To form a more detailed and comprehensive synthesis of the literature, work should first be done to find the source and discuss its importance and relevance to the current study. An in-depth study of this issue among peer-reviewed scientific papers reveals the very high popularity of unidirectional works on the connection between patients taking ACE inhibitors and the development of lung cancer. The search strategy discussed earlier has already demonstrated the variety of sources found initially for this paper; nevertheless, the objective of this section is to create a more structured and holistic system for further literary synthesis.
As stated earlier, the author of this paper has found 43 scientific sources from three electronic databases: Google Scholar (24), PubMed by NCBI (10), and Elsevier (9). It should be recalled that these are professional and widely used platforms on which digital copies of peer-reviewed articles are regularly posted. At the same time, it is essential to clarify that a large number of issues, typical for Google Scholar, are not always unambiguously associated with the quality of works, and consequently, the primary and then the secondary selection of used sources should be accompanied by an assessment of their reliability: peer-reviewability, citation, scientific status, namely, H-index, of the author(s). In addition, the nature of the research is decisive for scientific works. About half of the materials found were secondary or even tertiary, which was expressed by using other authors’ results, meta-analysis, systematic review, or even opinions. Such works did not meet the requirements set by the author, and therefore, their use was excluded. Moreover, an important note should be made: keywords were described in a previous document.
A total of six criteria were developed, which formed the basis for the initial processing of the materials found. Four of them were related to inclusion: the source should have been written in professional English, published not earlier than 2016, have a high degree of reliability, and the location of the study should have been in the United States (optional). Two criteria, namely, writing in non-English and a large number of limitations, were sufficient reasons to exclude papers. The secondary processing of the sources was subject to stricter requirements. In particular, any work used must have strictly defined research objectives as well as a suitable methodology and project design. In addition, the materials used should be based on a quantitative or qualitative approach, but the priority was given to those authors who were focused on conducting a statistical experiment or observation. At the same time, work that has not been evaluated was not accepted for discussion. Where researchers themselves pointed to the low reliability of results in larger samples, such work was not considered. Necessary clarification: only open databases where digital materials are available without a paid subscription were used to select works.
As a result, five primary sources meeting all the established requirements were selected for further literary synthesis. For PubMed, the syntax (ACE inhibitors) AND (lung cancer) was used, while for Elsevier and Google Scholar, the following grammar was utilized: “ACE inhibitors” AND “lung cancer.” Although this is only preliminary information, which can be checked independently in these databases if one wants, more works were found in PubMed and Scholar, while Elsevier offered materials for the same search queries that were not similar to the search subject. More specifically, two works were found in PubMed (Hicks et al. 2018; Zheng & Huang, 2020), two in Scholar (Danilov et al. 2019; Lin et al., 2020), and one in Elsevier (Perini et al., 2020). In addition, four out of the five papers have a focus on the association between ACE inhibitors and the development of lung cancer, but one paper discusses the feedback, namely the potential use of drugs to treat cancer. A detailed reading of each of the sources creates a pool of the most common research limitations. This includes (i) the lack of assessment of broader factors of cancer development, including the socio-economic status of patients, (ii) the inability to track the entire course of patient treatment and to monitor the regularity of medication, (iii) the difficulty of identifying small cellular or nascent stages of neoplasm.
Since the final papers have higher requirements, the relevance of selected sources to the topic of the current study should be discussed in detail. First of all, the orientation of all authors is built around the problem of the correlation between lung tissue cancer and taking medications for hypertension and heart failure. Being a qualitatively quantitative study, the articles answer the question about the nature of the connection and, in most cases, lead the reader to the conclusion that prolonged ACE inhibitors lead to the development of malignant tumors. Since the “Intervention, I” section of the PICO question implies treatment with these drugs, the article, which was written by Perini et al. (2020), allows a different perspective on the unambiguous association between the two factors and the understanding that inhibitors can also be used for cancer treatment. It is also worth discussing the reliability of the journals in which the sources were published. For ease of perception, the author of the current work presents Table 1, which provides summary information on five articles
Table 1. Summary of works in use.
For reliability assessment, the H-index of the first author of the research and the SJR index of the journals in which the article was placed are given, as illustrated in Table 2.
Table 2. Summary information about the first author and the reliability of the magazines was carried out with the help of Web of Science, ORCID, and SJR Online tools.
Based on the two tables, it can be noted that the works utilized are characterized by an increased degree of reliability since the authors, in most cases, have solid parameters of citation and recognition, and the journals in which the articles were placed are popular.
References
Danilov, S. M., Metzger, R., Klieser, E., Sotlar, K., Trakht, I. N., & Garcia, J. G. (2019). Tissue ACE phenotyping in lung cancer. PloS ONE, 14(12), 1-13.
Hicks, B. M., Filion, K. B., Yin, H., Sakr, L., Udell, J. A., & Azoulay, L. (2018). Angiotensin converting enzyme inhibitors and risk of lung cancer: Population based cohort study. BMJ, 363(4209), 1-7.
Lin, S. Y., Lin, C. L., Lin, C. C., Hsu, W. H., Lin, C. D., Wang, I., & Kao, C. H. (2020). Association between angiotensin-converting enzyme inhibitors and lung cancer — A nationwide, population-based, propensity score-matched cohort study. Cancers, 12(3), 747-757.
Perini, M. V., Dmello, R. S., Nero, T. L., & Chand, A. L. (2020). Evaluating the benefits of renin-angiotensin system inhibitors as cancer treatments. Pharmacology & Therapeutics, 211(1), 2-18.
Zheng, Y., & Huang, J. (2020). Angiotensin-converting enzyme gene insertion/deletion polymorphism and high-altitude pulmonary edema: An updated meta-analysis. Journal of The Renin-Angiotensin-Aldosterone System, 21(1), 748-757.