Researchers say that while their findings, presented at the American Association for Cancer Research's Seventh Annual International Conference on Frontiers in Cancer Prevention Research, confirm risk factors previously associated with these cancers, they don't explain the rising incidence of these tumors, especially esophageal adenocarcinoma (EAC) and gastric cardia adenocarcinoma (GCA), a cancer of the upper stomach area, where it joins the esophagus.
"The results of this study again confirm recommendations for a healthy lifestyle, namely not to smoke and to drink alcohol in moderation," said study author, Jessie Steevens, M.Sc., of the Department of Epidemiology at Maastricht University, in Maastricht. "But it also suggests that there must be other risk factors for EAC and GCA," she said. "Smoking is a risk factor for both cancers, but since a decreasing part of the population smokes, this cannot explain why the incidence is rising so rapidly for both cancers in Western countries in recent decades.
"Other factors that might be associated with the risk of these cancers include obesity, diet and nutrition, exercise, occupational exposures, medical factors and so forth, which we are beginning to study," Steevens said.
Their findings are from one of the first large cohort studies to investigate risk factors in esophageal adenocarcinoma and gastric cardia adenocarcinoma, as well as in esophageal squamous cell carcinoma (ESCC), which resembles head and neck cancer.
ESCC, which can occur anywhere along the esophagus, was at one time responsible for more than 90 percent of all esophageal cancers, but now EAC, which is typically found in the lower esophagus, makes up more than half of this cancer type. Esophageal cancer, in general, had been linked to alcohol and tobacco use, but this study sought to refine that risk between different cancer subtypes.
Researchers in the Netherlands Cohort Study, which began in 1986, administered lifestyle questionnaires to participants, who were healthy when they enrolled, and then followed the group to see who developed cancer. After 16 years, investigators identified 120 ESCC cases, 168 EAC cases, and 187 GCA cases among the group of 120,852 enrollees.
For esophageal squamous cell carcinoma, they found a dose-response relationship between alcohol use and cancer development. "For example, a person drinking four glasses of alcohol had five times the risk of developing the cancer compared to a person who does not drink alcohol," Steevens said.
"Another way to explain this is that a person's lifetime risk of developing ESCC is one in 250 if that person doesn't drink alcohol and the lifetime risk would be about one in 50 if the person drinks four glasses of alcohol per day," she said.
Former and current smoking was associated with an increased risk of all three cancers, although the risks of ESCC were higher than those of EAC and GCA.
"It appeared that current smokers have the highest risks, and former smokers have an intermediate risk compared with never smokers. This was true for ESCC, EAC and GCA. These are the results when no other aspects of smoking were considered, such as the amount of cigarettes smoked per day and the number of years a person smoked," Steevens said. "When we took into account the smoking duration and frequency, it appeared that the difference in risk between former smokers and current smokers could partly be explained by these other aspects of smoking. This is also logical, because a former smoker, for example, has usually smoked fewer years than a current smoker."
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