Top Line: Considering the lack of imaging modalities to visualize post-prostatectomy recurrences until very recently, traditional salvage prostate bed radiation volumes were largely borne out of radiographic guesswork.
The Study: Fluciclovine PET/CT recurrences post-prostatectomy in 45 men were used as cases to assess whether adequate coverage would be achieved with traditional 2010 RTOG prostate bed/nodal contouring guidelines versus the newer 2020 GFRU prostate bed / NRG nodal contouring guidelines. Of 30 prostate bed recurrences, RTOG contours covered 20 (67%) versus 27 (90%) with GFRU contours. Of 43 nodal recurrences, RTOG contours covered 29 (67%) versus 43 (100%) with NRG contours. Nearly all marginal and gross prostate bed misses with RTOG volumes occurred at the posterior border, highlighting the superiority of GFRU’s more liberal posterior coverage wrapping around the rectum to the anterior border of the levator ani. Of note here, the GFRU contours are actually less liberal anteriorly compared to RTOG as it uses only the lower two-thirds of—rather than the entire—pubic symphysis as the anterior border, sparing much of the superior bladder trigone. The difference in nodal coverage occurred due to NRG’s more liberal superior / inferior and vascular margin boundary recommendations.
TBL: Be sure to reference the latest 2020 contouring guidelines for your next salvage prostate radiation case. | Harmon, Int J Radiat Oncol Biol Phys 2021