On pelvic tilt.
Top Line: How do international experts approach SBRT re-irradiation in the pelvis?
The Study: Funny you should ask. Here’s a Delphi consensus from 23 international experts in the field who went through dozens of “statements” about pelvic re-irradiation for SBRT to find common ground. Statements were considered a consensus when there was at least 75% agreement. There were many practical consensus statements including don’t SBRT something invading into a luminal organ, but what we really wanna know are the prescription doses and cumulative OAR dose limits. “Acceptable” schedules included 30-37.5 Gy in 5-6 fractions or 21-27 Gy in 3 fractions. Consensus was only reached for dose limits to the bladder and cauda equina/sacral plexus. Twelve months after prior RT, the bladder may receive up to a maximum cumulative EQD2(3) of 110 Gy to 0.5 cc (this didn’t reach consensus, but max cumulative bladder dose should be limited to 80 Gy EQD2(3) to 0.5 cc if assuming no recovery). If not accounting for recovery, the cauda equina and sacral plexus should receive no more than a cumulative 67 Gy(2) EQD2 to 0.1 cc (this didn’t reach consensus, but after 12 months, the cauda equina and sacral plexus cumulative max dose can be limited to 85 Gy(2) EQD2 to 0.1 cc). What about bowel dose, though? There was majority agreement, but not consensus regarding cumulative small bowel and colon/rectum doses. Most agreed that small bowel should be limited to a cumulative max dose of 70 Gy(3) EQD2 to 0.5cc if assuming no recovery and up to 90 Gy(3) EQD2 to 0.5 cc after 12 months since prior RT. Most agreed that the colon/sigmoid/rectum should be limited to a cumulative max dose of 80 Gy(3) EQD2 to 0.5 cc if assuming no recovery and up to 100 Gy(3) EQD2 to 0.5 cc after 12 months since prior RT.
TBL: These expert consensus statements should help guide you in the considering pelvic SBRT re-irradiation. | Slevin, Radiother Oncol 2021