Lung Cancer
[FONT="]Lung cancer was not common prior to the 1930s but increased dramatically over the following decades as tobacco use is increased. In many developing countries, the incidence of lung cancer is beginning to fall following public education about the dangers of cigarette smoking and effective smoking-cessation programs. Nevertheless, lung cancer remains among the most common types of cancers in both men and women worldwide.[/FONT]
Symptoms : The growth of the cancer and invasion of lung tissues and surroundings may interfere with breathing, leading to symptoms such as cough, shortness of breath, wheezing, chest pain, and coughing up blood. If the cancer has invaded nerves, for example, it may cause shoulder pain that travels down the outside of the or paralysis of the vocal. Invasion of the esophagus may lead to difficulty swallowing. If a large airway is obstructed, collapse of a portion of the lung may occur.
Diagnosis
Doctors use a wide range of diagnostic procedures and tests to diagnose lung cancer. These include:
- Breathing difficulties, airway obstruction, or infections in the lungs. A bluish color of the skin and the mucous membranes due to insufficient oxygen in the blood, suggests compromised function of the lung. Likewise, changes in the tissue of the nail beds, known as clubbing, may also indicate lung disease.
- The chest x-ray is the most common first diagnostic step when any new symptoms of lung cancer are present. The chest x-ray procedure often involves a view from the back to the front of the chest as well as a view from the side. Like any x-ray procedure, chest x-rays expose the patient briefly to a minimum amount of radiation. Chest x-rays may reveal suspicious areas in the lungs but are unable to determine if these areas are cancerous. In particular, calcified nodules in the lungs or benign tumors may be identified on a chest x-ray and simulate lung cancer.
- CT (computerized axial tomography scan, or CAT scan) scans may be performed on the chest, abdomen, and/or brain to examine for both metastatic and primary tumor. A CT scan of the chest may be ordered when x-rays are negative or do not yield sufficient information about the extent or location of a tumor. CT scans are x-ray procedures that combine multiple images with the aid of a computer to generate cross-sectional views of the body. The images are taken by a large donut-shaped x-ray machine at different angles around the body. One advantage of CT scans is that they are more sensitive than standard chest x-rays in the detection of lung nodules. Sometimes intravenous contrast material is given prior to the procedure to help delineate the organs and their positions. A CT scan exposes the patient to a minimal amount of radiation. The most common side effect is an adverse reaction to intravenous contrast material that may have been given prior to the procedure. A technique called a low-dose helical CT scan (or spiral CT scan) is sometimes used in screening for lung cancers. This procedure requires a special type of CAT scanner and has been shown to be an effective tool for the identification of small lung cancers in smokers and former smokers. However, it has not yet been proven whether the use of this technique actually saves lives or lowers the risk of death from lung cancer. The heightened sensitivity of this method is actually one of the sources of its drawbacks, since lung nodules requiring further evaluation will be seen in approximately 20% of people with this technique. Of the nodules identified by low-dose helical screening CTs, 90% are not cancerous but require up to two years of costly and often uncomfortable follow-up and testing. Trials are underway to further determine the utility of spiral CT scans in screening for lung cancer.
- MRI scans may be indicated when precise detail about a tumor's location is required. The MRI technique uses magnetism, radio waves, and a computer to produce images of body structures. As with CT scanning, the patient is placed on a moveable bed which is inserted into the MRI scanner. There are no known side effects of MRI scanning, and there is no exposure to radiation. The image and resolution produced by MRI is quite detailed and can detect tiny changes of structures within the body. People with heart pacemakers, metal implants, artificial heart valves, and other surgically implanted structures cannot be scanned with an MRI because of the risk that the magnet may move the metal parts of these structures.
- PET scanning is a specialized imaging technique that uses short-lived radioactive substances to produce three-dimensional colored images of those substances functioning within the body. While CT scans and MRI scans look at anatomical structures, PET scans measure metabolic activity and functioning of tissue. PET scans can determine whether a tumor tissue is actively growing and can aid in determining the type of cells within a particular tumor. In PET scanning, the patient receives a short half-lived radioactive drug and receives approximately the amount of radiation exposure as with two chest x-rays. The drug discharges positrons from wherever they are used in the body. As the positrons encounter electrons within the body, a reaction producing gamma rays occurs. A scanner records these gamma rays and maps the area where the drug is located.
- Bone scans are used to create images of bones on a computer screen or on film. Doctors may order a bone scan to determine whether a lung cancer has metastasized to the bones. In a bone scan, a small amount of radioactive material is injected into the bloodstream and collects in the bones, especially in abnormal areas such as those involved by metastatic tumors. The radioactive material is detected by a scanner, and the image of the bones is recorded on a special film for permanent viewing.
- Sputum cytology: The diagnosis of lung cancer always requires confirmation of malignant cells by a pathologist, even when symptoms and x-ray studies are suspicious for lung cancer. The simplest method to establish the diagnosis is the examination of sputum under a microscope. If a tumor is centrally located and has invaded the airways, this procedure, known as a sputum cytology examination, may allow visualization of tumor cells for diagnosis. This is the most risk-free and inexpensive tissue diagnostic procedure, but its value is limited since tumor cells will not always be present in sputum even if a cancer is present. Also, noncancerous cells may occasionally undergo changes in reaction to inflammation or injury that makes them look like cancer cells.
- Bronchoscopy Examination of the airways by bronchoscopy (visualizing the airways through a thin probe inserted in a tube through the nose or mouth) may reveal areas of tumor that can be sampled for pathologic diagnosis. A tumor in the central areas of the lung or arising from the larger airways is accessible to sampling using this technique. Bronchoscopy may be performed using a rigid or a flexible, fiberoptic bronchoscope and can be performed in a same-day outpatient bronchoscopy suite, an operating room, or on a hospital ward. The procedure can be uncomfortable and require sedation or anesthesia. While the procedure is relatively safe, the procedure must be carried out by a lung specialist (pulmonologist or surgeon) experienced in the procedure. When a tumor is visualized and adequately sampled, an accurate cancer diagnosis is generally possible. Some patients may cough up dark-brown blood for one to two days after the procedure. More serious, and rare, complications include a greater amount of bleeding, decreased levels of oxygen in the blood.
- Needle biopsy (FNA) through the skin, most commonly performed with radiological imaging for guidance, may be useful in retrieving cells for diagnosis from tumor nodules in the lungs. Needle biopsies are particularly useful when the lung tumor is peripherally located in the lung and not accessible to sampling by bronchoscopy. A small amount of local anesthetic is given prior to insertion of a thin needle through the chest wall into the abnormal area in the lung. Cells are suctioned into the syringe and are examined under the microscope for tumor cells. This procedure is generally accurate when the tissue from the affected area is adequately sampled, but in some cases, adjacent or uninvolved areas of the lung may be mistakenly sampled. A small risk (3%-5%) of an air leak from the lungs, which can easily be treated) accompanies the procedure.
- Thoracentesis: Sometimes lung cancers involve the lining tissue of the lungs (pleura) and lead to an accumulation of fluid in the space between the lungs and chest wall (called a pleural effusion). Aspiration of a sample of this fluid with a thin needle (thoracentesis) may reveal the cancer cells and establish the diagnosis. As with the needle biopsy, a small risk of a pneumothorax is associated with this procedure.
- Major surgical procedures: If none of the aforementioned methods yields a diagnosis, surgical methods must be employed to obtain tumor tissue for diagnosis. These can include mediastinoscopy (examining the chest cavity between the lungs through a surgically inserted probe with biopsy of tumor masses or lymph nodes) or thoracotomy (surgical opening of the chest wall with removal of as much tumor as possible). Thoracotomy is rarely able to completely remove a lung cancer, and both mediastinoscopy and thoracotomy carry the risks of major surgical procedures (complications such as bleeding, infection, and risks from anesthesia and medications). These procedures are performed in an operating room, and the patient must be hospitalized.
- Blood tests: While routine blood tests alone cannot diagnose lung cancer, they may reveal biochemical or metabolic abnormalities in the body that accompany cancer. For example, elevated levels of calcium or of the enzyme alkaline phosphatase may accompany cancer that is metastatic to the bones. Likewise, elevated levels of certain enzymes normally present within liver cells, including AST or SGOT and ALT or SGPT, signal liver damage, possibly through the presence of metastatic tumor
[FONT="]Treatment[/FONT][FONT="]: Treatment for lung cancer depends on the cancer's specific cell type, and its progress. Common treatments include chemotherapy, surgery, and radiation.[/FONT]
Surgery
[FONT="]Before going to surgery, it is used to determine whether the disease is localised and amenable to surgery or whether it has spread to the point where it cannot be cured surgically.[/FONT]
[FONT="]Surgery itself has an operative death rate of about 4.4%, depending on the patient's lung function. Surgery is usually only an option in non-small cell lung carcinoma limited to one lung, up to stage IIIA. [/FONT]
[FONT="]Procedures include removal of part of a lobe, removal of an anatomic division of a particular lobe of the lung, one lobe, two lobes or whole lung. [/FONT]
Chemotherapy
[FONT="]Small cell lung carcinoma is treated primarily with chemotherapy and radiation, as surgery has no demonstrable influence on survival. Primary chemotherapy is also given in metastatic non-small cell lung carcinoma.[/FONT]
[FONT="]The combination regimen depends on the tumor type. Non-small cell lung carcinoma is often treated with , cisplatin or in combination with other drugs. In small cell lung carcinoma, cisplatin and etoposide are most commonly used. It can be combine with carboplatin, gemcitabine, paclitaxel, vinorelbine, and topotecan.[/FONT]
Radiotherapy is often given together with chemotherapy, and may be used with curative intent in patients with non-small cell lung carcinoma who are not eligible for surgery. This form of high intensity radiotherapy is called radical radiotherapy.
[FONT="]For both non-small cell lung carcinoma and small cell lung carcinoma patients, smaller doses of radiation to the chest may be used for symptom control [/FONT]
Targeted therapy
[FONT="]In recent years, various molecular targeted therapies have been developed for the treatment of advanced lung cancer. [/FONT]
[FONT="]Gefitinib (Iressa) is one such drug, which targets the tyrosine kinase domain of the EGF-R which is expressed in many cases of non-small cell lung carcinoma. [/FONT]
[FONT="]Erlotinib (Tarceva), another tyrosine kinase inhibitor, has been shown to increase survival in lung cancer patients and has recently been approved by the FDA for second-line treatment of advanced non-small cell lung carcinoma. Similar to gefitinib, it appeared to work best in females, Asians, non-smokers and those with bronchioloalveolar carcinoma.[/FONT]