Mine emerged a year later -- the side-effect that was most prominent was bladder irritation, which came to my attention with a string of urinary-tract infections and visible blood in my urine, then resulted in a difficult summer where I was nervous leaving the house for long because of bladder issues. At the worst point, I was waking every 20-30 minutes at night. A cystoscopy confirmed that the bottom of my bladder near the prostate looked angry and red compared to the rest, due from the radiation damage. A colonoscopy a year later confirmed the same for my rectum, but that hasn't caused any issue for me, aside from a bit of a mild burn after eating spicy food.

To get it under control, the urology oncologist I was referred to prescribed Myrbetriq (which eliminated most of the issue in a few weeks, once we had the right dose), and I reduced my intake of caffeine and carbonated beverages for a few months. The problem started in the spring, and by fall it was mostly cleared up, so I was able to start titrating off Myrbetriq. I still feel the irritation: it's probably permanent for me, but it's mild and has little impact on my daily life.

Note that long-term irritation is rare. In my case, with stage-4 cancer, it's good that the radiation wasn't overprecise, because that meant the radiation had a chance to attack cancer cells near the prostate as well as those in it. For most people who get urinary-tract irritation and incontinence, it starts a few weeks after radiation therapy and ends within a couple of months, and with proton therapy (which is highly-focused, and thus, wouldn't have been suitable for my stage of cancer), there's a good chance you won't experience it at all.