The most recent study, by Brasky, et al, was a very poorly designed study. It was retrospective and the control group was flawed. It was a very controversial study among us in the medical community and was essentially laughed at by urologists.
The media is constantly trumpeting alarming "findings" and misleading the public. It drives us doctors crazy! Once a misleading headline comes out (because today's journalistic standards are so low, they probably don't have anybody do any fact checking, or even have people who can tell whether a study is well-designed or not) then we have to do damage control and try to get people back on their medicines or supplements.
Fish oil in reasonable amounts, that would be 1000-2000 mg daily, has been shown to help prevent dementia, help with inflammation, and may help prevent heart disease. Heart disease, hands down, is the largest killer of Americans today. It kills FAR more people than prostate cancer!
The best thing your DH can do is discuss it with his doctor, not Dr. Google:) and see what he/she says. If his doctor is well-informed, he will tell DH what to do that would be best for him. I have my DH take fish oil every day!
Sorry to get on my soapbox, but the media does a lot of damage with their overzealous reporting on poorly designed studies.