What is the quality of hydrogel spacer insertions? and which patients will benefit? A literature review

Abstract

Aim: To evaluate the quality of rectal hydrogel spacer (HS) insertions from literature in patients undergoing radical radiotherapy for prostate cancer. The secondary aim is to assess the benefit of HSs in patients with risk factors more likely to have rectal complications, such as non-conventional radiotherapy dose fractionations and high-risk disease. Method and materials: A literature search of peer-reviewed electronic articles was carried out using Boolean connectors and Medical Subject Headings in the databases. Databases searched included ScienceDirect, Medline and Cinahl. The articles were assessed using relevant critical appraisal skills programme tools. Results: From the 26 studies used, HS showed a clinically significant relative reduction in rectal planning dose volumes for both high- and low-risk prostate cancer patients in a range of radiotherapy treatment modalities including volumetric modulated arc therapy, intensity-modulated radiotherapy, intensity-modulated proton therapy, stereotactic ablative body radiotherapy and brachytherapy. Spacer placements were successfully inserted in 99% of patients. However, rectal wall infiltration occurrence was 6% and ≥2 cm unsymmetrical placements in 2%. Findings: A spacer scoring system based on the HS symmetry has provided evidence of the quality of the position inserted, which was visually aided by T2-wieghted MRIs. Despite optimal HS placements ranging from 62 to 72%, HS had a clinically significant reduction of ≥25% in planned rectal V70 dose in 97% of patients.

In regard to ‘What is the quality of hydrogel spacer insertions? and which patients will benefit? A literature review’

“…A literature review' by Drabble and Drury-Smith with great interest. 1 Their conclusions support previous studies assessing the role of hydrogel spacer (HS) in increasing distance between the prostate and rectum, resulting in rectal dose reduction in prostate radiotherapy. Despite many studies that have evaluated the effectiveness of HS insertion in prostate cancer radiotherapy over the last decade, [2][3][4][5] it still remains an active area of research.…”

“…We agree with authors who reported there is conflicting view on the use of HS on highrisk patients. 1 There are three potential routes of tumour spread to the rectal wall, including direct invading through Denonvilliers' fascia and infiltration into the rectum, extension by the lymphatic and seeding on biopsy. 8 It should be noted, however, that Denonvilliers' fascia, as a thick capsule, is an effective barrier for the spread of tumour cells into the rectal wall.…”

SpaceOAR Hydrogel Spacer for Reducing Radiation Toxicity During Radiotherapy for Prostate Cancer. A Systematic Review

“…Nine other reviews were identified during the search, which reported similar findings on the dosimetric and clinical outcomes associated with the use of a perirectal hydrogel spacer. 5,[36][37][38][39][40][41][42][43] Afkhami Ardekani 2019 5 reported on brachytherapy only, including three comparative studies, both in EBRT plus BT (two in HDR-BT 26,27 and one in LDR-BT 29 ), and concluded that the hydrogel spacer significantly reduces rectal dose and toxicity without influencing prostate immobilisation. The most recent systematic literature review that included a metaanalysis, was reported by Miller 2020.…”

Validation of a Quality Metric Score to Assess the Placement of Hydrogel Rectal Spacer in Patients Treated With Prostate Stereotactic Radiation Therapy

“…To evaluate the quality of the rectal spacer implantation, several studies have been focusing on long-term follow-up after radiation therapy for prostate cancer with and without rectal hydrogel spacer. 13 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 As highlighted in a recent review, 25 accurate spacer placement is essential, suggesting the need for quantitative measures evaluating the spacer quality. This study quantitatively measured, using the SQS score, the quality of the hydrogel rectal spacer score placed in the patients and by retrospectively analyzing the dose received by the rectum during prostate SABR treatments.…”

“…The dosimetric benefits associated with injection of hydrogel rectal spacers are well documented within the literature, 12 , 15 , 17 , 26 , 27 , 28 , 29 demonstrating the efficacy of the spacers in reducing the rectal dose during external beam radiation therapy. The value of being able to identify the quality of the inserted hydrogel spacer was mentioned in the review by Drabble et al 25 …”