When treating prostate cancer with moderate hypo-fractionation, what urethral dose constraints do you consider when boosting the dominate intraprostatic lesion?  

At this point in time, I don't think there is a good answer to this question. The CHHiP trial, which led to the adoption of the 60 Gy in 3 Gy fraction schedule, did not have a dose constraint for the urethra. The FLAME trial, which demonstrated safety and efficacy for an SIB to a dominant intraprost...

As Dr. @Anscher mentions, the FLAME protocol did not utilize a urethral constraint; however, in a post hoc analysis, they did suggest a constraint of D0.01cc ≤ 80 Gy in 35 fractions (Groen et al., PMID 34968470). It is hard to know how to apply this given the uncertainty regarding the approp...

I reference the NRG-GU010 protocol, which limits 0.03 cc to 107% of the prescription dose, though 110% is an acceptable variation. This constraint exists for the bladder, rectum, and urethra when prescribing a simultaneous boost to the dominant intraprostatic lesion. In practice, when prescribing 70...