Understanding Lung Cancer -- the Basics
Small Cell Lung Cancer
Small-cell lung cancer is the most aggressive form of lung cancer. This cancer usually originates in the large, central bronchi. It spreads quickly, usually within 90 days, often before symptoms appear, making it particularly threatening. In fact, in up to 75% of patients with this type of cancer, the disease has spread by the time it’s diagnosed. It frequently spreads (metastasizes) to the liver, bone, and brain. Although responsive to chemotherapy, small-cell lung cancer is rarely associated with long-term survival.
About 224,000 people in the U.S. will be diagnosed with lung cancer in 2014. It is the second most common cancer in both men and women. However, it is the leading cause of cancer deaths in both sexes -- killing almost 160,000 people each year.
An individual cancer sufferer's prognosis will vary according to the type of lung cancer involved, the person's overall health, and the stage of the cancer at the time of initial diagnosis.
What Causes Lung Cancer?
About 85% of lung cancer is caused by smoking and, as with any cancer, each person's genetics. The fact that lung cancer runs in some families suggests that a predisposition can be inherited. Additionally, certain genetic traits have been identified that make some people more susceptible than others to cancer-causing substances like those found in tobacco smoke.
Nonetheless, anyone who smokes one pack of cigarettes daily is 20 times more likely than a nonsmoker to develop lung cancer. For people who smoke more than two packs a day, the risk more than triples. Breaking the smoking habit reduces risk significantly, yet former smokers are always slightly more susceptible than nonsmokers.
Secondhand tobacco smoke can also cause lung cancer, giving nonsmokers who live or work with smokers a somewhat higher lung cancer risk than those in smoke-free environments. In fact, approximately 3,000 people die each year of lung cancer associated with second hand smoke exposure. And those living in a home with a smoker have a 30% higher risk of developing lung cancer than in a smoke-free home.
Cancer-causing substances other than those found in tobacco or tobacco smoke can also cause lung cancer if inhaled over time. However, experts disagree about how much exposure to specific cancer-causing substances is dangerous. Workers who are exposed on a daily basis to asbestos have a 90-fold increase of getting lung cancer when compared to non-exposed persons. Workers exposed to uranium dust or the radioactive gas radon are also much more likely than the average person to develop lung cancer, especially if they are smokers.
Lung tissue that has been scarred by disease or infection, such as scleroderma or tuberculosis, is more susceptible to tumor growth within the scar tissue (called a scar carcinoma). Because of a high frequency of lung cancer among people who eat large amounts of fat and cholesterol, some researchers speculate that diet may also influence lung cancer risk.