Based on this Polymarket:

This market will resolve to "Yes" if definitive evidence confirming that Joe Biden was diagnosed with prostate cancer during his presidency (January 20, 2021, to January 20, 2025) is made public by July 31, 2025, 11:59 PM ET. Otherwise, this market will resolve to "No".

Statements from Joe Biden, his personal office, or doctors who treated Biden during his presidency, confirming a prostate cancer diagnosis during his presidency will qualify for a “Yes” resolution.

Unverified allegations, anonymous claims, or documents not substantiated by credible reporting will not qualify.

The primary resolution source will be a consensus of credible reporting, as well as official statements from Joe Biden’s office, medical professionals involved in his care, or U.S. government sources.

This market will resolve identically to the Polymarket unless it is a clear misresolution.