The FDA regulates blood donation for all blood centers in the U.S., Red Cross (about
50% of centers) and independent centers (the other 50%). The eligibility requirements are that you wait one year from the end of treatment, for example, surgery or seed implants, and that there be no recurrence or further treatment.
I have been a regular blood donor for many years and celebrated my one-year anniversary of prostatectomy in June 2007 by donating blood. Regrettably, I was booted off the national Bone Marrow Donor registry, which is a lifetime ban after prostate cancer diagnosis.
It goes without saying that you have to meet all the other eligibility requirements.