Dear Researchers,

As the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial nears the close of its active follow-up phase, we are writing to share important updates regarding the future of the samples in the PLCO biorepository and to notify you of a research opportunity involving PLCO samples.

PLCO currently holds approximately 3.4 million biospecimen vials (0.2 to 1.8 ml), representing one of the most deeply characterized population-based resources available for cancer research. However, as we plan for the long-term sustainability of this resource, we must reduce the volume of specimens stored. This culling effort is essential to manage rising storage costs and to free up freezer space for samples from new and ongoing NCI-supported studies.

Culling Overview

Our goal is to reduce the biorepository to approximately 1.9 million vials by Spring 2026. This will be achieved through two types of removals: 1. Samples with quality or consent-related problems will be discarded outright. These include broken or contaminated vials, samples with missing or invalid participant identifiers, and specimens collected without adequate consent. 2. Excess samples that are scientifically usable but unlikely to be needed in the future will also be removed. These include multiple vials of the same material type from participants who did not develop cancer during follow-up.

Repurposing Opportunity

Importantly, these “excess” samples will be made available to the scientific community for repurposing. All repurposed samples will be from PLCO participants who did not develop cancer during follow-up, except for red blood cells and whole blood samples collected at year 3, for which case samples will be available. The following sample types will be repurposed: • Red blood cells (multiple timepoints): ~161,000 vials • Whole blood (T3, cases and non-cases): ~360,000 vials • Buffy coat: ~51,000 vials • Serum (multiple timepoints, including zinc-free serum): ~155,000 vials • Plasma (multiple timepoints, Sodium heparin and EDTA): ~210,000 vials

Demographic and clinical data associated with the samples will be available for download or upon request via a data only request process. Details are available on the Cancer Data Access System (CDAS) PLCO website at https://cdas.cancer.gov/plco/.

Proposal Submission and Eligibility Criteria

Researchers interested in applying for these samples should prepare a brief description of the sample types requested and the intended purpose of the request. This proposal should be submitted through the PLCO website (https://cdas.cancer.gov/learn/plco/instructions/?type=eems) and given a title that starts with the term “Repurposing:”.

To ensure scientific value and operational feasibility, we will prioritize sample repurposing proposals that meet the following criteria: • Submitted by a credible investigator or research group • Include a minimum request of 2,000 samples (larger requests encouraged) • Have simple or no matching criteria • Demonstrate capacity to receive and store biospecimens • Commit to receiving samples by Spring 2026 • Provide a short scientific justification for sample use

If the proposal is approved, NCI will cover costs associated with pulling and shipping samples and will initiate a material transfer agreement (MTA).

If you have questions about the proposal process, you can submit your inquiries through the CDAS website (https://cdas.cancer.gov/) using the “contact us” link. Please select “PLCO” then “Biospecimen availability” from the subject and topic dropdowns and note that you are asking about “Repurposing” in the first sentence of your message.

Timeline

Proposal submissions will be accepted through December 2025, with final decisions made in January 2026. Sample pulls and shipments will occur in the Spring of 2026.

We recognize the extraordinary contributions of PLCO participants and are committed to maximizing the long-term value of their donated specimens. We hope this repurposing initiative will enable a new wave of discovery built on the foundation PLCO has laid.