PD15-12 IMPACT OF MRI DETECTED HYDROGEL SPACER RECTAL WALL INFILTRATION ON RADIATION-RELATED TOXICITY FOLLOWING 5-FRACTION PROSTATE STEREOTACTIC BODY RADIATION THERAPY

Abstract

You have accessJournal of UrologyCME1 Apr 2023PD15-12 IMPACT OF MRI DETECTED HYDROGEL SPACER RECTAL WALL INFILTRATION ON RADIATION-RELATED TOXICITY FOLLOWING 5-FRACTION PROSTATE STEREOTACTIC BODY RADIATION THERAPY Jonathan W. Lischalk, Jonathan A. Haas, Vianca Santos, Christopher Mendez, Astrid Sanchez, Ankur Doshi, David Sadowsky, Samir S. Taneja, Aaron Katz, and Angela Tong Jonathan W. LischalkJonathan W. Lischalk More articles by this author , Jonathan A. HaasJonathan A. Haas More articles by this author , Vianca SantosVianca Santos More articles by this author , Christopher MendezChristopher Mendez More articles by this author , Astrid SanchezAstrid Sanchez More articles by this author , Ankur DoshiAnkur Doshi More articles by this author , David SadowskyDavid Sadowsky More articles by this author , Samir S. TanejaSamir S. Taneja More articles by this author , Aaron KatzAaron Katz More articles by this author , and Angela TongAngela Tong More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003262.12AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: The use of rectal spacers in the treatment of localized prostate cancer treated with definitive radiotherapy has revolutionized the ability to minimize radiation dose to the rectum. In the present study, we investigate MRI identified rectal wall involvement and the subsequent clinical manifestations following prostate SBRT. METHODS: We identified all patient treated with 5-fraction SBRT for localized prostate cancer from 1/2020 to 9/2021 who underwent pre-treatment hydrogel rectal spacer placement. All MRIs were evaluated for the following spacer parameters: prostate-rectal distance, symmetry, and degree of rectal wall infiltration. Prostate-rectal distance was measured at the level of the prostatic apex, midgland, and base. Symmetry of rectal spacer was measured using right or left lateralization from midgland. Degree of rectal wall invasion was categorized as follows: none, muscularis, submucosal, and intraluminal. Radiation toxicity was assessed using the Common Terminology Criteria for Adverse Events (CTCAE) v5. RESULTS: A total of 336 patients underwent MRI following hydrogel rectal spacer placement from 1/2020 to 9/2021. The mean prostate-rectal distance measured at the apex, midgland, and base was 9 mm, 11 mm, and 14 mm, respectively. Spacer symmetry relative to midgland was within 0-10 mm in the vast majority of cases (n=289, 86%), and less commonly either 10-20 mm (n=42, 13%) or >20 mm (n=5, 1%). There was no MRI evidence of rectal wall invasion in the bulk of cases (n=229, 68%). For those with any invasion, the spacer commonly infiltrated only into the muscularis (n=83, 25%). However, in the remaining patients there was more dramatic evidence of invasion submucosally (n=21, 6%) or through the entire rectum into the luminal space (n=3, 1%). Of the patients who were found to have submucosal or intraluminal invasion, there were no patients who developed grade 2+ GI toxicity with a median follow up of 10.7 months (sans spacer historical rate of <4%). Of note, the only hydrogel placement parameter found to be significantly different in those patients with submucosal invasion or higher was midgland prostate-rectal distance (13 vs. 11 mm, p=0.04). CONCLUSIONS: Evidence of MRI detected hydrogel spacer rectal wall invasion is common and was observed in 32% of our cohort of 336 patient. However, only 7% of patients demonstrated rectal invasion beyond the muscularis, and in these cases we observed no grade 2 or higher CTCAE GI toxicity. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e423 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Jonathan W. Lischalk More articles by this author Jonathan A. Haas More articles by this author Vianca Santos More articles by this author Christopher Mendez More articles by this author Astrid Sanchez More articles by this author Ankur Doshi More articles by this author David Sadowsky More articles by this author Samir S. Taneja More articles by this author Aaron Katz More articles by this author Angela Tong More articles by this author Expand All Advertisement PDF downloadLoading ...