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WHY IS LUNG CANCER A SERIOUS PROBLEM?
Lung cancer kills more men and women than any other form of cancer. It is estimated that by the year 2000, over three hundred thousand people will die from lung cancer in the United States alone. The economic loss is calculated to be over two billion dollars a year.
Most lung cancers begin to grow silently, without any symptoms. Patients with lung cancer often do not develop symptoms until the cancer is in an advanced stage. The actual time from when one cell becomes cancerous until it is large enough to be diagnosed or produce symptoms may take as long as 10 to 40 years. Since the majority of lung cancer is diagnosed at a relatively late stage, only 10% of all lung cancer patients are ultimately cured. If the patient cannot be cured by surgery at the time the cancer is found, there is a 50% chance that death will occur in less than one year.
WHAT CAUSES LUNG CANCER?
Eighty percent of lung cancers are due to tobacco smoke. There are over 2,000 known cancer-causing chemicals in tobacco smoke. Normal human cells change into cancer cells when exposed to carcinogens (chemicals which cause cancer). Other well established carcinogens of the lung include radon, asbestos, bischolomethylether, nickel, chromates, coal tar, copper radioactive materials and arsenic.
Many occupations have an increased risk for developing lung cancer. For example, asbestos insulation workers have 92 times the risk of developing of lung cancer, and smelter workers have 3-8 times the risk of developing lung cancer. The risk of lung cancer is also increased in people who work in the manufacturing of certain industrial gases, pharmaceuticals, soaps and detergents, paints, inorganic pigments, plastics, and synthetic rubber.
The risk of developing lung cancer is related to the amount of exposure to the cancer causing agent. For example, the risk of lung cancer in humans is proportional to the number of cigarettes smoked. The risk of developing lung cancer is 8-20 times greater in smokers compared to people who have never smoked. A smaller, but real risk exists for cigar and pipe smokers. Some cancer causing agents react together to significantly worsen the risk of developing cancer. The combined exposure to asbestos and tobacco smoke clearly multiplies the risk of developing lung cancer.
The risk of lung cancer is greater for those living in urban areas. This risk is approximately 1.2 to 2.3 times that of people living in rural areas. There is also an increased risk of lung cancer in smokers whose close relatives have had lung cancer. Scarring in the lungs from previous infections or injury can be associated with and increased risk of cancer.
WHAT ARE THE TYPES OF LUNG CANCER?
Lung cancers are broadly classified into small cell or non-small cell. Non-small cell cancers are further divided into adenocarcinomas, bronchoalveolar-alveolar, squamous cell and large cell carcinomas. Approximately, 75-85% of lung cancers are non-small cell cancers and 15-25% are small cell cancers of the lung.
Non-Small Cell Cancer of the Lung
Adenocarcinoma is the most common non-small cell cancer of the lung that occurs in the United States. The majority of these cancers develop in the periphery (outer part) of the lung. Since these cancers are in the outer portion of the lung, the patient often does not have any symptoms when the cancer is found on a chest x-ray. Adenocarcinomas tend to metastasize (spread to other parts of the body) to the bone, the central nervous system (the brain and spinal cord), the adrenal glands, the liver and the opposite lung.
Frequently, there is scarring in adenocarcinomas. Sometimes, the cancer arises in an area of old scarring of the lung. In other cases, the scar appears to arise secondary to the growth of the cancer.
Bronchoalveolar carcinoma or alveolar cell carcinoma is a non-small cell carcinoma that can be found throughout the respiratory tract. When it is discovered as a single mass on a patient's x-ray, this type of lung cancer has an excellent prognosis. Five year survival after surgery is in the 75-90% range. If, however, it is found in its diffuse form (meaning it has spread beyond a single mass), the prognosis is quite poor.
Squamous cell carcinomas comprise 30-40% of non-small cell carcinomas of the lung. This type of cancer tends to be located in the more central portion of the lung. Often, this is in a bronchus (a large airway of the lung). Since these cancers are located near or in these airways, they can cause symptoms earlier in their growth. Coughing and production of phlegm (sputum) that is bloody are common symptoms. The cancer can block airways which can lead to shortness of breath or pneumonia.
Large cell carcinomas represent about 10% of non-small cell cancers of the lung. This form of lung cancer has fewer structural characteristics when viewed under a microscope. It is sometimes difficult to distinguish this form of lung cancer from cancers which have spread to the lung from another place in the body.
Small Cell Cancer of the Lung
Small cell cancer is the most aggressive type of lung cancer and has the worst prognosis. These cancers tend to grow rapidly and metastasize to other parts of the body early.
Small cell cancer of the lung is usually seen as a mass located in the central portion of the chest on chest x-ray. The primary cancer spreads to lymph nodes of the chest and also enters the blood stream which carries it to other organs such as the liver, bone, brain and spinal cord, kidneys, pancreas, and adrenal glands.
It is rare that small cell cancer of the lung can be cured with surgery because either the primary cancer is too large to be removed or it has already spread to other parts of the body. However, small cell cancer of the lung is generally quite responsive to radiation therapy and chemotherapy.
WHAT SYMPTOMS CAN PATIENTS WITH LUNG CANCER HAVE?
Lung cancers such as squamous cell and small cell cancers can cause symptoms such as cough, shortness of breath, bloody sputum, chest pain, wheezing or pneumonia. Adenocarcinomas are generally more common in the outer portion of the lung and can cause chest pain with breathing, coughing or shortness of breath. Most commonly patients have no symptoms when the disease is first detected on a chest x-ray .
Small cell cancers and adenocarcinomas of the lung are also first seen with symptoms of metastatic disease. In other words, the problems and symptoms are those involving the organs or structures to which the cancer has spread and not necessarily the lungs.
Symptoms that may indicate the cancer has spread include hoarseness of the voice (due to spread of the cancer to nerves which control the vocal cords), difficulty in swallowing, and swelling of the face, arms and neck. Metastatic spread of the cancer outside the lung and chest can occur with any of the lung cancer types, but most commonly with small cell cancers and adenocarcinomas. Headaches, weakness, numbness or paralysis may indicate spread of the cancer to the brain or spinal cord. This requires urgent treatment. Bone pain or pain in the abdomen can be symptoms of cancer spread to these areas.
HOW IS LUNG CANCER DIAGNOSED?
Lung cancer can be diagnosed once it is suspected in one of four ways:
Examination of the sputum can show cancer cells. The sputum is generally collected over a three day period to increase the likelihood of making a correct diagnosis as compared to a single sputum collection.
Fiberoptic bronchoscopy utilizes a small flexible lighted tube which is passed into the nasal canal and then into the appropriate bronchus (airway) to the cancer, which is then biopsied. A biopsy (a small piece of tissue) is obtained by either brushing the surface of the lesion or inserting a needle into the lesion and withdrawing a small sample of tissue.
Percutaneous needle biopsy involves inserting a thin needle into the mass through the skin and chest wall. This is useful for lesions that are close to the surface of the lung. This approach is often aided by the use of a CAT scan to guide the needle into the mass. In a small number of cases, a slight collapse of the lung ( pneumothorax ) occurs. This is usually self-limiting and only in about 5% of cases is it necessary to insert a tube into the chest to re-expand the lung.
Excision or surgical removal of the suspected mass can lead to the diagnosis. This can be performed through a small incision into the chest (thoracotomy), or more recently with thoracoscopy. This procedure involves inserting a small thin video camera into the chest and removing a small wedge of lung tissue using either a mechanical stapling device or laser.
HOW IS METASTASIS EVALUATED?
Metastasis of lung cancer is present in over 50% of patients at the time of the diagnosis of the lung cancer. The type of screening for metastatic disease depends on the patient's cancer type, potential for complete surgical removal, the extent of cancer in the chest, and the planned therapy.
Mediastinoscopy, or looking into the central portion of the chest through a small incision made just below the collar line, is used to sample the lymph nodes in the central portion of the chest (mediastinum). This helps evaluate the extent of the tumor. If the cancer has spread to these lymph nodes, the chance of surgically curing the lung cancer is eliminated.
Bone metastasis is suggested by bone pain or abnormal blood tests (elevated serum calcium, or elevated alkaline phosphatase). X-rays or bone scans are used to evaluate the areas suspected of being cancerous.
Liver metastasis may result in pain in the upper right portion of the abdomen, swelling of the abdomen, or abnormal blood tests of the liver. The diagnosis can be made by liver scan, CT scan or liver biopsy.
HOW IS LUNG CANCER TREATED?
Treatment choices and chances of long term survival in lung cancer depend on the type of cancer, its location and size, lymph node involvement, and whether there is evidence of cancer spread to other parts of the body outside of the lungs.
Currently, surgery is the only treatment which may offer a definitive or complete cure. Unfortunately, only one-half of patients with lung cancer are surgical candidates. If the spread of cancer to the lymph nodes is found at the time of removal of the lung cancer, the chances of the cancer recurring is quite high.
Preoperative evaluation is extremely important, not only to exclude non-resectable cancers (i.e. those cancers which technically cannot be surgically removed), but to exclude patients with severe heart or lung problems who might not survive the operation. Palliative surgical resection of the tumor is sometimes performed, whereby the cancer is removed knowing that this will not cure the patient, but will likely improve the quality of life remaining for the patient.
Mortality rate for surgery is 5-10%. Of all lung cancer patients, 25-40% undergo surgery. 20 to 33% undergo an attempted curative resection. 5 to 8% of cancers cannot be removed because they are too widespread. Another 5% receive palliative resections.
Surgical resection for lung cancer generally involves removing the cancer along with a portion of normal lung tissue and adjacent lymph nodes (lobectomy). In some cases the surgery requires removal of the entire lung on one side of the chest (pneumonectomy).
Radiation therapy is the local treatment of cancer using various types of radioactive x-ray beams. These treatments prolong life in some patients, and improve the quality of life while relieving pain in others. It rarely cures patients of lung cancer. The major role of radiation therapy is to relieve symptoms.
Chemotherapy is the use of medications and drugs which are known to kill cancer cells. Chemotherapy is widely accepted as the primary treatment for small cell cancers. In early small cell cancers of the lung, there is a higher success rate with chemotherapy, especially if the cancer is only in the chest.
In cases of non-small cell cancers of the lung, chemotherapy can be used alone or in combination with radiation therapy.
HOW WILL LUNG CANCER BE ADDRESSED IN THE FUTURE?
Currently, the success in curing lung cancer is dismally low. Therefore, prevention of lung cancer is the best hope of limiting this terrible condition. Even with early detection and screening programs for lung cancer, many studies show no significant survival benefit. Avoidance or limiting exposure to agents known to cause lung cancer, primarily cigarette smoking, is the best means of preventing lung cancer.
The treatment of lung cancer in the future might involve antibody- directed radiation techniques, whereby antibodies directed against cancer cells carry "radioactive bullets" which specifically attack and destroy the cancer. Further studies are ongoing to determine optimal medical and surgical treatment regimens for the various forms of this devastating disease.
LUNG CANCER AT A GLANCE
- Lung cancer kills more men and women than any other form of cancer.
- Since the majority of lung cancer is diagnosed at a relatively late stage, only 10% of all lung cancer patients are ultimately cured.
- 8 out of 10 lung cancers are due to tobacco smoke.
- Lung cancers are classified as either small cell or non-small cell cancers.
- Persistent cough and bloody sputum can be symptoms of lung cancer.
- Lung cancer can be diagnosed based on examination of sputum, or tissue examination with biopsy using bronchoscopy, needle through the chest wall, or surgical excision.
- The treatment of lung cancer depends on the type of cancer, its location and size as well as the age and health of the patient.
As a manufacturer of radiation therapy equipment and related solutions, we are unable to provide you with specific medical advice regarding your health conditions.
Your physicians and care givers are the most knowledgeable resources for your particular disease, and are the most qualified to answer your questions.
Nevertheless, there are a number of high-quality online resources that you may find useful. Among them, the American Cancer Society and the US National Cancer Institute have high-quality information resources that are multi-lingual and available worldwide.
Professional organizations dedicated to cancer treatment also have resources that may be useful. These include the American Society for Radiation Oncology the American Society of Clinical Oncology and the European Society for Therapeutic Radiation Oncology.