Lung Pet Scan

One of the most important uses of Positron Emission Tomography (PET) technology is its use in diagnosing and treating lung cancer. Lung cancer is the leading cause of cancer death in both men and women. The American Cancer Association estimates that 173,770 new cases of lung cancer will be diagnosed in 2004. Additionally, the American Cancer Association estimates that lung cancer deaths will reach a level of 160,400, which will account for approximately 28% of all cancer deaths in 2004.

About Lung Cancer

Lung cancer is the leading cause of cancer death and it is estimated that during their lifetime, 1 in 21 women will develop lung cancer and 1 in 11 men will develop this disease. Lung cancer occurs when lung cells become abnormal and form more cells in an uncontrolled manner. A tumor, which is a mass of tissue, develops out of these extra cells and can either be benign (non-cancerous) or malignant (cancerous). Although, there are a variety of types of lung cancer, this disease can be classified in two groups:

  • Small cell lung cancer (SCLC):
    C cancer cells are small but quickly form large tumors that can progress to other parts of the body such as the lymph nodes, brain, liver, and bones. Also known as oat cell cancer, SCLC accounts for approximately 20% of all lung cell cancers.
  • Non-small cell lung cancer (NSCLC):
    The most common form of lung cancer that incorporates a variety of cancer sub-types such as Squamous cell carcinoma, adenocarcinoma, and large cell carcinoma. This type of cancer also spreads to other parts of the body but tends to progress slowly to different parts of the body slower than SCLC.

The principal cause of lung cancer is cigarette smoking. Before cigarette smoking became popular in the early 20th century, lung cancer was a rare occurrence. However, cases of lung cancer have exploded over the last century with an estimated 87% of lung cancer cases stemming from smoking. Cigarette smoke contains over 4,000 different chemicals and many of these cancers have been proven to be carcinogens (cancer-causing substances). The probability of lung cancer increases with the amount of time and quantity an individual smokes. Additionally, the use of smokeless tobacco products and the smoking of other forms of tobacco products are major causes of lung cancer.

Another major cause of lung cancer is second-hand smoke, which is a byproduct of smoking. Chemicals present in tobacco smoke affect nonsmokers who are inhaling the smoke, and second hand smoke has been identified as causing approximately 3,000 lung cancer deaths per year. Second hand smoke has also been identified as causing approximately 50,000 deaths from heart disease per year.

The second biggest cause of lung cancer is exposure to radon: an invisible, odorless, and radioactive gas. Radon gas is commonly found in mines as well as in the home. It often emerges from soil underneath a building that enters through gaps and cracks in a building’s foundation or insulation. Radon can also enter a home through other openings such as pipes, drains, and walls. Currently, it is estimated that radon exposure makes up 12% of all lung cancer deaths, causing between 15,000 and 22,000 lung cancer deaths per year.

An additional cause of lung cancer is on-the-job exposure to carcinogens. The most common carcinogen is asbestos, (a substance commonly used in shipbuilding, insulation work, and brake repair) which if inhaled can cause cell damage that increases the potential of lung cancer. Additional carcinogens that are often found on work sites include: uranium, arsenic, and certain petroleum products.

Symptoms of Lung Cancer

Regardless of the type of lung cancer, the PET scan is an important tool that can be used to reverse its effects. Often described as a silent killer, lung cancer is a difficult disease to diagnose while in its early stages, as it does not contain any symptoms. Although lung cancer is a disease that takes many years to develop, exposure to carcinogens produce immediate changes to the lung. Following exposure to carcinogens, a few abnormal cells may appear in the lining of the bronchi, which are the main breathing tubes. If a person is continually exposed to carcinogens, the number of abnormal cells will increase and these cells will progressively become malignant and thus more cancerous. These abnormal cells may eventually form a tumor. However, if a person avoids exposure to carcinogens, normal cells will replace these abnormal cells and the risk of lung cancer will drastically reduce.

As lung cancer takes many years to develop and do not produce symptoms in its early stages, most cases of lung cancer are diagnosed when a patient is between 55 to 65 years old. By that point, the lung cancer has progressed to the point that cancerous cells have broken away and spread to other parts of the body. Consequently, the overall five-year survival rate for these patients is less than 10%. However, if lung cancer is found in its early stage where the cancerous have yet to spread to other organs, the overall five-year survival rate improves to 35% to 45%. Approximately 15% of lung cancers are found in this early stage although lung cancer continues to be a difficult disease to notice.

Although lung cancer symptoms are vague, you may want to visit a doctor if you are experience these phenomena:

  • The presence of a chronic cough that doesn’t go away or worsens
  • Instances of coughing up blood
  • The presence of constant chest pain
  • The condition of wheezing, hoarseness, or general shortness of breath
  • Repeated problems with pneumonia or bronchitis
  • Instances of neck and facial swelling
  • Appetite loss or weight loss
  • A feeling of general fatigue
  • The presence of a fever without a known reason.
PET and Lung Cancer Diagnosis

Positron Emission Tomography is an effective procedure used in the diagnosis and treatment of lung cancer in the various medical stages of treatment. PET scans for lungs are one of the most effective imaging tools in diagnosing lung cancer. As lung cancer has very little symptoms in its early stages, it is usually detected through an anatomical imaging procedure such as chest x-rays or a computerized tomography scan that was performed for another medical reason. Although these anatomical imaging techniques are useful in detecting the size and location of a lung mass that can be indicative of a cancerous tumor, a lung cancer PET scan will be able to detect whether or not this abnormality is benign (alive tissue and non-cancerous) or malignant (dead tissue and cancerous).

PET imaging is able to detect cancerous cells, as it is a metabolic imaging tool. With PET scans, the chemical function of the lung and other targeted organs or tissues are examined. PET images are able to visualize biochemical changes caused by disease. This function differentiates the PET from such anatomic imaging tools as x-rays, computed tomagraphy (CT), and magnetic resonance imaging (MRI), as these tools are only able to produce images detailing body structure.

PET scans involve the administering of a radioactive tracer that is a combination of a radioisotope (a radioactive compound whose movements are detectable by a PET scanner) with a natural body compound. In lung cancer diagnosis, the radioactive tracer used in the Positron Emission Tomography procedure is Fluorodeoxyglucose (FDG), which combines the natural body compound glucose with the radioisotope Fluorine-18. This radioactive tracer, or radiopharmaceutical, is used in lung cancer detection as the radioactive compound that it uses has a short half-life and will disappear from the body within hours. Therefore, PET scan for lungs are safe and the patient should free themselves of any worry about the radiation content of this procedure.

Additionally, lung cancer PET scan uses FDG as it contains the body compound glucose. The use of FDG, which shares a similar structure to glucose, is important, as the absorption of glucose is effective in determining whether a cell is healthy or cancerous. PET imaging traces the absorption rate of FDG by cells and can determine whether cancerous cells are present in the lung and other organs or tissues, as glucose (which FDG shares a similar structure) is absorbed at a faster rate by cancerous cells compared to healthy cells. By tracing the movement of FDG in a patient’s organ, the physician is able to determine whether the lung mass detected through anatomic imaging is benign (non-cancerous) or malignant (cancerous). From the images produced by the PET scan, a physician will be able to make an informed diagnosis, as these images are able to show whether the lung is normal and healthy or if there is the presence of lung cancer. This will reduce the number of unnecessary surgeries performed on patients who have tumors present in their body, but whose tumors are actually benign and therefore not indicative of cancer.

In this way, the PET scan is able to provide the same information (in a non-invasive manner) that a biopsy would, which often involves the insertion of a bronchoscope (a small tube) through the patient’s nose or mouth that goes down the patient’s throat that takes a sample, or biopsy, of the tumor from the patient’s airways and lungs.

PET and Lung Cancer Staging

Besides detection, PET scans are effective in the treatment of lung cancer when it is used during the staging phases. Staging commences following lung cancer diagnosis and is used to determine if or how much the lung cancer has spread or metastasize. PET scan lung metastasis is an important component of the staging phase of lung cancer treatment is critical as it provides the necessary information for physicians in determining an appropriate medical course of lung cancer treatment.

Through PET imaging, a physician is able to determine whether or not cancerous cells have spread from the lungs to other parts of the body. Positron Emission Tomography involves the administration of a radioactive tracer that combines a radioisotope, a radioactive compound that is detected by a PET scanner, with a natural body compound, which the body is able to integrate into its system without any negative effects. In lung cancer screening, the radioactive tracer used is Fluorodeoxyglucose (FDG) that combines the natural body compound glucose with the radioisotope Fluorine-18. Although many patients have concerns about the radioactive component contained in PET imaging, Fluorine-18 contains a short half-life and disappears from the body within hours. Consequently, the PET procedure is a safe one for patients.

In the staging process, PET scans are the most effective imaging tool in determining the spread of cancerous cells. Other imaging tools such as computerized tomography (CT), magnetic resonance imaging (MRI), and x-rays are able to determine the possibility of cancer spread by examining changes in the anatomical structure of organs and tissues. Lung cancer mainly spreads to the brain, bone, and liver, although it can spread to nearly anywhere in the body.

These imaging tools then detect cancer spread by examining other body organs for anatomical changes. Consequently, these anatomic imaging tools detect cancer spread by identifying instances where organs or tissues have shown increased mass sizes.

However, PET determines cancer spread more comprehensively than these other imaging tools, as it detects biochemistry changes among these organs and tissues. By tracing the spread of FDG in a patient’s body, PET imaging is able to establish patterns of cancer spread based on the body’s chemical reactions to FDG. As it is similar in structure to glucose, PET determines cancer spread by studying the absorption of FDG by the patient’s organs and tissues. FDG is absorbed at a faster rate by cancerous organs and tissues than healthy organs and tissues. By studying the biochemical reaction of the patient’s body, PET scan is able to produce the most accurate analysis of whether lung cancer has spread to other areas of the body.

This information is critical in determining an accurate outlook of patient recovery. For example, through a PET scan, a physician is able to view whether cancerous cells have spread to lymph nodes or other organs. If this is not the case and surgery has been undertaken, the five-year survival rate of this surgery will increase to approximately 42%. PET imaging contains an 82% accuracy rating in determining whether lung cancer has spread to the lymph nodes compared to the 68% accuracy rating of CT scanning. Consequently, PET imaging is the most accurate staging diagnostic imaging tool that will aid a physician’s decision in recommending the appropriate treatment option.

In cases where PET imaging has shown that cancerous tumors are located in an appropriate location within the lung, surgery is often the best option. Surgery can cure lung cancer but its use depends on such variables as its location in the lung and also its size. Other medical treatments to lung cancer include: radiation therapy, which is a high energy X-ray that kills cancer cells; and chemotherapy, which uses drugs to effectively treat lung cancer.

The medical course of action used to treat lung cancer is often determined by staging. Staging is a vital step in the patient’s road to health recovery, as all of these treatment options are contingent on the size of the cancerous tumor, the spread of cancerous cells, and the location of the cancerous tumor. A PET scan is the most effective lung cancer staging tool and is a vital tool used by physicians in providing a specialized, medical plan to eradicate lung cancer from the patient.

PET and Lung Cancer Follow-Up

Another valuable function of Positron Emission Tomography in lung cancer treatment is its role in studying the patient’s recovery. Following staging, a physician will recommend a medical course of action that they feel are the most appropriate and effective. In most instances, chemotherapy, radiation therapy, or a combination of both is used to treat lung cancer. Although these treatments are usually effective, an important component of lung cancer treatment is determining whether active cancer cells have remained in the body following treatment.

Prior to the clinical use of PET scan, physicians applied radiation therapy and chemotherapy according to standard rules. However, with PET imaging, it is now possible for physicians to specifically cater lung cancer treatment to your particular situation. This is because Positron Emission Tomography allows a physician to view the location, extent, and resilience of a patient’s lung cancer.

Additionally, PET imaging is the most effective diagnostic tool in detecting lung tumor response to therapy. PET scans study the chemical function of the lung and other organs and tissues and is able to produce images that show visual biochemical changes in the body caused by lung cancer. Unlike such anatomic imaging tools as x-rays, computed tomagraphy (CT), and magnetic resonance imaging (MRI) that detail changes in body structure such as the presence of tumors, PET imaging is able to determine whether a tumor is benign (alive tissue and non-cancerous) or malignant (dead tissue and cancerous). Therefore, a PET scan lung metastasis is an important method used by physicians to examine recurrence of cancer in the patient.

PET scans involve the administration of the radioactive tracer, Fluorodeoxyglucose (FDG) that combines the natural body compound glucose with the radioisotope Fluorine-18. FDG safely travels through the body where a PET scanner monitors its movement within the body. A radioactive tracer that disappears from the body within hours, FDG is able to detect cancer recurrence in successfully treated lesions as well as determine whether tumors identified in an anatomic imaging scan are cancerous or not.

This is because FDG is similar in structure to glucose, which cancerous cells absorb at a faster rate than healthy cells. By tracing the absorption rates of FDG by the targeted cells, a physician is able to determine whether successfully treated lesions are showing signs of cancer recurrence. Additionally, PET imaging is able to detect cancer recurrence in lymph nodes and/or scar tissue from surgery from surgery or another lesion sooner than an anatomical imaging procedure. PET scans are also able to distinguish between cancerous and non-cancerous tumors that are detected by anatomical imaging and are still present despite lung cancer treatment.



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