Chamberlain J
Eff Health Care. 1985;2(5):179-88.
Screening healthy women in order to detect the earliest signs of breast cancer may offer a possibility of curing many breast cancer patients who would be incurable if left until they developed symptoms. However, the natural history of breast cancer is very variable, probably indicating a wide spectrum of different growth rates of the tumour. Therefore it cannot necessarily be assumed that cancers detected by screening at an apparently early stage will behave in the same way as symptomatic cancers at that stage. To prove that screening enables cancer to be cured one needs to compare the number of deaths in a group of women who have been offered screening with those in a comparable group who have not. Unlike the situation in clinical trials of different treatments, comparison of the survival of screen-detected cancers with symptom-detected cancers is inadequate proof, because of selection bias, lead-time bias and length-bias. One randomized controlled trial of screening for breast cancer has so far been published and this shows that women in the group who were offered screening suffered one third fewer deaths from breast cancer than women in the control group, the difference persisting for up to 14 years from the first screening invitation. Further trials are now under way in Canada and various European countries, hoping to confirm this finding and to explore various other issues. Of the screening test methods currently available mammography seems the most sensitive and specific and its radiation hazard is now of almost negligible proportions provided that regular careful monitoring of the equipment is carried out. However it may have the disadvantage of overdiagnosing cases of borderline non-invasive neoplasia which might not progress to invasive cancer within the woman's lifetime. Clinical examination of the breasts is a less satisfactory test in older women but it may be useful in premenopausal women in whom mammography is less sensitive. The validity of self-examination of the breasts by women themselves is still largely unknown, but it is unlikely that compliance with regular breast self-examination will be as high as women's acceptance of screening. Further research is required into the optimal frequency of screening and into its cost-effectiveness.
对健康女性进行筛查以发现乳腺癌的最早迹象，可能为治愈许多乳腺癌患者提供可能，若任由病情发展至出现症状，这些患者将无法治愈。然而，乳腺癌的自然病程差异很大，这可能表明肿瘤的生长速度有很大范围的不同。因此，不能必然假定通过筛查在明显早期阶段发现的癌症会与该阶段出现症状的癌症表现相同。为证明筛查能治愈癌症，需要将接受筛查的一组女性的死亡人数与未接受筛查的可比组女性的死亡人数进行比较。与不同治疗方法的临床试验情况不同，将筛查发现的癌症与症状发现的癌症的生存率进行比较并不能充分证明，因为存在选择偏倚、领先时间偏倚和长度偏倚。迄今为止，已发表了一项乳腺癌筛查的随机对照试验，结果表明，接受筛查的组中的女性死于乳腺癌的人数比对照组中的女性少三分之一，这一差异从首次筛查邀请起持续了长达14年。加拿大和欧洲各国目前正在进行进一步试验，希望证实这一发现并探讨其他各种问题。在目前可用的筛查测试方法中，乳房X线摄影似乎最敏感和特异，并且只要对设备进行定期仔细监测，其辐射危害现在几乎可以忽略不计。然而，它可能存在过度诊断临界非侵袭性肿瘤病例的缺点，这些病例在女性一生中可能不会发展为侵袭性癌症。对老年女性来说，乳房临床检查是一种不太令人满意的测试，但对乳房X线摄影不太敏感的绝经前女性可能有用。女性自行进行乳房自我检查的有效性在很大程度上仍不明确，但女性定期进行乳房自我检查的依从性不太可能像她们接受筛查那样高。需要进一步研究筛查的最佳频率及其成本效益。
