Abstract ED06-01: PLCO biospecimen resource for etiologic and early marker research
Authors: Zhu Claire 
Published: May 2012

ED06-01

The Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial is a large randomized trial evaluating the effects of screening on cancer-related mortality and cancer incidence. Ten screening centers located across the United States have enrolled 76,705 men and 78,237 women, ages 55 to 74, and randomized them to an intervention arm or control arm. Participants in the intervention arm of the trial receive screening for the PLCO cancers during their first 6 years of participation in the trial and follow-up continues for at least 7 additional years. Participants in the control arm are followed for at least 13 years after enrollment, but do not receive the screening examination as part of the trial.

Blood samples were collected from screen arm subjects during annual screens. Approximately 2.9 million specimens are stored centrally in the PLCO biorepository. Several characteristics highlight the value of this resource: 1) up to 6 annually collected serial specimens are available; 2) specimens are collected prospectively, before cancer diagnosis; 3) specimens are linked to detailed epidemiological and clinical data; 4) large sample size allows statistical power. Specimens available include serum, plasma, buffy coat, red blood cells, and cryo-preserved whole blood from screened arm subjects; and buccal cells from control arm subjects. Epidemiological and clinical data available include baseline demographic and risk factor information; food frequency questionnaire; information on all-cancer incidence and selected other medical conditions (Table1 & 2).

A newly added PLCO resource provides Tissue Microarrays (TMA) of tumor samples from PLCO participants who developed cancer. TMAs for colorectal cancer, colorectal adenomas, and ovarian cancer are now available. TMA construction for prostate cancer and lung cancer is under way. Additional collections for other cancers may be added. A unique advantage of the PLCO tumor samples is the availability of corresponding pre-diagnostic blood samples from the same patients.

The longitudinally collected, pre-diagnostic serum/plasma samples are particularly suitable for the validation of promising early detection or screening biomarkers. Recently, PLCO embarked on an effort to coordinate biomarker validation studies using PLCO samples. The goal of this coordination effort is to: 1) ensure proper study design; 2) maximize the amount of useful information that may be obtained from studies using high-quality PLCO specimens; 3) ensure proper reporting of key results in publications. The study design, approach, statistical data analysis plan developed in this effort should be informative for other investigators who wish to conduct high-quality biomarker validation studies. Results from these studies will be available in the near future.

The PLCO biospecimens resource has been providing samples to the entire scientific community since 2005. PLCO samples been extensively used for genetic and biochemical investigations of risk factors for cancers. For example, SNPs in genes in various genetic pathways have been identified to be associated with risk of cancers; serum levels of Vitamin D metabolites have been examined for correlation with risk of prostate cancer, breast cancer, and colorectal adenomas; a NCI cohort consortium pooling project is looking into Vitamin D in rare cancers. Other projects include dietary, BMI, alcohol, smoking and other life style factors and risk of cancers.

A wealth of data has been published using PLCO samples. For example, genome-wide association study (GWAS) data is now available for prostate cancer and breast cancer through the NCI Data Access Committee (http://cgems.cancer.gov/). GWAS studies for pancreatic, lung, colorectal cancer are currently on-going from which data will also become available in the near future. Over 50 peer-reviewed research articles have been published using PLCO samples. The PLCO biospecimen and data resource is available to all qualified researchers through a panel review process. Applications are accepted twice a year in June and December. Detailed information about the panel review process, sample collection protocol, and application materials are available on the PLCO program website: www.parplco.org.

Table1: Summary of Data and Specimens Available

Table2: Cancer cases with biospecimens

Abstract for AACR, November 16, 2008

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Citation Information: Cancer Prev Res 2008;1(7 Suppl):ED06-01.