Top Line: Does simultaneous elective pelvic lymph node treatment increase toxicity from 5-fraction prostate SBRT?
The Study: Early phase clinical trials (SATURN and pHART8, UTSW) have evaluated 5-fraction elective pelvic lymph node (PLN) radiation when delivering SBRT for prostate cancer. While toxicity data has been encouraging, these trials were fairly small. Here’s a larger retrospective study from Tata Memorial Centre of 220 patients treated with either prostate-only (PO) SBRT (53.6%) or “whole pelvis” (WP) SBRT (46.4%). In the PO-SBRT cohort, most patients had high risk disease (60%). Most patients in the prostate-only cohort had high risk, node negative disease (60%), while everyone in the prostate and PLN cohort had either node positive (79%) or high risk (21%) disease. Most patients received 36.25 Gy (35-37.5 Gy) to the prostate and 25 Gy to the pelvis all in 5 fractions (OAR constraints listed in the manuscript). A few patients received 30-35 Gy to gross nodal disease. No patients had rectal spacers. Acute and late grade 3 events were rare (<3%), however there were more notable differences in grade 2 toxicity. Acute grade 2 GU toxicity was numerically higher with pelvic RT (36.3% v 25.9%), and acute grade 2 GI toxicity was more than doubled (29.4% v 14.7%). In contrast, the rate of late grade 2 GU toxicity was significantly higher after pelvic RT (45.6% v 25.0%) while late grade 2 GI toxicity was similar (18.9% v 13.4%). What the study doesn’t tell us is whether better outcomes are worth the increased toxicity.
TBL: Simultaneously treating pelvic lymph nodes during 5-fraction SBRT for prostate cancer significantly increases acute grade 2 GI toxicity and late grade 2 GU toxicity.
- Murthy, Int J Radiat Oncol Biol Phys 2022