MEDICAL MONDAYS: News Notes
Monday, March 14, 2011
TOPIC: Lung Cancer Awareness
Jim Wudel, MD: thoracic surgeon
Saint Thomas Lung Cancer & Thoracic Center
News notes via www.webmd.com
Understanding Lung Cancer - the Basics
What Is Lung Cancer?
Although lung cancer is the leading cause of cancer death in the U.S. in both men and women, it is also one of the most preventable kinds of cancer. At least four out of five cases are associated with cigarette smoking, and the cause-and-effect relationship has been extensively documented. During the 1920s, large numbers of men began to smoke cigarettes, presumably in response to increased advertising. Twenty years later, the frequency of lung cancer in men climbed sharply. In the 1940s, significantly more women became smokers. Twenty years later, there was a similar dramatic increase in lung cancer among women.
Lung tumors almost always start in the spongy, pinkish gray walls of the bronchi -- the tubular, branching airways of the lungs. More than 20 types of malignant tumors that originate in the lung itself -- primary lung caner -- have been identified. The major types are small-cell lung cancer and non-small-cell lung cancer. The more common non-small variety is further divided into squamous cell carcinoma, adenocarcinoma, and large-cell carcinoma. Mixed tumors may also occur.
Non-Small Cell Lung Cancer
Squamous cell carcinoma usually starts in cells of the central bronchi, the largest branches of the bronchial tree. It accounts for 30% of lung cancers, and occurs more commonly in men and in smokers. It's is the easiest to detect early, since its distinctive cells are likely to show up in tests of mucus samples. It also tends to be most curable if found early because it spreads relatively slowly and often times does not spread outside of the lung.
Adenocarcinoma is the most common type of lung cancer accounting for 40% of all lung cancer cases with its incidence increasing. It is most commonly seen in women and nonsmokers. It tends to originate along the outer edges of the lungs in the smaller airways. Adenocarcinoma often spreads to spaces between the lungs and the chest wall, and its typical location makes early detection difficult.
Large-cell carcinomas are a group of cancers with large, abnormal-looking cells that tend to originate along the outer edges of the lungs. They are the least common of the non-small-cell lung cancers accounting for 10-15% of all cases. However, this type of tumor has a high tendency to spread to nearby lymph nodes and distant sites.
Small Cell Lung Cancer
Small-cell lung cancer is the most aggressive form of the disease; it is also called oat-cell cancer because, under a microscope, its cells resemble oat grains. Like squamous cell carcinoma, this cancer usually originates in the large, central bronchi. It spreads quickly, often before symptoms appear, making it particularly threatening. In fact, up to 75% of patients with this type of cancer have metastatic disease at the time the cancer is diagnosed. It frequently spreads (metastasizes) to the liver, bone, and brain. Although responsive to chemotherapy, small-cell lung cancer is rarely ever cured because it usually is not discovered before it has spread.
About 250,000 people in the U.S. are diagnosed with lung cancer each year, most are between the ages of 40 and 70. It is the most common cancer in men and the second most common cancer in women. Only 1% of lung cancer patients are younger than 30, and only 10% are older than 70. The number of people that survive five years or more is increasing and now stands at about 15% and increases by 1% every 10 years. However, about 175,000 persons with lung cancer die each year of their disease. An individual cancer sufferer's prognosis will vary according to the type of lung cancer involved, the person's overall health, and the status of the cancer at the time of diagnosis.
What Causes It?
About 85% of lung cancer is caused by smoking and as with any cancer, each person's genetic pattern influences susceptibility. The fact that lung cancer runs in some families suggests that a predisposition can be inherited. Additionally, certain genetic traits have been identified that make some people more susceptible than others to cancer-causing substances like those found in tobacco smoke.
Nonetheless, anyone who smokes one pack of cigarettes daily is 20 times more likely than a nonsmoker to develop lung cancer. For people who smoke more than two packs a day, the risk more than triples. Breaking the smoking habit reduces risk significantly, yet former smokers are always slightly more susceptible than nonsmokers. Secondhand tobacco smoke can also cause lung cancer, giving nonsmokers who live or work with smokers a somewhat higher lung cancer risk than those in smoke-free environments. In fact, approximately 1,000 people die each year of lung cancer associated with second hand smoke exposure.
Cancer-causing substances other than those found in tobacco or tobacco smoke can also cause lung cancer if inhaled in quantity over time. However, experts disagree about how much exposure to specific cancer-causing substances is dangerous. Workers who are exposed on a daily basis to asbestos, have a 90 fold increase of getting lung cancer when compared to non-exposed persons. Workers exposed to silica, mineral dusts, coal dust, arsenic, or the radioactive gas radon are also much more likely than the average person to develop lung cancer, especially if they are smokers.
Lung tissue that has been scarred by disease or infection, such as scleroderma or tuberculosis, is more susceptible to tumor growth. Because of a high frequency of lung cancer among people who eat large amounts of fat and cholesterol, some researchers speculate that diet may also influence lung cancer risk.
Lung Cancer Symptoms
One fourth of all people with lung cancer have no symptoms when the cancer is diagnosed. These cancers are usually identified incidentally when a chest x-ray is performed for another reason. The other three fourths of people develop some symptoms. The symptoms are due to direct effects of the primary tumor; to effects of metastatic tumors in other parts of the body; or to malignant disturbances of hormones, blood, or other systems.
Symptoms of primary lung cancers include cough, coughing up blood, chest pain, and shortness of breath.
Symptoms of metastatic skin rashes depend on the location and size. About 30-40% of people with lung cancer have some symptoms or signs of metastatic disease.
Paraneoplastic syndromes are the remote, indirect effects of cancer not related to direct invasion. Symptoms include the following:
Types of Lung Cancer
What are the types of lung cancer?
Lung cancers, also known as bronchogenic carcinomas ("carcinoma" is another term for cancer), are broadly classified into two types: small cell lung cancers (SCLC) and non-small cell lung cancers (NSCLC). This classification is based upon the microscopic appearance of the tumor cells themselves. These two types of cancers grow and spread in different ways, so a distinction between these two types is important.
SCLC comprise about 20% of lung cancers and are the most aggressive and rapidly growing of all lung cancers. SCLC are strongly related to cigarette smoking with only 1% of these tumors occurring in non-smokers. SCLC metastasize rapidly to many sites within the body and are most often discovered after they have spread extensively. Referring to a specific cell type often seen in SCLC, these cancers are sometimes called oat cell carcinomas.
NSCLC are the most common lung cancers, accounting for about 80% of all lung cancers. NSCLC has three main types that are named based upon the type of cells found in the tumor. They are:
Other types of cancers can arise in the lung; these types are much less common than NSCLC and SCLC and together comprise only 5-10% of lung cancers:
As discussed previously, metastastatic cancers from other primary tumors in the body are often found in the lung. Tumors from anywhere in the body may spread to the lungs either through the bloodstream, through the lymphatic system, or directly from nearby organs. Metastatic tumors are most often multiple, scattered throughout the lung and concentrated in the peripheral rather than central areas of the organ.
Lung Cancer Diagnosis
How Is Lung Cancer Diagnosed? | Your doctor may suspect lung cancer if a routine physical exam reveals:
Some lung cancers produce abnormally high blood levels of certain hormones or substances such as calcium. If a person shows such evidence and no other cause is apparent, a doctor should consider lung cancer.
Lung cancer, which originates in the lungs, can also spread to other parts of the body, such as distant bones, the liver, adrenal glands, or the brain. It may be first discovered in a distant location, but is still called lung cancer if there is evidence it started there.
Once lung cancer begins to cause symptoms, it is usually visible on an X-ray. Occasionally, lung cancer that has not yet begun to cause symptoms is spotted on a chest X-ray taken for another purpose. A CT scan of the chest may be ordered for a more detailed exam.
Though exams of mucus or lung fluid may reveal fully developed cancer cells, diagnosis of lung cancer is usually confirmed through a lung biopsy. With the patient lightly anesthetized, the doctor guides a thin, lighted tube through the nose and down the air passages to the site of the tumor, where a tiny tissue sample can be removed. This is called a bronchoscopy and the scope is called a bronchoscope. This is useful for tumors near the center of the lung.
If the biopsy confirms lung cancer, other tests will determine the type of cancer and how far it has spread. Nearby lymph nodes can be tested for cancer cells with a procedure called a mediastinoscopy, while imaging techniques such as CT scans, PET scans, bone scans, and either an MRI or a CT scan of the brain can detect cancer elsewhere in the body.
If fluid is present in the lining of the lung, removal of the fluid with a needle (called a thoracentesis) may help diagnose cancer as well as improve breathing symptoms. If the fluid tests negative for cancer cells -- which occurs about 60% of the time -- then a procedure known as a video-assisted thoracoscopic surgery (or VATS) may be performed to examine the lining of the lung for tumors.
Because saliva, mucus, and chest X-rays have not proved particularly effective in detecting small tumors characteristic of early lung cancer, annual chest X-rays for lung cancer screening are not recommended by the American Cancer Society, the National Cancer Institute, or the American College of Radiology.
Screening CT scan clinical trials have been performed and some are completed. In one study, over 31,000 people were screened with CT scans and 484 -- or 1.5% -- were found to have lung cancer. Other studies, however, have shown no reduction in lung cancer deaths with CT scanning. Other clinical trials are ongoing. One of the problems with CT scan screening is the increased risk of radiation exposure and subsequent development of radiation related cancers.
Lung Cancer Surgery
Surgery is the preferred treatment for patients with early stage NSCLC. Unfortunately, 60-80% of all patients who have advanced or metastatic disease are not suitable for surgery.
Surgery is not widely used in SCLC. Because SCLC spreads widely and rapidly through the body, removing it all by surgery is usually impossible. An operation for lung cancer is major surgery. Many people experience pain, weakness, fatigue, and shortness of breath after surgery. Most have problems moving around, coughing, and breathing deeply. The recovery period can be several weeks or even months.