USPSTF所引用的研究中包括一项来自欧洲的研究，该研究表，有一个子类的人获得了微弱的生存优势，但生命质量并未显著改善。
Of the studies cited by the USPSTF, one, conducted in Europe, showed a minor benefit in a subset of men, with no significant quality-of-life improvement.