Definition and Overview
Lung cancer is a term used to refer to a group of diseases caused by malignant growths in the lungs. There are two major types of lung cancer: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). Both look different under the microscope and are treated differently. Between the two, NSCLS is more common accounting for approximately 85% of all lung cancers. SCLC, on the other hand, is less common but grows more quickly and is more likely to spread to other organs.
There are three types of NSCLCs including squamous cell lung carcinoma, which usually begins in the larger bronchi or in the tissue that lines the main passageway into the lungs. It accounts for about 30% of all NSCLCs. The other two types are adenocarcinoma lung (the most common form of lung cancer) and large cell carcinoma, which accounts for about 10% of all NSCLS tumours.
Lung cancer remains to be the leading cause of cancer deaths throughout the world. This is because the lungs contain a very rich network of lymphatic channels as well as blood vessels through which cancer cells can easily spread to even distant organs. Common sites of spread include the adrenal glands, liver, the brain, and the bones.
Causes of Condition
Cancer develops when cells undergo an abnormal transformation that causes them to grow and multiply uncontrollably. Although scientists are yet to establish what causes this transformation, they theorise that lung cancer is caused by anything that a patient breathes. The majority of lung cancers are related to tobacco smoking. Based on clinical studies, a person who smokes at least one pack of cigarettes per day has up to 25% increased risk of lung cancer than those who do not smoke. When patients decide to quit smoking, their risk gradually goes down. After about 15 years of not smoking, their risk of lung cancer is the same as those who have never smoked in their life.
Other environmental exposures or substances that can increase one’s risk of lung cancer include:
Air pollution from factories and motor vehicles
Industrial substances including diesel exhaust, arsenic, coal products, and nickel chromates
Radon, which is released by some rocks and soil that contain uranium
Exposure to asbestos
Passive or secondhand smoking
Previous history of lung cancer
Lung cancer can also occur if a patient is suffering from other types of lung diseases including tuberculosis and chronic obstructive pulmonary disease (COPD) that cause scarring to the lung tissue.
Squamous cell carcinoma of bronchus, just like other types of NSCLCs, does not usually produce symptoms until the disease is well advanced. In fact, the disease is often diagnosed when patients undergo a chest x-ray for another reason. Thus, patients who have risk factors, particularly those who smoke, are encouraged to undergo regular check-ups so doctors are able to catch the disease during its early stages. Patients are also advised to stop smoking immediately.
Meanwhile, some patients experience symptoms of lung cancer when the malignant tumour affects the functions of other systems of the body. These symptoms include:
Chronic respiratory infections including pneumonia and bronchitis
Cough that does not go away or gets worse over time
Hemoptysis or coughing up blood
Persistent, dull chest pain
Shortness of breath caused by airflow blockage in the lung
If the cancer has already spread, patients will experience additional symptoms, which vary depending on the metastatic site. These may include unexplained weight loss, bone pain, weakness on one side of the body, difficulties with vision, and seizures. If the cancer is causing some organs of the body to malfunction, patients will also have low sodium and potassium levels as well as high calcium levels leading to the formation of new bones and clubbing of fingers, among others.
Who to See and Types of Treatments Available
Patients showing signs of lung cancer should see their primary physician or general practitioner who can order screening procedures and make an initial diagnosis. Standard diagnostic tests are computed tomography (CT), positron emission tomography (PET), and magnetic resonance imaging (MRI) scans. If imaging tests suggest the presence of lung cancer, patients undergo a biopsy either during a bronchoscopy or through a needle biopsy wherein a small piece of tissue from the lung is obtained and examined under a microscope. Pathologists then interpret the results and provide crucial information in which the treatment will be based on. Such information includes whether the cancer is NSCLC or SCLC, its stage, and whether or not the disease was caused by gene mutations.
NSCLCs including squamous cell carcinoma of bronchus are treated with multimodality therapies that may combine surgery with radiation, immunotherapy, chemotherapy, or targeted treatments.
The lobe or section of the lung that contains the malignant tumour is removed via surgery, which can now be performed using a minimally invasive method called video-assisted thoracoscopic surgery (VATS). Instead of a large incision, VATS uses small cuts in the chest where a thoracoscope (a thin, flexible viewing tube) is inserted. The tumour is removed using the scope with the help of an x-ray machine that provides the surgeon with imaging guidance.
If the tumour cannot be surgically removed, the main treatment is chemotherapy and definitive high-dose radiation. For patients with stage 3 lung cancer, adjuvant therapies are performed to kill remaining cells and to prevent recurrence. In patients with stage 4 lung cancer, chemotherapy is performed as a palliative treatment to ease lung cancer symptoms.
Targeted therapy, in which normal cells are spared, has been shown to benefit some people with specific types of lung cancer. The same is true for immunotherapy that works by strengthening the patient’s immune system so it can fight cancer cells. Unlike other treatment options, immunotherapy does not result in major side effects.
College of American Pathologists. Lung: Squamous Cell Carcinoma. Accessed 10/30/12. http://www.cap.org/apps/docs/reference/myBiopsy/LungSquamousCellCarcinoma.pdf
Sheth, S. Current and emerging therapies for patients with advanced non-small cell lung cancer. American Journal of Health-System Pharmacy. 2010. 67(1 Suppl 1):S9-14.