TUESDAY, May 4 (HealthDay News) -- While rates of lower stomach cancer continue to decline for most groups in the United States, a new study finds that among young, white men and women the rate is increasing.
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The main cause of lower stomach cancer is infection with the bacteria Helicobacter pylori, while cancer in the upper stomach is often caused by acid reflux. Most stomach cancers are found in those aged 65 and older. In the United States, blacks, Asian Americans and Hispanics have the highest rates of stomach cancer, according to the researchers.
"We confirmed what had been previously understood about gastric cancer, that in most groups it has been declining over the last 30 years," said lead researcher Dr. Charles Rabkin, a senior investigator at the U.S. National Cancer Institute.
"We found one exception to that trend, which was that young, white Americans, ages 25 to 39, actually had increasing rates of gastric cancer," he said. "That was an unexpected finding, and a disturbing finding."
The report is published in the May 5 issue of the Journal of the American Medical Association.
For the study, Rabkin's team used data from the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) program, which identified 39,003 cases of gastric cancer diagnosed from 1977 through 2006.
The researchers compared differences in the rates of stomach cancer over the period by age, race and other factors.
They found that, over 30 years, the rate of lower stomach cancer dropped from 5.9 to 4.0 per 100,000 people among whites, from 13.7 to 9.5 per 100,000 among blacks, and from 17.8 to 11.7 per 100,000 among other racial groups.
However, among whites, although the rates fell for most people, they increased for men and women aged 25 to 39. "The increase is estimated to be about 2.7% per year," Rabkin said. "That may sound like a small number, but over a number of years that percentage can grow just like compound interest on a loan."
The primary cause of lower stomach cancer is the bacteria H. pylori. Changes in the infection patterns over the last 50 years might explain the increasing rates of stomach cancer among younger whites, the researchers noted.
In older whites, the drop in lower stomach cancer is consistent with declines in H. pylori infection. This decline in infection is due to improved hygiene and less crowding during childhood, when the infections are often acquired.
"We don't know why the rate of gastric cancer is rising in young whites," Rabkin said.
It could indicate a change in the age when they become infected or an increase in the prevalence of the infection, the researchers added. It is also possible that something else is causing the cancer brought on by the eradication of H. pylori.
Dietary factors, such as eating salt and salt-preserved foods, are also associated with noncardia gastric cancer. Smoking is another risk factor for upper and lower stomach cancers, the researchers noted.
Dr. Jaffer A. Ajani, an oncologist in the Department of Gastrointestinal Medical Oncology at the University of Texas M.D. Anderson Cancer Center and co-author of an accompanying journal editorial, said that "this is a novel finding -- I don't think we need to be alarmed about this."
However, Ajani thinks the trend needs to be investigated. "One possibility is that these are Eastern Europeans, who have come to the United States. Eastern Europeans have gastric cancer in different places," he said.
The trend may be just a blip, which is already disappearing, Ajani said. "My personal opinion is that it is just among Eastern Europeans," he said.
"This probably needs further investigation," noted Dr. Ahmedin Jemal, strategic director for cancer occurrence at the American Cancer Society.
"Anything that occurs in the younger age group indicates a burden in the future," Jemal said. "So, it is important to find out what is contributing to this increase so you can avert the future cancer burden."
In another report in the same journal, researchers with the Global Advanced/Adjuvant Stomach Tumor Research International Collaboration (GASTRIC) Group studied whether surgery alone or in combination with chemotherapy offered the best survival for stomach cancer patients. They looked at 17 clinical trials that included over 3,800 patients. Among 1,857 patients who had surgery, 1,067 died within seven years of the procedure, compared with 1,000 deaths among 1,924 patients who also had chemotherapy.
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SOURCES: Charles Rabkin, M.D., senior investigator, U.S. National Cancer Institute, Rockville, Md.; Ahmedin Jemal, D.V.M., Ph.D., strategic director for cancer occurrence, American Cancer Society; Jaffer A. Ajani, M.D., oncologist, Department of Gastrointestinal Medical Oncology, University of Texas M.D. Anderson Cancer Center, Houston; May 5, 2010, Journal of the American Medical Association