Lung cancer overview: Difference between revisions
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{{Lung cancer}} | {{Lung cancer}} | ||
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==Overview== | ==Overview== | ||
Prior to the introduction of [[cigarette]] [[smoking]] and industrial [[carcinogens]], lung cancer was thought to be a [[rare disease]]. Of all the [[tumors]] detected on [[autopsy]], lung cancer accounted for only 1% of [[cancers]] in the 1800s. The majority of cases of lung cancer were associated with occupational hazards due to [[radon]] exposure. The association between lung cancer and [[smoking]] was not defined until the mid-20th century. Primary lung cancers may be [[Classification|classified]] into [[small cell lung cancer]] (~15%) and [[non small cell lung cancer]] (~85%). [[Non small cell lung cancer]] are a [[heterogeneous]] group of lung cancers that are often grouped together because they share similar clinical features (e.g. [[prognosis]] and management). The 2015 [[World Health Organization|WHO]] [[Histology|histological]] [[classification]] of [[tumors]] of the [[lung]] categorized [[lung]] [[tumors]] into [[malignant]] [[epithelial]] [[tumors]], [[benign]] [[epithelial]] [[tumors]], [[Lymphoproliferative disorders|lymphoproliferative tumors]], miscellaneous [[tumors]], and [[metastatic]] [[tumors]]. The [[pathophysiology]] of lung cancer includes both [[genetic]] and [[Environmental factor|environmental factors]]. [[Causality]] of the majority of lung cancer is linked to [[Tobacco|tobacco usage.]] [[Carcinogen|Carcinogenic]] effects of [[tobacco smoking]] may result in [[DNA]] mis-replication and [[mutation]]. [[Smoking]] starts a [[cascade]] of events that leads to [[cancer]] development, even decades after [[smoking cessation]]. Besides [[Smoking|smokers]], [[Patient|patients]] with the history of prior [[Respiratory tract neoplasm|respiratory tract]] or [[gastrointestinal tract cancer]] comprise a high-risk population. Other [[Environmental factor|environmental factors]] include [[radon]], [[asbestos]], [[viral infections]], and states of [[Pulmonary inflammation|chronic lung inflammation]], all of which may [[Predisposition|predispose]] to [[cellular]] damage and [[DNA mutations]] that [[Predisposition|predispose]] to the development of lung cancers. The direct cause of lung cancer is [[DNA mutations]] that often result in either activation of [[Proto-oncogene|proto-oncogenes]] (e.g. '''[[KRAS|K-RAS]]''') or the inactivation of [[Tumor suppressor gene|tumors suppressor genes]] (e.g. '''[[TP53]]''') or both. The risk of these [[genetic mutations]] may be increased following exposure to environmental insults. Lung cancer must be differentiated from other conditions that cause [[hemoptysis]], [[cough]], [[dyspnea]], [[Wheeze|wheezing]], [[chest pain]], [[dysphonia]], [[dysphagia]], unexplained [[weight loss]], unexplained [[loss of appetite]], and [[fatigue]]. These conditions include [[pneumonia]], [[bronchitis]], [[metastatic cancer]] from a non-[[Chest|thoracic]] primary site, [[infectious]] [[granuloma]], [[Tuberculosis|pulmonary tuberculosis]], [[Trachea|tracheal]] [[Tumor|tumors]], and a [[thyroid]] mass. Lung cancer is the most common cause of [[cancer]]-associated [[mortality]] and the second most common type of [[cancer]] among both genders. Individuals > 50 years of age who have a history of [[smoking]] are at increased risk. Historically, the [[incidence]] of lung cancer is significantly higher among [[Male|males]] compared to [[Female|females]]. This increased ratio is thought to be attributed to the increased rates of [[smoking]] among [[Male|men]]. However, more [[Female|women]] are being [[Diagnosis|diagnosed]] with lung cancer due to the increased rate of [[smoking]] among [[Female|women]]. In 2014, the [[incidence]] of [[lung cancer]] in the United States was approximately 70 cases per 100,000. The most potent [[risk factor]] in the development of lung cancer is [[tobacco]] [[smoking]]. Other [[Risk factor|risk factors]] include [[Passive smoking|second hand smoke]], [[air pollution]], [[family history]] of lung cancer, [[radiation therapy]] to the [[chest]], and exposure to [[radon]], [[asbestos]] and other [[chemical]] [[carcinogens]]. Lung cancer [[Screening (medicine)|screening]] is a strategy used to identify early lung cancer in people, before they develop [[Symptom|symptoms]]. [[Screening (medicine)|Screening]] refers to the use of [[Medicine|medical]] [[Test|tests]] to detect [[disease]] in [[asymptomatic]] people. [[Screening (medicine)|Screening]] studies for lung cancer have only been done in high risk populations, such as [[Smoking|smokers]] and workers with occupational exposure to certain substances. This is because [[radiation exposure]] from [[Screening (medicine)|screening]] could actually induce [[carcinogenesis]] in a small percentage of [[Screening|screened]] subjects, so this risk should be mitigated by a (relatively) high [[prevalence]] of lung cancer in the population being [[Screening|screened]]. A [[pulmonary nodule]] larger than 5 - 6 mm is considered a positive result for [[Screening (medicine)|screening]] with [[x-ray]] or [[computed tomography]]. The majority of lung cancers present with advanced [[disease]] because the [[symptoms]] tend to occur later in the course of the [[disease]]. [[Patient|Patients]] experience non-specific [[Symptom|symptoms]] such as [[cough]], [[hemoptysis]], [[dyspnea]], [[chest pain]], [[Dysphonia|difficulty speaking]], [[Dysphagia|difficulty swallowing]], [[lack of appetite]], [[weight loss]], and [[fatigue]] from 3 weeks to 3 months before seeking medical attention. There are a variety of [[complications]] associated with lung cancer, such as [[pleural effusion]], [[leg weakness]], [[paresthesias]], [[Urinary bladder|bladder]] dysfunction, [[seizures]], [[hemiplegia]], [[cranial nerve palsies]], [[confusion]], [[personality changes]], [[Skeleton|skeletal]] [[pain]], [[pleuritic pain]], [[atelectasis]], and [[bronchopleural fistula]]. The [[prognosis]] of lung cancer is poor if [[Diagnosis|diagnosed]] at the advanced stages. [[Chest]] [[Computed tomography|CT scan]] is the modality of choice in the [[diagnosis]] of lung cancer. Findings on [[Computed tomography|CT scan]] suggestive of lung cancer include a [[Pulmonary nodule|solitary pulmonary nodule]], centrally located [[Tumor|masses]], [[Mediastinum|mediastinal]] [[Invasive (medical)|invasion]] [[Computed tomography|CT scans]] help [[Cancer staging|stage]] the lung cancer. A [[Computed tomography|CT scan]] of the [[abdomen]] and [[brain]] can help visualize the common sights of [[Metastasis|metastases]] such as [[Adrenal gland|adrenal glands]], [[liver]], and [[brain]]. [[Computed tomography|CT scans]] [[Diagnosis|diagnose]] lung cancer by providing [[anatomical]] detail to locate the [[tumor]], demonstrating proximity to the nearby structures, and deciphering whether [[lymph nodes]] are enlarged in the [[mediastinum]]. Common symptoms of lung cancer include [[Dyspnea|difficulty breathing]], [[hemoptysis]], [[Chronic cough|chronic coughing]], [[chest pain]], [[Cachexia|weakness and wasting]], [[Dysphonia|difficulty speaking]], and [[Symptom|symptoms]] related to [[paraneoplastic syndromes]]. Common [[physical examination]] findings of lung cancer include decreased/absent [[breath sounds]], [[pallor]], low-grade [[fever]], and [[tachypnea]]. The [[Medical laboratory|laboratory]] findings associated with lung cancer are the following [[neutropenia]], [[hyponatremia]], [[hypokalemia]], [[hypercalcemia]], [[respiratory acidosis]], [[hypercarbia]], [[hypoxia]], and [[Tumor cell|tumor cells]] in [[sputum]] and [[pleural effusion]] [[cytology]]. Performing a [[chest x-ray]] is the first step if a [[patient]] reports [[Symptom|symptoms]] that may be suggestive of lung cancer. Lung cancers are usually detected on a routine [[Chest X-ray|chest x-ray]] in a person experiencing no [[Symptom|symptoms]]. There are no [[echocardiography]]/[[ultrasound]] findings associated with lung cancer. [[Chest]] [[Computed tomography|CT scan]] is the modality of choice in the [[diagnosis]] of lung cancer. Findings on [[Computed tomography|CT scan]] suggestive of lung cancer include a [[Pulmonary nodule|solitary pulmonary nodule]], centrally located [[Tumor|masses]], [[Mediastinum|mediastinal]] [[Invasive (medical)|invasion]] [[Computed tomography|CT scans]] help [[Cancer staging|stage]] the lung cancer. A [[Computed tomography|CT scan]] of the [[abdomen]] and [[brain]] can help visualize the common sights of [[Metastasis|metastases]] such as [[Adrenal gland|adrenal glands]], [[liver]], and [[brain]]. [[Computed tomography|CT scans]] [[Diagnosis|diagnose]] lung cancer by providing [[anatomical]] detail to locate the [[tumor]], demonstrating proximity to the nearby structures, and deciphering whether [[lymph nodes]] are enlarged in the [[mediastinum]]. The [[Indication (medicine)|indication]] of [[Magnetic resonance imaging|MRI]] in lung cancer is when there is a suspicion of [[spinal cord]] canal [[Invasive (medical)|invasion]] and/or in the presence of [[pancoast tumor]] ([[Sulcus (anatomy)|superior sulcus]] [[tumor]]) and [[brachial plexus]] [[Tumor|tumors]]. There are no other [[imaging]] findings associated with lung cancer. Other [[Diagnosis|diagnostic]] studies include [[bone]] [[scintigraphy]], [[PET scan]], and [[molecular]] [[Test|tests]]. [[Medical]] [[therapy]] for lung cancer consists of [[radiation therapy]], [[chemotherapy]], and targeted [[therapy]]. Lung cancer [[surgery]] involves the [[Excision|surgical excision]] of the [[Cancer|cancerous]] [[Tissue (biology)|tissue]]. It is used mainly in [[non-small cell lung cancer]] with the intention of [[Cure|curing]] the [[patient]]. Effective measures for the [[Prevention (medical)|primary prevention]] of lung cancer include [[smoking cessation]] and avoidance of [[Passive smoking|second hand smoking]]. Lifestyle changes, such as [[Health|healthy]] [[Diet (nutrition)|diet]] rich with [[Fruit|fruits]] and [[Vegetable|vegetables]] and regular [[Physical exercise|exercise]], might decrease the risk of developing cancer in general. [[Prevention (medical)|Secondary prevention]] of lung cancer consists of [[smoking cessation]] and [[Screening (medicine)|screening]]. Secondary chemoprevention focuses on blocking the development of lung cancer in individuals in whom a [[precancerous]] [[lesion]] has been detected. | |||
==Historical Perspective == | |||
Prior to the introduction of [[cigarette]] [[smoking]] and industrial [[carcinogens]], lung cancer was thought to be a [[rare disease]]. Of all the [[tumors]] detected on [[autopsy]], lung cancer accounted for only 1% of [[cancers]] in the 1800s. The majority of cases of lung cancer were associated with occupational hazards due to [[radon]] exposure. The association between lung cancer and [[smoking]] was not defined until the mid-20th century. | |||
==Classification== | |||
Primary lung cancers may be [[Classification|classified]] into [[small cell lung cancer]] (~15%) and [[non small cell lung cancer]] (~85%). [[Non small cell lung cancer]] are a [[heterogeneous]] group of lung cancers that are often grouped together because they share similar clinical features (e.g. [[prognosis]] and management). The 2015 [[World Health Organization|WHO]] [[Histology|histological]] [[classification]] of [[tumors]] of the [[lung]] categorized [[lung]] [[tumors]] into [[malignant]] [[epithelial]] [[tumors]], [[benign]] [[epithelial]] [[tumors]], [[Lymphoproliferative disorders|lymphoproliferative tumors]], miscellaneous [[tumors]], and [[metastatic]] [[tumors]]. | |||
==Pathophysiology== | |||
The [[pathophysiology]] of lung cancer includes both [[genetic]] and [[Environmental factor|environmental factors]]. [[Causality]] of the majority of lung cancer is linked to [[Tobacco|tobacco usage.]] [[Carcinogen|Carcinogenic]] effects of [[tobacco smoking]] may result in [[DNA]] mis-replication and [[mutation]]. [[Smoking]] starts a [[cascade]] of events that leads to [[cancer]] development, even decades after [[smoking cessation]]. Besides [[Smoking|smokers]], [[Patient|patients]] with the history of prior [[Respiratory tract neoplasm|respiratory tract]] or [[gastrointestinal tract cancer]] comprise a high-risk population. Other [[Environmental factor|environmental factors]] include [[radon]], [[asbestos]], [[viral infections]], and states of [[Pulmonary inflammation|chronic lung inflammation]], all of which may [[Predisposition|predispose]] to [[cellular]] damage and [[DNA mutations]] that [[Predisposition|predispose]] to the development of lung cancers. | |||
==Causes== | |||
The direct cause of lung cancer is [[DNA mutations]] that often result in either activation of [[Proto-oncogene|proto-oncogenes]] (e.g. '''[[KRAS|K-RAS]]''') or the inactivation of [[Tumor suppressor gene|tumors suppressor genes]] (e.g. '''[[TP53]]''') or both. The risk of these [[genetic mutations]] may be increased following exposure to environmental insults. | |||
==Differential Diagnosis== | |||
Lung cancer must be differentiated from other conditions that cause [[hemoptysis]], [[cough]], [[dyspnea]], [[Wheeze|wheezing]], [[chest pain]], [[dysphonia]], [[dysphagia]], unexplained [[weight loss]], unexplained [[loss of appetite]], and [[fatigue]]. These conditions include [[pneumonia]], [[bronchitis]], [[metastatic cancer]] from a non-[[Chest|thoracic]] primary site, [[infectious]] [[granuloma]], [[Tuberculosis|pulmonary tuberculosis]], [[Trachea|tracheal]] [[Tumor|tumors]], and a [[thyroid]] mass. | |||
==Epidemiology and Demographics== | |||
Lung cancer is the most common cause of [[cancer]]-associated [[mortality]] and the second most common type of [[cancer]] among both genders. Individuals > 50 years of age who have a history of [[smoking]] are at increased risk. Historically, the [[incidence]] of lung cancer is significantly higher among [[Male|males]] compared to [[Female|females]]. This increased ratio is thought to be attributed to the increased rates of [[smoking]] among [[Male|men]]. However, more [[Female|women]] are being [[Diagnosis|diagnosed]] with lung cancer due to the increased rate of [[smoking]] among [[Female|women]]. In 2014, the [[incidence]] of [[lung cancer]] in the United States was approximately 70 cases per 100,000. | |||
==Risk Factors== | |||
The most potent [[risk factor]] in the development of lung cancer is [[tobacco]] [[smoking]]. Other [[Risk factor|risk factors]] include [[Passive smoking|second hand smoke]], [[air pollution]], [[family history]] of lung cancer, [[radiation therapy]] to the [[chest]], and exposure to [[radon]], [[asbestos]] and other [[chemical]] [[carcinogens]]. | |||
==Screening== | |||
Lung cancer [[Screening (medicine)|screening]] is a strategy used to identify early lung cancer in people, before they develop [[Symptom|symptoms]]. [[Screening (medicine)|Screening]] refers to the use of [[Medicine|medical]] [[Test|tests]] to detect [[disease]] in [[asymptomatic]] people. [[Screening (medicine)|Screening]] studies for lung cancer have only been done in high risk populations, such as [[Smoking|smokers]] and workers with occupational exposure to certain substances. This is because [[radiation exposure]] from [[Screening (medicine)|screening]] could actually induce [[carcinogenesis]] in a small percentage of [[Screening|screened]] subjects, so this risk should be mitigated by a (relatively) high [[prevalence]] of lung cancer in the population being [[Screening|screened]]. A [[pulmonary nodule]] larger than 5 - 6 mm is considered a positive result for [[Screening (medicine)|screening]] with [[x-ray]] or [[computed tomography]]. | |||
==Natural History, Complications, and Prognosis== | |||
The majority of lung cancers present with advanced [[disease]] because the [[symptoms]] tend to occur later in the course of the [[disease]]. [[Patient|Patients]] experience non-specific [[Symptom|symptoms]] such as [[cough]], [[hemoptysis]], [[dyspnea]], [[chest pain]], [[Dysphonia|difficulty speaking]], [[Dysphagia|difficulty swallowing]], [[lack of appetite]], [[weight loss]], and [[fatigue]] from 3 weeks to 3 months before seeking medical attention. There are a variety of [[complications]] associated with lung cancer, such as [[pleural effusion]], [[leg weakness]], [[paresthesias]], [[Urinary bladder|bladder]] dysfunction, [[seizures]], [[hemiplegia]], [[cranial nerve palsies]], [[confusion]], [[personality changes]], [[Skeleton|skeletal]] [[pain]], [[pleuritic pain]], [[atelectasis]], and [[bronchopleural fistula]]. The [[prognosis]] of lung cancer is poor if [[Diagnosis|diagnosed]] at the advanced stages. | |||
==Diagnosis== | |||
=== Diagnostic Study of Choice === | |||
[[Chest]] [[Computed tomography|CT scan]] is the modality of choice in the [[diagnosis]] of lung cancer. Findings on [[Computed tomography|CT scan]] suggestive of lung cancer include a [[Pulmonary nodule|solitary pulmonary nodule]], centrally located [[Tumor|masses]], [[Mediastinum|mediastinal]] [[Invasive (medical)|invasion]] [[Computed tomography|CT scans]] help [[Cancer staging|stage]] the lung cancer. A [[Computed tomography|CT scan]] of the [[abdomen]] and [[brain]] can help visualize the common sights of [[Metastasis|metastases]] such as [[Adrenal gland|adrenal glands]], [[liver]], and [[brain]]. [[Computed tomography|CT scans]] [[Diagnosis|diagnose]] lung cancer by providing [[anatomical]] detail to locate the [[tumor]], demonstrating proximity to the nearby structures, and deciphering whether [[lymph nodes]] are enlarged in the [[mediastinum]]. | |||
===History and Symptoms=== | |||
Common symptoms of lung cancer include [[Dyspnea|difficulty breathing]], [[hemoptysis]], [[Chronic cough|chronic coughing]], [[chest pain]], [[Cachexia|weakness and wasting]], [[Dysphonia|difficulty speaking]], and [[Symptom|symptoms]] related to [[paraneoplastic syndromes]]. | |||
===Physical Examination=== | |||
Common [[physical examination]] findings of lung cancer include decreased/absent [[breath sounds]], [[pallor]], low-grade [[fever]], and [[tachypnea]]. | |||
==Diagnostic Studies== | |||
=== Diagnostic study of choice === | |||
[[CT scan|Chest CT scan]] is the modality of choice in the diagnosis of lung cancer. Findings on [[CT scan]] suggestive of lung cancer include, a [[solitary pulmonary nodule]], centrally located masses, [[Mediastinal Mass|mediastinal invasion]]. A CT scan of the [[abdomen]] and [[brain]] can help visualize the common sites of [[metastases]]: [[adrenal glands]], [[liver]], and [[brain]]. CT scans diagnose lung cancer by providing anatomical detail to locate the tumor, demonstrating proximity to nearby structures, and deciphering whether [[lymph nodes]] are enlarged in the [[mediastinum]]. | |||
===Laboratory Findings=== | |||
The [[Medical laboratory|laboratory]] findings associated with lung cancer are the following [[neutropenia]], [[hyponatremia]], [[hypokalemia]], [[hypercalcemia]], [[respiratory acidosis]], [[hypercarbia]], [[hypoxia]], and [[Tumor cell|tumor cells]] in [[sputum]] and [[pleural effusion]] [[cytology]]. | |||
===[[Electrocardiograpgy]]=== | |||
[[ECG]] is a simple [[method]] for finding evidence of [[pulmonary artery stenosis]] in [[metastatic]] [[lung cancer]] and should be routinely performed in such [[patients]]. Findings on [[ECG]] associated [[mediastinal]] [[metastatic]] of [[lung cancer]] led to [[pulmonary artery stenosis]] and [[right ventricular]] [[strain]] include [[right axis deviation]], deepened S wave in lead 1, sustantial R wave in lead avR, inverted/flattened T waves in [[limb]] and [[precordial]] [[leads]]. | |||
===X-ray=== | |||
Performing a [[chest x-ray]] is the first step if a [[patient]] reports [[Symptom|symptoms]] that may be suggestive of lung cancer. Lung cancers are usually detected on a routine [[Chest X-ray|chest x-ray]] in a person experiencing no [[Symptom|symptoms]]. | |||
===Echocardiography and Ultrasound === | |||
There are no [[echocardiography]]/[[ultrasound]] findings associated with lung cancer. | |||
===CT scan=== | |||
[[Chest]] [[Computed tomography|CT scan]] is the modality of choice in the [[diagnosis]] of lung cancer. Findings on [[Computed tomography|CT scan]] suggestive of lung cancer include a [[Pulmonary nodule|solitary pulmonary nodule]], centrally located [[Tumor|masses]], [[Mediastinum|mediastinal]] [[Invasive (medical)|invasion]] [[Computed tomography|CT scans]] help [[Cancer staging|stage]] the lung cancer. A [[Computed tomography|CT scan]] of the [[abdomen]] and [[brain]] can help visualize the common sights of [[Metastasis|metastases]] such as [[Adrenal gland|adrenal glands]], [[liver]], and [[brain]]. [[Computed tomography|CT scans]] [[Diagnosis|diagnose]] lung cancer by providing [[anatomical]] detail to locate the [[tumor]], demonstrating proximity to the nearby structures, and deciphering whether [[lymph nodes]] are enlarged in the [[mediastinum]]. | |||
===MRI=== | |||
The [[Indication (medicine)|indication]] of [[Magnetic resonance imaging|MRI]] in lung cancer is when there is a suspicion of [[spinal cord]] canal [[Invasive (medical)|invasion]] and/or in the presence of [[pancoast tumor]] ([[Sulcus (anatomy)|superior sulcus]] [[tumor]]) and [[brachial plexus]] [[Tumor|tumors]]. | |||
===Other Imaging Findings=== | |||
There are no other [[imaging]] findings associated with lung cancer. | |||
===Other Diagnostic Studies=== | |||
Other [[Diagnosis|diagnostic]] studies include [[bone]] [[scintigraphy]], [[PET scan]], and [[molecular]] [[Test|tests]]. | |||
==Treatment== | |||
===Medical Therapy=== | |||
[[Medical]] [[therapy]] for lung cancer consists of [[radiation therapy]], [[chemotherapy]], and targeted [[therapy]]. | |||
===Surgery=== | |||
Lung cancer [[surgery]] involves the [[Excision|surgical excision]] of the [[Cancer|cancerous]] [[Tissue (biology)|tissue]]. It is used mainly in [[non-small cell lung cancer]] with the intention of [[Cure|curing]] the [[patient]]. | |||
===Primary Prevention=== | |||
Effective measures for the [[Prevention (medical)|primary prevention]] of lung cancer include [[smoking cessation]] and avoidance of [[Passive smoking|second hand smoking]]. Lifestyle changes, such as [[Health|healthy]] [[Diet (nutrition)|diet]] rich with [[Fruit|fruits]] and [[Vegetable|vegetables]] and regular [[Physical exercise|exercise]], might decrease the risk of developing cancer in general. | |||
===Secondary Prevention=== | |||
[[Prevention (medical)|Secondary prevention]] of lung cancer consists of [[smoking cessation]] and [[Screening (medicine)|screening]]. Secondary chemoprevention focuses on blocking the development of lung cancer in individuals in whom a [[precancerous]] [[lesion]] has been detected. | |||
{{reflist|2}} | {{reflist|2}} | ||
{{Tumors}} | {{Tumors}} | ||
[[Category:Disease]] | [[Category:Disease]] | ||
[[Category:Types of cancer]] | |||
[[Category:Pulmonology]] | [[Category:Pulmonology]] | ||
[[Category:Lung cancer]] | [[Category:Lung cancer]] | ||
{{WikiDoc Help Menu}} | {{WikiDoc Help Menu}} | ||
{{WikiDoc Sources}} | {{WikiDoc Sources}} | ||
[[Category:Up-To-Date]] | |||
[[Category:Oncology]] | |||
[[Category:Medicine]] | |||
[[Category:Pulmonology]] | |||
[[Category:Surgery]] | |||
Latest revision as of 06:28, 28 July 2021
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Lung cancer Microchapters |
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Lung cancer overview On the Web |
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American Roentgen Ray Society Images of Lung cancer overview |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Dildar Hussain, MBBS [2];Kim-Son H. Nguyen M.D.;Saarah T. Alkhairy M.D;Cafer Zorkun, M.D., Ph.D. [3]
Overview
Prior to the introduction of cigarette smoking and industrial carcinogens, lung cancer was thought to be a rare disease. Of all the tumors detected on autopsy, lung cancer accounted for only 1% of cancers in the 1800s. The majority of cases of lung cancer were associated with occupational hazards due to radon exposure. The association between lung cancer and smoking was not defined until the mid-20th century. Primary lung cancers may be classified into small cell lung cancer (~15%) and non small cell lung cancer (~85%). Non small cell lung cancer are a heterogeneous group of lung cancers that are often grouped together because they share similar clinical features (e.g. prognosis and management). The 2015 WHO histological classification of tumors of the lung categorized lung tumors into malignant epithelial tumors, benign epithelial tumors, lymphoproliferative tumors, miscellaneous tumors, and metastatic tumors. The pathophysiology of lung cancer includes both genetic and environmental factors. Causality of the majority of lung cancer is linked to tobacco usage. Carcinogenic effects of tobacco smoking may result in DNA mis-replication and mutation. Smoking starts a cascade of events that leads to cancer development, even decades after smoking cessation. Besides smokers, patients with the history of prior respiratory tract or gastrointestinal tract cancer comprise a high-risk population. Other environmental factors include radon, asbestos, viral infections, and states of chronic lung inflammation, all of which may predispose to cellular damage and DNA mutations that predispose to the development of lung cancers. The direct cause of lung cancer is DNA mutations that often result in either activation of proto-oncogenes (e.g. K-RAS) or the inactivation of tumors suppressor genes (e.g. TP53) or both. The risk of these genetic mutations may be increased following exposure to environmental insults. Lung cancer must be differentiated from other conditions that cause hemoptysis, cough, dyspnea, wheezing, chest pain, dysphonia, dysphagia, unexplained weight loss, unexplained loss of appetite, and fatigue. These conditions include pneumonia, bronchitis, metastatic cancer from a non-thoracic primary site, infectious granuloma, pulmonary tuberculosis, tracheal tumors, and a thyroid mass. Lung cancer is the most common cause of cancer-associated mortality and the second most common type of cancer among both genders. Individuals > 50 years of age who have a history of smoking are at increased risk. Historically, the incidence of lung cancer is significantly higher among males compared to females. This increased ratio is thought to be attributed to the increased rates of smoking among men. However, more women are being diagnosed with lung cancer due to the increased rate of smoking among women. In 2014, the incidence of lung cancer in the United States was approximately 70 cases per 100,000. The most potent risk factor in the development of lung cancer is tobacco smoking. Other risk factors include second hand smoke, air pollution, family history of lung cancer, radiation therapy to the chest, and exposure to radon, asbestos and other chemical carcinogens. Lung cancer screening is a strategy used to identify early lung cancer in people, before they develop symptoms. Screening refers to the use of medical tests to detect disease in asymptomatic people. Screening studies for lung cancer have only been done in high risk populations, such as smokers and workers with occupational exposure to certain substances. This is because radiation exposure from screening could actually induce carcinogenesis in a small percentage of screened subjects, so this risk should be mitigated by a (relatively) high prevalence of lung cancer in the population being screened. A pulmonary nodule larger than 5 - 6 mm is considered a positive result for screening with x-ray or computed tomography. The majority of lung cancers present with advanced disease because the symptoms tend to occur later in the course of the disease. Patients experience non-specific symptoms such as cough, hemoptysis, dyspnea, chest pain, difficulty speaking, difficulty swallowing, lack of appetite, weight loss, and fatigue from 3 weeks to 3 months before seeking medical attention. There are a variety of complications associated with lung cancer, such as pleural effusion, leg weakness, paresthesias, bladder dysfunction, seizures, hemiplegia, cranial nerve palsies, confusion, personality changes, skeletal pain, pleuritic pain, atelectasis, and bronchopleural fistula. The prognosis of lung cancer is poor if diagnosed at the advanced stages. Chest CT scan is the modality of choice in the diagnosis of lung cancer. Findings on CT scan suggestive of lung cancer include a solitary pulmonary nodule, centrally located masses, mediastinal invasion CT scans help stage the lung cancer. A CT scan of the abdomen and brain can help visualize the common sights of metastases such as adrenal glands, liver, and brain. CT scans diagnose lung cancer by providing anatomical detail to locate the tumor, demonstrating proximity to the nearby structures, and deciphering whether lymph nodes are enlarged in the mediastinum. Common symptoms of lung cancer include difficulty breathing, hemoptysis, chronic coughing, chest pain, weakness and wasting, difficulty speaking, and symptoms related to paraneoplastic syndromes. Common physical examination findings of lung cancer include decreased/absent breath sounds, pallor, low-grade fever, and tachypnea. The laboratory findings associated with lung cancer are the following neutropenia, hyponatremia, hypokalemia, hypercalcemia, respiratory acidosis, hypercarbia, hypoxia, and tumor cells in sputum and pleural effusion cytology. Performing a chest x-ray is the first step if a patient reports symptoms that may be suggestive of lung cancer. Lung cancers are usually detected on a routine chest x-ray in a person experiencing no symptoms. There are no echocardiography/ultrasound findings associated with lung cancer. Chest CT scan is the modality of choice in the diagnosis of lung cancer. Findings on CT scan suggestive of lung cancer include a solitary pulmonary nodule, centrally located masses, mediastinal invasion CT scans help stage the lung cancer. A CT scan of the abdomen and brain can help visualize the common sights of metastases such as adrenal glands, liver, and brain. CT scans diagnose lung cancer by providing anatomical detail to locate the tumor, demonstrating proximity to the nearby structures, and deciphering whether lymph nodes are enlarged in the mediastinum. The indication of MRI in lung cancer is when there is a suspicion of spinal cord canal invasion and/or in the presence of pancoast tumor (superior sulcus tumor) and brachial plexus tumors. There are no other imaging findings associated with lung cancer. Other diagnostic studies include bone scintigraphy, PET scan, and molecular tests. Medical therapy for lung cancer consists of radiation therapy, chemotherapy, and targeted therapy. Lung cancer surgery involves the surgical excision of the cancerous tissue. It is used mainly in non-small cell lung cancer with the intention of curing the patient. Effective measures for the primary prevention of lung cancer include smoking cessation and avoidance of second hand smoking. Lifestyle changes, such as healthy diet rich with fruits and vegetables and regular exercise, might decrease the risk of developing cancer in general. Secondary prevention of lung cancer consists of smoking cessation and screening. Secondary chemoprevention focuses on blocking the development of lung cancer in individuals in whom a precancerous lesion has been detected.
Historical Perspective
Prior to the introduction of cigarette smoking and industrial carcinogens, lung cancer was thought to be a rare disease. Of all the tumors detected on autopsy, lung cancer accounted for only 1% of cancers in the 1800s. The majority of cases of lung cancer were associated with occupational hazards due to radon exposure. The association between lung cancer and smoking was not defined until the mid-20th century.
Classification
Primary lung cancers may be classified into small cell lung cancer (~15%) and non small cell lung cancer (~85%). Non small cell lung cancer are a heterogeneous group of lung cancers that are often grouped together because they share similar clinical features (e.g. prognosis and management). The 2015 WHO histological classification of tumors of the lung categorized lung tumors into malignant epithelial tumors, benign epithelial tumors, lymphoproliferative tumors, miscellaneous tumors, and metastatic tumors.
Pathophysiology
The pathophysiology of lung cancer includes both genetic and environmental factors. Causality of the majority of lung cancer is linked to tobacco usage. Carcinogenic effects of tobacco smoking may result in DNA mis-replication and mutation. Smoking starts a cascade of events that leads to cancer development, even decades after smoking cessation. Besides smokers, patients with the history of prior respiratory tract or gastrointestinal tract cancer comprise a high-risk population. Other environmental factors include radon, asbestos, viral infections, and states of chronic lung inflammation, all of which may predispose to cellular damage and DNA mutations that predispose to the development of lung cancers.
Causes
The direct cause of lung cancer is DNA mutations that often result in either activation of proto-oncogenes (e.g. K-RAS) or the inactivation of tumors suppressor genes (e.g. TP53) or both. The risk of these genetic mutations may be increased following exposure to environmental insults.
Differential Diagnosis
Lung cancer must be differentiated from other conditions that cause hemoptysis, cough, dyspnea, wheezing, chest pain, dysphonia, dysphagia, unexplained weight loss, unexplained loss of appetite, and fatigue. These conditions include pneumonia, bronchitis, metastatic cancer from a non-thoracic primary site, infectious granuloma, pulmonary tuberculosis, tracheal tumors, and a thyroid mass.
Epidemiology and Demographics
Lung cancer is the most common cause of cancer-associated mortality and the second most common type of cancer among both genders. Individuals > 50 years of age who have a history of smoking are at increased risk. Historically, the incidence of lung cancer is significantly higher among males compared to females. This increased ratio is thought to be attributed to the increased rates of smoking among men. However, more women are being diagnosed with lung cancer due to the increased rate of smoking among women. In 2014, the incidence of lung cancer in the United States was approximately 70 cases per 100,000.
Risk Factors
The most potent risk factor in the development of lung cancer is tobacco smoking. Other risk factors include second hand smoke, air pollution, family history of lung cancer, radiation therapy to the chest, and exposure to radon, asbestos and other chemical carcinogens.
Screening
Lung cancer screening is a strategy used to identify early lung cancer in people, before they develop symptoms. Screening refers to the use of medical tests to detect disease in asymptomatic people. Screening studies for lung cancer have only been done in high risk populations, such as smokers and workers with occupational exposure to certain substances. This is because radiation exposure from screening could actually induce carcinogenesis in a small percentage of screened subjects, so this risk should be mitigated by a (relatively) high prevalence of lung cancer in the population being screened. A pulmonary nodule larger than 5 - 6 mm is considered a positive result for screening with x-ray or computed tomography.
Natural History, Complications, and Prognosis
The majority of lung cancers present with advanced disease because the symptoms tend to occur later in the course of the disease. Patients experience non-specific symptoms such as cough, hemoptysis, dyspnea, chest pain, difficulty speaking, difficulty swallowing, lack of appetite, weight loss, and fatigue from 3 weeks to 3 months before seeking medical attention. There are a variety of complications associated with lung cancer, such as pleural effusion, leg weakness, paresthesias, bladder dysfunction, seizures, hemiplegia, cranial nerve palsies, confusion, personality changes, skeletal pain, pleuritic pain, atelectasis, and bronchopleural fistula. The prognosis of lung cancer is poor if diagnosed at the advanced stages.
Diagnosis
Diagnostic Study of Choice
Chest CT scan is the modality of choice in the diagnosis of lung cancer. Findings on CT scan suggestive of lung cancer include a solitary pulmonary nodule, centrally located masses, mediastinal invasion CT scans help stage the lung cancer. A CT scan of the abdomen and brain can help visualize the common sights of metastases such as adrenal glands, liver, and brain. CT scans diagnose lung cancer by providing anatomical detail to locate the tumor, demonstrating proximity to the nearby structures, and deciphering whether lymph nodes are enlarged in the mediastinum.
History and Symptoms
Common symptoms of lung cancer include difficulty breathing, hemoptysis, chronic coughing, chest pain, weakness and wasting, difficulty speaking, and symptoms related to paraneoplastic syndromes.
Physical Examination
Common physical examination findings of lung cancer include decreased/absent breath sounds, pallor, low-grade fever, and tachypnea.
Diagnostic Studies
Diagnostic study of choice
Chest CT scan is the modality of choice in the diagnosis of lung cancer. Findings on CT scan suggestive of lung cancer include, a solitary pulmonary nodule, centrally located masses, mediastinal invasion. A CT scan of the abdomen and brain can help visualize the common sites of metastases: adrenal glands, liver, and brain. CT scans diagnose lung cancer by providing anatomical detail to locate the tumor, demonstrating proximity to nearby structures, and deciphering whether lymph nodes are enlarged in the mediastinum.
Laboratory Findings
The laboratory findings associated with lung cancer are the following neutropenia, hyponatremia, hypokalemia, hypercalcemia, respiratory acidosis, hypercarbia, hypoxia, and tumor cells in sputum and pleural effusion cytology.
Electrocardiograpgy
ECG is a simple method for finding evidence of pulmonary artery stenosis in metastatic lung cancer and should be routinely performed in such patients. Findings on ECG associated mediastinal metastatic of lung cancer led to pulmonary artery stenosis and right ventricular strain include right axis deviation, deepened S wave in lead 1, sustantial R wave in lead avR, inverted/flattened T waves in limb and precordial leads.
X-ray
Performing a chest x-ray is the first step if a patient reports symptoms that may be suggestive of lung cancer. Lung cancers are usually detected on a routine chest x-ray in a person experiencing no symptoms.
Echocardiography and Ultrasound
There are no echocardiography/ultrasound findings associated with lung cancer.
CT scan
Chest CT scan is the modality of choice in the diagnosis of lung cancer. Findings on CT scan suggestive of lung cancer include a solitary pulmonary nodule, centrally located masses, mediastinal invasion CT scans help stage the lung cancer. A CT scan of the abdomen and brain can help visualize the common sights of metastases such as adrenal glands, liver, and brain. CT scans diagnose lung cancer by providing anatomical detail to locate the tumor, demonstrating proximity to the nearby structures, and deciphering whether lymph nodes are enlarged in the mediastinum.
MRI
The indication of MRI in lung cancer is when there is a suspicion of spinal cord canal invasion and/or in the presence of pancoast tumor (superior sulcus tumor) and brachial plexus tumors.
Other Imaging Findings
There are no other imaging findings associated with lung cancer.
Other Diagnostic Studies
Other diagnostic studies include bone scintigraphy, PET scan, and molecular tests.
Treatment
Medical Therapy
Medical therapy for lung cancer consists of radiation therapy, chemotherapy, and targeted therapy.
Surgery
Lung cancer surgery involves the surgical excision of the cancerous tissue. It is used mainly in non-small cell lung cancer with the intention of curing the patient.
Primary Prevention
Effective measures for the primary prevention of lung cancer include smoking cessation and avoidance of second hand smoking. Lifestyle changes, such as healthy diet rich with fruits and vegetables and regular exercise, might decrease the risk of developing cancer in general.
Secondary Prevention
Secondary prevention of lung cancer consists of smoking cessation and screening. Secondary chemoprevention focuses on blocking the development of lung cancer in individuals in whom a precancerous lesion has been detected.