Lung cancer is a type of cancer that begins in the lungs. Your lungs are two spongy organs in your chest that take in oxygen when you inhale and release carbon dioxide when you exhale.
Lung cancer is the leading cause of cancer deaths worldwide.
People who smoke have the greatest risk of cancer, though cancer can also occur in people who have never smoked. The risk of this 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 cancer.
Lung cancer typically doesn’t cause signs and symptoms in its earliest stages. Signs and symptoms of this cancer typically occur when the disease is advanced.
Signs and symptoms may include:
- A new cough that doesn’t go away
- Coughing up blood, even a small amount
- Shortness of breath
- Chest pain
- Losing weight without trying
- Bone pain
When to see a doctor
Make an appointment with your doctor if you have any persistent 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 counselling, medications and nicotine replacement products.
Smoking causes the majority of lung cancers — both in smokers and in people exposed to secondhand smoke. But this 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 cancer.
How smoking causes lung cancer
Doctors believe smoking causes 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 cancer you have.
The two general types include:
- Small cell lung cancer. it occurs almost exclusively in heavy smokers and is less common than non-small cell cancer.
- Non-small cell lung cancer. it is an umbrella term for several types of lung cancers. Non-small cells include squamous cell carcinoma, adenocarcinoma and large cell carcinoma.
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 include:
- Smoking. 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 cancer increases if you’re exposed to secondhand smoke.
- Previous radiation therapy. If you’ve undergone radiation therapy to the chest for another type of cancer, you may have an increased risk of developing cancer.
- 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.
- Exposure to asbestos and other carcinogens. Workplace exposure to asbestos and other substances are known to cause cancer — such as arsenic, chromium and nickel — can increase your risk of developing lung cancer, especially if you’re a smoker.
- Family history. People with a parent, sibling or child with cancer have an increased risk of the disease.