Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial

前列腺、肺、结直肠癌和卵巢癌（PLCO）癌症筛查试验是一项大规模的随机对照试验，旨在确定某些筛查试验是否会减少这些癌症的死亡人数。PLCO是一项多机构临床试验，在美国各地的10个地点进行，这些地点在地理和人口统计学上都不同。这项对照试验是进行人体受试者研究的第三阶段试验。PLCO招募了154,942名男女参与者。PLCO的参与者相当于美国的一般人口。研究人员收集了参与者的生活方式、饮食和风险因素信息。干预组接受肺癌检查，每年进行四次胸部后前位（PA） x光检查（从不吸烟者除外，每年接受三次筛查），在入组时进行柔性乙状结肠镜检查（FSG），并根据入组时间在第四或第六次年度筛查间隔进行结肠直肠癌筛查。对于前列腺癌，男性每年接受6次前列腺特异性抗原（PSA）筛查和4次直肠指检（DRE）。每年用CA-125抗原进行6次卵巢癌筛查，每年用阴道超声（TVU）进行4次筛查。常规护理（对照）组接受初级保健提供者的定期保健。干预组采集全血、序贯血清和1份血浆样本。通过与癌症流行病学和遗传学部（DCEG）的合作，这些样本的份额被储存在PLCO生物库中。常规护理组提供口腔细胞DNA样本，这些样本也储存在PLCO生物库中。PLCO生物库目前有超过290万份标本可用于病因学和早期标志物研究。PLCO正在收集那些已经患上癌症的参与者的结肠直肠、卵巢、前列腺和肺肿瘤组织。然后构建组织微阵列。

The Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial is a large scale, randomized controlled trial to determine whether certain screening tests will reduce the number of deaths from these cancers. PLCO is a multi-institutional clinical trial being conducted at ten sites, geographically and demographically disparate, around the U.S. This controlled trial is a Phase III trial conducting human subjects research. PLCO enrolled 154,942 male and female participants. The PLCO participants are comparable to the general United States population. Life style, dietary and risk factor information was collected from participants. The intervention arm received for lung cancer, posterior-anterior (PA) chest x-ray annually for four screens (except never smokers who received three annual screens), flexible sigmoidoscopy (FSG) at enrollment and again at the fourth or sixth annual screening interval depending on time of enrollment to screen for colorectal cancer. For prostate cancer, men received six annual prostate screens with prostate-specific antigen (PSA) and four digital rectal exams (DRE). Women were screened for ovarian cancer with CA-125 antigen for six annual screens and with transvaginal ultrasound (TVU) for four annual screens. The usual care (control) arm received regular health care from their primary care provider. Whole blood, sequential serum samples and one plasma sample were collected from the intervention arm. Aliquots from these samples are stored in the PLCO Biorepository through collaboration with the Division of Cancer Epidemiology and Genetics (DCEG). The usual care arm provided buccal cell DNA samples which are also stored in the PLCO Biorepository. The PLCO Biorepository currently has over 2.9 million specimens that can be used for etiologic and early marker studies. PLCO is collecting colo-rectal, ovarian, prostate and lung tumor tissue from those participants who have developed cancer. Tissue microarrays are then constructed. STUDY DESIGN The PLCO is a two-armed, randomized trial in which more than 38,000 men were screened for lung, colorectal, and prostate cancers and approximately 39,000 women were screened for lung, colorectal, and ovarian cancers. Equal numbers of men and women participating as controls continue their usual medical care practices. The eligible age range at entry was 55-74 years. Both screened and control participants are to be followed for at least 13 years from randomization for cancer and death ascertainment to determine if the screening regimen results in reduced disease-specific mortality. Baseline information including demographic characteristics, known risk factors for the cancers under study, and screening history were collected from all participants. In addition, participants completed dietary, food frequency questionnaires and subsequently a risk factor questionnaire that supplements the baseline data provided at the time they enrolled. Blood samples collected at each screening visit were processed into separate components and stored for future molecular analyses. Control participants provided Buccal cell DNA. Participants in both the intervention and control arms completed a dietary questionnaire. All participants also provide annual health status information. Special efforts made to enhance the recruitment of minorities occurred at several screening locations. One site in Detroit, MI focused efforts on increasing the participation of African Americans. A site in Denver, CO hired Spanish speaking staff to enhance the number of Hispanic Americans enrolled in PLCO. BIOREPOSITORY The PLCO Biorepository contains approximately 2.9 million biologic specimens collected during the six screening years. These samples include serum, plasma and buffy coat and DNA samples. These specimens are an invaluable resource for cancer research. Some of the characteristics that make the PLCO biospecimens uniquely valuable include: - Large sample size allows statistical power - Specimens are collected prospectively, before cancer diagnosis - Serial specimens are collected at each of the 6 annual screenings - Detailed background and clinical data are available The PLCO Etiology and Early Marker Studies (EEMS) component is an integral part of the PLCO Trial. The PLCO EEMS has two main focuses: etiologic studies that investigate the environmental, biochemical and genetic risk factors for cancer; and early detection studies that aim to develop reproducible, diagnostics-ready biomarkers of early disease. The PLCO EEMS directly addresses the following strategic priorities of the National Cancer Institute: - Understand the causes and mechanisms of cancer - Improve early detection and diagnosis