The average nadir for maximal side effects from external beam radiation therapy is 3 years after treatment ends.
I am currently enjoying those maximum side effects a bit more than 3 years after my (80 Gy over 40 treatments) EBRT. (The radiation side effects are much worse now for me than they were immediately after treatment ended) My colon lining is covered with large gas blisters. I have pictures of those my gastroenterologist took 2 months ago when I got a routine colonoscopy. He cut one
open and it deflated.
They are likely the source of my cramping and the continuation of my 'radiation craps', which started a couple of months after I was done with the radiation. My hemorrhoids bleed
profusely every other week as well - much worse than they ever did before. I have adjusted my schedule to accommodate my 'new' (since radiation treatment) bowel habits which remain frequent, loose and explosive when they are not 'radiation craps' (lots of painful effort for very small returns with noticeable quantities of mucous). They are limited to a regular time window, however, so this is not too big a deal. Often delays my morning run with my Labrador, no worse.
Some of the side effects from radiation take a very long time to show up, then take a much longer time to fade away. My doc told me that ADT chemo duration started at 3 years a while back, then they dropped it more and more down to about
3 months, when the stats started looking bad. Since that time, he says, they have been increasing at back upwards. My effective duration was 3 years and it has been very slow recovering from it. Still is. Details below.