Bronchogenic Carcinoma (Bronchial Carcinomas)

Bronchogenic carcinoma is the leading cause of cancer death throughout the world and tobacco smoking is shown to be the single most important risk factor. Symptoms may include cough, dyspnea, hemoptysis and chest pain and the diagnosis is made using clinical, imaging and histopathologic criteria. Despite available therapy, the prognosis is poor, primarily because the majority of patients receive a late diagnosis.


Presentation

The clinical presentation may be nonspecific, but cough, hemoptysis, dyspnea and chest pain are lung-related symptoms that are reported in variable percentages [4]. In up to 25% of cases, however, an asymptomatic course is observed, which significantly impedes the ability to make the diagnosis [6].

Workup

A thorough physical examination must be performed, but imaging studies are necessary to make a preliminary diagnosis [3]. Chest X-ray, CT, or MRI can identify the location of the tumor and bronchoscopy with subsequent histopathological examination, guided by findings from imaging studies, is mandatory in order to identify the underlying subtype [7].

Treatment

For stages I and II, surgical removal of the tumor is indicated, whereas adjuvant chemotherapy or radiation therapy may be administered with a goal of maximizing the effects of surgery [5]. Etoposide, carboplatin, cislatin or irinotecan are recommended chemotherapeutic agents. In more advanced stages of the disease (III and IV), chemotherapy and possibly palliative radiation is used [6], but because the prognosis is very poor, palliative and symptomatic care is equally important to provide the patient with an adequate level of support.

Prognosis

Unfortunately, about 80% of patients who are diagnosed with lung cancer are already in advanced stages of the disease and the prognosis is very poor, even with all available therapy [3]. The TNM staging is used for classification of patients, ranging from I (localized disease) to IV (presence of distant metastases) [5]. With treatment, 5-year survival ranges from 67% in stage I to < 1 % in stage IV [6]. Moreover, SCLC recognized in early stages has a 5-year survival between 20-25%, whereas almost no patients survives five years when the tumor is diagnosed late [8].

Etiology

The exact cause remains unknown, but various carcinogenic events have been documented after use of tobacco and exposure to other carcinogens such as asbestos and radon [6]. There are two main types of lung cancer: small-cell (SCLC, constituting 15% of cases) and more commonly non-small cell (NSCLC), which is further divided into adenocarcinoma, squamous cell carcinoma and large cell carcinoma [8].

Epidemiology

In the United States, more than 220,000 new cases and almost 160,000 deaths occurred in 2015, making lung cancer the most common cause of cancer death [1]. A slight predilection toward male gender was observed [1], whereas the single most important risk factor is cigarette smoking [7]. Alcohol consumption, exposure to radon, asbestos and other occupational or environmental pollutants that are known lung carcinogens, but also genetic factors have shown to be additional risk factors [5]. Elderly patients are most frequently diagnosed, as a marked increase in incidence rates are seen after 60 years of life [7].

Sex distribution
Age distribution

Pathophysiology

The exact pathogenesis model remains to be elucidated, but several key mutations that presumably occur after exposure to tobacco and other carcinogenic substances have been discovered so far. Abnormal expression of epidermal growth factor receptor (EFGR), inactivity of p53, one of the main tumor suppressor genes, as well as K-RAS mutations are some of the most important [4].

Prevention

Avoidance and cessation of smoking is by far the most important preventive strategy against lung cancer [5]. Although implementation of mass screening is still not suggested, the use of imaging studies such as CT in regular screening of at-risk patients has been recommended [8].

Summary

Bronchogenic carcinoma, one of the most common malignant diseases worldwide, is the leading cause of death from cancers in the United States and the rest of the world [1]. The pathogenesis model almost invariably include mutations of various genes involved in cell cycle as a result of exposure to tobacco and other carcinogenic substances (asbestos, radon, alcohol, etc) [2]. Lung cancer is classified into small-cell (SCLC) and non-small cell (NSCLC) carcinoma, both having a very poor prognosis. The clinical presentation may be nonspecific, with respiratory complaints such as cough, hemoptysis, chest pain and breathing difficulties, but the onset is often insidious and the diagnosis is made in advanced stages of the disease in 80% of patients [3]. Imaging studies such as computed tomography (CT) or magnetic resonance imaging (MRI) and subsequent bronchoscopy with histopathological examination to determine the exact subtype is necessary to confirm the location and the type of bronchogenic carcinoma [3]. Treatment principles include surgery, chemotherapy and radiation, but overall 5-year survival rates are around 15% [4]. For this reason, cessation of tobacco smoking and avoiding exposure to other substances that are known to be involved in the pathogenesis is vital in reducing the burden of this fatal malignant disease [5].

Patient Information

Bronchogenic carcinoma (lung cancer) is the leading cause of death from a malignant disease worldwide, with more than 160,000 deaths in the United States in 2015. Its development is still incompletely understood, but various mutations as a result of tobacco exposure have been documented, suggesting the direct role of tobacco in this tumor. Additional substances that are brought into connection with lung cancer are radon and asbestos, whereas genetic factors have also been proposed. Signs and symptoms include breathing difficulties, cough that may be accompanied by blood expectoration (termed hemoptysis) and chest pain, but in up to a quarter of patients, an asymptomatic course is observed. Imaging studies such as plain radiography, computed tomography (CT scan) or magnetic resonance imaging (MRI) can be used to determine the location and size of the tumor, but to identify the exact subtype, a biopsy is necessary. Treatment depends on the stage of the tumor and includes surgery, chemotherapy and radiation, but despite available therapy, the prognosis is very poor, with overall 5-year survival rates of only 15%. For this reason, cessation of tobacco smoking and avoiding exposure is mandatory in reducing the risk of this highly fatal malignancy.

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References

  1. Siegel RL, Miller KD, Jemal A. Cancer statistics, 2016. CA Cancer J Clin 2016;66:7.
  2. Dela Cruz CS, Tanoue LT, Matthay RA. Lung Cancer: Epidemiology, Etiology, and Prevention. Clin Chest Med. 2011;32(4):10.1016/j.ccm.2011.09.001.
  3. Al Jahdali H. Evaluation of the patient with lung cancer. Ann Thorac Med. 2008;3(6):74-78.
  4. Aster, JC, Abbas, AK, Robbins, SL, Kumar, V. Robbins basic pathology. Ninth edition. Philadelphia, PA: Elsevier Saunders; 2013.
  5. Molina JR, Yang P, Cassivi SD, Schild SE, Adjei AA. Non–Small Cell Lung Cancer: Epidemiology, Risk Factors, Treatment, and Survivorship. Mayo Clin Proc. 2008;83(5):584-594.
  6. Porter RS, Kaplan JL. Merck Manual of Diagnosis and Therapy. 19th Edition. Merck Sharp & Dohme Corp. Whitehouse Station, N.J; 2011.
  7. Wender R, Fontham ET, Barrera E Jr, et al. American Cancer Society lung cancer screening guidelines. CA Cancer J Clin. 2013;63(2):107-117.
  8. Jett JR, Schild SE, Kesler KA, Kalemkerian GP. Treatment of small cell lung cancer: Diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest. 2013;143(5):e400S-419S.

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