Blood Type and Cancer
Luke G. Huber
The correlation between blood type and cancer is an issue that impacts many primary care physicians, especially naturopaths. The success of the recent bestseller "Eat Right 4 Your Type" has created a large population of patients who are concerned about the impact of their blood type on their health. By gaining knowledge on this subject the physician will be more prepared to field questions and allay fears.
Risk factors for cancer have been assessed over the years and many strong associations have been discovered. Blood type is an easily accessible factor in patients' genetic makeup. In his book, "Eat Right 4 Your Type," Peter D'Adamo, ND claims that Blood Type (especially Type A) predisposes people to certain types of cancer. A review of the research shows modest support for his claims.
Gastric cancer appears to show some correlation with blood type A. In one Taiwanese study, patients with gastric cancer were compared with controls . Each group was separated into blood type A or non-A. The gastric cancer group had an increased likelihood of being type A (OR 1.61, p<0.01). A Japanese study compared 1,233 gastric cancer patients to 2,200 patients with benign gastroduodenal diseases . A higher frequency of blood type A was seen in gastric cancer patients with a positive family history of cancer. A Chinese study examined risk factors for intestinal metaplasia and gastric dysplasia . Subjects with chronic atrophic gastritis were taken from a general population at a high risk for stomach cancer. Risk of transition to dysplasia was increased among those with a family history of stomach cancer and blood type A.
Pancreatic cancer also seems to be associated with blood type. A study in Serbia, Yugoslavia compared 100 pancreatic cancer patients to hospital controls matched for age, sex and place of residence . There was an increased prevalence of blood type A in the pancreatic cancer group (OR 2.70, p<0.01). There was a decreased prevalence of Blood type O Rh + in the experimental group compared to controls (OR 0.25, p 0.0027). In a 1960 study published in the BMJ, Aird et. al. found an association between blood type A and pancreatic cancer . 46.0% of pancreatic cancer patients were blood type A as compared to 40.1% of controls. The authors postulate that this may be due to an increased rate of diabetic patients being blood type A, and diabetes is a risk factor for pancreatic cancer. One hospital based study, that has been collecting hospital admissions in six different countries, compared 108 pancreatic cancer patients to age, sex and hospital matched controls . A modest excess risk was found among those with blood type A (RR 1.52, 95% Cl: 0.85-2.67).
Breast cancer and blood type has shown variable results in the literature. Anderson and Haas found sister pedigrees with breast cancer to have an increased rate of type A compared to type 0 121. One of the two facilities M the study found the risk ratio A:O = 2.11 (p<0.01) the other facility found A:O = 2.36 (p<0.01). The authors propose that. based on this and previous studies, there is a small association between blood type A and breast cancer development. Anderson and Haas suggest that in a consecutive series of patients an excess of 7-20% type A would be found. A 1988 Iceland study looked at the risk of bilateral breast cancer in familial and sporadic cases with regard to ABO typing . Familial cases of bilateral breast cancer had a 2-fold higher prevalence of type B than did sporadic cases. A study of rapidly progressive breast cancer in Tunisian women found a slightly increased risk of a positive diagnosis in blood type A . The general population of type A was 33% whereas those positive for rapidly progressive breast cancer were 4-3% of the study group.
In one Japanese study 100 prostate cancer patients were compared to age, hospital and admission date matched controls [121. No significant relative risk for ABO or Rh type was found. Urinary tract cancers may show some association with type A. In a 1988 article, increased rates of upper urinary tract tumors were found in those with blood type A (p<0.05) and Rhesus + (p<0.0-5) . In 1995 Japanese study, risk factors for bladder cancer were assessed in 303 males and controls . A significantly lower control adjusted OR for bladder cancer in men was associated with blood type O.
A 1997 Chinese study investigated risk factors for epithelial ovarian cancer [161. Blood type A was found to be one of the high risk factors for the disease. A 1995 study compared correlation of ABO blood type to gynecologic tumors in terms of risk and survival rates 191. Endometrial and ovarian cancer occurred more frequently in females with type A than in those with other blood types. In the same tumors, type A was associated with a poor prognosis.
In a 1988 letter to the British Journal of Cancer, Roberts et. al. studied 86 patients who had resection of lung cancers between 1978 and 1983 . Those patients who were blood type B or AB had a significantly shorter survival than those with other blood types (p< 0.0017).
In conclusion, it appears that stomach and pancreatic cancer have the strongest association with blood type. Type A seems to have an increased risk in both. Breast cancer may have an association with blood group, but different blood groups are associated with different manifestations of the disease. Other cancers show various risk or lack of risk associated with blood group. Type A individuals appear to be at a moderately increased risk for many cancers.
The information on blood type as a risk factor for cancer is one of many tools naturopaths may use when creating a plan for preventative medicine with their patients. The studies seem to show a fairly consistent modest correlation between several cancers and ABO type. Blood type needs to be considered together with other risk factors to understand the individual patient's risk.
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