Are there any bladder constraints for preoperative short course rectal RT?

RAPIDO and Myerson paper don’t mention any and it looks like T4 patients were treated, presumably covering external iliacs which would likely have given a significant dose to bladder?

2 Answers

Mednet MemberInvited Expert

Radiation Oncology · Henry Ford Health System

Answered on

While I appreciate thoughts on constraints by Fields et al., PMID 31673654 (14 patients), or even our paper from Myerson et al., PMID 24606849 (76 patients), I think these are superseded by the higher level of evidence from the RAPIDO study (462 patients w/ SCRT).

The RAPIDO study (appendix F, page 82) did not have any bladder or bowel constraints. Nor femur constraints. 3 or 4 field plans.

In routine daily practice, I just make sure there are no hot spots in the bowel.

Mednet Member

Radiation Oncology · Michigan Healthcare Professionals, PC

Answered on

@Dr. First Last has a study for VMAT/IMRT for short course rectal and I use these constraints:

PTV

>98% dose to >93% volume
<10% getting >105%
<5% getting >110%
Max dose of 115%

Bowel

19.5 Gy to <180 mL
22.2 Gy to <100 mL
25 Gy to <65 mL
Max dose of 27.8 Gy

Femoral heads

22.2 Gy to <40%, 25 Gy to <25%
Max dose of 27.8 Gy

Bladder

22.2 Gy to <40%, 25 Gy to <15%
Max dose of 27.8 Gy