Dr. @Parikh is correct, in the North American trials prostate has been included in the lower dose CTV on grounds that urethral and prostatic stroma can both be involved and to recapitulate surgical treatment where the prostate would be removed with the cystoprostatectomy. A study in PRO last ye...

The concept is that the prostatic urethra has transitional cells and is potentially at risk. I presume there are some surgical series showing some cancer cells in there and thus the dogma was to treat. However, I do not treat it unless I have some suspicion that there is cancer there. It is obv...