Fletcher S W, Black W, Harris R, Rimer B K, Shapiro S
American College of Physicians, Philadelphia, PA 19106-1572.
J Natl Cancer Inst. 1993 Oct 20;85(20):1644-56. doi: 10.1093/jnci/85.20.1644.
Over the past 30 years, eight major randomized controlled trials of breast cancer screening--with mammography and/or clinical breast examination--have been conducted. Results from several trials have been updated during the past year, and initial results of three other trials have been reported.
The National Cancer Institute held an International Workshop on Screening for Breast Cancer in February 1993 to conduct a thorough and objective critical review of the world's most recent clinical trial data on breast cancer screening, consider the new evidence, assess the current state of knowledge, and identify issues needing further research.
Investigators representing the eight randomized controlled trials of breast cancer screening in women aged 40-74 presented published and unpublished data. Evidence relating to the effectiveness of breast cancer screening in different age groups, especially women aged 40-49, was presented.
For women aged 40-49, randomized controlled trials consistently demonstrated no benefit from screening in the first 5-7 years after study entry. A meta-analysis of six trials found a relative risk of 1.08 (95% confidence interval = 0.85-1.39) after 7 years' follow-up. After 10-12 years of follow-up, none of four trials have found a statistically significant benefit in mortality; a combined analysis of Swedish studies showed a statistically insignificant 13% decrease in mortality at 12 years. Only one trial (Health Insurance Plan) has data beyond 12 years of follow-up, and results show a 25% decrease in mortality at 10-18 years. Statistical significance of this result is disputed, however. In women aged 50-69, all studies show mortality reductions; three of four studies show reductions of about 30% at 10-12 years after study entry. Results from two of these trials were statistically significant. Too few women over age 70 have been included in studies for adequate analysis.
For women aged 40-49, randomized controlled trials of breast cancer screening show no benefit 5-7 years after entry. At 10-12 years, benefit is uncertain and, if present, marginal; thereafter, it is unknown. For women aged 50-69, screening reduces breast cancer mortality by about a third. Currently available data for women age 70 or older are inadequate to judge the effectiveness of screening.
Randomized trials have provided stronger scientific evidence regarding the effectiveness of screening for breast cancer than for any other cancer. However, much still needs to be learned. Periodic gatherings of scientists in the field should speed the process.
在过去30年里，已经开展了八项关于乳腺癌筛查的大型随机对照试验——采用乳房X线摄影和/或临床乳房检查。过去一年里，几项试验的结果得到了更新，另外三项试验的初步结果也已公布。
1993年2月，美国国立癌症研究所举办了一次乳腺癌筛查国际研讨会，对世界上最新的乳腺癌筛查临床试验数据进行全面、客观的批判性审查，审议新证据，评估当前的知识状况，并确定需要进一步研究的问题。
代表八项针对40 - 74岁女性乳腺癌筛查随机对照试验的研究人员展示了已发表和未发表的数据。展示了与不同年龄组，尤其是40 - 49岁女性乳腺癌筛查有效性相关的证据。
对于40 - 49岁的女性，随机对照试验一致表明，在研究开始后的前5 - 7年进行筛查没有益处。对六项试验的荟萃分析发现，随访7年后相对风险为1.08（95%置信区间 = 0.85 - 1.39）。在随访10 - 12年后，四项试验均未发现对死亡率有统计学上的显著益处；瑞典研究的综合分析显示，12年时死亡率有统计学上不显著的13%的下降。只有一项试验（健康保险计划）有超过12年的随访数据，结果显示10 - 18年时死亡率下降了25%。然而，这一结果的统计学显著性存在争议。在50 - 69岁的女性中，所有研究都显示死亡率降低；四项研究中有三项显示在研究开始后的10 - 12年里降低了约30%。其中两项试验的结果具有统计学显著性。纳入研究的70岁以上女性数量太少，无法进行充分分析。
对于40 - 49岁的女性，乳腺癌筛查随机对照试验显示在开始后的5 - 7年没有益处。在10 - 12年时，益处不确定，即便有也很微小；此后则未知。对于50 - 69岁的女性，筛查可将乳腺癌死亡率降低约三分之一。目前可获得的70岁及以上女性的数据不足以判断筛查的有效性。
随机试验为乳腺癌筛查的有效性提供了比其他任何癌症都更强有力的科学证据。然而，仍有许多需要了解的地方。该领域科学家的定期聚会应能加快这一进程。
