Blood Type A is Associated with Increased Risk of Gastric Carcinoma
Blood group A individuals have a significantly higher risk of developing gastric carcinoma compared to those with blood group O, with an odds ratio of approximately 1.19 (95% CI: 1.13-1.25). 1
Evidence for Blood Type and Gastric Cancer Risk
- Blood group A is consistently associated with an increased risk of gastric cancer across multiple large-scale studies 2, 3, 1
- Blood group AB also shows an elevated risk of gastric cancer (OR = 1.09,95% CI: 1.03-1.16) compared to other blood types 1
- Blood group O demonstrates a protective effect against gastric cancer development (OR = 0.91,95% CI: 0.89-0.94) 2
- A large cohort study of over 1 million blood donors followed for up to 35 years confirmed the increased risk of gastric cancer among individuals with blood group A (incidence rate ratio = 1.20,95% CI: 1.02,1.42) 3
Mechanisms Behind Blood Type Association
- Blood group A individuals are more prone to Helicobacter pylori infection, a major risk factor for gastric cancer 2
- The risk relationship is modified by H. pylori cagA status - blood type A carriers of cagA positive H. pylori strains have a significantly higher risk of intestinal metaplasia or dysplasia (OR = 1.42,95% CI: 1.09-1.86) compared to blood type O individuals 4
- The combined effect of blood type A and a parental history of gastric cancer further increases the risk of dysplasia (OR = 2.61,95% CI: 1.59-4.30), suggesting genetic factors play an important role 5
Clinical Implications
- Blood type A should be considered a risk factor when evaluating patients for gastric cancer screening, particularly in high-risk populations 2, 1
- Individuals with blood type A and additional risk factors (family history of gastric cancer, H. pylori infection) may benefit from more intensive surveillance 5
- The National Comprehensive Cancer Network recommends screening for family history of gastric cancers as part of the standard workup for all patients 6
- For high-risk individuals, endoscopic surveillance should be considered, especially in regions with high gastric cancer prevalence 6
Geographical Considerations
- The association between blood type A and gastric cancer appears consistent across different populations, though the magnitude may vary 2, 1
- In Western countries, gastric cancer tumors are predominantly located in the proximal stomach, while in Japan and other parts of Asia, distal tumors remain predominant 7
- The risk association may be particularly important in high-incidence regions such as East Asia 2
Pitfalls and Limitations
- Blood type is just one of many risk factors for gastric cancer and should be considered alongside other established risk factors such as H. pylori infection, smoking, diet, and family history 6, 2
- The strength of association between blood type A and gastric cancer may vary depending on the study population and methodology 4, 1
- While blood type is a non-modifiable risk factor, focusing on modifiable risk factors (H. pylori eradication, smoking cessation) remains crucial for gastric cancer prevention 6