|
The vast majority (80–90%) of cases of lung cancer are due to long-term exposure to tobacco smoke.[1][2] About 10–15% of cases occur in people who have never smoked.[3] These cases are often caused by a combination of genetic factors[4] and exposure to radon gas,[4] asbestos,[5] or other forms of air pollution,[4] including second-hand smoke.[6][7] Lung cancer may be seen on chest radiographs and computed tomography (CT) scans. The diagnosis is confirmed by biopsy[8] which is usually performed by bronchoscopy or CT-guidance.
Treatment and long-term outcomes depend on the type of cancer, the stage (degree of spread), and the person's overall health, measured by performance status. Common treatments include surgery, chemotherapy, and radiotherapy. NSCLC is sometimes treated with surgery, whereas SCLC usually responds better to chemotherapy and radiotherapy.[9] Overall, 16.8% of people in the United States diagnosed with lung cancer survive five years after the diagnosis,[10] while outcomes on average are worse in the developing world. Worldwide, lung cancer is the most common cause of cancer-related death in men and women, and was responsible for 1.56 million deaths annually, as of 2012.[11]
Depending on the type of tumor, paraneoplastic phenomena—symptoms not due to the local presence of cancer—may initially attract attention to the disease.[12] In lung cancer, these phenomena may include Lambert–Eaton myasthenic syndrome (muscle weakness due to autoantibodies), hypercalcemia, or syndrome of inappropriate antidiuretic hormone (SIADH, abnormally concentrated urine and diluted blood). Tumors in the top of the lung, known as Pancoast tumors, may invade the local part of the sympathetic nervous system, leading to Horner's syndrome (dropping of the eyelid and a small pupil on that side), as well as damage to the brachial plexus.[1]
Many of the symptoms of lung cancer (poor appetite, weight loss, fever, fatigue) are not specific.[8] In many people, the cancer has already spread beyond the original site by the time they have symptoms and seek medical attention.[13] Symptoms that suggest the presence of metastatic disease include weight loss, bone pain and neurological symptoms (headaches, fainting, convulsions, or limb weakness).[1] Common sites of spread include the brain, bone, adrenal glands, opposite lung, liver, pericardium, and kidneys.[13] About 10% of people with lung cancer do not have symptoms at diagnosis; these cancers are incidentally found on routine chest radiography
Contents
1 Signs and symptoms
2 Causes
2.1 Smoking
2.2 Radon gas
2.3 Asbestos
2.4 Air pollution
2.5 Genetics
2.6 Other causes
3 Pathogenesis
4 Diagnosis
4.1 Classification
4.2 Metastasis
4.3 Staging
5 Prevention
5.1 Smoking ban
5.2 Screening
5.3 Other prevention strategies
6 Management
6.1 Surgery
6.2 Radiotherapy
6.3 Chemotherapy
6.4 Palliative care
7 Prognosis
8 Epidemiology
9 History
10 Research directions
11 References
12 External links
Signs and symptoms[edit]
Signs and symptoms which may suggest lung cancer include:[1]
Respiratory symptoms: coughing, coughing up blood, wheezing or shortness of breath
Systemic symptoms: weight loss, fever, clubbing of the fingernails, or fatigue
Symptoms due to the cancer mass pressing on adjacent structures: chest pain, bone pain, superior vena cava obstruction, difficulty swallowing
If the cancer grows in the airways, it may obstruct airflow, causing breathing difficulties. The obstruction can lead to accumulation of secretions behind the blockage, and predispose to pneumonia.[1]
Causes:
how a general increase in sales of tobacco products in the USA in the first four decades of the 20th century (cigarettes per person per year) led to a corresponding rapid increase in the rate of lung cancer during the 1930s, '40s and '50s (lung cancer deaths per 100,000 male population per year)
Cancer develops following genetic damage to DNA and epigenetic changes. These changes affect the normal functions of the cell, including cell proliferation, programmed cell death (apoptosis) and DNA repair. As more damage accumulates, the risk of cancer increases.[15]
Smoking:
Cross section of a human lung: The white area in the upper lobe is cancer; the black areas are discoloration due to smoking.
Smoking, particularly of cigarettes, is by far the main contributor to lung cancer.[16] Cigarette smoke contains at least 73 known carcinogens,[17] including benzo[a]pyrene,[18] NNK, 1,3-butadiene and a radioactive isotope of polonium, polonium-210.[17] Across the developed world, 90% of lung cancer deaths in men during the year 2000 were attributed to smoking (70% for women).[19] Smoking accounts for 80–90% of lung cancer cases.[1]
Passive smoking—the inhalation of smoke from another's smoking—is a cause of lung cancer in nonsmokers. A passive smoker can be defined as someone living or working with a smoker. Studies from the US,[20][21][22] Europe[23] and the UK[24] have consistently shown a significantly increased risk among those exposed to passive smoke.[25] Those who live with someone who smokes have a 20–30% increase in risk while those who work in an environment with secondhand smoke have a 16–19% increase in risk.[26] Investigations of sidestream smoke suggest it is more dangerous than direct smoke.[27] Passive smoking causes about 3,400 deaths from lung cancer each year in the USA.[22]
Marijuana smoke contains many of the same carcinogens as those in tobacco smoke.[28] However, the effect of smoking cannabis on lung cancer risk is not clear.[29][30] A 2013 review did not find an increased risk from light to moderate use.[31] A 2014 review found that smoking cannabis doubled the risk of lung cancer.[32]
Radon gas[edit]
Radon is a colourless and odorless gas generated by the breakdown of radioactive radium, which in turn is the decay product of uranium, found in the Earth's crust. The radiation decay products ionize genetic material, causing mutations that sometimes turn cancerous. Radon is the second-most common cause of lung cancer in the USA,[33] causing about 21,000 deaths each year.[34] The risk increases 8–16% for every 100 Bq/m³ increase in the radon concentration.[35] Radon gas levels vary by locality and the composition of the underlying soil and rocks. About one in 15 homes in the US has radon levels above the recommended guideline of 4 picocuries per liter (pCi/l) (148 Bq/m³).[36]
Asbestos[edit]
Asbestos can cause a variety of lung diseases, including lung cancer. Tobacco smoking and asbestos have a synergistic effect on the formation of lung cancer.[5] In smokers who work with asbestos, the risk of lung cancer is increased 45-fold compared to the general population.[37] Asbestos can also cause cancer of the pleura, called mesothelioma (which is different from lung cancer).[38]
Air pollution[edit]
Outdoor air pollution has a small effect on increasing the risk of lung cancer.[4] Fine particulates (PM2.5) and sulfate aerosols, which may be released in traffic exhaust fumes, are associated with slightly increased risk.[4][39] For nitrogen dioxide, an incremental increase of 10 parts per billion increases the risk of lung cancer by 14%.[40] Outdoor air pollution is estimated to account for 1–2% of lung cancers.[4]
Tentative evidence supports an increased risk of lung cancer from indoor air pollution related to the burning of wood, charcoal, dung or crop residue for cooking and heating.[41] Women who are exposed to indoor coal smoke have about twice the risk and a number of the by-products of burning biomass are known or suspected carcinogens.[42] This risk affects about 2.4 billion people globally,[41] and is believed to account for 1.5% of lung cancer deaths.[42]
Genetics[edit]
About 8% of lung cancer is due to inherited factors.[43] In relatives of people with lung cancer, the risk is increased 2.4 times. This is likely due to a combination of genes.[44] Polymorphisms on chromosomes 5, 6 and 15 are known to affect the risk of lung cancer.[45]
Other causes[edit]
Numerous other substances, occupations, and environmental exposures have been linked to lung cancer. The International Agency for Research on Cancer (IARC) states there is "sufficient evidence" to show the following are carcinogenic in the lungs:[46]
Some metals (aluminum production, cadmium and cadmium compounds, chromium(VI) compounds, beryllium and beryllium compounds, iron and steel founding, nickel compounds, arsenic and inorganic arsenic compounds, underground hematite mining)
Some products of combustion (incomplete combustion, coal (indoor emissions from household coal burning), coal gasification, coal-tar pitch, coke production, soot, diesel engine exhaust)
Ionizing radiation (X-radiation, gamma radiation, plutonium)
Some toxic gases (methyl ether (technical grade), Bis-(chloromethyl) ether, sulfur mustard, MOPP (vincristine-prednisone-nitrogen mustard-procarbazine mixture), fumes from painting)
Rubber production and crystalline silica dust.
for its treatments information visit my next content....(how treatment of lungs cancer goes on
|
|
0 comments:
Post a Comment