ESTRO 2024 - Abstract Book

S2395

Clinical - Urology

ESTRO 2024

Use of iodinated hydrogel spacer[SpaceOAR Vue] in prostate SABR: rectal dosimetry and acute toxicity

Mohd Samuji 1 , Kevin M Jie Liu 2 , Tom Huxford 1 , Sarah Leonard 1 , Kieran Condon 1 , Eoin Toomey 1 , Karen Molan 1 , Bennett Erica 1 , Paul J Kelly 1 1 Bon Secours Radiotherapy Cork in partnership with UPMC Hillman Cancer Centre, Bon Secours Hospital, Cork, Ireland. 2 University College Cork, College of Medicine and Health, Cork, Ireland

Purpose/Objective:

Hydrogel spacers have the potential to reduce rectal dose and resultant toxicity when placed prior to prostate Stereotactic Ablative Radiotherapy (SABR). Here we retrospectively review prospectively collected rectal dosimetry and acute toxicity in men undergoing prostate SABR who opted for the placement of an iodinated hydrogel spacer, SpaceOAR Vue TM prior to treatment.

Material/Methods:

Between October 2021 and July 2023, 49 men underwent prostate SABR following the placement of a hydrogel spacer simultaneous with fiducial markers. Each patient underwent same-day planning MRI and CT, and all patients were treated as per the PACE-C protocol with CTV dose 40Gy and PTV dose 36.25Gy in 5 fractions. In all cases, prostate SABR was delivered on a Varian Edge with CBCT and fiducial tracking IGRT.

Results:

Median age was 72.2 years and median PSA of this cohort was 7.5. The majority of patients (73%) had Gleason score 3+4=7 adenocarcinoma (Table 1). Median prostate volume was 38.4cc. 18% (N=9) were taking an anti-platelet agent and 10% (N=5) were taking a DOAC at the time of treatment. No patient experienced a significant spacer complication defined as bleed, infection, pain or symptomatic rectal wall infiltration. Device deficiency was noted in 2 cases [gel dispersal]. Asymmetric gel placement was the most frequently noted practical issue.

Median rectal D1cc, D2cc and V50% were 30.2Gy (IQR 4.1), 27.5Gy (IQR 3.8) and 7.9cc (IQR 5.1) respectively. PTV coverage was excellent, median V36.25Gy was 98.8%.

No acute rectal toxicity was reported in 39 patients (80%). 18% experienced RTOG grade 1 acute rectal toxicity. One patient reported a Grade 2 toxicity (diarrhoea). No grade 3 or higher toxicity was observed (Figure 1). No patient developed rectal bleeding.

Table 1 Characteristics of Participants

median

IQR

Age (years)

72.2

5.4