H Pylori eradication and reduced risk of gastric cancer

A recent systematic review/meta-analysis looked at the effects of H pylori eradication and the incidence of gastric cancer (see hpylori rx and dec gastric ca gastro2016​ in dropbox, or doi.org/10.1053/j.gastro.2016.01.028). ​
details:

--background:
    --there are >720,000 deaths/yr from gastric cancer worldwide
    --H pylori infection is the most important etiologic factor, infecting approximately 50% of the global population, and estimated to cause 78% of gastric cancers
    ​--mechanistically, H pylori causes chronic gastric inflammation, leading to precancerous changes of atrophic gastritis, and also to gastric mucosal genetic instability through decreased acid secretion, "which can promote the growth of gastric microbiome that processes dietary components into carcinogens"
--​24 studies, with a total of 715 incident gastric cancers among a total of 48,064 patients and 340,255 person-years of followup. almost all of the studies were from Korea, China and Japan. 14 studies were in asymptomatic individuals and 10 were in those who had undergone endoscopic resection of early gastric cancers
--results: 
    --253 gastric cancers developed in 20,484 individuals who received H pylori treatment and 462 of 27,580 who did not get the treatment
    ​--baseline incidence of gastric cancer in those not getting treatment varied widely from 34.3 to 10,265.4/100K person-years
    ​--those with H pylori eradication had 46% lower incidence of gastric cancer (pooled incidence rate ratio of 0.54 (0.46-0.65), with little heterogeneity among the studies.
    --eradication of H pylori in asymptomatic individuals still had significant benefit (pooled incidence rate ratio of 0.62 (0.49-0.79)
    --the benefit of eradication in the group with endoscopic gastric cancer resection was even better, with pooled incidence rate ratio of 0.46 (0.35-0.60)    
    ​--the benefit of eradication was (not surprisingly) more significant in areas with a high baseline rate of gastric cancer (if 2,970 to 10,256.4/100K person-years​, then pooled incidence rate ratios were 0.45); decreased in those with intermediate rates (314.3-2914.2/100K person-years,  pooled incidence rate ratios were 0.49; and was not significant if low rates (34.2-253.6/100K person-years, ​ pooled incidence rate ratios were 0.80)

so,

--in another study by the current authors, a population-based mass eradication program on Matsu Island of Taiwan, found that H pylori eradication reduced atrophic gastritis in patients with premalignant lesions and reduced cancer incidence by 25% (from 40.3 to 30.4/100K person-years)
--unlike some other studies, the systematic review above found that even treating those with early gastric cancers had some benefit
--i am a little concerned about generalizing these results to other areas of the world, since these studies are mostly from Asia, and more developed regions of Asia at that. for example, in many countries with high rates of H pylori, there are not the epidemiologic data on the real incidence/prevalence of either H pylori or gastric cancer. i am also not sure that the strains/variants of H pylori are the same in different regions, or even have the same association with gastric cancer. that being said, i spoke with a public health-minded physician from Cape Verde, an area where many of our patients come from, and he was under the impression that there was a lot of gastric cancer there. but there are no concrete data, and the prevalence could well vary from island to island. i did decide to test and treat my patients after i found a few cases of gastric cancer in Capeverdean patients (long live anecdotes ....​)
--I have sent out many blogs on H pylori in the past, since it is  such a big issue in much of the world and so prevalent in many of the immigrant communities in the US. see:  

http://gmodestmedblogs.blogspot.com/2014/05/gastric-cancer-screeningprevention-h.html which comments on endoscopic screening for high risk patients (again, in Korea, Japan, and China). 

http://gmodestmedblogs.blogspot.com/search/label/H%20Pylori for an array of articles on H pylori regimens (including salvage regimens) and one on the increased risk of GI bleeding in patients with H pylori and taking NSAIDs

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