I have honestly never heard fish oil mentioned as a way to reduce cancer. I guess a lot of people have been taking/hyping it for that, but I've always only heard of it as a means of lowering your risk of heart problems. (And it sounds like the results of this study are that it dramatically lowers the risk of heart attack, as much or more as any prescription medication, so I agree with other commenters who say it's weird to describe this study as showing "disappointing" results for fish oil and heart disease.)