By Mayo Clinic staff

November is National Lung Cancer Screening Month and thepurpose of this article is to provide a knowledge base on Lung Cancer and its risk factors.

Definition: Lung cancer is a type of cancer that begins in the lungs. Your lungs take in oxygen when you inhale and release carbon dioxide when you exhale.

Lung cancer is the leading cause of cancer deaths in the United States, among both men and women. Lung cancer claims more lives each year than do colon, prostate, ovarian and breast cancers combined.

People who smoke have the greatest risk of lung cancer. The risk of lung cancer increases with the length of time and number of cigarettes you’ve smoked. If you quit smoking, even after smoking for many years, you can significantly reduce your chances of developing lung cancer.

Symptoms

Lung cancer typically doesn’t cause signs and symptoms in its earliest stages. Signs and symptoms of lung cancer typically occur only when the disease is advanced (which contributes to the high mortality rate).

Signs and symptoms of lung cancer may include:

• A new cough that doesn’t go away
• Changes in a chronic cough or “smoker’s cough”
• Coughing up blood, even a small amount
• Shortness of breath
• Chest pain
• Wheezing
• Hoarseness
• Losing weight without trying
• Bone pain
• Headache

When to see a doctor
Make an appointment with your doctor if you have any signs or symptoms that worry you.

If you smoke and have been unable to quit, make an appointment with your doctor. Your doctor can recommend strategies for quitting smoking, such as counseling, medications and nicotine replacement products.

Causes

Smoking causes the majority of lung cancers — both in smokers and in people exposed to secondhand smoke. But lung cancer also occurs in people who never smoked and in those who never had prolonged exposure to secondhand smoke. In these cases, there may be no clear cause of lung cancer.

How smoking causes lung cancer
Doctors believe smoking causes lung cancer by damaging the cells that line the lungs. When you inhale cigarette smoke, which is full of cancer-causing substances (carcinogens), changes in the lung tissue begin almost immediately. At first your body may be able to repair this damage. But with each repeated exposure, normal cells that line your lungs are increasingly damaged. Over time, the damage causes cells to act abnormally and eventually cancer may develop.

Types of lung cancer
Doctors divide lung cancer into two major types based on the appearance of lung cancer cells under the microscope. Your doctor makes treatment decisions based on which major type of lung cancer you have. The two general types of lung cancer include:

• Small cell lung cancer. Small cell lung cancer occurs almost exclusively in heavy smokers and is less common than non-small cell lung cancer.
• Non-small cell lung cancer. Non-small cell lung cancer is an umbrella term for several types of lung cancers that behave in a similar way. Non-small cell lung cancers include squamous cell carcinoma, adenocarcinoma and large cell carcinoma.

Risk Factors

A number of factors may increase your risk of lung cancer. Some risk factors can be controlled, for instance, by quitting smoking. And other factors can’t be controlled, such as your family history. Risk factors for lung cancer include:

• Smoking. Smoking remains the greatest risk factor for lung cancer. Your risk of lung cancer increases with the number of cigarettes you smoke each day and the number of years you have smoked. Quitting at any age can significantly lower your risk of developing lung cancer.
• Exposure to secondhand smoke. Even if you don’t smoke, your risk of lung cancer increases if you’re exposed to secondhand smoke.
• Exposure to radon gas. Radon is produced by the natural breakdown of uranium in soil, rock and water that eventually becomes part of the air you breathe. Unsafe levels of radon can accumulate in any building, including homes. Radon testing kits, which can be purchased at home improvement stores, can determine whether levels are safe. If unsafe levels are discovered, remedies are available.
• Exposure to asbestos and other chemicals. Workplace exposure to asbestos and other substances known to cause cancer — such as arsenic, chromium and nickel — also can increase your risk of developing lung cancer, especially if you’re a smoker.
• Family history of lung cancer. People with a parent, sibling or child with lung cancer have an increased risk of the disease.
• Excessive alcohol use. Drinking more than a moderate amount of alcohol — no more than one drink a day for women or two drinks a day for men — may increase your risk of lung cancer.
• Certain smoking-related lung diseases. Smokers with certain lung diseases, such as emphysema, may have an increased risk of lung cancer.

Exercise Helps you Live Longer

Numerous studies have shown that exercise can protect against disease and early death. Jonathan Myers, PhD, a clinical assistant professor of medicine at Stanford University School of Medicine, points out recent research findings that support this view:

1. The U.S. Government Recommends 30 Min of Exercise Daily. How much exercise helps you live longer? The Surgeon General’s report on physical activity and health recommends that adult engage in at least 30 min of activity – walking, cycling, yard work, swimming or the like – on most, preferably all, days of the week.
2. Moderate Exercise Can Be Enough. The government recommendations may seem modest. However, a study headed by Steven Blair, PED, senior scientific editor of the Surgeon General’s report, found that survival gains achieved by going from sedentary to moderately active were greater than those achieved by going from moderately active to very active.
3. Walking 2 Miles per Day Can Prolong Life. As part of the Honolulu heart program, researchers studied the benefits of walking at least two miles per day (enough to meet the Surgeon General’s recommendations) versus walking under a mile per day. The subjects were retired men. During the 12-year follow-up, the mortality rate for those who walked less than a mile daily was nearly twice as high as it was for those who walked more than two miles per day.
4. Exercise Lowers Woman’s Risk of Heart Attack. In the Nurses’ Health Study, researchers found that the age-adjusted risk of suffering a coronary event was 54% lower for the most active women than it was for the sedentary women. Even slightly active women had a 23% lower risk than the sedentary group.
5. Frequent Walking Helps. In the same Nurses’ Health Study, women who walked at a brisk pace for 3 or more hours per week significantly reduced their risk of having a heart attack. In fact, walking this much was just about as beneficial as regular vigorous exercise.
6. Obese People Who Stay Fit Live Longer. For the Aerobics Center Longitudinal Study in Dallas, researchers followed more than 25,000 adults for an average of 13 years. The investigators found that obese subjects who were fit were not at a significantly higher risk of early death than their fit, normal-weight counterparts. However, the risk increased more than threefold for unfit, obese subjects.
7. Leisure Time Exercise Yields Benefits. During a 14 ½-year study, researchers from Copenhagen, Denmark, found that the mortality rate of the most physically active subjects was approximately half that of the least active subjects. This trend was consistent, regardless of gender or age.
8. It’s No Good Relying on the Past. In the Framingham Heart Study, researchers found that recent exercise provides more health benefits than exercise performed long ago. So someone who has been sedentary for 40 years cannot rely on an athletic career in college for protection against heart attack. On the positive side, it is never too late to start an exercise program.
9. A Long-Term Program Is Key for Heart Attack Survivors. In a follow-up to the National Exercise and Heart Disease Project, researchers compared men who had suffered heart attacks 19 years earlier. Some had participated in a cardiac rehabilitation exercise program; others had not. At the three-year follow-up, the exercisers had a 31% lower death rate that the non-exercisers. However, after 10 years, there appeared to be no benefit to the exercise. It was clearly important to continue exercising, as the protective mechanisms associated with the rehab program were short-term in nature.
10. Physical Activity Extends Life for Men With Diabetes. In more research from the Aerobics Center Longitudinal Study, researchers studied men with type 2 Diabetes. During the follow-up years, all-cause mortality was more than twice as high for men with a low fitness level as it was for fit men.