LUNG CANCER

Issah J. kiswagala

(M.B.B.S)

PHYSIOLOGICAL ANATOMY

The Lungs

• A major organ of the respiratory system.
• The main function of the lungs is to perform the exchange of oxygen and carbon dioxide with air from the atmosphere. To this end, the lungs exchange respiratory gases across a very large epithelial surface area—about 70 square meters—that is highly permeable to gases.

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• The lungs are pyramid-shaped, paired organs that are connected to the trachea by the right and left bronchi; on the inferior surface, the lungs are bordered by the diaphragm.

• The right lung is shorter and wider than the left lung, and the left lung occupies a smaller volume than the right.
• The apex of the lung is the superior region, whereas the base is the opposite region near the diaphragm. The costal surface of the lung borders the ribs. The mediastinal surface faces the midline.
• Each lung is composed of smaller units called lobes. Fissures separate these lobes from each other. The right lung consists of three lobes: the superior, middle, and inferior lobes. The left lung consists of two lobes: the superior and inferior lobes.
• A pulmonary lobule is a subdivision formed as the bronchi branch into bronchioles. Each lobule receives its own large bronchiole that has multiple branches

LUNG CANCER

EPIDEMIOLOGY

• Lung cancer is the leading cause of cancer death in the United States and around the world. Almost as many Americans die of lung cancer every year than die of prostate, breast, and colon cancer combined.

TYPES OF LUNG CANCER�

• lung cancer is divided into two major types that account for about 95% of all cases, based on the appearance of lung cancer cells under the microscope.
• They are called small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). NSCLC includes several subtypes 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 cancer is diagnosed.
• About 5% of lung cancers are of rare cell types, including carcinoid tumor, lymphoma, and others.

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• The specific types of primary lung cancers are as follows:
• Adenocarcinoma (an NSCLC) is the most common type of lung cancer, making up 30% to 40% of all cases. A subtype of adenocarcinoma is called bronchoalveolar cell carcinoma, which creates a pneumonia-like appearance on chest X-rays.
• Squamous cell carcinoma (an NSCLC) is the second most common type of lung cancer, making up about 30% of all cases.
• Large cell cancer (another NSCLC) makes up 10% of all cases.
• SCLC makes up 20% of all cases.
• Carcinoid tumors account for 1% of all cases

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SPREAD OF LUNG CANCER

• The lung is a bad place for a cancer to arise because it contains a very rich network of both blood vessels and lymphatic channels through which cancer cells can spread.
• The tumors can spread to nearby lymph nodes or through the bloodstream to other organs. This process of spread is called metastasis.
• When lung cancer metastasizes, the tumor in the lung is called the primary tumor, and the tumors in other parts of the body are called secondary or metastatic tumors. Some tumors in the lung are metastatic from cancers elsewhere in the body.

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•  About 30% to 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 may cause a loss of appetite, feeling full early on while eating, and otherwise unexplained weight loss.
• Metastatic lung cancer in the adrenal glands also typically causes no symptoms.
• Metastasis to the bones is most common with small cell 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 large bones of the thigh (the femurs), the pelvic bones, 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.

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AETIOLOGY/RISK FACTORS

1. Cigarette smoking is the most important cause of lung cancer. Cigarette smoke contains more than 4,000 chemicals, many of which have been identified as causing cancer.

• A person who smokes more than one pack of cigarettes per day has a 20-25 times greater risk of developing lung cancer 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.
• About 90% of lung cancers arise due to tobacco use.

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2. Passive smoking, or secondhand smoke, presents another risk for lung cancer. Even if you don't smoke, your risk of lung cancer increases if you're exposed to secondhand smoke.

3. Air pollution from motor vehicles, factories, and other sources probably increase the risk for lung cancer, and many experts believe that prolonged exposure to polluted air is similar to prolonged exposure to passive smoking in terms of risk for developing lung cancer.

4. Asbestos exposure increases the risk of lung cancer nine times. A combination of asbestos exposure and cigarette smoking raises the risk to as much as 50 times. Another cancer known as mesothelioma is also strongly associated with exposure to asbestos.

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5. Family history of lung cancer. People with a parent, sibling or child with lung cancer have an increased risk of the disease.

6. Lung diseases, such as tuberculosis (TB) and chronic obstructive pulmonary disease(COPD), also create a risk for lung cancer. A person with COPD has a four to six times greater risk of lung cancer even when the effect of cigarette smoking is excluded.

7. Radon gas exposure poses another risk. Radon is a byproduct of naturally occurring radium, which is a product of uranium. The risk for lung cancer increases with significant long-term exposure to radon, although no one knows the exact risk. in the U.S. Radon gas is the second leading cause of lung cancer in the United States after cigarette smoking. 

8. Certain occupations where exposure to arsenic, chromium, nickel, aromatic hydrocarbons, and ethers occurs may increase the risk of lung cancer.

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CLINICAL PRESENTATION

Lung cancer typically doesn't cause signs and symptoms in its earliest stages. Signs and symptoms of lung cancer typically occur only when the disease is advanced. Signs and symptoms of lung cancer may include:

• A new cough that doesn't go away
• Coughing up blood (Hemoptysis) even a small amount
• Sudden Shortness of breath
• Persistent Chest pain
• Wheezing or hoarseness may signal blockage or inflammation in the lungs that may go along with cancer.
• Unexplained weight loss without trying

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• Unexplained deep aches or pains.
• Bone pain.
• Headache.
• Unexplained persistent fatigue.
• Sudden vision problems.

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DIFFERENTIAL DIAGNOSIS

• Tuberculosis (TB)
• Viral Pneumonia
• Mycoplasma Pneumonia
• Bacterial Pneumonia
• Bronchitis
• Carcinoid Lung Tumors
• Pleural Effusion
• Pneumothorax
• Superior Vena Cava Syndrome in Emergency Medicine

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INVESTIGATIONS

• Complete blood count
• The X-ray may or may not show an abnormality. Unless severe hemoptysis is occurring, a chest X-ray will most likely be performed first to look for a cause of the respiratory symptoms. Types of abnormalities seen in lung cancer include a small nodule or nodules or a large mass.
• Sputum testing (Cells in the sputum can be examined to see if they are cancerous but is not a completely reliable test)
• Bronchoscopy can usually be used to determine the extent of the tumor.
• Thoracentesis: This a procedure that removes a sample of fluid from the pleural cavity (pleural effusion), Lung cancers, both primary and metastatic, can cause fluid to collect in the sac surrounding the lung. This fluid is taken for lab tests

TREATMENT

• Perform pre-referral management and then refer.
• In the higher centers, Treatment decisions in lung cancer depend first on whether SCLC or NSCLC is present.
• Treatment also depends on tumor stage
• The most commonly used treatments today for lung cancer involve surgery, radiation therapy, chemotherapy, and targeted therapies.
• Surgery is not widely used in SCLC. Because SCLC spreads widely and rapidly through the body, removing it all by surgery usually is impossible.

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PROGNOSIS

• Prognosis is poor
• Overall (considering all types and stages of lung cancer), 18% of people with lung cancer survive for at least 5 years. Survival rates tend to be low when compared to the 65% 5-year survival rate for colon cancer, 91% for breast cancer, and over 99% for prostate cancer.
• People with extensive nonoperable lung cancer have an average survival duration of 9 months or less.
• Less than 5% of people with extensive-stage SCLC (small cell cancers) are alive after 2 years, with a median survival range of eight to 13 months.

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FOLLOW UP

• Following surgery for operable lung cancer cases, there is an increased risk of developing a second primary lung cancer as well as risk that the original tumor will come back.
• Many lung cancers come back within the first 2 years after treatment.
• Regular testing should be performed so that any recurrence can be identified as early as possible.
• A person who has undergone surgery should receive follow-up care and examinations according to recommendations from the treatment team.

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PREVENTIVE MEASURES

• Prevention is primarily focused on smoking cessation.
• Passive tobacco smoke exposure as secondhand smoke should be discouraged.
• Decrease pollution and being exposured to those areas.
• Avoid carcinogens at work. Take precautions to protect yourself from exposure to toxic chemicals at work
• Eat a diet full of fruits and vegetables. Choose a healthy diet with a variety of fruits and vegetables. Food sources of vitamins and nutrients are best.
• Test your home for radon. Have the radon levels in your home checked, especially if you live in an area where radon is known to be a problem.
• Exercise most days of the week. If you don't exercise regularly, start out slowly. Try to exercise most days of the week.

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COMPLICATIONS

• Fluid in the chest (pleural effusion)
• Cancer that spreads to other parts of the body (metastasis). Lung cancer often spreads (metastasizes) to other parts of the body, such as the brain and the bones.
• Pain. Advanced lung cancer that spreads to the lining of a lung or to another area of the body, such as a bone, can cause pain
• Coughing up blood. Lung cancer can cause bleeding in the airway, which can cause you to cough up blood (hemoptysis). Sometimes bleeding can become severe.