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.