Cigarette smoking is the most preventable risk factor for human diseases. As per WHO out of 1.3 billion active smokers worldwide half die due to smoking related diseases. There has been enough evidence that smoking is associate with various types of cancers among other life threatening diseases, thus making it a major concern in public health.
Number of studies have shown that smoking is a major cause of gastrointestinal cancers. Tobacco smoking induces chronic inflammation of the gastrointestinal tract leading to mutagenesis and tumor formation. Smoking (nicotine) has a direct causation with the promotion of cancers in the esophagus, stomach, pancreas and colon& rectum (types of abdominal cancers).
Cigarette smoking is one of the important risk factors for esophageal cancer. Individuals who began smoking at a younger age had a higher risk of developing esophageal cancer compared with normal population. This population also has a higher mortality risk due to esophageal cancer once developed.
Stomach (gastric) cancer–
Smoking increases the incidence of this cancer by approximately 1.5-2.5 times than non-smokers. Nicotine promotes gastric tumor growth and neovascularization. Studies have shown that smoking significantly increases the risk of gastric cancer in ever smokers than in non-smokers.
Tobacco is an established risk factor for pancreatic cancer. Smoking increases the risk of pancreatic cancer and mortality in patients with pancreatic cancer.
History of smoking (ever smokers) is significantly associated with a shorter disease free survival and higher recurrence rates in patients of colonic cancers even after effective treatment.
Mechanism by which smoking promotes gastrointestinal / abdominal cancers-
Cigarette smoking induce pathogenic and carcinogenic processes in gastrointestinal tract. They lead to severe chronic inflammation and development of cancer at the inflammation sites. Smoking induces cellular death in gastrointestinal tract and the inhibition of mucosal cell renewal. It also interferes with the protective mechanisms of the GI tract by decreasing blood flow in the mucosa and by weakening the mucosal immune system. Chronic inflammation induced by smoking releases many inflammatory components like cytokines, IL-6 etc., which are capable of promoting tumor growth and spread (metastases).
In conclusion, Although, cigarette smoke is a detrimental factor increasing the risk of cancer formation in GI tract, the best part is that it is totally a preventable cause.