Investigating the Relationship be tween Smoking and Colorectal Cancer

Background: The number of smokers worldwide has increased to ۱.۱ billion in ۲۰۱۹, and in ۲۰۲۰,۲۲.۳% of global population used tobacco. Tobacco kills more than ۸ million people annually.Colorectal Cancer (CRC) accounts for about ۱۰% of cancers and is the second most commoncause of cancer mortality worldwide. Smoking is a major risk factor for CRC and is associatedwith an increase in mortality due to it. Evidence supports the relationship of modulating lifestylefactors, including smoking, in relation to CRC prevention. In this study, by collecting andanalyzing the available studies in this field, we investigated the relationship between smoking andthe second deadliest cancer in the world.Methods: The present study was carried out by a review method. For this purpose, a search wasmade in the databases: PubMed, SID, noormagz, Magiran by keywords: Smoking, Cigarette,Colorectal Cancer, Colon Cancer, Rectal Cancer and their Persian equivalents. Then, the articleswere reviewed based on the abstract and title, and those that were related to the topic and met theinclusion criteria were selected (=۳۳). Inclusion criteria were: Persian and English language,publication in the last ۵ years and be free full text articles. In the next step, the articles were reexamined,duplicates were removed and finally ۲۵ articles were included in the study. At the end,concepts and data were analyzed.Results: Predictive variables of CRC showed a combination of genetic markers and lifestyle inincreasing the risk of CRC. Tobacco smoke can be a source for intestinal microbiota. Dysbiosis ofintestinal microbiota due to smoke changes metabolites and disrupts intestinal permeability.Proliferation and apoptosis of colorectal epithelial cells and inflammatory response also changeafter smoking. Smoking can suppress the immune response in the tumor microenvironment and byaffecting the function of macrophages and polarization, it causes development of tumors. Smokingas an independent factor was associated with low recurrence-free survival (RFS) and poor overallsurvival (OS) and is a risk factor for recurrence, poor prognosis and mortality in CRC patients.Smokers are ۴۸% more exposed to CRC. Avoiding smoking can compensate a significant part ofthe genetic risk of CRC.Conclusion: Smoking increases the risk of developing colorectal cancer and also weakens theprognosis of smokers with CRC. Therefore, the need for wider training in the first level ofprevention is necessary as a modifiable factor; because withdraw may not be compensated afterthe diagnosis

Keywords:

Smoking , Cigarette , Colorectal Cancer , Colon Cancer , Rectal Cancer.