoli become irritated, inflamed, and swollen. The adjacent alveoli may fill with fluid or become consolidated or collapse. In addition, as the tumor protrudes into the tracheobronchial tree, excessive mucous production and airway obstruction develop. As the surrounding blood vessels erode, blood enters the tracheobronchial tree. Peripheral tumors also may invade the pleural space and impinge on the mediastinum, chest wall, ribs, or diaphragm. A secondary pleural effusion is often seen in lung cancer. A pleural effusion further compresses the lung and causes atelectasis.

The major pathologic or structural changes associated with bronchogenic carcinoma are as follows:

Etiology and Epidemiology

Lung cancer is the leading cause of cancer deaths in the United States. According to the American Cancer Society 2008 surveillance report, it is estimated that more than 214,000 new cases of lung cancer are reported in the United States annually—about 114,000 in males and about 100,000 in females. Although lung cancer accounts for about 15% of all cancers in both men and women, it is responsible for about 31% of all cancer deaths in men and about 26% of all cancers in women. Among women, the lung cancer death rate is now higher than the death rate of any other cancer, including breast cancer (15% for breast cancer versus 26% for lung cancer). The higher incidence of lung cancer in women is primarily because of their increased rate of cigarette smoking. Death from lung cancer generally begins when patients are 35 to 44 years of age. A sharp increase in lung cancer deaths is seen among patients 45 to 55 years of age. The incidence of lung cancer death progressively increases to 74 years of age and then levels off and decreases in extremely old individuals.

Cigarette smoking is the most common cause of lung cancer. Although various studies and professional organizations report slightly different numbers, all the figures are grim. For example, according to the Centers for Disease Control and Prevention (CDC) and the Surgeon General’s report, male smokers are 22 times more likely to develop lung cancer than nonsmokers, whereas female smokers are 12 times more likely than female nonsmokers to develop lung cancer. Heavy smokers are 64 times more likely to develop lung cancer. It is estimated that cigarette smoke contains more than 4000 different chemicals, many of which have proved to be carcinogens. Passive, or second-hand, smoking is associated with as much as a 30% increase in the risk for lung cancer. A genetic predisposition toward developing lung cancer also plays a role in the incidence of lung cancer.

Environmental or occupational risk factors for lung cancer include the following:

Types of Cancers

There are four major types of bronchogenic tumors: (1) squamous (epidermoid) cell carcinoma, (2) adenocarcinoma (including bronchial alveolar cell carcinoma), (3) large cell carcinoma, and (4) small cell (oat cell) carcinoma (see Figure 26-1). For therapeutic reasons, these bronchogenic tumors are commonly divided into the following two groups:

image
FIGURE 26-1 Cancer of the lung. A, Squamous cell carcinoma. B, Adenocarcinoma. C, Large cell carcinoma. D, Small cell (oat cell) carcinoma.

Each group grows and spreads in different way. For example, SCLC spreads aggressively and responds best to chemotherapy and radiation therapy. It occurs almost exclusively in smokers and accounts for over 20% of all lung cancers in the United States. NSCLC is more common and accounts for about 80% of all lung cancers in America. When confined to a small area and identified early, this type of cancer often can be removed surgically. Table 26-1 provides general characteristics of these cancer cell types, including growth rates, metastasis, and means of diagnosis. A more in-depth description of each cancer cell type follows.

Table 26-1

Characteristics of Lung Cancers

Tumor Type Growth Rate Metastasis Means of Diagnosis
Squamous cell carcinoma Slow Late; mostly to hilar lymph nodes Biopsy, sputum analysis, bronchoscopy, electron microscopy, immunohistochemistry
Adenocarcinoma Moderate Early Radiography, fiberoptic bronchoscopy, electron microscopy
Large cell carcinoma Rapid Early and widespread Sputum analysis, bronchoscopy, electron microscopy (by exclusion of other cell types)
Small cell (oat cell) carcinoma Very rapid Very early; to mediastinum or distally in lung Radiography, sputum analysis, bronchoscopy, electron microscopy, immunohistochemistry, and clinical manifestations (cough, chest pain, dyspnea, hemoptysis, localized wheezing)

image

Modified from McCance KL, Huether SE: Pathophysiology: the biologic basis for disease in adults and children, ed 5, St Louis, 2006, Mosby.

Non–Small Cell Lung Carcinoma

Squamous cell carcinoma

Squamous cell carcinoma constitutes approximately 30% of the bronchogenic carcinomas. The incidence of this type of cancer has sharply declined over the past two decades. This type of tumor is commonly located near a central bronchus or hilus and projects into the large bronchi. Squamous cell tumors are often seen projecting into the bronchi during bronchoscopy. The tumor originates from the basal cells of the bronchial epithelium and grows through the epithelium before invading the surrounding tissues.

The tumor has a slow growth rate and a late metastatic tendency (mostly to hilar lymph nodes). These tumors generally remain fairly well localized and tend not to metastasize until late in the course of the lung cancer. Cavitation and necrosis within the center of the cancer is a common finding. Surgical resection is the preferred treatment if metastasis has not taken place. In about one third of the cases, squamous cell carcinoma originates in the periphery. Because of the location in the central bronchi, obstructive manifestations are generally nonspecific and include a nonproductive cough and hemoptysis. Pneumonia and atelectasis are often secondary complications of squamous cell carcinoma. Cavity formation with or without an air-fluid interface is seen in 10% to 20% of the cases (see Figure 26-1, A).

Adenocarcinoma

Adenocarcinoma arises from the mucous glands of the tracheobronchial tree. In fact, the glandular configuration and the mucous production caused by this type of cancer are the pathologic features that distinguish adenocarcinoma from the other types of bronchogenic carcinoma. It accounts for 35% to 40% of all bronchogenic carcinomas. Adenocarcinoma has the weakest association with smoking. However, among people who have never smoked, adenocarcinoma is the most common form of lung cancer. Adenocarcinoma tumors are usually smaller than 4 cm and are most commonly found in the peripheral regions of the lung parenchyma. The growth rate is moderate and the metastatic tendency is early. Secondary cavity formation and pleural effusion are common (see Figure 26-1, B). When the cancer is discovered early, surgical resection is possible in a high percentage of cases.

Bronchial alveolar cell carcinoma is included under the category of adenocarcinoma. These tumors typically arise from the terminal bronchioles and alveoli. They have a slow growth rate, and their metastasis pattern is unpredictable.

Small Cell Lung Carcinoma

Small cell carcinoma accounts for about 14% of all bronchogenic carcinomas. Most of these tumors arise centrally near the hilar region. They tend to arise in the larger airways (primary and secondary bronchi). Cell size ranges from 6 to 8 µm. The tumor grows very rapidly, becoming quite large, and metastasizes early. Because the tumor cells often are compressed into an oval shape, this form of cancer is commonly referred to as oat cell carcinoma. Staging for small cell carcinoma is divided into only two categories: limited disease (20% to 30%) or extensive disease (70% to 80%). Small cell carcinoma has the poorest prognosis. The average survival time for untreated small cell carcinoma is about 1 to 3 months. Small cell carcinoma has the strongest correlation with cigarette smoking and is associated with the worst prognosis (see Figure 26-1, A).

Screening and Diagnosis

A routine chest x-ray is the most common screening test used to identify an abnormal mass or nodule in a patient’s lung. Computed tomography (CT) and positron emission tomography (PET) scans are also frequently used to reveal extremely small lesions and determine whether the cancer has spread to other areas. A definitive diagnosis, however, can be made only by viewing a tissue sample (biopsy) under a microscope. Common procedures used to obtain a tissue biopsy include bronchoscopy, thoracoscopy, mediastinoscopy, transbronchial needle biopsy or open-lung biopsy, sputum cytology, thoracentesis, and videothoracoscopy (see Chapter 8).

Staging of Lung Cancer

Staging is the process of classifying information about cancer. The staging system describes the cancer cell type, the size of the tumor, the level of lymph node involvement, and the extent to which the cancer has spread. The patient’s prognosis and treatment depend, to a large extent, on the staging results. The system most often used for the staging of lung cancer is the TNM classification (Table 26-2). T represents the extent of the primary tumor, N denotes the lymph node involvement, and M indicates the extent of metastasis. On the basis of the TNM findings, roman numerals are used to identify stages I through IV, with 0 being the least advanced and IV the most advanced. Figure 26-2 provides five representative illustrations of the staging of lung cancer by the TNM classification system. A general overview and description of the staging process for non–small cell lung cancer and small cell lung cancer follows*:

Table 26-2

1997 Revised International System for Staging Lung Cancer

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Symbol Definition
Primary Tumor (T)
T0 No evidence of tumor
Tx Tumor that cannot be assessed or is not apparently radiologically or bronchoscopically (malignant cells in bronchopulmonary secretions)
Tis Carcinoma in situ
T1 Tumor with the following characteristics:
 a  Size: ≤3 cm
 b  Airway location: in lobar bronchus or distal airways
 c  Local invasion: none, surrounded by lung or visceral pleura
T2 Tumor with any of the following characteristics:
 a  Size: >3 cm
 b  Airway location: tumor in the main bronchus (within 2 cm of the carina) or tumor with atelectasis involvement of the main bronchus (distance to the carina is 2 cm or more) or presence of atelectasis or obstructive pneumonitis that extends to hilar region but does not involve the entire lung
 c  Local invasion: involvement of the visceral pleura
T3 Tumor with the following location or invasion:
 a  Size: any
 b  Airway location: tumor in the main bronchus (within 2 cm of the carina) or tumor with atelectasis or obstructive pneumonitis of the entire lung
 c  Local invasion: invasion of chest wall (including superior sulcus tumors), diaphragm,mediastinal pleura, or parietal pericardium
T4 Tumor with the following location or invasion:
 a  Size: any
 b  Airway location: satellite tumor nodule(s) within the ipsilateral primary-tumor lobe of the lung
 c  Local invasion: invasion of the mediastinum, heart, great vessels, trachea, esophagus, vertebral body, or carina; or presence of malignant pleural/pericardial effusion
Lymph Nodes (N)
Nx Regional lymph nodes cannot be assessed
N0 Absence of regional lymph node involvement
N1 Presence of metastasis to ipsilateral peribronchial or ipsilateral hilar lymph nodes or both (including direct extension to intrapulmonary nodes)
N2 Presence of metastasis to ipsilateral mediastinal or subcarinal lymph nodes or both
N3 Presence of metastasis to any of the following lymph node groups: contralateral mediastinal, contralateral hilar, ipsilateral or contralateral scalene, or supraclavicular
Distant Metastasis (M)
Mx

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