Large study links tobacco to stomach cancer

  Article date: 2002/10/28,List Of Tobacco-Related Health Problems Continues To Grow

While not common in the US, stomach cancer is the second most common cancer in the world, as well as one of the leading causes of cancer deaths.

In recent years researchers have linked many cases of stomach cancer with infection by a specific type of bacteria, Helicobacter pylori. But an old villain — tobacco — may now be back in the spotlight after once being let off the hook.

In a large study that followed more than 1 million people for 15 years, American Cancer Society (ACS) researchers found that tobacco use greatly increased the risk of dying from stomach cancer.

"Tobacco products are associated with increased risk of stomach cancer death in both men and women," said Ann Chao, PhD, ACS research scholar in the department of epidemiology and surveillance research, and lead author of the study. The results were reported in the International Journal of Cancer (Vol. 101: 380-389).
Link Not New, But Hard to Prove

Stomach cancer is much more widespread in parts of Asia and South America than in the US, although at one time it was more common here as well. While researchers are unsure of the exact reason for this, they point to several possible risk factors for the disease.

Eating foods that are smoked or salted is known to increase risk, a practice which is much more common in other parts of the world. And rates of infection with Helicobacter pylori, a type of bacteria that thrives in the stomach, are known to differ worldwide. Other factors, such as family history, may also play a small role.

The relationship between stomach cancer and tobacco use, however, has remained an area of debate. Some studies have found a link, while others have not.

According to the study authors, the US Surgeon General listed stomach cancer among the tobacco-related cancers in 1987, but later removed it from the list because the link was not clear cut.

According to Chao, however, in June of 2002 the International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO), concluded that there is sufficient evidence in humans that tobacco smoking causes cancer of the stomach.

This is in addition to cancers of the lung, head and neck, esophagus, pancreas, liver, kidney, bladder, cervix, and certain types of leukemia.
New Study Shows Clear Link

The researchers examined the impact of the use of various tobacco products among men, and of cigarette smoking among women.

They looked at people taking part in the Cancer Prevention Study II (CPS II), a group of more than 1 million people who have been followed since the early 1980s.

After adjusting for other factors, the researchers found that men who smoked cigarettes or cigars were more than twice as likely to die from stomach cancer as those who did not smoke. The rates were higher for those who had smoked longer. Former smokers had about a 50% increased risk.

Among men who reported having a history of ulcers or chronic heartburn, cigarette smoking increased the risk more than three-fold, while cigar smoking raised the risk to more than nine times that of a non-smoker. Other studies have linked smoking directly to stomach ulcers in the past.

Women who smoked also had about a 50% increased risk. Those with a history of smoking had a risk increase of about 35%.

Overall, the researchers estimated that if tobacco directly causes stomach cancer, it is responsible for 28% of stomach cancer deaths among men and 14% of the deaths among women in the US.
Results May Have Widespread Implications For The Future

Because the results are from the US, which has lower rates of stomach cancer than many other countries, there are "major implications for countries with much higher stomach cancer rates and increasing smoking prevalence," said Chao.

"If tobacco use causes stomach cancer, then the emerging and maturing tobacco epidemic in intermediate- to high-risk areas for stomach cancer will likely contribute to substantial increases in stomach cancer incidence and mortality worldwide," the authors concluded.

For those in the US, the message is simple, according to Chao: "Avoid all tobacco products to decrease the risk of stomach cancer, the second most common cancer in the world."

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