It should be admitted that there are many diseases related to environmental conditions, health habits, and work routines. However, lung cancer seems to be among the most severe ones in this regard. A plethora of chemical substrates provides carcinogenic effects on lung tissues – starting from a polycyclic aromatic hydrocarbon that is an element of the output of thermal treatments of coal and oil (for instance, resin, coke, and gas) and ending with metal and its compounds. Nowadays, lung cancer has become a significant problem that is to be continuously investigated. In this paper, the crucial peculiarities of the mentioned disease, as well as reasons that cause it, will be discussed.
The impact of industrial emission, as well as internal combustion engines, are the reasons for air-polluting accompanied by carcinogens. Significantly, plenty of gasoline is created given forced operations of an engine, during accelerations and braking of a vehicle, and during takeoffs and landings of a jet airliner. The industrial hazards are present as well – during the first years of the 20th century, it was figured out that the considerable incidences of lung cancer amongst miners in Saxony is directly related to a substantial concentration of radioactive adulterations in the pieces of ore. The impact of ionizing radiation has also been indicated during surveys of uranium miners in the US (Yang et al., 2019).
Then, it should also be noted that incidences of lung cancer are spread amongst in steel and woodworking industry, as well as asbestos-cement and phosphate production. At the same time, industrial polluting and occupational dangers in this regard could not have had such a significant part in the rates of morbidity if they were not accompanied by a critically lousy habit – smoking (Groot et al., 2018). A smoker in a uranium mine, as well as one in the asbestos industries, tend to have lung cancer more frequently than a non-smoker. The growth of the incidences of the disease around the globe is directly associated with the rise in cigarette consumption and the total number of smokers. Nevertheless, near 10% of lung cancer patients in the US have never turned to smoke. [6]. Until now, the reasons influencing the occurrence of various subtypes of lung cancer have not been studied. The highest incidence of adenocarcinoma is noted in nonsmoking women [7, 8]. The cumulative unfavorable impact of various external agents and hereditary predispositions have an essential part within the scope of the development of a precancerous background change, as well as the pathogeneses of the disease. [9, 10].
Amid the common clinical and anatomical formations of this disease, there is a central one that occurs in large bronchi, as well as a peripheral that originates either from the epithelium of smaller bronchi or located within the lung’s parenchyma.
In the framework of central cancer, the established medical practice determines exophytic cancer (in cases the tumors grow into the lumens of the bronchi); endophytic cancer (in cases of predominant tumors’ expansion into the thick of lung parenchyma); branched cancer that is characterized by tumors growth in the shape of the muff around the bronchus. However, it should be noted that a combined nature of tumors expansion with the prevalence of one particular component is more likely to take place in practice.
In peripheral cancer, nodular rounded tumors, pneumonia-alike cancer, and cancer of the apexes of lungs accompanied by the syndrome of Pancoast are distinguished. With a tumor diameter of more than 5 cm, due to insufficient blood supply to its entire mass, necrosis and decay in the center of the node with the formation of a cavity can be observed. Its inner surface is bumpy, the walls have different thicknesses, and the cavity rarely has a connection with the bronchial lumen. This form of peripheral cancer is called cavitary. In some morphological forms of malignant lung tumors (bronchioloalveolar cancer (adenocarcinoma subtype), lung lymphoma, etc.), changes on radiographs have the form of a pneumonia-like infiltrate.
Multiple metastatic lesions of the median lymph nodes without established localization of the primary tumor in the lung is considered to be a mediastinal form of lung cancer. This clinical and anatomical form is observed more often in small cell carcinoma. In connection with the development of highly informative methods of X-ray, ultrasound examinations, which make it possible to identify the primary focus in the lung, such a diagnosis is extremely rare.
According to the International Histological Classification of Malignant Lung Tumors, various variants of epithelial neoplasms are distinguished: squamous cell (epidermoid), glandular, large cell, mucoepidermoid, and small cell carcinoma. The existence of dimorphic tumors (glandular squamous cell carcinoma, etc.) is possible.
From a clinical point of view, the types of lung cancer are distinguished by their growth rate and prognosis. Differentiated squamous cell or glandular carcinoma develops most slowly; undifferentiated cancer develops faster. Most scientific publications use the term non-small cell cancer (NSCLC), which includes all types of lung cancer except small cells. This is the most unfavorable undifferentiated form, characterized by rapid development, rapid and abundant lymphogenous, as well as early hematogenous metastasis. Lung carcinoid, a rare malignant neuroendocrine tumor, is isolated separately.
In order to systematize the extent of prevalence of the tumor processes, the generally accepted international categorization of lung cancer in accordance with the TNM approach is utilized. In this abbreviation, T characterizes the size or localization of the primary tumor, N – the state of regional lymph nodes, M – the presence or absence of distant metastases (Detterbeck et al., 2017). The combination of the mentioned three symbols provides a specialist with the opportunity to define the stage of the prevalence of the tumor’s processes.
Therapeutic tactics for lung cancer due to the biological characteristics of the disease and the variety of morphological types are not unambiguous. For the correct choice of the method of treatment, one should know the main prognostic factors: the stage of lung cancer according to the accepted classification of the TNM approach, the historical structures of the tumors, the extent of differentiation, as well as of severity of accompanying maladies, and dynamic detectors of essential organs and systems. The method of therapy in itself is one of the decisive prognostic factors, the value of which is the greater, the closer the variant is to the radical one. The following methods are utilized in the treatment of patients with NSCLC: surgical, radiation, chemoradiation, drug (polychemotherapy), combined (surgery is provided in combination with radiation and/or chemotherapy) (Robin et al., 2018).
At present, at stages I and II, especially in the non-ovarian cell morphological subtype of SCLC, surgical treatment with subsequent polychemotherapy is possible. Some researchers consider it expedient to carry out neoadjuvant and adjuvant polychemotherapy even in stage III SCLC. The five-year survival rate after combined treatment in combination with the surgical method at stages I-II is 28–36%, the most significant outcomes are observed in the absence of metastasis in the lymph nodes (45–49%). At stage III (N2 +), the information is contradictory: from 5 to 40% of patients survive> 5 years.
Patients with inoperable stage III-IV SCLC receive conservative antitumor treatment that combines radiation and chemotherapy. Modern techniques allow 80–90% of patients to obtain a direct, objectively recorded effect, and in 20–30% of them, complete tumor regression. The securing of complete clinical remission after the main course of treatment improves survival and opens up the prospect of cure (Kay et al., 2018). Thus, it is possible to treat stage I-II NSCLC with satisfactory long-term results. Expanded combined operations with resection of organs and great vessels of the mediastinum and adequate removal of mediastinal lymph nodes in locally advanced NSCLC (stage III) are justified within the scope of combined treatment, which allows increasing the life expectancy of a patient.
To conclude, it seems reasonable to state that lung cancer remains an acute issue that is caused by various factors. Today, in the conditions of industrial emissions and – to an exact extent – the spread of smoking, the discussed disease is to be monitored and investigated. The above research shows that there are many varieties and aspects to take into account while developing an appropriate and evidence-based plan for a patient with lung cancer. Detection of the disease in the early stages remains the main organizational medical measure of practical public health, which will improve the results of treatment.
References
Detterbeck, F. C., Boffa, D. J., Kim, A. W., & Tanoe, L. T. (2017). The eighth edition lung cancer stage classification. Chest, 151(1), 193–203.
Groot, P. M., Wu, C. C., Carter, B. W., & Munden, R. F. (2018). The epidemiology of lung cancer. Translational Lung Cancer Research, 7(3), 220–233.
Kay, F. U., Kandathil, A., Batra, K., Saboo, S. S., Abbara, S., & Rajah, P. (2017). Revisions to the Tumor, Node, Metastasis staging of lung cancer (8th edition): rationale, radiologic findings and clinical implications. World Journal of Radiology, 9(6), 269–279.
Robin, T. P., Jones, B. L., Amini, A., Koshy, M., Gaspar, L. E., Liu, A. K., Nath, S. K., Kavanagh, B. D., Camidge, D. R., & Rusthoven, C. G. (2018). Radiosurgery alone is associated with favorable outcomes for brain metastases from small-cell lung cancer. Lung Cancer, 120(1), 88–90.
Yang, D., Liu, Y., Bai, C., Wang, X., Powel, C. A. (2019). Epidemiology of lung cancer and lung cancer screening programs in China and the United States. Cancer Letters, 468(1), 82–87.