Article updated and reviewed by Kevin Knopf, MD, MPH; Director of Clinical Research, Annapolis Oncology Center and Associate Staff, Johns Hopkins Oncology Center on July 22, 2005.
lung cancer. Lung cancer is either small cell (see below) or non-small cell depending on the size of the cells under the microscope.
What Is Cancer?
Normally, body cells divide and reproduce in an orderly manner, so that people replace worn-out tissue and repair any injuries. Sometimes, however, cells divide without control and form masses known as tumors.
Tumors may invade or destroy normal tissue, interfere with body functions, and require removal by surgery. Benign tumors do not spread to other parts of the body. Cancerous or malignant tumors do spread to other parts of the body.
By a process known as metastasis, cells break away from the original malignant tumor and spread through the lymph and blood systems to form more malignant tumors elsewhere in the body. This spread can occur rapidly or over a period of years.
Lung cancer is now the leading cause of cancer deaths among men and women. The peak incidence of lung cancer occurs between ages 55 and 65 years.
At the time of diagnosis, only about 20 percent of all lung cancer patients will have local disease, while about 25 percent will have disease that has spread to regional lymph nodes and about 55 percent will have distant metastatic cancer.
Cigarette smoking is the most important cause of lung cancer in both men and women in the US.
Primary carcinoma of the lung is a major health problem with a generally poor prognosis. However, an orderly approach to diagnosis, staging, and treatment based on knowledge of the clinical behavior of lung cancer allows selection of the best treatment for either potential cure, maximal length of life, or relief of symptoms related to lung cancer. This approach is often multidisciplinary, involving the interaction of internists, chest physicians, pathologists, supportive care personnel, and medical, radiation, and surgical oncologists.
Cancers that originate in the skin, glands, or lining of internal organs (such as the lungs), are known as carcinomas. There are four main types of carcinomas of the lungs which can be further categorized as non-small or small cell cancers. The four major cell types make up 95 percent of all primary lung neoplasms.
Small Cell Carcinoma
Also called oat cell carcinoma because the cells are shaped like grains of oats, this form of lung cancer accounts for 20 percent to 25 percent of lung cancers. It is the most aggressive form, and the most likely to have spread by the time of diagnosis.
(Squamous or Epidermoid). These arise from the flat, scaly cells that line the air passages. It accounts for 30 to 35 percent of all lung cancers. Squamous cell carcinoma tends to be centrally located.
This type of tumor can begin in the mucous membrane of both smaller or larger bronchi. It accounts for about 35 to 40 percent of all lung cancers. Adenocarcinoma is now the most common type of lung cancer overall. It can be caused by smoking, but to a lesser degree than other forms of lung cancer. Most patients who develop lung cancer who are non-smokers develop adenocarcinoma. A subtype of adenocarcinoma called bronchoalveolar carcinoma has some unique features, including special sensitivity to newer agents like Iressa or Tarceva.
Large Cell Carcinoma
This is the least common form of lung cancer, accounting for 15 percent of all cases. It usually develops in the bronchus and is characterized by large, round cells.
Lung cancer's exact cause remains unclear. Risk factors include tobacco smoking, exposure to carcinogenic and industrial air pollutants (asbestos, arsenic, chromium, coal dust, iron oxides, nickel, radioactive dust, and uranium) and genetic predisposition.
Ninety percent of the patients with lung cancer of all histological types are cigarette smokers.
Lung cancer rarely gives an early warning of its presence. The earliest symptoms are likely to be so ordinary - such as coughing or wheezing - that they are often dismissed as minor irritants. This is especially true of the heavy smoker, long accustomed to smoker's cough.
The most common symptoms are persistent cough and blood in the sputum. Other symptoms include repeated bouts of pneumonia, fever, weakness, worsening shortness of breath, weight loss, and chest pain.
More advanced disease may be signaled by hoarseness, shortness of breath, swollen lymph nodes in the neck, shoulder and arm pain, difficulty in swallowing, and drooping of the upper eyelids.
In many cases, patients first notice symptoms caused by the spread of the disease, rather than the primary lung cancer. These symptoms can include headaches, blurred vision, dizziness, and bone pain.
There are a variety of methods physicians use to confirm the presence of lung cancer and to identify the type and the extent or stage of disease. The physician first needs to evaluate the overall health of the patient and learn the medical history. He or she needs to determine if the patient smokes, how many years and how many cigarettes a day.
Chest x-rays are valuable in locating suspected tumors. Lung cancer usually appears on the x-ray as a centrally located tumor.
Computed Tomography scans (CT scans) use an x-ray beam that rotates around the body to produce a series of x-rays taken from different angles. This information is then processed by a computer to produce a complete picture of a cross-section of a selected body area. By showing the relationship of a lung tumor to other structures in the chest, the CT scan can indicate the extent of the tumor and whether it involves other organs.
Sputum cytology is a microscopic examination of cells coughed up from the lungs. In some cases, sputum cytology can reveal lung cancers in patients with normal x-rays or can determine the type of lung cancer. However, this is not used so much anymore.
Bronchoscopy is a procedure in which a flexible tube with lighting and magnifying devices is inserted through a nostril or the mouth and into the bronchus. The physician can then obtain samples of cells, discover the precise location of the tumor, and judge whether the tumor can be completely removed.
Needle biopsy is particularly useful for patients who are not considered candidates for surgery, but who need a diagnosis prior to planning other treatments. Guided by a fluoroscope, or by CT scanning, an x-ray machine that profiles the image on a fluorescent screen, a physician can insert a long, thin needle into the tumor to draw out a tissue sample. While bronchoscopy is a good way to obtain tissue for lesions that are central, lesions near the periphery are easier biopsied by a CT-guided needle biopsy.
Other tests and procedures may include: thoracotomy, lymph node biopsy, radionuclide scans, and MRI (Magnetic Resonance Imaging). PET scanning, a type of radionuclide scan, has become very important in the staging of lung cancer.
PET scans give a picture of activity of the body by injecting a small amount of radioactive glucose (sugar) and seeing how it distributes. PET scan can be useful in detecting the extent and spread of lung cancer, although it is not 100% accurate. For example, most cancer lesions between 0.6 centimeter to one centimeter will not be detectable on PET scan.
Staging Lung Cancer
Lung cancer staging determines the location and size of the tumor and the extent to which it may have spread to lymph nodes and other organs. This information helps the physician suggest the most appropriate treatment for the patient.
Various combinations of surgery, radiation and chemotherapy are the primary methods of treating lung cancer. The specific treatment depends on the patient's general health, the type of cancer and the stage of the disease. For non-small cell lung cancer, the first question to determine is whether the cancer can be removed surgically with curative intent. This is the case for many early-stage cancers.
Surgery involves removal of part of the lung or the whole lung depending on the extent of the tumor. Five-year survival rates for patients with early stages of non-small cell carcinoma varies from 40 to 70 percent.
When a lung cancer is removed, an area surrounding the tumor is also removed and examined for cancer cells. Patients recovering from surgery usually need to use a machine to help them breathe in the first few days after surgery. They may need to limit their physical activity somewhat, depending on the amount of lung removed and the remaining function of the lungs as well as overall health.
In the past three years, it has become apparent that giving chemotherapy after surgery (adjuvant chemotherapy) can increase the cure rate by eight to 15 percent beyond surgery alone.
Sometimes preoperative (before surgery) radiation therapy is used to reduce tumor bulk to allow for surgical resection and may also improve response rates. Radiation may be used along with surgery to deal with any remaining tumor or distant spread of the cancer. It is used in place of surgery when that treatment is not a possibility, because it may relieve pain and other symptoms.
Side effects of radiation therapy may include a general feeling of fatigue, temporary dry or sore throat and scarring of the lungs.
Chemotherapy is becoming more important in the treatment of lung cancer. Chemotherapy drugs may include fluorouracil, gemcitabine, premetrexed, navelbine, cisplatin, carboplatin, etoposide, paclitaxel, and docetaxel. Chemotherapeutic drugs are often used in combination in an attempt to increase effectiveness. A newer type of chemotherapy called targeted therapy is exemplified by Tarceva, a pill with less side effects than traditional chemotherapy used in refractory cases of lung cancer.
Side effects of chemotherapy depend on the drugs used. Some common side effects include hair loss, nausea and vomiting, changes in blood count and fatigue.
Are there any tests that need to be done to diagnose the condition?
Or the extent of the disease?
Are there any risks associated with these tests?
What can be expected from the tests?
What type of cancer is it?
What kind of treatment will you recommend?
Are there side effects to the treatment?
Should a specialist be consulted?
Is there a clinical trial I can participate in?
Will surgery be recommended?
What can be expected from the surgery?
Are there any support groups in the area?
Editorial review provided by VeriMed Healthcare Network.