HR being the hazard ratio (indication of greater or lesser risk), and overall averages of HR being around 0.88, apparently one can reduce the risk of almost any cancer by 10% using a vegetarian diet.

Diet seemed to have the greatest influence on occurrence of these:

• stomach cancer: HR 0.55
• cancer of the lymphatic system: HR 0.75
• colorectal cancer: HR 0.79

So, if one has occurrences of those in family or is predisposed by environment to a higher risk of those - changing diet can reduce risk. :)