Hydrogel rectum-prostate spacers mitigate the uncertainties in proton relative biological effectiveness associated with anterior-oblique beams

Underwood, Tracy; Voog, Justin C.; Moteabbed, M.; Tang, Suqin; Soffen, Edward M.; Cahlon, Oren; Lu, Hsiao‐Ming; Zietman, Anthony L.; Efstathiou, Jason A.; Paganetti, Harald

doi:10.1080/0284186x.2016.1275781

Cited by 14 publications

(11 citation statements)

References 33 publications

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“…Optimization based upon biologically relevant parameters such as LET d is not yet available in clinical treatment planning systems. Consistent with published studies [25][26][27][28][29][30][31] our findings demonstrated that baseof-skull IMPT plans deemed acceptable under the assumption of a fixed RBE (1.1) did not satisfy OAR constraints when variable RBE modeling was applied. We additionally found the impact of variable RBE modeling to be greater than that of the physical 'worst case' analysis.…”

Section: Discussionsupporting

confidence: 88%

“…Proton RBE is also known to depend on the intrinsic biological properties of the irradiated cells and the exact biological endpoint considered (e.g., an endpoint of in vitro clonogenic cell survival versus an endpoint of an in-vivo tissue reaction) [24]. Over recent years, there have been a number of published warnings on the possible impact of LET upon clinical treatment plans, including for prostate [25][26][27][28][29][30][31][32], breast [30], thoracic [27,31], liver [32], head and neck [27,31,33], pituitary [27] and various brain tumors [31,32,[34][35][36]. These studies consistently demonstrate that we cannot assume treatment plans to be robust to uncertainties in proton RBE.…”

Section: Introductionmentioning

confidence: 99%

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The impact of proton LET/RBE modeling and robustness analysis on base-of-skull and pediatric craniopharyngioma proton plans relative to VMAT

Gutiérrez

Rompokos

et al. 2019

Acta Oncologica

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Purpose: Pediatric craniopharyngioma, adult base-of-skull sarcoma and chordoma cases are all regarded as priority candidates for proton therapy. In this study, a dosimetric comparison between volumetric modulated arc therapy (VMAT) and intensity modulated proton therapy (IMPT) was first performed. We then investigated the impact of physical and biological uncertainties. We assessed whether IMPT plans remained dosimetrically superior when such uncertainty estimates were considered, especially with regards to sparing organs at risk (OARs).Methodology: We studied 10 cases: four chondrosarcoma, two chordoma and four pediatric craniopharyngioma. VMAT and IMPT plans were created according to modality-specific protocols. For IMPT, we considered (i) variable RBE modeling using the McNamara model for different values of (α/β)x, and (ii) robustness analysis with ±3 mm set-up and 3.5% range uncertainties.Results: When comparing the VMAT and IMPT plans, the dosimetric advantages of IMPT were clear: IMPT led to reduced integral dose and, typically, improved CTV coverage given our OAR constraints. When physical robustness analysis was performed for IMPT, some uncertainty scenarios worsened the CTV coverage but not usually beyond that achieved by VMAT. Certain scenarios caused OAR constraints to be exceeded, particularly for the brainstem and optical chiasm. However, variable RBE modeling predicted even more substantial hotspots, especially for low values of (α/β)x. Variable RBE modeling often prompted dose constraints to be exceeded for critical structures.Conclusion: For base-of-skull and pediatric craniopharyngioma cases, both physical and biological robustness analyses should be considered for IMPT: these analyses can substantially affect the sparing of OARs and comparisons against VMAT. All proton RBE modeling is subject to high levels of uncertainty, but the clinical community should remain cognizant possible RBE effects. Careful clinical and imaging follow-up, plus further research on end-of-range RBE mitigation strategies such as LET optimization, should be prioritized for these cohorts of proton patients.

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Section: Discussionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

The impact of proton LET/RBE modeling and robustness analysis on base-of-skull and pediatric craniopharyngioma proton plans relative to VMAT

Gutiérrez

Rompokos

et al. 2019

Acta Oncologica

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“…Although only considering ±35 proton beams and only using the Wedenberg model, their conclusion was similar to ours as they also were unable to meet the tumor and rectal constraints for both fixed and variable RBE models. Rectal spacers were not included in the patient cohort in our study, but have been shown to be efficient when using AO fields in treatment of prostate cancer [22]. Hence, for the rectum, this could potentially have improved the outcome of our results (e.g., the D 1cm 3 constraint), which proved to be hard to fulfill when evaluated with the variable RBE models.…”

Section: Discussionmentioning

confidence: 99%

Biological dose and complication probabilities for the rectum and bladder based on linear energy transfer distributions in spot scanning proton therapy of prostate cancer

et al. 2017

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“…Four beams were used to generate a more robust plan for stereotactic radiation delivery. The optimal beam arrangement was determined to be opposed lateral and 2 anterior oblique beams, which have been shown to be more robust to modeled RBE elevations when a spaceOAR is in place [ 36 ]. While patients in this study were treated before spaceOAR was routinely used at our institution, it is expected that spaceOAR would be used if this technique is in use clinically.…”

Section: Methodsmentioning

confidence: 99%

Simulation of an HDR “Boost” with Stereotactic Proton versus Photon Therapy in Prostate Cancer: A Dosimetric Feasibility Study

Remick

Sabouri

Zhu

et al. 2021

International Journal of Particle Therapy

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Purpose/Objectives To compare the dose escalation potential of stereotactic body proton therapy (SBPT) versus stereotactic body photon therapy (SBXT) using high-dose rate prostate brachytherapy (HDR-B) dose-prescription metrics. Patients and Methods Twenty-five patients previously treated with radiation for prostate cancer were identified and stratified by prostate size (≤ 50cc; n = 13, > 50cc; n = 12). Initial CT simulation scans were re-planned using SBXT and SBPT modalities using a prescription dose of 19Gy in 2 fractions. Target coverage goals were designed to mimic the dose distributions of HDR-B and maximized to the upper limit constraint for the rectum and urethra. Dosimetric parameters between SBPT and SBXT were compared using the signed-rank test and again after stratification for prostate size (≤ 50cm3 and >50cm3) using the Wilcoxon rank test. Results Prostate volume receiving 100% of the dose (V100) was significantly greater for SBXT (99%) versus SBPT (96%) (P ≤ 0.01), whereas the median V125 (82% vs. 73%, P < 0.01) and V200 (12% vs. 2%, P < 0.01) was significantly greater for SBPT compared to SBXT. Median V150 was 49% for both cohorts (P = 0.92). V125 and V200 were significantly correlated with prostate size. For prostates > 50cm3, V200 was significantly greater with SBPT compared to SBXT (14.5% vs. 1%, P = 0.005), but not for prostates 50cm3 (9% vs 4%, P = 0.11). Median dose to 2cm3 of the bladder neck was significantly lower with SBPT versus SBXT (9.6 Gy vs. 14 Gy, P < 0.01). Conclusion SBPT and SBXT can be used to simulate an HDR-B boost for locally advanced prostate cancer. SBPT demonstrated greater dose escalation potential than SBXT. These results are relevant for future trial design, particularly in patients with high risk prostate cancer who are not amenable to brachytherapy.

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Hydrogel rectum-prostate spacers mitigate the uncertainties in proton relative biological effectiveness associated with anterior-oblique beams

Abstract: Paganetti (2017) Hydrogel rectum-prostate spacers mitigate the uncertainties in proton relative biological effectiveness associated with anterior-oblique beams, Acta Oncologica, 56:4, 575-581,

Cited by 14 publications

References 33 publications

The impact of proton LET/RBE modeling and robustness analysis on base-of-skull and pediatric craniopharyngioma proton plans relative to VMAT

The impact of proton LET/RBE modeling and robustness analysis on base-of-skull and pediatric craniopharyngioma proton plans relative to VMAT

Biological dose and complication probabilities for the rectum and bladder based on linear energy transfer distributions in spot scanning proton therapy of prostate cancer

Simulation of an HDR “Boost” with Stereotactic Proton versus Photon Therapy in Prostate Cancer: A Dosimetric Feasibility Study

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