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home - Stomach - Gastric Cancer - Stomach Cancer Epidemiology Written by Dr Sebastian Zeki

Stomach Cancer Epidemiology

Host Related Risk Factors:Blood group- 20 % excess of gastric cancer (especially diffuse)- assoc with gp A antigen genes Inc pernicious anaemia rate.Familial predisposition- Due to H. pylori clustering, genetic prediscposition to atrophic gastritis and genetic syndromes.Cytokine polymorphisms (cf pathogenesis of gastric cancer).Gastric polyps-May have malignant potential.Hypertrophic gastropathy (inc. Menetrier’s disease) and immunodeficiency syndromes.Gastric ulcer: Probably because of H. pylori.Pernicious anemia: 3x excess risk of intestinal type cancer. Amines, amides, and amino acids N-nitroso compounds D i e t a r y N i t r a t e s Nitrite Factors ‘protective’ for gastric cancer:Vegetables, fruits (esp citrus- probably related to vitamin C content- cooked fruit and veg not protective).Milk.Vitamin A.Cereal fibre protective for diffuse, not intest-nal type.Alcohol (daily wine may be protective). Associations With Gastric Cancer:-Fried food and processed meat (RR of gastric Ca=1.15 for of 30 g of processed meat per day (=1/2 average serving) esp if H.pylori +ve).Fish.Alcohol.Pickled foods.Salt esp if H.pylori or atrophic gastritis.Smoking (reduces to normal 10 yrs after smoking cessation).2x risk if social class V esp distal.Gastric surgery (Bilroth II> I. Increasing risk starting 15-20 yrs post op. Possibly related to regurgitation of alkaline bile and pan-creatic juice.Epstein-Barr virus- associated in 10% of gastric cancers.CIMP type tumours.Male predominance, preferential location in the gastric cardia, lymphocytic infiltr-tion and a diffuse type of histology in most.Helicobacter pylori.H.pylori virulence factors (vacAs1-, vacAm1-, and cagA-positive). 50% gastric ca related to H. pylori. Booze EBV V H.pylori E-cadherin gene Promoter CpG hypermethylation one <50 years old/>3 any age Dietary nitrates absorbed in stomach and concentrated in saliva and reduced to nitrites by oral bacteria.Nitrites can react with amines and other nitrosable like to form N-nitroso compounds. Gastric Cancer Epidemiology Hereditary diffuse gastric cancer (autosomal dominant) CDH1 associated gastric cancer Pathogenesis involves promoter CpG hypermethylation of E-cadherin gene which occurs in patients with CDH1 mutations. (80% of patients without specific mutations also have this).The lifetime cumulative risk of gastric cancer is 60%(M), and 75%(F).Average age of onset is 38. Also increased risk of gastric carcinoid tumors (possibly due to argyrophilic cell hyper-plasia secondary to hypergastrinaemia).AGA guidelines suggest a single endoscopy to rule out malignancy in patients with PA.No role for surveillance. Written by Dr Sebastian Zeki Management Guidelines for familial gastric cancer:Start genetic testing at 16 ys.Annual surveillance chromoendoscopy age 16-20 (<1% risk gastric cancer).Prophylactic gastrectomy if > 20. (4 % risk by age 30 without) or further surveillance.Mammography and breast USS yearly for females as increased breast cancer risk. Criteria for the diagnosis of familial gastric cancer:a) >2 cases of diffuse type gastric cancer in 1st/2nd degree relatives with one <50 years old.....OR b) >3 cases of diffuse type gastric cancer in 1st/2nd degree relatives of any age.

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