Lung Cancer: Overview and Symptoms
Lung cancer is the most common cause of cancer death for men and women worldwide. It is usually an aggressive cancer with a five-year survival rate of less than 15 percent. In the United States, there are nearly 200,000 cases diagnosed every year and 150,000 deaths.
Environmental exposures, particularly tobacco smoke and, to a lesser extent, air pollution, asbestos, and radon, are the chief causes of lung cancer. Tobacco smoking accounts for more than 90 percent of cases.
In advanced stages, the cancer invades surrounding organs and spreads (or "metastasizes") elsewhere in the body. Sites of spread include the brain, liver, and bone.
There are four types of lung cancer, which have different clinical features.
- Squamous cell carcinoma is the most common type, accounting for 40 percent of cases. It begins in the central and upper parts of the lung and generally grows slowly.
- Adenocarcinoma accounts for 25 percent of cases. It usually occurs in the outer sections of the lung. These also grow slowly, but they can spread beyond the lung faster than squamous cell carcinoma.
- Small cell carcinoma accounts for 20 percent of cases. Virtually all cases are attributable to tobacco use. These cancers are aggressive. They grow quickly and spread beyond the lung early in the course of the disease.
- Large cell carcinoma accounts for about 15 percent of cases. This type also advances quickly and spreads beyond the lung aggressively.
- Generalized weakness and fatigue
- Persistent cough: More than 90 percent of lung cancer patients complain of a gradually worsening cough. As the disease progresses, patients often cough up blood (hemoptysis).
- Chest pain: The pain is usually sharp and may be associated with breathing.
- Weight loss and loss of appetite
- Persistent fever
- Shortness of breath
- Difficulty swallowing or painful swallowing
- Recurring infections, such as bronchitis and pneumonia
- Advanced cases that spread beyond the lung may cause bone pain, neurologic changes (e.g., numbness, weakness, dizziness, seizures), jaundice (yellowish discoloration of the skin), and other symptoms.
- Cigarette smoking: This accounts for at least 90 percent of cases.
- Passive smoking: Epidemiologic evidence suggests that exposure to "secondhand" smoke increases the risk of lung cancer by 20 to 25 percent in nonsmokers.
- Occupational hazards: Regular occupational exposure to asbestos, chromium, nickel, benzopyrene, acroleine, nitrous monoxide, hydrogen cyanide, formaldehyde, nicotine, radioactive lead, carbon monoxide, insecticides or pesticides containing arsenic, glass fibers, or coal dust increases workers' risk of lung cancer.
- Family history: Smokers who have a family history of lung cancer have more than 10 times increased risk of developing lung cancer themselves.
- Air pollution: In industrialized areas with high rates of air pollution, the death rate from lung cancer is up to five times greater than in rural, less polluted areas.
- Chronic or recurrent respiratory diseases, such as pneumonias, bronchitis, and tuberculosis.
- Ionizing radiation exposure, such as X-rays and radon gas.
- Diet and nutrition: See Nutritional Considerations.
- The first step is a medical history and physical examination.
- Blood testing is often performed.
- Chest X-ray can detect cancers up to two years before symptoms appear. It defines the tumor size and location and can track progression or remission.
- Several tests are available to further visualize and define a lung tumor, including CT scan, bronchoscopy, ultrasound, and other tests.
- Ultimately, definitive diagnosis requires a biopsy of the tumor.
Prevention is clearly the most effective strategy. Smoking cessation is strongly recommended-both for lung cancer patients and their families. Smokers who quit experience a gradual risk reduction over time. When prevention has failed, the following treatment steps apply:
- The primary treatment for most cases of lung cancer is surgery. Surgery may involve removal of part or the entire diseased lung.
In many cases, surgery will not cure the disease. However, it may significantly improve symptoms and prolong survival.
- Radiation therapy is usually recommended in early stages of cancer and may be used with or without surgery to remove the tumor. Newer techniques have been developed to improve the effect of the radiation and decrease side effects.
A potential side effect of radiation is severe lung dysfunction (called "irradiated lung"). Symptoms include severe shortness of breath, cough, chest pain, fever, and malaise.
- Chemotherapy is the primary treatment for small cell lung cancers, and is used in addition to surgery and radiation for other types of lung cancers.
- Additional therapies to address the symptoms of lung cancers include pain medications, sleep medications, cough medicines, and antibiotics.
Lung Cancer: Nutritional Considerations
While avoiding tobacco and other carcinogens is critical for preventing lung cancer, the following nutritional factors are also associated with lower risk of lung cancer in research studies, and may play a role in prevention:
- A plant-based diet: Some studies suggest that vegetarian diets are associated with a lower risk for lung cancer. Other studies have associated red meat (particularly ham, sausage, and liver), saturated fat, and dairy products with an increased risk.
- Fruits and vegetables: Several studies show that individuals with diets rich in vegetables and fruits have a reduced risk for lung cancer. This may be due to various nutrients, including antioxidants, carotenoids, vitamin C, flavonoids, and folic acid.
A study of antioxidant consumption found that individuals with the highest antioxidant consumption from fruits and vegetables had a significantly lower risk for lung cancer. However, there appears to be no decrease in lung cancer risk in people who take antioxidant supplements, and there is some evidence that beta-carotene supplements may actually raise lung cancer risk in some groups of people. In other words, antioxidants from foods are helpful in reducing lung cancer risk; those from supplements are not.
- Limited alcohol intake: Individuals with the highest intakes of beer and spirits appear to have an increased risk of lung cancer, as much as three times the risk compared with nondrinkers.
Part (though not all) of the increased risk from alcohol may be due to its association with smoking. Another reason may be that acetaldehyde, which is formed as a metabolite of alcohol in the body, is a known carcinogen.
In contrast, some studies suggest that moderate consumption of wine is associated with reduced risk for lung cancer. Cause and effect has not been established, however, and alcohol should not be used as a cancer-prevention strategy.