I consume a small amount of fish oil daily and eat fish like sardines and salmon 3 or 4 times a week along with a balanced healthy diet, broccoli sprouts, unsweetened cranberry juice, exercise, reduced alcohol and weight management. I would be surprised if consuming Omega 3 fatty acids is actually causing or leading to metastatic prostate cancer. There is obviously no magic supplement or diet that prevents or cures prostate cancer. But like anything else balance and moderation seem like a reasonable approach.