What does it mean when blood comes out of my penis. I had radiation therapy prior to removal of cancerous prostate and bladder.

Get it evaluated. After radiation some local irritation is present in tissues near prostate location, including bladder, urethra or rectum. If you are on blood thinners, sometimes blood is seen in urine or rectum. Often transient or self limited. However, blood in urine can be sign of other bad things like bladder tumor, or other conditions like one passing a kidney stone etc. Get it evaluated.
Concerning . This is an alarming sign that could be related to radiation therapy or related to cancer and needs urgent evaluation in ED if significant active bleeding still occurring.