The Dartmouth researchers found that, of the estimated 138,000 breast cancers detected annually in the US, the test did not help 120,000-134,000 of the afflicted women. The cancers either were growing so slowly that they did not pose a problem, or they would have been treated successfully if discovered clinically later (or they were so aggressive that little could be done).
达特茅斯的研究者们发现，在全美每年检测出的13.8万乳腺癌案例中，乳房X光测试对其中12~13.4万遭受病痛折磨的妇女们并无帮助。那些癌瘤要么太小以至于未能威胁，要么在过一段时间后的临床检测中发现后（或者疯狂扩散而使人无计可施）反而更能得到有效治疗。