A comparison between hydrogel spacer and endorectal balloon: An analysis of intrafraction prostate motion during proton therapy

Hedrick, Samantha G.; Fagundes, Marcio; Robison, B; Blakey, Marc; Renegar, Jackson; Artz, Mark; Schreuder, Niek

doi:10.1002/acm2.12051

Cited by 30 publications

(25 citation statements)

References 10 publications

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“…The use of hydrogel spacers could serve to move the rectal wall out of the high‐dose region, meaning that the relative dose changes we observe around unplanned gas cavities would result in lower absolute dose increases. Furthermore, using an air‐ or a liquid‐filled EndoRectal Balloon (ERB) to create a planned cavity could potentially avoid large unplanned air cavities forming . Another option could be to employ a new gas‐release balloon, originally designed for proton treatment, which has been seen to reduce the frequency of trapped air …”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, using an air-or a liquid-filled EndoRectal Balloon (ERB) to create a planned cavity could potentially avoid large unplanned air cavities forming. 16,[41][42][43] Another option could be to employ a new gas-release balloon, originally designed for proton treatment, which has been seen to reduce the frequency of trapped air. 44…”

Section: A Implications Of Unplanned Gas In the Rectal Wallmentioning

confidence: 99%

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Assessing localized dosimetric effects due to unplanned gas cavities during pelvic MR‐guided radiotherapy using Monte Carlo simulations

et al. 2019

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Purpose It has been proposed that beam modulation and opposing beam configurations can cancel effects of the Electron Return Effect (ERE) during MR‐guided radiotherapy (MRgRT). However, this may not always be the case for unplanned gas cavities outside of the target in the pelvic region. We evaluate dosimetric effects, including effects in the rectal wall, due to unplanned spherical air cavities during MRgRT. Methods Nine virtual cuboid water phantoms containing spherical air cavities (0.5–7.5 cm diameter) and a reference phantom without air were created. Monte Carlo dose calculations of 7 MV photons under the influence of a 1.5 T transverse magnetic field were produced using Monaco 5.19.02 Treatment Planning System (TPS) (Elekta AB, Stockholm, Sweden). Cavities in the path of a single and multiple beam plans were considered. Dose distributions of phantoms with and without air cavities were compared (ΔD%) using a spherical coordinate system originating in the center of the cavity. Effects in the rectal wall were quantified by comparing dose volume histogram (DVH) parameters for solid and gaseous filling from simulated rectal wall structures. Results Max(ΔD%) of ~70% and 20% were observed around large cavities in the path of a single and multiple beam plans, respectively. Approximately 45 cm3 of phantom surrounding the largest cavity in a single beam received dose changes of >10%. Dmean in the rectal wall was unchanged when comparing gaseous and solid filling in the path of a single beam; however, D1cc and Dmax increased by up to ~45% and ~63%, respectively. Conclusions Unplanned gas cavities in the path of a single beam during pelvic MRgRT with a 1.5 T transverse magnetic field cause dose changes which may impact toxicity in the rectal wall, depending on local dose and fractionation. Effects are reduced but not eliminated with a five‐beam plan.

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Section: Discussionmentioning

confidence: 99%

Section: A Implications Of Unplanned Gas In the Rectal Wallmentioning

confidence: 99%

Assessing localized dosimetric effects due to unplanned gas cavities during pelvic MR‐guided radiotherapy using Monte Carlo simulations

et al. 2019

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“…Reducing the volume of rectum in the intermediate-and high-dose regions by using endorectal balloons has been reported to reduce late rectal toxicities [30]. However, endorectal balloons must be inserted daily for the duration of radiation therapy, which introduces challenges both for patient comfort and treatment logistics [31]. In contrast, injectable tissue spacers require a single injection into the rectoprostatic fascia before starting radiation therapy while also providing a dosimetric benefit to the rectal wall.…”

Section: Discussionmentioning

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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“…Non-metastatic prostate cancer patients are eligible for treatment options, including active surveillance, radical prostatectomy, brachytherapy and external beam radiation with photons or protons Prior to radiation treatment planning, fiducial markers may be placed to permit image-guided treatment using pre-treatment kilovoltage imaging (i.e., standard X-rays) 23 . In addition, a hydrogel spacer may also be inserted prior to CT simulation to create a gap between the rectum and prostate to further limit dose to the rectal tissues 24,25 . During treatment planning, patients should be simulated in the supine position with the pelvis immobilized using a customized cushion device.…”

Section: Representative Resultsmentioning

confidence: 99%

Proton Therapy Delivery and Its Clinical Application in Select Solid Tumor Malignancies

Kaiser

Eley

Onyeuku

et al. 2019

JoVE

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Radiation therapy is a frequently used modality for the treatment of solid cancers. Although the mechanisms of cell kill are similar for all forms of radiation, the in vivo properties of photon and proton beams differ greatly and maybe exploited to optimize clinical outcomes. In particular, proton particles lose energy in a predictable manner as they pass through the body. This property is used clinically to control the depth at which the proton beam is terminated, and to limit radiation dose beyond the target region. This strategy can allow for substantial reductions in radiation dose to normal tissues located just beyond a tumor target. However, the degradation of proton energy in the body remains highly sensitive to tissue density. As a consequence, any changes in tissue density during the course of treatment may significantly alter proton dosimetry. Such changes may occur through alterations in body weight, respiration, or bowel filling/gas, and may result in unfavorable dose deposition. In this manuscript, we provide a detailed method for the delivery of proton therapy using both passive scatter and pencil beam scanning techniques for prostate cancer. Although the described procedure directly pertains to prostate cancer patients, the method may be adapted and applied for the treatment of virtually all solid tumors. Our aim is to equip readers with a better understanding of proton therapy delivery and outcomes in order to facilitate the appropriate integration of this modality during cancer therapy. Video Link The video component of this article can be found at https://www.jove.com/video/58372/ The basic principles behind RT are straightforward. With the application of radiation, energy is deposited into cells through the ionization of atoms. This energy, though it may raise the temperature of an irradiated region by only a few microkelvin, produces free radicals that can directly damage exposed cells by way of DNA injury 12,13. Much of our understanding of high-energy particle radiation and its interaction with matter comes from theoretical and experimental studies of cosmic rays and their interactions in the upper atmosphere carried out in the early 20 th century 14. High-energy (MeV to GeV) charged particles interact with matter primarily via the electromagnetic force: as these particles pass

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A comparison between hydrogel spacer and endorectal balloon: An analysis of intrafraction prostate motion during proton therapy

Cited by 30 publications

References 10 publications

Assessing localized dosimetric effects due to unplanned gas cavities during pelvic MR‐guided radiotherapy using Monte Carlo simulations

Assessing localized dosimetric effects due to unplanned gas cavities during pelvic MR‐guided radiotherapy using Monte Carlo simulations

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

Proton Therapy Delivery and Its Clinical Application in Select Solid Tumor Malignancies

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