Non-Small-Cell Lung Cancer
Non-Small-Cell Lung Cancer
Lung cancer has been the leading cause of cancer death among men in the United States for years, and since 1988, it has become the number-one cause of cancer death among women. An estimated 226,160 new cases of lung cancer are expected in 2012, and 160,340 deaths due to this disease are expected to occur, roughly 28% of all cancer deaths. This exceeds the combined number of deaths from cancer of the next leading sites (breast, prostate, and colon). Lung cancer accounts for 6% of all deaths in the United States.
Lung cancer develops from pulmonary parenchymal or bronchial supportive tissues. Although multiple cell types are often found within a single lung tumor, one type usually predominates. Based on the therapeutic approach, there are two major subdivisions of lung cancer: small-cell lung cancer (SCLC) and non–small-cell lung cancer (NSCLC). Non–small-cell tumors account for approximately 85% of all lung cancers. The three major tumor types included under this category are adenocarcinoma, squamous cell carcinoma, and large-cell carcinoma.
This chapter provides basic information on the epidemiology, etiology, screening, prevention, and signs and symptoms of lung cancer in general and then focuses specifically on the diagnosis, staging, pathology, and treatment of NSCLC and carcinoid tumors of the lungs, as well as on the pulmonary evaluation of lung cancer patients and follow-up of long-term survivors.
The following chapter provides information on the staging, pathology and pathophysiology, and treatment of the far less common small-cell lung cancer and concludes with brief discussions of mesothelioma and thymoma.
In October 2012, the US Food and Drug Administration (FDA) approved nab-paclitaxel (Abraxane) for use in combination with carboplatin in patients with locally advanced or metastatic NSCLC who are not candidates for curative surgery or radiation. Approval was based on results of CA031, a phase III randomized, open-label trial involving 1,052 patients randomized to receive a weekly infusion of nab-paclitaxel at 100 mg/m2 (n = 521) or an infusion of paclitaxel at 200 mg/m2 every 3 weeks (n = 531). Patients in both treatment arms also received carboplatin at the same dose and schedule (area under the concentration-time curve [AUC] of 6 mg/mL/min ) every 3 weeks. The CA031 trial met its primary endpoint, demonstrating a statistically significantly higher overall response rate for patients in the nab-paclitaxel–containing arm of 33% (95% confidence interval [CI], 29–37) compared with 25% (95% CI, 21–28) for patients in the paclitaxel-containing arm (P = .005). The durability of responses was similar for responding patients in the two treatment groups, with median response durations of 6.9 months and 6 months for the nab-paclitaxel and paclitaxel arms, respectively.
Also in October, the FDA expanded the labeling for pemetrexed (Alimta) to include continuation maintenance, in light of recent research. Results of PARAMOUNT, a phase III randomized clinical trial involving 539 patients with locally advanced or metastatic non-squamous NSCLC, showed that first-line pemetrexed plus cisplatin therapy followed by continuation maintenance with pemetrexed (compared with placebo) yielded significant improvements in both progression-free and overall survival (hazard ratio [HR] = 0.62; 95% CI, 0.49–0.79; P < .0001).
In the United States, the estimated number of new lung cancer cases for 2012 is 116,470 for men and 109,690 for women. Although the incidence of lung cancer had been rising in women, the rate of increase has begun to slow recently. The incidence is decreasing in men.
The age of patients at which lung cancer is diagnosed varies widely, but the median age at diagnosis is approximately 70 years.
In the United States, the highest incidence of lung cancer in men and women is found in African Americans (102.7/100,000 for men and 51.4/100,000 for women), followed by Caucasians (83.7/100,000 for men and 57.2/100,000 for women).
There are geographic variations in the incidence of lung cancer, with the highest rates worldwide observed in North America and Eastern Europe; in the United States, the highest rates are found in northern urban areas and along the southern coast from Texas to Florida. The state with the highest incidence of lung cancer is Kentucky, with an incidence of 130.1/100,000 in men and 79.5/100,000 in women.
The overall 5-year survival rate for lung cancer is 16%, of which there has been a 1% improvement each decade for the past 30 years.
Approximately 87% of all cases of lung cancer in the United States are related to cigarette smoking. There is a relatively strong dose-response relationship between cigarette smoking and the development of this cancer. The greater the number of cigarettes smoked on a daily basis and the greater the number of years of smoking, the greater is the risk of lung cancer. An individual who smokes one pack of cigarettes daily has a 20-fold increased risk of lung cancer compared with a nonsmoker.
The overall incidence of cigarette smoking decreased from 1974 through 1992. Smoking cessation decreases the risk of lung cancer, but a significant decrease in risk does not occur until approximately 5 years after discontinuation, and the risk remains higher in former smokers than in nonsmokers for at least 25 years. The benefit of smoking cessation is greater if it occurs at a younger age.
Smoking cessation is difficult. Recent data have suggested that a variety of hereditary factors increase the risk of addiction to nicotine among some individuals. Nevertheless, millions of former smokers have quit successfully. Smoking cessation programs that address both physical withdrawal from nicotine and psychological dependence appear to be more effective than either of these approaches alone. In addition, continued efforts are needed to prevent adolescents and preadolescents from beginning to smoke and to encourage them to quit after a brief period of experimentation.
Several cancer centers have recently reported that more than half of their patients with newly diagnosed lung cancer are former smokers, having quit more than 1 year before diagnosis. Healthy ex-smokers represent a large group of individuals who may benefit from effective tools for early detection and/or chemoprevention of lung cancer.
Not only is smoking risky for those who smoke, but it also poses a hazard to nonsmokers who either live or work with smokers. It is estimated that approximately 3,000 lung cancer deaths per year in the United States are due to secondhand smoke. Individuals who live in a household with a smoker have a 30% increase in the incidence of lung cancer compared with nonsmokers who do not live in such an environment.
Exposure to asbestos is another risk factor for lung cancer. Cigarette smokers who are exposed to asbestos develop lung cancer at an extremely high rate. There is a 90-fold increase compared with unexposed individuals. Exposure to asbestos is also a major risk factor for the development of mesothelioma (see discussion of this cancer in the following chapter).
Radioactive Dust and Radon Exposure
Uranium miners who have been exposed to radioactive dust and radon gas also have an increased incidence of lung cancer. Although there has been some controversy about the risk posed by exposure to residential radon gas, a study conducted in Sweden showed an increased incidence of lung cancer in individuals who were exposed to a high level of radon in their homes.