What high dose rectal constraints do you use when using a hypofractionated prostate regimen?

Of course the answer is different depending on which hypofractionated regimen that you use.

If you are using the CHHiP regimen (60 Gy in 20 fractions) the trial investigators have updated their recommended constraints based on the observed toxicities in the trial.

In a preproof online they have provided a table.

Recommended dose constraints for anorectum

V20 Gy 85%

V30 Gy 57%

V40 Gy 38%

V50 Gy 22%

V60Gy <0.01%

I don't know how one can meet the V60 Gy constraint routinely without cheating the CTV-PTV marg...

When we switched towards hypofractionation for intact prostate cancer (going from 39 fx to 20 fx) we adopted a pragmatic approach towards dose constraints. Our constraints for a 78 Gy prescription [e.g. rectal V70, V65, V40 Gy get <10%, 20%, and 40%] were proportionally matched to a 60 Gy prescription resulting in the table of constraints below. This approach enabled us to push plans in the same fashion and aim for aggressive rectal sparing with the expectation that further sparing of the rectum...