The cause of lung cancer is well known and remains tobacco smoking. About 10% of smokers will ultimately develop lung cancer while about 10% of lung cancer will develop in nonsmokers.

Lung cancer can be divided in two broad categories based on the histology: small cell lung cancer and non-small cell lung cancer.

Small Cell Lung Cancer, or oat cell carcinoma, is rapidly growing and spreading cancer that is very sensitive to chemotherapy and radiotherapy but rapidly regrowing.

Non-Small Cell Lung Cancer is made up of different types, such as adenocarcinoma, squamous, or epidermoid carcinoma, and large cell carcinoma. However, their behavior is fairly similar. They grow slower, spread less frequently to other organs than small cell lung cancer.

The cause of lung cancer is well known and remains tobacco smoking. About 10% of smokers will ultimately develop lung cancer while about 10% of lung cancer will develop in nonsmokers. These facts are due to the discovery that tobacco smoke contains a large number of chemical compounds which have to be activated before becoming able to induce cancer.

That means that they are pro carcinogens. These compounds are activated by a series of enzymes within the smoker's body, but not everybody has those enzymes while certain other enzymes may inactivate the resulting carcinogens.

In nonsmokers, the appearance of lung cancer is due to second-hand exposure to tobacco smoke or to exposure to asbestos, radioactive products, arsenic nickel, cadmium, etc. Chromosomal changes in the lining of the airways do not disappear as soon as a person stops smoking and may persist for decades. This explains why most patients diagnosed with lung cancer are ex-smokers and that curing a patient from a lung cancer may give time for appearance of a second cancer years later. Similarly, many patients with lung cancer may have had other smoking-related cancer in the past, such as head and neck cancer, bladder cancer, or esophageal cancer. In addition, because tobacco smoke can also be a factor in the development of cardiac disease or stroke, many of our patients have a past history of coronary artery disease, strokes, or emphysema.

The screening of lung cancer is reserved to those persons who have been heavy smokers, as there is a strict relationship between cumulative exposure and rising risk of lung cancer. However, yearly chest x-rays have not been shown to be effective in reducing mortality or in obtaining earlier diagnosis.

Recent studies using annual spiral CT scans have been much more promising in diagnosing earlier lung lesions. A concern is that many such abnormalities may be benign and will have to be confirmed by repeat studies about three months later.

American Cancer Society Lung Cancer Trial
If you are a current or former smoker between the ages of 55 - 74 and interested in participating in a research study comparing two ways of detecting lung cancer, click here

Lung cancer can be divided in two broad categories based on the histology: small-cell lung cancer and non-small cell lung cancer.

Small Cell Lung Cancer, or oat cell carcinoma, is rapidly growing and spreading cancer that is very sensitive to chemotherapy and radiotherapy - but rapidly regrowing.

Only 15%-30% are limited to the chest and of those 25%-40% will be long-term survivors at 2-3 years after combined therapy with chemotherapy and radiation therapy. Those with more extensive disease have an overall survival of 8-10 months with chemotherapy. Other treatments, such as surgery or radiotherapy, have not been shown to be of benefit in patients with extensive disease except as palliation.

Non-Small Cell Lung Cancer is made up of different types, such as adenocarcinoma, squamous, or epidermoid carcinoma, and large cell carcinoma. However, their behavior is fairly similar. They grow slower, spread less frequently to other organs than small cell lung cancer. Nonetheless, only few are diagnosed early enough to be considered a candidate for surgery. Non-small cell lung cancer are staged by the size and extent of the primary, the presence of lymph node involvement, and the presence of metastasis via blood bone spreads, such as to the brain, bone, liver, kidney, or adrenals. The treatment must be tailored to the stage of disease. Although CT scan, bone scan, and blood tests are useful, they are not full proof and can either miss the spread of cancer or give misleading information. MRI can be useful in case of adrenal abnormalities, better than that of a CT scan. PET (positive emission tomography) scan may be able to pick up spread of the cancer in the lymph node and other organs.

In general, surgery is the best treatment to achieve a cure. In tumors less than 3 cm with no lymph node involvement, the 5-year survivorship is about 65%. On the other extreme, in cases of ipsilateral lymph node involvement, surgery yields only a 15% 5-year survivorship. These poor results have led to the use of chemotherapy, with or without radiation therapy, before or after surgery. This field is rapidly evolving but, in general, treatment before surgery is becoming accepted as the new standard of care while, if give after surgery, it should be considered experimental. In case of inoperable non-small cell lung cancer, radiotherapy alone was a standard mode of care, but there are very few patients who are cured with a median survival of about 14 months. The addition of chemotherapy before or during radiation therapy is superior to radiotherapy alone. The proper sequence in choice of drugs is being heavily investigated during the last few years.

Multiple new drugs have become available over the last 10 years. They include Taxol, Taxotere, Gemcitabine, Navelbine, Topotecan, Irinotecan, and Tirapazamine. Their combination with older agents, such as Platinol and Carboplatin, has led to a modest but definite improvement in the incidence of objective tumor regression and in the length of survivorship, such that some patients with widespread cancer may live longer than one year. In addition, better drugs are now available to prevent severe nausea and vomiting, to treat anemia (Procrit) and avoid infection (Neupogen).

In summary, much progress has been done but the overall improvement has been slow with a 5-year overall survivorship of all lung cancers rising from 8% in the 1970's to 14%. Therefore, prevention by avoidance of tobacco is strongly advised.

Last Updated: January 30, 2001
Source: Paul Y. Holoye, M.D.
Texas Cancer Institute ^®