If using 26-fraction moderate hypofractionation, what dose do you use for the intraprostatic dominant nodule SIB?

The definition of a nominal prescription dose for a focal boost is a confusing topic as often times the coverage at a given prescription dose is outside the realm of what is usually considered a valid prescription dose (i.e., coverage at a requested prescription dose is < 95%), and a prior thread also discussed the possible challenges of extrapolating this regimen to other fractionation schedules. In their primary publication (Kerkmeijer et al., PMID 33471548) as well as in a secondary publicati...

If giving 70 Gy/28 Fx to the prostate, my default Rx for the DIL is 84 Gy/28 fx, work backward from there if I cannot meet urethra/rectal dose constraints.

Agree with the thorough posts above. In line with trying to avoid toxicity and the absence of data on 26-fx regimens, we currently prescribe prostate to 70.2 in 26 and DIL to 78.

The NRG-GU010 micro boost doses are all aiming for BED3 of 180, so for 26 fractions, that would be 3.3 Gy/fx to a total of 85.8 Gy. In practice though, I have found it rare that we can obtain reasonable coverage at these suggested doses while meeting urethra and rectum constraints; so to help clarify the planning intentions, I have usually asked for 5-10 Gy (cumulative dose) less than these suggested doses, looking for ~70 to 90+ percent coverage, which seems to be in line with Dr. @Dr. First La...