DISCUSSION
Colon cancer is one of the leading causes of cancer related mortality and morbidities worldwide. Studies were conducted regarding its etiology exploring the place of a high-fat animal-based diet, consumption of low-fiber foods, smoking (21). There were recent studies focusing on the probability of infectious agents, especially H. pylori, as well. H. pylori infection is considered as the most important risk factor in gastric IM development (4,21,22). Sporadic colorectal cancers mostly originate from adenomatous polyps. With early diagnosis and treatment of colorectal polyps, a significant decrease can be achieved in the incidence and mortality of colorectal cancers (7,23).
The latest research has focused on the role of infectious agents in the prevention of colorectal cancers and the polyp – cancer spectrum (24,25). Although it is not fully understood how H. pylori infection increases the risk of colorectal neoplasia, according to the most commonly described pathogenesis, IM occurs after a long term H. pylori infection, and IM replaces normal gastric cells both in the corpus and the antrum (26). The reduced gastric acid secretion triggered by IM causes hypergastrinemia, which may contribute to colorectal carcinogenesis. In addition, hypochlorhydria affects protein absorption and causes bacterial overgrowth, hence causing an increase in the metabolites and unabsorbed nutrients; and these events may contribute to the formation of colonic diseases and colorectal carcinogenesis (27,28).
The association between H. pylori infection and colorectal neoplasia was first reported in 1997 (9). It was shown in several previous studies that there was a positive correlation between H. pylori infection and colorectal neoplasia (11,29-31). In addition, this correlation was supported in other studies (16,32-34). In their 11-study meta analysis, Zumkeller et al. stated that H. pylori infection caused a minor increase in colorectal cancer risk (35). In our study, it was seen that there was not a significant association between H. pylori infection and gender and age. Contrary to other publications stating that there was a correlation between H. pylori and colorectal neoplasia, in our study, a correlation was not found between H. pylori infection and colon neoplasm risk (p=0.310). This outcome supports the publications reporting that H. pylori does not increase the colorectal neoplasia risk.
AG and IM prevalence was found to be significantly higher in males in comparison with females (36). There were many studies reporting that 50 years of age and above was an independent risk factor, and IM incidence increased in proportion to age (37,38). Similar to these studies, in our study, IM incidence was found as 41% in the group aged under 50, and 59% in the group aged 50 and over. Besides, IM incidence was found to be higher in male patients in comparison with female patients.
In a comprehensive case-control study conducted on 156.000 registered patients, a positive correlation was presented between IM and colorectal adenomas (13). In their 2016 study conducted on 1641 patients aged 40 and over in China, Ye et al. analyzed gastric and colorectal biopsy results and found that Hp infection was significantly associated with a higher risk of colorectal adenoma (39). In addition, an increase in the colorectal adenoma risk was seen in IM positive cases. Moreover, in a more recent study, it was found that individuals with IM had a higher risk of having high-grade intraepithelial neoplasia (40). There are very few studies evaluating the association between H. pylori and IM in our country. In our study, it was found that the IM positive group of patients had a significantly higher risk of colorectal neoplasia in comparison with the IM negative group of patients. There was not any significant difference in terms of colon neoplasia incidence in the analysis of four subgroups including both IM and HP. This result of the group analysis conducted according to the presence of IM supports other publications stating that IM brings a higher risk of colorectal adenoma. Having a limited number of patients in the groups might be the reason why the subgroup analysis gave this result.
In conclusion, even though our study supports the notion that H. pylori infection increases the risk of colorectal neoplasia, this still remains a controversial issue. However, IM, which is considered a chronic sequela of H. pylori and a precursor lesion for gastric adenocarcinoma, was found to be a risk factor for colorectal neoplasia, similar to findings of many previous studies. In our study, although H. pylori infection was not found to be a risk factor for colorectal neoplasia, it can be accepted as a potential risk factor for colorectal neoplasia development with IM. Therefore, patients with H. pylori infection and IM could be encouraged for colonoscopic examination in early stages of life to lower the colorectal neoplasia risk. However, it is obvious that there is a need for large-scale studies on this matter.
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