May 6, 2010 — There's an anomaly in the incidence of noncardia gastric cancer in the United States.
The incidence rate for noncardia gastric cancer declined in all race and age groups from 1977 to 2006, with 1 exception — the rate increased in whites 25 to 39 years of age.
The authors of a new epidemiology study explored several possible explanations for this "divergent" finding, but are ultimately left guessing.
The study appears in the May 5 issue of the Journal of the American Medical Association.
The majority of noncardia gastric cancers, also known as lower stomach cancers, are attributable to chronic mucosal infection by the bacterium Helicobacter pylori, write the study authors, led by William Anderson, MD, from the Division of Cancer Epidemiology and Genetics, National Cancer Institute (NCI), Rockville, Maryland.
These noncardia cancers are distinct from cardia gastric cancer, which are tumors in the upper part of the stomach near the esophagus and might be related to gastroesophageal reflux, they explain.
Dr. Anderson and his colleagues found that, over the past 3 decades, the incidence of noncardia gastric cancer increased in the United States by 67% in whites residents from 25 to 39 years of age.
The increase is "noteworthy" when compared with what is happening in other white age groups and in other racial groups, according to an editorial that accompanies the new study.
The incidence of noncardia gastric cancer declined by 1% to 2% per year for everybody else, observe Manish Shah, MD, from Memorial Sloan-Kettering Cancer Center in New York City, and Jaffer Ajani, MD, from the University of Texas M.D. Anderson Cancer Center in Houston.
However, the editorialists place the anomalous finding about young white people in perspective.
"The absolute incidence of gastric cancer in this age range remains low (presently 0.45 cases per 100,000)," they write.
It is also important to note that although incidence rates declined among other racial groups of 25 to 39 year olds and whites in this age had an increase, the other racial groups still had higher rates of noncardia gastric cancer than whites.
Guesses About What's Happening
The investigators used data from the NCI's Surveillance, Epidemiology and End Results (SEER) program and identified 39,003 cases of noncardia gastric cancer that were diagnosed from 1977 to 2006.
They found that the overall incidence rates of noncardia or lower gastric cancers declined over the 30-year study period for all races.
The incidence rate — or cases per 100,000 people — dropped from 5.9 to 4.0 among whites, from 13.7 to 9.5 among blacks, and from 17.8 to 11.7 among other racial groups.
But among whites, different age groups had widely differing incidence rates.
Among whites, for people 60 to 84 years of age, the incidence rate dropped from 20 to 13; for those 40 to 59 years of age, the rate dropped from 3 to 2.
But for the above-mentioned 25 to 39 year age group, the incidence rate increased from 0.27 to 0.45.
The editorialists suspect that immigration patterns might explain the increase among young white people.
Ultimately, they dismiss the idea that white Hispanics, who have been distinguished from non-Hispanic whites since 1992, might be behind the mysterious incidence rate.
However, they also say that another immigration pattern — from Eastern Europe — warrants investigating.
The study investigators run through a number of possible explanations in their paper. Their guesses are derived from what is understood about noncardia or lower gastric cancers.
According to the study authors, H pylori infection is commonly acquired in childhood, generally not later. The infection is also associated with poor living conditions and overcrowding. Eating salt and salt-preserved foods is associated with increased incidence, but eating fresh fruits and vegetables is protective.
Thus, there are a number of hypothetical explanations: that the long-term decline in the prevalence of H pylori has been reversed; that the age of infection may have changed; that there is a new carcinogenic process involving another pathogen; and that salt intake is to blame.
In their paper, the study authors also make an observation: the increase is among whites born since 1952.
And they add one more explanation: "The possible role of long-term gastric acid inhibitory therapy as a potential cancer initiator should also be considered. Histamine 2 receptor blockers were in widespread use at the beginning of our study period, supplanted by the more potent proton-pump inhibitors, starting in September 1989."
However, the hypothesis is unlikely, say the authors, because both older and younger cohorts used these drugs.
The study was funded by the National Cancer Institute. The study authors and Dr. Shah have disclosed no relevant financial relationships. Dr. Ajani reports receiving research support from ACT Biotech, Ascenta Therapeutics, Bristol-Myers Squibb, Genta, Imclone, IPCT/CRF, Mebiopharm, Novartis, Sanofi-Aventis, and Taiho Pharma; and honoraria from Abraxis BioScience, ACT Biotech, Bayer Healthcare, Bristol-Myers Squibb, Merck, NCCN, Novartis, Sanofi-Aventis, Taiho Pharma, and Genta.
Medscape Medical News © 2010 Medscape, LLC
Send press releases and comments to email@example.com.
Cite this: Noncardia Gastric Cancer Declines in US, Except in One Group -- Young Whites - Medscape - May 06, 2010.