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WEDNESDAY, July 2 (HealthDay News) -- Smokeless tobacco products (STPs), which include products such as snuff and chew tobacco, do increase the user's risk of cancer -- just not as much as smoking does.

So say researchers who examined worldwide patterns of STP use and the associated risk of cancer.

Reporting in the July issue of The Lancet Oncology, a team led by Dr. Paolo Boffeta, of the International Agency for Research on Cancer, in France, noted that STPs contain more than 30 carcinogens, including nitrosamines and metals.

Their analysis of studies from around the world found that STP users had an overall 80 percent increased risk of oral cancer and a 60 percent increased risk of esophageal cancer. They also had a similar increase in the risk of pancreatic cancer. European studies suggest no increased risk of lung cancer among STP users, but American studies suggest an 80 percent increased risk of lung cancer, the team said.

Cancer rates associated with STPs vary between countries. For example, more than 50 percent of oral cancers in India and Sudan are attributable to STPs, compared with 4 percent in the U.S.

The findings are published in a special edition of the journal devoted to lung cancer.

Overall, studies do support a strong association between STPs and cancer, said the authors, who did not recommend smokeless tobacco as a substitute for smoking.

"We do not intend to address explicitly the use of smokeless tobacco to reduce the risk from tobacco smoking -- e.g., by promoting smokers to switch to smokeless products or by introducing these products in a population where the habit is not prevalent," the researchers concluded.

"Nevertheless, several conclusions can be reached based on the available data ... the risk of cancer, especially that of oral and lung cancer, is probably lower in smokeless tobacco users in the USA and northern Europe than in smokers, and the risk of cancer is higher in smokeless tobacco users than in non-users of any form of tobacco," the team wrote. "Available data for a possible benefit of switching from smoking to smokeless tobacco come from few studies and models from the USA and Sweden."

Another article in the July issue of The Lancet Oncology suggests that DNA screening for certain biomarkers could help assess lung cancer risk in people exposed to secondhand smoke.

Many carcinogens in cigarette smoke are known to cause DNA lesions called DNA adducts and many carcinogens are known to leave unique signatures on cancer-related genes in the form of specific mutations at specific locations, noted Dr. Ahmad Besaratinia and Dr. Gerd Pfeifer, of the Beckman Research Institute of the City of Hope National Medical Center in Duarte, Calif.

They noted that a technique called DNA-lesion footprinting, in conjunction with mutagenicity analysis, is currently used to find carcinogen signatures. They proposed this technique be used in cancer-relevant genes, which are commonly mutated in smoke-related lung cancer.

In fact, this method has already been used successfully to find adducts connected with various smoke-derived carcinogens, the researchers said.

More information

The U.S. National Cancer Institute has more about smokeless tobacco and cancer.