Wednesday, February 2, 2011

New Study: Smokeless Tobacco is NOT Associated with Pancreatic Cancer

A new study documents that smokeless tobacco use is not associated with increased risk for pancreatic cancer. The study, from the International Pancreatic Cancer Case-Control Consortium and lead author Paolo Bertuccio of Milan, Italy, was published in Annals of Oncology (abstract here). It is a collaborative analysis of 6,000 cases of pancreatic cancer from 11 studies in North America and Europe.

With only 130 pancreatic cancer cases among ever smokeless tobacco users, the odds ratio (OR) is 0.98 (95% Confidence Interval, CI = 0.75 – 1.27). Twenty-three cases among exclusive users of smokeless tobacco produced an OR of 0.62 (CI = 0.37 – 1.04), which was almost significant for a PROTECTIVE EFFECT. Smokeless users who were also cigarette smokers had an OR of 1.36, which was not statistically significant (CI = 0.94 – 1.96) but confirms other studies that showed higher pancreatic cancer risks for smokers.

(The odds ratio is the measure used for case-control studies. Its interpretation is similar to that used for relative risks, which was discussed in this post.)

The importance of this study is hard to overestimate. First, it provides additional evidence that smokeless tobacco users are not at risk for pancreatic cancer. More importantly, it directly addresses a persistent question about the integrity of previous studies.

In September 2009, I described in detail the results of two meta-analyses of cancer risks among smokeless tobacco users (read my description here). The first report, published in 2008 by Paolo Boffetta and colleagues in Lancet Oncology, concluded that smokeless users had an increased risk for pancreatic cancer (RR = 1.6, CI = 1.1 – 2.2). But that study used cherry-picked data in an unscientific manner to artificially raise the cancer risks. The second study, by Peter Lee and Jan Hamling, using a more scientifically credible and valid approach, reported an RR for pancreatic cancer of 0.99 (CI = 0.71 – 1.60).

The results from the current study are in close agreement with the Lee-Hamling estimate, and at odds with the Boffetta estimate, which Bertuccio clearly acknowledges:

“Our results on smokeless tobacco use are in broad agreement with a recently published meta-analysis of all published data on the issue [Lee-Hamling], which reported NO EXCESS RISK OF PANCREATIC CANCER in case-control studies. They are, however, at variance with those from another meta-analysis [Boffetta], based mainly on data from two Nordic cohort studies, which suggested that smokeless tobacco is associated with an increased risk of pancreatic cancer.” (emphasis added)

Bertuccio actually cited a different Lee-Hamling publication (abstract here), but the data from this study is identical to the Lee-Hamling meta-analysis.

The Bertuccio study is significant because it endorses the Lee-Hamling analysis and clearly refutes the Boffetta analysis. But there is another, profound aspect to this report: Paolo Boffetta is a co-author. Thus, Dr. Boffetta is finally acknowledging that his 2008 meta-analysis was wrong.

American consumers have been deceived for decades by the myth that smokeless tobacco confers high risk for oral cancer (here ). Because of the misguided 2008 Boffetta meta-analysis, smokeless tobacco opponents have built a second unscientific line of attack around the issue of pancreatic cancer.

Regulatory authorities worldwide should now acknowledge that use of modern American and Swedish smokeless tobacco products is not a risk factor for cancers of the oral cavity or pancreas.

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