Lung cancer, the most common cause of cancer death according to the Merck Manual, has a very high mortality rate. The average survival rate at 5 years after diagnosis ranges from 3 percent for cancers that have spread, or metastasized to 52.9 percent for cancer discovered while still localized to one area, the American Cancer Society reports. Lung cancer is divided into two types: small cell and non-small cell, with non-small cell proving far more common, comprising 8 out of 9 cases. Substances that irritate the lungs over time cause lung cancer.
Smoking
Smoking, by far the most common cause of fatal lung cancer, directly causes around 85 percent of all lung cancer cases. Smoking has a cumulative effect on the lungs; the longer a person has smoked and the more packs a day he consumes, the more likely he is to develop lung cancer. Approximately 10 percent of former and current smokers will develop lung cancer, according to Merck. While non-smokers comprise 15 percent of patients with lung cancer, smokers, even former smokers, always have a higher rate of developing lung cancer.
While cigarette smokers have the highest rate of lung cancer, pipe and cigar smokers also have a much higher rate of lung cancer than non-smokers, almost as high as cigarette smokers. Small cell cancer, the most deadly type of lung cancer, occurs almost exclusively in cigarette smokers, MedlinePlus states. Marijuana smokers may also have an increased risk of lung cancer, especially if they also smoke cigarettes, says the American Cancer Society.
Radon Gas
Radon gas, the most common cause of fatal lung cancer in non-smokers and the second most common cause of lung cancer overall, according to the Environmental Protection Agency, is colorless, odorless and tasteless. Radon--released when uranium breaks down in rocks and soil--occurs naturally outside in such small concentration that it proves harmless. Indoors, especially in poorly ventilated below ground areas like basements, radon can accumulate, especially in houses built on top of uranium deposits. Radon testing can show where levels are high in a house. Ventilating the area reduces the risk of lung cancer, reports the American Cancer Society. People who smoke and also become exposed to radon gas have a cumulative effect on the lungs and a higher risk of lung cancer.
Secondhand Smoke
Non-smokers can develop lung cancer, especially if they have frequently been exposed to secondhand smoke. People who live in a house with smokers have an increased risk of 20 to 30 percent of developing fatal lung cancer over non-smokers not exposed regularly to smoke, the National Cancer Institute warns.
Other Carcinogens
Many people develop fatal lung cancer after exposure to carcinogens such as asbestos, arsenic, coal products, diesel exhaust and vinyl chloride at work. People who smoke in addition to this exposure have an increased risk of developing lung cancer.
