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The Cancer Data Access System (CDAS) is a website for requesting data recorded from the NLSTThe National Lung Screening Trial and PLCOThe Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial cancer studies. For some studies, images or biospecimens are also available.

CDAS provides extensive public documentation for each study, including a trial summary, an overview of the data collected, and a searchable database of research projects and publications.

If you are interested in obtaining study data, you may submit a project proposal. All projects are reviewed by NCI trial leadership. Upon approval, you will be granted access to the requested data for a limited period.

Cancer Studies on CDAS


The National Lung Screening Trial compared two ways of detecting lung cancer: low-dose helical computed tomography (CT) and standard chest X-ray. Both chest X-rays and low-dose helical CT scans have been used to find lung cancer early, but the effects of these screening techniques on lung cancer mortality rates had not been determined. NLST enrolled approximately 54,000 current or former heavy smokers from 33 sites and coordinating centers across the United States.

Learn more about NLST Begin New NLST Project


The Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial is a large-scale, randomized study to determine whether certain screening tests will reduce the number of deaths from these cancers. PLCO is being conducted at ten sites, geographically and demographically disparate, around the U.S. The Trial enrolled approximately 155,000 male and female participants between the ages of 55 and 74 from 1993 to 2001.

Learn more about PLCO Begin New PLCO Project

The CDAS development team would like to acknowledge the National Heart, Lung, and Blood Institute and its BioLINCC Program for the programming code used in the implementation of this website. The CDAS code was based on the BioLINCC framework, which shares many of the same advanced features and a well-defined yet flexible workflow for request submission and fulfillment.