The Big Picture of Lung Cancer
The major cause of cancer deaths in men and women is lung cancer; this situation is relatively new and is mainly due to cigarette smoking. In 1876, a machine was invented to make rolled-up cigarettes and thus provided cheap tobacco products to almost everyone. At that time, lung cancer was relatively rare. Smoking dramatically increased and so did lung cancers following this innovation. Currently about 90% of all lung cancers are related to smoking. Radon gas, pollution, toxins, and other factors contribute to the remaining 10%.
How Does Smoking Cause Lung Cancer?
Cigarettes and cigarette smoke contains over 70 cancer-causing chemicals (carcinogens). In addition, cigarette smoke damages and can kill hair-like projections on airway cells termed cilia. The cilia normally sweep out toxins, carcinogens, viruses, and bacteria. When the cilia are damaged or destroyed by smoke, all of these items may accumulate in the lungs and may cause problems such as infections or lung cancer.
Symptoms of Lung Cancer
Unfortunately, lung cancers often have either no early symptoms or nonspecific early symptoms that people often dismiss. Early nonspecific symptoms may include one or more of the following:
- Cough (chronic, recurrent)
- Weight loss
- Short of breath or wheezing
- Coughing up phlegm that contains blood
- Chest pain
Screening for Lung Cancer
Screening for lung cancer is usually done by three methods:
- A physical exam, patient history of smoking, and a chest X-ray
- A sputum cytology exam (cells examined by a pathologist)
- A spiral CT exam
A study by researchers suggested that people aged 55 to 74 years old who had smoked at least one pack of cigarettes a day for 30 or more years may benefit from a spiral CT study of the lungs. At best, the screening methods find about 30% of lung cancers leaving the bulk (about 70%) cancers of lung undetected. In addition, some test results are not clearly diagnostic which can lead to patient concerns and possibly unnecessary biopsies or surgeries.
Lung Cancer Diagnosis
If the screening tests suggest a person has lung cancer, definitive diagnostic tests may be done by a pathologist. The pathologist will examine the patient’s lung cells in sputum, phlegm, or from a biopsy sample to type and stage the cancer (see following slides for type and staging information).
As stated previously, a tissue sample taken from the patient’s suspected cancer is usually the best method to establish a definitive diagnosis. In general, lung biopsies are obtained by either needle biopsy, a lung bronchoscopy technique, or by surgical removal of tissue. Many other tests may be done to get more information about the cancer’s spread.
Types of Lung Cancer
There are only two major types of lung cancers, small cell and non-small cell lung cancers. Non-small cell lung cancers account for about 90% of all lung cancers and are less aggressive (spread to other tissues and organs slowly) than small cell cancers.
Stages of Lung Cancer
After the type of lung cancer is determined, the type is then assigned a stage. The stage indicates how much the cancer has spread in the body (for example, to the lymph nodes or to distant organs like the brain). Stages for non-small cell cancers are different from small cell cancers. The stages listed below are taken from the National Cancer Institute’s lung cancer staging information:
The following two stages are used for small cell lung cancer:
- extensive-stage small cell cancer.
The following stages are used for non-small cell lung cancer:
- Occult (hidden) stage
- Stage 0 (carcinoma in situ)
- Stage I
- Stage II
- Stage IIIA
- Stage IIIB
- Stage IV
Survival Rates for Lung Cancer
The American Cancer Society statistics are currently based on people diagnosed between 1998 and 2000 so the data may not reflect the effects of newer treatments. The data indicates that survival rates of patients living 5 years after being diagnosed with non-small cell cancers was dependent on the stage of the disease. Stage I was about 49% while stage IV survival was about 1%. Small cell lung cancers are more aggressive and the data, like that for non-small cell lung cancers, is not reflective of current survival rates. However, even some data collected as late as 2008 indicates slow progress in increasing 5-year survival rates:
- Small cell lung cancer: The overall rate of both limited-stage and extensive-stage is about 6%.
- Non-small cell lung cancer: The overall rate of all stages (I to IV combined) is about 15%.
Early-Stage Lung Cancer Treatment
Early stage (stage 0 or even some stage I) cancer treatment of non-small cell cancer may benefit from surgery. Part or all of a lung segment that contains the cancer may be removed; in some individuals, this may result in a cure. However, many patients still undergo chemotherapy, radiation therapy, or both to kill any cancer cells not removed by surgery. Because small cell lung cancers are almost never diagnosed early, surgery (and other treatments) may prolong life but rarely, if ever, result in a cure.
Advanced Lung Cancer Treatment
Most small cell and non-small-cell cancers are treated with chemotherapy; they may also be treated with radiation therapy and surgery. In many patients with advanced disease, these methods may be used together, depending on the patient's condition and recommendations by their cancer doctors.
New therapeutic treatments are being tried; for example some therapies termed targeted therapies are designed to prevent or stop lung cancer cells from growing by targeting the new blood vessels that are needed to allow the cancer cells to survive and grow; other treatments target growth and multiplication of lung cancer cells by interfering with chemical signals required by growing or multiplying cancer cells (illustrated in this slide).
Clinical Trials for Lung Cancer
In addition to targeted therapies, there are a number of clinical trials that a person may qualify for. Some may be available in your hometown. These clinical trials have patients try the newest potentially helpful therapeutic methods and drugs to combat lung cancers. The National Cancer Institute’s web site listed below offers a list of current clinical trials; you and your doctor may find a clinical trial that may help you with this disease.
Life After Diagnosis
After a diagnosis of lung cancer, it is not unusual to feel depressed and upset. However, research is ongoing and it is possible to survive and extend your life with treatment. Even with the diagnosis, there is evidence that people who develop a healthy lifestyle and stop smoking do better than those who do not change.
Lung Cancer and Secondhand Smoke
Tobacco smokers put others at risk of developing lung cancer. A nonsmoker (wife, child, significant other) who lives with a smoker has a 20% to 30% increase in risk of developing lung cancer.
Lung Cancer and Work Exposures
Although smoking results in the highest risk of causing lung cancers, other environmental exposures to certain compounds and chemicals increase the risk of lung cancer. Such agents as asbestos, uranium, arsenic, benzene, and many others increase the risk for developing lung cancers. Exposure to asbestos may cause lung cancer (mesothelioma) many years after the initial exposure so people may be at risk for lung disease for decades (10 to 40 years).
Lung Cancer and Radon Gas
Another chemical, radon gas, is considered to be the second leading cause of lung cancer. It occurs naturally but can seep into homes and collect in basements and crawl spaces. It is colorless and odorless but can be detected with relatively simple and inexpensive test kits. Smokers exposed to this gas have a higher risk of developing lung cancer than nonsmokers.
Lung Cancer and Air Pollution
There are a number of investigators that suggest air pollution contributes to the development of lung cancers. Several studies present data that airborne pollutants like diesel exhaust may cause some people to develop lung cancers. Researchers estimate that about 5% of lung cancers are due to air pollutants.
Additional Risk Factors for Lung Cancer
Although much is understood about lung cancers, there are still many things and situations that are unclear. For example, it is unclear why some families have a history of individuals with lung cancer and no clear risk factors. The same is true for some patients who develop lung cancers with no clear risk factors. Another occurrence such as drinking water that has high arsenic concentrations may increase lung cancer risk but how the process happens is not clear. In addition, why adenocarcinoma in the lungs is more common in nonsmokers than smokers is also not known.
Lung Cancer Prevention
For the majority of lung cancers, prevention is possible if a person never smokes and avoids second-hand smoke. For smokers who quit -- within 10 years -- the risk of getting lung cancer drops to about the same risk as if they had never smoked. Avoiding other risk factors (for example, certain chemicals or compounds like benzene or asbestos or air pollution) may also prevent some people from developing lung cancers.
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