National Lung Screening Trial (NLST)

2002年9月启动的全国肺部筛查试验(NLST)仍然是NCI消除肺癌死亡和痛苦目标的一个至关重要的组成部分。不幸的是，肺癌仍然是癌症死亡的主要原因。到目前为止，胸部X光和痰细胞学等筛查方式的随机对照试验尚未证明对肺癌死亡率有任何影响。因此，如果没有有效的筛查或有效治疗方法的实质性改进，在降低肺癌死亡率方面几乎没有取得什么进展。有希望的是，技术的进步，特别是低剂量技术的出现，以及快速、计算机化的螺旋计算机断层扫描，使得检测到更小的肺结节成为可能。其他潜在的早期检测策略，如血清、血浆和痰生物标记物目前还处于初步阶段，需要在肺癌筛查的随机对照试验中进行检查之前进行实质性的改进和验证。NLST将确定当前最有希望的早期检测策略--低剂量螺旋CT(LDCT)是否能降低肺癌死亡率。 NLST旨在通过使用LDCT而不是胸部X光(CXR)来检测肺癌死亡率降低20%或更多，如果存在这样的好处的话。这项试验建立在PLCO癌症筛查试验的基础上，该试验正在研究CXR筛查与社区护理相比的有用性。梅奥诊所CT队列研究发表的结果为螺旋CT筛查提供了一个警示。研究人员将历史悠久的梅奥肺项目(密集的CXR筛查)的结果与他们的CT参与者的结果进行了比较，这些参与者在肺癌风险因素方面与前一项研究的参与者相似，显示肺癌死亡率没有差异。 NLST是一项功能强大的随机对照临床试验，能够以充足的统计能力评估肺癌死亡率。NLST始于2002年9月，随机对超过53,000名重度和/或长期吸烟者进行低剂量螺旋计算机断层扫描(CT)或胸部X射线(CXR)检查。参与者接受了最初的和随后的两次筛查考试。收到阳性或可疑筛查结果的参与者将被通知并转介给他们的初级保健医生，以确定适当的后续程序。 筛查在放射科的尖端设备上进行，拥有高素质的工作人员，他们在NLST程序中接受过专门培训和认证。螺旋CT设备反映了目前在美国各地的学术实践中使用的这一点。通用电气、西门子、飞利浦和东芝是代表的CT制造商。他们代表了世界上这种特殊设备的所有制造商。重要的是，在机构进行资本投资时，需要最低限度的四面板探测器，设备升级到8、16和面板探测器。已经制定了一项密集的质量保证计划，以确保遵守统一的图像采集参数、图像质量和剂量最小化参数。 低剂量螺旋CT的概念是以尽可能低的剂量优化图像采集，并利用肺部充气提供的对比度。所有地点的所有设备都受到仔细的辐射剂量监测和控制。美国国家科学院最近公布的证据表明，将辐射暴露降到最低限度是谨慎的，因为10？100毫西弗范围内的剂量与原子弹幸存者癌症死亡风险的增加有关。在NLST的55？74岁吸烟者中，实施的低剂量筛查与低辐射风险是一致的。 将每年与参与者联系，以确定当前的健康状况。随访包括确定不良医疗结果、癌症发病率、死亡原因和对死亡率的影响。

The National Lung Screening Trial (NLST), launched in September 2002, continues to be a critically important component of the NCI goal to eliminate death and suffering from lung cancer. Unfortunately, lung cancer remains the leading cause of cancer death. To date, randomized controlled trials of screening modalities such as chest x-ray and sputum cytology have not demonstrated any impact on lung cancer mortality. Therefore, without effective screening or substantive improvements in effective therapies little progress has been made in lowering lung cancer mortality. Promisingly, technological advances, specifically, the advent of low-dose techniques with rapid, computerized helical computed tomography, have allowed detection of smaller lung nodules. Other potential early detection strategies such as serum, plasma and sputum biomarkers are currently preliminary, and require substantial refinement and validation before examination in a randomized, controlled trial for lung cancer screening. The NLST will determine whether the most promising current strategy for early detection, low-dose helical CT (LDCT) lowers lung cancer mortality. The NLST was designed to detect a 20% or greater reduction in lung cancer mortality with the use of LDCT over chest X-ray (CXR), should such a benefit exist. The trial built upon the PLCO Cancer Screening Trial, which is studying the usefulness of CXR screening compared with community care. Published findings from the Mayo Clinic CT cohort study provide a cautionary note about screening with spiral CT. The researchers compared findings from the historic Mayo Lung Project (intense CXR screening) with findings from a subset of their CT participants who were comparable to the former study's participants in terms of lung cancer risk factors and showed ¿no difference in ¿ lung cancer mortality rates¿. NLST is a well-powered, randomized controlled clinical trial able to assess lung cancer mortality with ample statistical power. NLST began in September 2002 and randomized over 53,000 heavy and/or long-term smokers to low-dose, helical computed tomography (CT) or chest X-ray (CXR). Participants received an initial and two subsequent screening exams. Participants who receive a positive or suspicious screening result are notified and referred to their primary care practitioner to determine appropriate follow up procedures. Screening occurs on sophisticated state-of-the-art equipment in radiology departments with highly qualified staff specifically trained and certified in NLST procedures. The helical CT equipment reflects that currently in use in academic practices across the United States. GE, Siemens, Philips and Toshiba are the CT manufacturers represented. They represent all the manufacturers of this specialty equipment in the world. Importantly, a minimum four-panel detector is required and equipment upgrades to 8, 16 and 64 panel detectors occur as the institutions make capital investments. An intensive quality assurance program has been developed to ensure adherence to harmonized, image acquisition parameters, image quality and dose-minimization parameters. The concept of low-dose helical CT is to optimize image acquisition with the lowest dose possible and take advantage of the contrast provided by lung aeration. Radiation dose is carefully monitored and controlled for all equipment at all sites. Recent evidence announced by the National Academy of Sciences indicates the prudence of minimizing radiation exposure, as doses in the 10 ¿ 100 mSv range have been associated with an elevated risk of cancer death in atomic bomb survivors. The low dose screen administered is consonant with a low radiation risk in the 55 ¿ 74 year old smokers in the NLST. Participants will be contacted annually to determine current health status. Follow up includes ascertainment of adverse medical outcomes, cancer incidence, cause of death, and mortality impact.