Lung Cancer

(An Overview)

EARLY DETECTION

Since symptoms of lung cancer often do not appear until the disease is advanced, only about 15% of the lung cancer cases are found in the early stages, before the cancer has spread to nearby lymph nodes or elsewhere. The five-year survival rate for people with lung cancer is 50% if there is no evidence of cancer in lymph nodes at the time of surgery. Unfortunately in many others, spread of their cancer has already occurred even if not detected by current medical tests. In contrast, when all lung cancer stages are considered together the five-year survival rate is only about 14%.

Many early lung cancers are diagnosed incidentally, meaning they are found as a result of tests that are done for an unrelated medical condition. For example, a diagnosis may be made by imaging tests (such as a chest x-ray or chest CT scan), bronchoscopy (viewing the inside of bronchi through a flexible lighted tube), or sputum cytology (microscopic examination of cells in coughed up phlegm) performed for other reasons in patients with heart disease, pneumonia or other lung conditions.

Although most lung cancers do not cause any symptoms until they have spread too far to be cured, symptoms do occur in some patients with early lung cancer. Prompt attention to symptoms, leading to early diagnosis and treatment can result in a cure for some patients. For others, prompt attention to symptoms can improve the likelihood that treatment can extend their life and relieve many of their symptoms.

Common signs and symptoms of lung cancer include:

A cough that does not go away

Chest pain, often aggravated by deep breathing

Hoarseness

Weight loss and loss of appetite

Bloody or rust-colored sputum (spit or phlegm)

Shortness of breath

Fever without a known reason

Recurring infections such as bronchitis and pneumonia

New onset of wheezing

When lung cancer spreads to distant organs, it may cause:

Bone pain

Neurologic changes (such as weakness or numbness of a limb, dizziness)

Jaundice (yellow coloring of the skin and eyes)

Masses near the surface of the body, due to cancer spreading to the skin or to lymph nodes (collection of immune system cells) in the neck or above the collarbone.

If you have any of these problems, see a doctor right away.

Less often, people with lung cancer may have certain syndromes (groups of symptoms and findings detected by examinations or tests).

Horner's Syndrome: Cancer of the upper part of the lungs may damage a nerve that passes from the upper chest into the neck. Doctors sometimes call these cancers Pancoast tumors. Horner's syndrome is the medical name for the group of symptoms consisting of drooping or weakness of one eyelid reduced or absent perspiration of one side of the face and a smaller pupil (dark part in the center of the eye) on one side.

Paraneoplastic Syndromes: The cells of some lung cancers may produce hormones or other substances that enter the blood stream and cause problems with distant tissues and organs, even when the cancer has not spread to those tissues or organs. These problems are called paraneoplastic (Latin for "tumor-related") syndrome. Sometimes these syndromes may occur with early lung cancers and may be the first symptoms of the cancer. Because the symptoms affect other organs, it is common for patients and doctors to suspect at first that they are due to diseases other than lung cancer.

Patients with small cell lung cancer and those with non-small cell lung cancer often have different paraneoplastic syndromes. The most common paraneoplastic syndromes associated with small cell lung cancer are:

SIADH (abbreviation for syndrome of inappropriate antidiuretic hormone) causes sodium (salt) levels of the blood to become too low. Symptoms of SIADH include fatigue, loss of appetite, muscle weakness or cramps, nausea, vomiting, restlessness and confusion. Without treatment, severe cases may lead to seizures and coma.

Production of substances that activate the clotting system, causing blood clots to form. These clots may clog up important vessels and interrupt blood flow to the limbs, lungs, brain, or other internal organs.

Unexplained loss of balance and unsteadiness in arm and leg movement (cerebellar degeneration)

The most common paraneoplastic syndromes caused by non-small cell lung cancer are:

Hypercalcemia (high blood calcium levels) causes urinary frequency, constipation, weakness, dizziness, confusion and other nervous system problems.

Excess growth of certain bones, especially that of the finger tips. The medical term for this is hypertrophic osteoarthropathy.

Production of substances that activate the clotting system, leading to blood clots.

Excess breast growth in men. The medical term for this condition is gynecomastia.

Screening tests for lung cancer:

Screening is the use of tests or examinations to detect a disease in people without symptoms of that disease. For example, the Pap test is used for cervical cancer screening. Because lung cancer usually spreads beyond the lungs before causing any symptoms, an effective screening program for early detection of lung cancer could save many lives.

Use of chest x-rays and sputum cytology (checking phlegm under the microscope to find cancer cells) was tested several years ago. Most studies concluded that these tests could not find many lung cancers early enough to improve a patient's chance for a cure. For this reason, lung cancer screening is not a routine practice for the general public or even for people at increased risk, such as smokers.

Imaging tests:

Imaging tests use x-rays, magnetic fields, sound waves or radioactive substances to create pictures of the inside of the body. Several imaging tests are often used to find lung cancer and determine where in the body it may have spread.

A chest x-ray is done to look for any mass or spot on the lungs. Computed tomography (CT scan) will provide more precise information about the size, shape, and position of a tumor, and can help find enlarged lymph nodes that might contain cancer that has spread from the lung. CT scans are more sensitive then a routine chest x-ray in finding early lung cancers. This test is also used in detecting masses in the liver, adrenal glands, brain and other internal organs that may be affected by the spread of lung cancer. The CT scan involves a special machine that rotates around the body taking x-ray pictures from many angles. A computer then combines their pictures into a very detailed cross-sectional image.

Magnetic resonance imaging (MRI) scans use powerful magnets and radio waves and computers to take detailed cross-sectional images. These images are similar to those produced by CT scanning, but are even more accurate in detecting spread of lung cancer to the brain or spinal cord. Unlike CT scanning, MRI does not involve x-rays.

Position emission tomography (PET) scans use a sensitive, low dose radioactive tracer that accumulates in cancerous tissues. It has recently received FDA approval for staging of lung cancer.

Bone scans involve injecting a small amount of radioactive substance into a vein. This substance accumulates in abnormal areas of bone that may be due to the spread of cancer. However, other noncancerous bone diseases can also cause abnormal bone scan results. Bone scans are routinely done in-patients with SCLC, and are done in NSCLC patients when other test results or symptoms suggest that the cancer has spread to the bones.

Sputum cytology: A sample of phlegm is examined under a microscope to see if cancer cells are present.

Needle biopsy: A needle is guided into the mass while the lungs are being viewed on a CT scan. A sample of the mass is removed and looked at under the microscope to see if cancer cells are present.

Bronchoscopy: A fiberoptic flexible, lighted tube is passed through the mouth into the bronchi (the larger tubes which carry air to the lungs). This can help find centrally located tumors or blockages in the lungs. It can also be used to take biopsies (samples of tissue) or fluids to be examined under a microscope for cancer cells.

Mediastinoscopy: A small cut is made in the neck and a hollow lighted tube is inserted behind the chest bone. Special instruments operated through this tube can be used to take a tissue sample from the mediastinal lymph nodes (along the windpipe and the major bronchial tube areas). Again, looking at the samples under a microscope can show if cancer cells are present.

Bone marrow biopsy: A needle is used to remove a cylindrical core of the bone about 1/16 inch across and 1 inch long. The sample is usually removed from the back of the hipbone and is checked for cancer cells under the microscope.

Blood tests: Certain blood tests are often done to help detect if the lung cancer has spread to the liver or bones and to help diagnose certain paraneoplastic syndromes.

STAGING

Staging is the process of finding out how localized or widespread a cancer is. It will show if the cancer has spread to which body structures and how far. The treatment and prognosis (outlook for survival) for a patient with lung cancer depends, to a large extent, on the cancer's stage.

Prevention and Risk Factors

In this section of the Lung Cancer Resource Center you'll find the answers to your questions about risk factors, prevention, and causes.

RISK FACTORS

A risk factor is anything that increases a person's chance of getting a disease such as cancer. Different cancers have different risk factors. For example, exposure to sunlight is a risk factor for skin cancer and a high-fat, low-fiber diet is a risk factor for colorectal cancer. Several risk factors make a person more likely to develop lung cancer:

Tobacco Smoking: By far the most important risk factor is tobacco smoking. More than 80% of lung cancers are thought to result from smoking. The longer a person has been smoking and the more packs per day smoked, the greater the risk. If a person stops smoking before a cancer develops, the damaged lung tissue starts to gradually return to normal. Even after ten years, the ex-smoker's risk still does not equal the lower risk of a person who never smoked. However, an ex-smoker's risk is about half the risk of people who continue to smoke.

Nonsmokers who breathe in the smoke of others (also called second hand smoke or environmental tobacco smoke) are also at increased risk for lung cancer. A nonsmoker who is married to a smoker has a 30% greater risk of developing lung cancer than the spouse of a nonsmoker develops.

Asbestos: Death from lung cancer is about seven times more likely to occur among asbestos workers than among the general population. Exposure to asbestos fibers is an important risk factor for lung cancer. Asbestos workers who smoke have a very high lung cancer risk: 50 to 90 times greater than that of people in general. This cancer is called mesothelioma. Because it is usually considered a tumor of the pleura and not a type of lung cancer, mesothelioma is discussed in the American Cancer Society document "Malignant Mesothelioma."

Cancer-causing Agents in the Workplace:

In addition to asbestos and radon, there are other cancer-causing agents (carcinogens) in the workplace. People at risk include miners who may breathe in radioactive ores such as uranium and workers exposed to chemicals such as arsenic, vinyl chloride, nickel chromates, coal products, mustard gas, and chloromethyl ethers. The government and industry have taken major steps in recent years to protect workers. But the dangers are still present, and those who work in these conditions should be very careful to avoid exposure.

Talcum Powder:

While no increased risk of lung cancer has been found from the use of cosmetic talcum powder, some studies of talc miners and millers suggest a higher risk of lung cancer and other respiratory diseases from their exposure to industrial grade talc. Talcum powder is made from talc, a mineral that in its natural form may contain asbestos. By law since 1973, all home-use talcum products (baby, body, and facial powders) have been asbestos-free.

Other Mineral Exposures:

People with silicosis and berylliosis (lung diseases caused by breathing in certain minerals) also have an increased risk of lung cancer.

Vitamin A Deficiency or Excess:

People who do not get enough vitamin A are at increased risk of lung cancer. On the other hand, taking too much vitamin A may also increase lung cancer risk.

Air Pollution:

In some cities, air pollution may slightly increase the risk of lung cancer. This risk is far less than that caused by smoking.

PREVENTION

The best way to prevent lung cancer is to not smoke. People should not start smoking, and those who already smoke should quit. Everyone should avoid breathing in other people's smoke. People should find out about cancer-causing chemicals they might be exposed to at work and take appropriate protective measures. People who live in areas where national uranium deposits in the soil release radon gas may consider testing radon levels in their homes.

HARRY KOCHAT
BioNumerik Pharmaceuticals Inc.
(An oncology based company based in San Antonio, Texas, USA)


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