Lung Cancer: Everything RT's need to know

Figure 1

In the United States, Lung Cancer is the second most common cancer for both men and women, with breast cancer in women and prostrate cancer in men topping both lists.  It is the leading cause of cancer related deaths among both men and women.

As you can see in figure 1 to the right lung cancer rates were relatively low before smoking consumption became common around the turn of the 20th century.  It just took lung cancer 10 years to catch up with the rising number of smokers. Since then, lung cancer rates have increased or decreased in parallel fashion right alongside cigarette consumption rates.

Other than cigarette smoke, other causes of lung cancer may include genetic factors (which causes most childhood lung cancers), radon gas, asbestos, and air pollution.

Lung cancer appears to be caused when airway epithelial cells divide. Cells divide all the time without a hitch. However, certain environmental factors -- and the chemicals in cigarette smoke is one of them -- can increase the likelihood that an error will occur during cell division. 

Inside every cell in your body is a copy of your genetic code. (You can learn more about genes by checking out my article, "What are genes?" When cells divide, exact copies of your genetic code are made. This code essentially is made of genes, and each gene tells a specific cell what to do.

Some of these genes tell airway epithelial cells what to do. For instance, these cells are told to be cilia cells or to secrete mucus. Sometimes, however, during cell division, errors occur on the genes that are responsible for these actions. It is these errors, often called gene mutations, that are responsible for the development of cancer cells, including lung cancer cells.

So, rather than acting as normal airway epithelial cells, cancer cells do something abnormal. Like other cells, cancer cells can also divide, creating more and more cells that do something abnormal. This division may occur uncontrollably to form lumps or masses of tissue called tumors. These interfere with normal lung function, and they release secretions that interfere with normal lung function.

When a cancer displays limited growth and stays in one spot it's considered malignant, yet most cases of lung cancer are considered to be malignant carcinoma's of the lung.

There are two types of lung cancer, and the treatment depends on the type:

1. Small Cell Carcinoma. This is slightly more common in men than women, although it's the least common type of lung cancer. It was formally referred to as oat cell carcinoma.  It responds to radiation and chemotherapy. This is the fastest growing type of cancer, and can quickly metastasize to other parts of the body, including the brain, liver, and bone. Because it spreads so quickly, it's usually not diagnosed until it is inoperable. Prognosis tends to be grim. 
2. Non Small Cell Carcinoma. It spreads slow enough that it can often be diagnosed early and can be treated with chemotherapy, radiation, and surgery.  

Unfortunately, at the present time the five year prognosis of any type of cancer is only 14%. However, this does depend upon how early the cancer is diagnosed and how aggressively it is treated.

Symptoms are generally non-specific, and so lung cancer is usually only suspected after other probable causes are ruled out. Diagnosis is made by x-ray or cat scan, although the cancer is generally confirmed by bronchoscopy, where a lung biopsy is performed.

Symptoms may include: Bloody sputum, chest pain, bone pain, cough, loss of appetite, dyspnea, weight loss, wheezing, facial swelling, fever, dysphagia, weakness, and clubbing of the fingernails.

It causes shortness of breath because it can block the air passages in your lungs, and leaves an accumulation of secretions behind the blockage, which predisposes these patients to pneumonia. Since lung cancers have fragile surfaces and receive a good supply of blood, they are prone to producing bloody secretions.

Again, there are many causes of lung cancer, although the most common is smoking cigarettes. It is estimated that about 80% of cases of lung cancer are caused by cigarettes. Male smokers have a 17.2% risk for developing lung cancer, while female smokers have an 11.6% risk.

I just thought I'd throw this in for comparison: male nonsmokers have a 1.4% risk of developing lung cancer, an female nonsmokers have a 1.3% risk. So, this shows the significance of the graphic above, which is truly telling. This data has been used by various organizations to increase awareness of lung cancer and the need to prevent kids from smoking, and to get smokers to quit.

References and further reading:

1. Thomas Latimer Cancer Foundation: Cancer Facts
2. American Cancer Society: How common is lung cancer
3. Medical News Today: Cancer facts, causes, symptoms, and research
4. Chemo.net: Lung Cancer