Hydrogel spacer distribution within the perirectal space in patients undergoing radiotherapy for prostate cancer: Impact of spacer symmetry on rectal dose reduction and the clinical consequences of hydrogel infiltration into the rectal wall

Fischer‐Valuck, Benjamin W.; Chundury, Anupama; Bosch, Walter; Michalski, Jeff M.

doi:10.1016/j.prro.2016.10.004

Cited by 66 publications

(70 citation statements)

References 15 publications

(28 reference statements)

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“…While the hydrogel placement in the first two patients exhibited a degree of asymmetry, it became increasing symmetric with each successive patient. Fischer-Valuck et al have reported that significant reduction of rectal dose can still be achieved even with asymmetric hydrogel spacer placement [29] and this was also observed in our study.…”

Section: Discussionsupporting

confidence: 90%

Efficacy of a rectal spacer with prostate SABR—first UK experience

King¹,

Osman

Fairmichael

et al. 2018

The British Journal of Radiology

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Section: Discussionsupporting

confidence: 90%

Efficacy of a rectal spacer with prostate SABR—first UK experience

King¹,

Osman

Fairmichael

et al. 2018

The British Journal of Radiology

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“…Our data are consistent with previous comparisons of IMRT with IMPT in demonstrating rectal dose reduction with biodegradable spacers. Absolute reductions of 8% to 10% were achieved for rectal V70 after spacer placement, with V70 values of 10% to 14% without a spacer versus 2% to 4% with a spacer [13][14][15]17]. We found that the rectal V70 without a spacer was 8.5% to 10% depending on the proton modality used and 1.5% with a spacer.…”

Section: Discussionmentioning

confidence: 86%

“…The 2 primary proton modalities, passive scattering proton therapy (PSPT) and intensity-modulated proton therapy (IMPT), have been compared for their relative ability to spare the rectum [10,11]. An emerging approach aimed at further rectal sparing involves the use of biodegradable hydrogel spacers that physically displace the prostate from the rectal wall during treatment [11][12][13][14][15][16]. In one randomized trial, use of such a spacer led to a relative reduction in mean rectal V70 of 74% [17].…”

Section: Introductionmentioning

confidence: 99%

Hydrogel Spacer Reduces Rectal Dose during Proton Therapy for Prostate Cancer: A Dosimetric Analysis

Polamraju

Bagley

Williamson

et al. 2019

International Journal of Particle Therapy

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Purpose: Proton therapy for prostate cancer may reduce bowel dose and risk of bowel symptoms relative to photon-based methods. Here, we determined the effect of using a biodegradable, injectable hydrogel spacer on rectal dose on plans for treating prostate cancer with intensity-modulated proton therapy (IMPT) or passive scattering proton therapy (PSPT). Materials and Methods: Pairs of IMPT and PSPT plans for 9 patients were created from fused computed tomography/magnetic resonance imaging scans obtained before and after spacer injection. Calculated values of rectal V40, V60, V70, V80, and maximum dose (Dmax) were compared with Wilcoxon signed rank tests. Displacements at the base (BP), midgland (MP), and apex (AP) of the prostate relative to the anterior rectal wall with the spacer in place were averaged for each patient and correlated with V70 by using linear regression models. Results: The presence of a spacer reduced all dosimetric parameters for both PSPT and IMPT, with the greatest difference in V70, which was 81.1% lower for PSPT-with-spacer than for IMPT-without-spacer. Median displacements at BP, MP, and AP were 12 mm (range 7-19), 2 mm (range 0-4), and 1 mm (range 0-5) without the spacer and 19 mm (range 12-23), 10 mm (range 8-16), and 7 mm (range 2-12) with the spacer. Modest linear trends were noted between rectal V70 and displacement for IMPT-with-spacer and PSPT-with-spacer. When displacement was ≥8 mm, V70 was ≤5.1% for IMPT-with-spacer and PSPT-with-spacer. Conclusion: Use of biodegradable hydrogel spacers for prostate cancer treatment provides a significant reduction of radiation dose to the rectum with proton therapy. Significant reductions in rectal dose occurred in both PSPT and IMPT plans, with the greatest reduction for IMPT-with-spacer relative to PSPT alone. Prospective studies are ongoing to assess the clinical impact of reducing rectal dose with hydrogel spacers.

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“…There is literature to suggest that a learning curve exists in regard to the uniformity and symmetry of SpaceOAR insertion. 21,22 The SpaceOAR cohort examined in our study were all reviewed and deemed to be of acceptable quality by the treating physician. No SpaceOAR patients were excluded from the trial due to poor insertion quality or adverse events.…”

Section: Limitationsmentioning

confidence: 99%

Rectal protection in prostate stereotactic radiotherapy: a retrospective exploratory analysis of two rectal displacement devices

Wilton

Richardson

Keats³

et al. 2017

J of Medical Radiation Sci

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IntroductionHigh rectal doses are associated with increased toxicity. A rectal displacement device (RDD) reduces rectal dose in prostate stereotactic body radiation therapy (SBRT). This study investigates any dosimetric difference between two methods of rectal displacement (Rectafix and SpaceOAR) for prostate SBRT.MethodsRectal dosimetry of 45 men who received SBRT within the PROMETHEUS trial was retrospectively examined, across two radiation therapy centres using the two RDD's. Men received a total dose (TD) of 19 or 20 Gy in two fractions followed by 46 Gy in 23 fractions. Centre 1 contributed 16 Rectafix and 10 SpaceOAR patients. Centre 2 contributed 19 Rectafix patients. Rectal dose volume histogram (DVH) data were recorded as a TD percentage at the following volume intervals; V1%, V2%, V5%, V10% and then 10% increments to V80%. As only one centre employed both RDD's, three sequential rectal dosimetry comparisons were performed; (1) centre 1 Rectafix versus centre 1 SpaceOAR; (2) centre 1 Rectafix versus centre 2 Rectafix and (3) centre 1+ centre 2 Rectafix versus centre 1 SpaceOAR.ResultsIn comparison (1) Rectafix demonstrated lower mean doses at 9 out of 11 measured intervals (P = 0.0012). Comparison (2) demonstrated a moderate difference with centre 2 plans producing slightly lower rectal doses (P = 0.013). Comparison (3) further demonstrated that Rectafix returned lower mean doses than SpaceOAR (P < 0.001). Although all dose levels were in favour of Rectafix, in absolute terms differences were small (2.6–9.0%).ConclusionsIn well‐selected prostate SBRT patients, Rectafix and SpaceOAR RDD's provide approximately equivalent rectal sparing.

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Hydrogel spacer distribution within the perirectal space in patients undergoing radiotherapy for prostate cancer: Impact of spacer symmetry on rectal dose reduction and the clinical consequences of hydrogel infiltration into the rectal wall

Abstract: Significant reduction of rectal dose can still be achieved even in the setting of asymmetric hydrogel spacer placement. RWI does not correlate with patient complications.

Cited by 66 publications

References 15 publications

Efficacy of a rectal spacer with prostate SABR—first UK experience

Efficacy of a rectal spacer with prostate SABR—first UK experience

Hydrogel Spacer Reduces Rectal Dose during Proton Therapy for Prostate Cancer: A Dosimetric Analysis

Rectal protection in prostate stereotactic radiotherapy: a retrospective exploratory analysis of two rectal displacement devices

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