Overview of lung cancer
Out of all the cancers that exist lung cancer is one of the leading cause of cancer deaths in both women and men throughout the world. Lung cancer is the number one cause of cancer deaths in men and has overtaken breast cancer as the leading cause of cancer deaths in women. People projected to die from lung cancer are much higher when compared with deaths due to colorectal, breast, and prostate cancer combined. Only about 15% of all people who develop lung cancer survive for 5 years. Cancer of the lung, like all cancers, results from an abnormality in the body’s basic unit of life, the cell. Normally, the body maintains a system of checks and balances on cell growth so that cells divide to produce new cells only when needed. Disruption of this system of checks and balances on cell growth results in an uncontrolled division and proliferation of
cells that eventually forms a mass known as a tumor. Cancer occurs when normal cells undergo a transformation that causes them to grow and multiply without the normal controls. The cells form a mass or tumor that differs from the surrounding tissues from which it arises.
Tumors are dangerous because they take oxygen, nutrients, and space from healthy cells.
Tumors can be benign or malignant; when we speak of "cancer" we refer to those tumors that are considered malignant. Benign tumors can usually be removed and do not spread to other parts of the body. Malignant tumors, on the other hand, grow aggressively and invade other tissues of the body, allowing entry of tumor cells into the bloodstream or lymphatic system which spread the tumor to other sites in the body. Since lung cancer tends to spread, or metastasize, very early in its course, it is a very life-threatening cancer and one of the most difficult cancers to treat. While lung cancer can spread to any organ in the body, certain organs – particularly the adrenal glands, liver, brain, and bone - are the most common sites for lung cancer metastasis. Metastasis is the process where the tumors can also spread to nearby lymph nodes or through the bloodstream to other organs.
When lung cancer metastasizes, the tumor in the lung is considered the primary tumor, and the tumors in other parts of the body are called secondary tumors or metastatic tumors. Some lung tumors are metastatic from cancers elsewhere in the body. The lungs are a common site for metastasis. Lung cancers are usually divided into 2 groups that account for about 95% of all cases.The division is based on the type of cells that make up the cancer.
The 2 types of lung cancer are classified based on the cell size of the tumor. They are called small cell lung cancer (SCLC) and non–small cell lung cancer (NSCLC). NSCLC includes several more types of tumors.
SCLCs are less common, but they grow more quickly and are more likely to metastasize than NSCLCs. Often, SCLCs have already spread to other parts of the body when the disease is diagnosed.
About 5% of lung cancers are of rare cell types, such as carcinoid tumor, lymphoma, or metastatic (cancers from other parts of the body that spread to the lungs).
The specific types of primary lung cancers are as follows:
Adenocarcinoma (an NSCLC) is the most common type of lung cancer, making
up 30-40% of all cases. A subtype of adenocarcinoma is called bronchoalveolar cell carcinoma, which creates a pneumonialike appearance on chest x-ray films.
Squamous cell carcinoma (an NSCLC) is the second most common type of lung cancer, making up about 30% of all lung cancers. Large cell cancer makes up 10% of all cases.
SCLC makes up 20% of all cases. Carcinoid lung cancer accounts for 1% of all cases.
Causes of lung cancer
Cigarette smoking is the most significant cause of lung cancer. Cigarette smoke contains more than 4000 chemicals, many of which have been identified as causing cancer. A person who smokes more than 1 pack of cigarettes per day has a risk of developing lung cancer 20-25 times greater than someone who has never smoked. Once a person quits smoking, his or her risk for lung cancer gradually decreases. About 15 years after quitting, the risk for lung cancer decreases to the level of someone who never smoked. The risk of developing lung cancer is related to the following factors:
The number of cigarettes smoked
The age at which a person started smoking
How long a person has smoked (or had smoked before quitting)
Passive smoking, or sidestream smoke, presents another risk for lung cancer. A person living with a smoker has twice the risk of lung cancer of someone not regularly exposed to smoke.
Air pollution from motor vehicles, factories etc.
Asbestos exposure increases the risk. A combination of asbestos exposure and cigarette smoking compounds the risk.
Lung diseases, such as tuberculosis (TB) and chronic obstructive pulmonary disease (COPD), also create a risk for lung cancer.
Symptoms of lung cancer
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.
A new cough in a smoker or a former smoker should raise concern for lung cancer.
A cough that does not go away or gets worse over time should be evaluated by a health care provider.
Coughing up blood. Any amount of coughed-up blood should cause alarm.
Chest pain. The pain is dull, aching, and persistent and may involve other structures surrounding the lung.
Shortness of breath usually results from a blockage in part of the lung, collection of fluid around the lung (pleural effusion), or the spread of tumor through the lungs.
Wheezing or hoarseness may signal blockage or inflammation in the lungs that may go along with cancer.
Repeated respiratory infections, such as bronchitis or pneumonia, can be a sign of lung cancer.
Symptoms of metastatic lung tumors depend on the location and size. About 30-40% of people with lung cancer have some symptoms or signs of metastatic disease.
Lung cancer most often spreads to the liver, the adrenal glands, the bones, and the brain.
Metastatic lung cancer in the liver usually does not cause any symptoms, at least at the time of diagnosis.
Metastatic lung cancer in the adrenal glands also typically causes no symptoms at the time of diagnosis.
Metastasis to the bones is most common with small cell type cancers but also occurs with other lung cancer types. Lung cancer that has metastasized to the bone causes bone pain, usually in the backbone (vertebrae), the thighbones, and the ribs.
Lung cancer that spreads to the brain can cause difficulties with vision, weakness on one side of the body, and/or seizures.
Paraneoplastic syndromes are the remote, indirect effects of cancer not related to direct invasion. Symptoms include the following:
Clubbing of fingers - The depositing of extra tissue under the nails
New bone formation - Along the lower legs or arms
Anemia - Low numbers of red blood cells and high calcium level or low sodium level in the blood
Other effects - Muscle weakness, skin rashes, and degeneration of the brain
Weight loss
Fatigue
Low sodium levels
Lung Cancer Treatment
The treatment of lung cancer depends on following:
. Whether the lung cancer is of type SCLC or NSCLC.
· Stage of tumor , particularly in NSCLC.
· A person's general physical condition is also taken into account.
· Most widely used therapies are surgery, chemotherapy, and radiation therapy.
