By SOLA OGUNDIPE
LUNG cancer, the leading cause of cancer death in adult men and women, occurs most commonly between the ages of 45 and 70, has become more prevalent in recent times no thanks to increase in smoking of cigarettes. Majority of lung cancers belong to the nonâ€“small cell lung carcinoma category.
This type of cancer grows more slowly than the small cell lung carcinoma. By the time about 40 per cent of people with lung cancer are diagnosed, the cancer has spread to other parts of the body outside of the chest.
Small cell lung carcinoma accounts for about 13 – 15 per cent of all lung cancers. It is very aggressive and spreads quickly. By the time that most people are diagnosed, the cancer has spread to other parts of the body.
Cigarette smoking is the leading cause of cancer, accounting for about 85 per cent of all cases. About 10 per cent of all smokers (former or current) eventually develop lung cancer, and both the number of cigarettes smoked and number of years of smoking seem to correlate with the increased risk. In people who quit smoking, the risk of developing lung cancer decreases, but former smokers will still always have a higher risk of developing lung cancer than people who never smoked.
However, about 15 per cent of people who develop lung cancer have never smoked. In these people, the reason why they develop lung cancer is unknown. Recent studies have found that some people with lung cancer who have never smoked have genetic mutations in the epidermal growth factor receptor (EGFR) gene.
Although an environmental association has not clearly been established, it is believed that exposure to radon (a rare gas) in the home may be a risk factor. Other possible risk factors include exposure to secondhand smoke and exposure to carcinogens such as asbestos, radiation, arsenic, chromates, nickel, chloromethyl ethers, mustard gas, or coke-oven emissions, encountered or breathed in at work.
It is believed that the risk of contracting lung cancer is greater in people who are exposed to these substances and who also smoke cigarettes. Air pollution and cigar smoke also contain carcinogens, and exposure to these substances is associated with an increased risk of cancer.
In rare incidences, lung cancers, especially adenocarcinoma and bronchioloalveolar cell carcinoma (a type of adenocarcinoma), develop in people whose lungs have been scarred by other lung disorders, such as tuberculosis.
Although smoking causes most cases, people who have never smoked may still get lung cancer. The symptoms of lung cancer depend on its type, its location, and the way it spreads. One of the more common symptoms is a persistent cough or, in people who have a chronic cough, a change in the character of the cough. Some people cough up blood or sputum streaked with blood.
Lung cancer may cause wheezing by narrowing the airway. Blockage of an airway by a tumor may lead to the collapse of the part of the lung that the airway supplies, a condition called atelectasis.
Other consequences of a blocked airway are shortness of breath and pneumonia, which may result in coughing, fever, and chest pain. If the tumour grows into the chest wall, it may produce persistent, unrelenting chest pain. Fluid containing cancerous cells can accumulate in the space between the lung and the chest wall and large amounts of fluid can lead to shortness of breath. If the cancer spreads throughout the lungs, the levels of oxygen in the blood drop and become low, causing shortness of breath and eventually enlargement of the right side of the heart and possible heart failure.
Lung cancer may grow into or near the throat, leading to difficulty swallowing or pain with swallowing. It may grow into the heart or in the mid-chest region, causing abnormal heart rhythms, blockage of blood flow through the heart, or fluid in the sac surrounding the heart. The cancer may grow into or compress one of the large veins in the chest. Obstruction of the superior vena cava causes blood to back up in other veins of the upper body. The veins in the chest wall enlarge. The face, neck, and upper chest wall – including the breasts – can swell, causing pain. The condition can also produce shortness of breath, headache, distorted vision, dizziness, and drowsiness. These symptoms usually worsen when the person bends forward or lies down.
Lung cancer may also spread through the bloodstream to other parts of the body, most commonly the liver, brain, adrenal glands, spinal cord, or bones. The spread of lung cancer may occur early in the course of disease, especially with small cell lung cancer.
Symptoms – such as headache, confusion, seizures, and bone pain – may develop before any lung problems become evident, making an early diagnosis more complicated. Doctors explore the possibility of lung cancer when a person, especially a smoker, has a persistent or worsening cough or other lung symptoms (such as shortness of breath or coughed-up sputum tinged with blood).
Usually, the first test is a chest x-ray, which can detect most lung tumors, although it may miss small ones. Sometimes a shadow detected on a chest x-ray done for other reasons (such as before surgery) provides doctors with the first clue, although such a shadow is not proof of cancer. A computed tomography (CT) scan may be done, to show characteristic patterns that help doctors make the diagnosis. They also can show small tumors that are not visible on chest x-rays and reveal whether the lymph nodes inside the chest are enlarged.
Newer techniques, such as positron emission tomography (PET) and a certain type of CT called helical (spiral) CT, are improving the ability to detect small cancers. Oncologists frequently use PET-CT scanners, which combine the PET and CT technology in one machine, to evaluate patients with suspected cancer.
Magnetic resonance imaging (MRI) can also be used if the CT or PET-CT scans do not give doctors sufficient information. A microscopic examination of lung tissue from the area that may be cancerous is usually needed to confirm the diagnosis. In rare cases, a sample of coughed-up sputum can provide enough material for an examination (called sputum cytology). Almost always, doctors need to obtain a sample of tissue directly from the tumour. One common way to obtain the tissue sample is with bronchoscopy.
The personâ€™s airway is directly observed and samples of the tumor can be obtained. If the cancer is too far away from the major airways to be reached with a bronchoscope, doctors can usually obtain a specimen by inserting a needle through the skin while using CT for guidance.
This procedure is called a needle biopsy. Sometimes, a specimen can only be obtained by a surgical procedure called a thoracotomy. Once cancer has been identified under the microscope, doctors usually do tests to determine whether it has spread. A PET-CT scan and head imaging (brain CT or MRI) may be done to determine if lung cancer has spread, especially to the liver, adrenal glands, or brain. If a PET-CT is not available, CT scans of the chest, abdomen, and pelvis and a bone scan are done. A bone scan may show that cancer has spread to the bones.
Because small cell lung cancer can spread to the bone marrow, doctors Â Â Â sometimes also do a bone marrow biopsy. Cancers are categorized on how large the tumour is, whether it has spread to nearby lymph nodes, and whether it has spread to distant organs. The different categories are used to determine the stage of the cancer.
The stage of a cancer suggests the most appropriate treatment and enables doctors to estimate the personâ€™s prognosis. Clinical trials are underway to determine the value of screening tests to detect lung cancer in people who do not have any symptoms. These trials use chest x-rays, CT scans, sputum examinations, or all these methods to try to detect cancer when it is at an early stage.
However, screening so far has not been shown to improve lung cancer detection, and therefore screening is not recommended for people who have no risk factors and no symptoms. Tests can be expensive and cause people undue worry if they produce false-positive results that incorrectly imply that a cancer is present. The opposite is also true. A screening test can give a negative result when a cancer really does exist. For these reasons, it is important for doctors to try to accurately determine a personâ€™s risk for a particular cancer before screening tests are done.
Prevention of lung cancer includes quitting smoking and avoiding exposure to potentially cancer-causing substances in the work environment. Doctors use various treatments for both small cell and nonâ€“small cell lung cancer. Surgery, chemotherapy, and radiation therapy can be used individually or in combination. The precise combination of treatments depends on the type, location, and severity of the cancer, whether the cancer has spread, and the personâ€™s overall health. Surgery is the treatment of choice for nonâ€“small cell lung cancer that has not spread beyond the lung (early-stage disease).
In general, surgery is not used for early-stage small cell lung cancer, because this aggressive cancer requires chemotherapy and radiation therapy. Surgery may not be possible if the cancer has spread beyond the lungs, if the cancer is too close to the windpipe, or if the person has other serious conditions (such as severe heart or lung disease).
Before surgery, doctors do pulmonary function tests to determine whether the amount of lung remaining after surgery will be able to provide enough oxygen and breathing function. If the test results indicate that removing the cancerous part of the lung will result in inadequate lung function, surgery is not possible.
The amount of lung to be removed is decided by the surgeon, with the amount varying from a small part of a lung segment to an entire lung. Although nonâ€“small cell lung cancers can be removed surgically, removal does not always result in a cure. Occasionally, cancer that begins elsewhere (for example, in the colon) and spreads to the lungs is removed from the lungs after being removed at the source. This procedure is recommended rarely, and tests must show that the cancer has not spread to any site outside of the lungs.
Radiation therapy is used in both non-small cell and small cell lung cancers. It may be given to people who do not want to undergo surgery, who cannot undergo surgery because they have another condition (such as severe coronary artery disease), or whose cancer has spread to nearby structures, such as the lymph nodes.
Although radiation therapy is used to treat the cancer, in some people, it may only partially shrink the cancer or slow its growth. Combining chemotherapy with radiation therapy improves survival. Other treatments are often needed for people who have lung cancer. Because many people who have lung cancer have a substantial decrease in lung function whether or not they undergo treatment, oxygen therapy and bronchodilators (drugs that widen the airways) may aid breathing. Many people with advanced lung cancer develop such extreme pain and difficulty in breathing that they require large doses of opioids in the weeks or months before their death.
Lung cancer has a poor treatment outcome. On average, people with untreated advanced nonâ€“small cell lung cancer survive six months. Even with treatment, people with extensive small cell lung cancer or advanced non-small cell lung cancer do especially poorly, with a five-year survival rate of less than 1 per cent. Early diagnosis improves survival. People with early nonâ€“small cell lung cancer have a five-year survival of 60 to 70 per cent.
However, people who are treated definitively for an earlier stage lung cancer and survive but continue to smoke are at high risk of developing another lung cancer. Survivors must have regular checkups, including periodic chest x-rays and CT scans to ensure that the cancer has not returned. Usually, if the cancer returns, it occurs within the first two years. However, frequent monitoring is recommended for five years after lung cancer treatment, and then people are monitored yearly for the rest of their lives.
Because many people die of lung cancer, planning for terminal care is usually necessary. Advances in end-of-life care, particularly the recognition that anxiety and pain are common in people with incurable lung cancer and that these symptoms can be relieved by appropriate drugs, have led to an increasing number of people being able to die comfortably at home, with or without hospital services.