The first limitation of breast-cancer screening is obvious: where effective diagnosis and treatment are not available, screening cannot have any impact. But there is more to the issue – namely, whether screening ultimately fulfills its intended purpose of reducing breast-cancer mortality rates.
乳腺癌筛查最重要的限制因素显而易见：没有有效的诊断和治疗手段，筛查起不了多大作用。但这个问题还有更重要的意义——即筛查最终能否降低乳腺癌死亡率。