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Alexei Trofimov – One of the best experts on this subject based on the ideXlab platform.

  • MO-A-213AB-09: Hypofractionated Proton Therapy of the Prostate: The Impact of the Uncertainties in Dose Delivery and Alpha/Beta Ratio on Tumor Dose Escalation.
    Medical physics, 2012
    Co-Authors: Yi Wang, Alexei Trofimov

    Abstract:

    Hypofractionation is expected to improve therapeutic Ratio for prostate radiotherapy, due to the relatively low alpha/beta Ratio of the prostate tumor (∼1.2 to 2.0 Gy). However, the gain in tumor equivalent dose in 2-Gy fractions (EQD2) is accompanied by the increased uncertainty in delivered dose due to inter-fractional variations. The purpose of this study is to evaluate how this trade-off is affected by the uncertainty of the tumor alpha/beta.
    We used serial CT images acquired from two prostate cancer patients. Target and normal organs were contoured on the simulation and daily images. A 3D conformal proton plan was designed based on standard fractionation (78 Gy in 39 fractions) and renormalized for hypofractionation (between 5 and 28 fractions). The fraction size of the hypofractionated protocols was adjusted so as to maintain the maximum rectal dose at 78 Gy-EQD2 (alpha/beta = 3 Gy). The fractional dose, calculated on each daily CT, was mapped to the simulation geometry via deformable registRation. The worst-case-scenario PTV dose for a hypofractionated protocol was estimated by summing the fractions (e.g., 28) with the lowest D97%. The target dose (e.g., D100%) was evaluated for alpha/beta of 1.2 to 2.0 Gy.
    The dose delivery uncertainty due to inter-fractional motion increased as the treatment became more hypofractionated. D100% was<78 Gy-EQD2 for protocols with 28, 26, 23 and 20 fractions when alpha/beta was >1.25, 1.46, 1.68 and 1.84 Gy, respectively. At alpha/beta of 2 Gy (1.2 Gy), D99% ranged from ∼79 (81) to 85 (98) Gy-EQD2 for treatments in 28 to 5 fractions. Below D97%, the target dose was predominantly determined by alpha/beta, and the motion impact was minimal.
    In prostate treatments, the impact of inter-fractional motion on tumor dose escalation is small for alpha/beta <2.0 Gy, and is of minimal concern to hypofractionated proton therapy. This study was supported by the Federal Share of program income earned by Massachusetts General Hospital on C06-CA059267, Proton Therapy Research and Treatment Center.
    © 2012 American Association of Physicists in Medicine.

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  • MO-A-213AB-09: Hypofractionated Proton Therapy of the Prostate: The Impact of the Uncertainties in Dose Delivery and Alpha/Beta Ratio on Tumor Dose Escalation.
    Medical Physics, 2012
    Co-Authors: Yi Wang, Alexei Trofimov

    Abstract:

    Purpose: Hypofractionation is expected to improve therapeutic Ratio for prostate radiotherapy, due to the relatively low alpha/beta Ratio of the prostate tumor (∼1.2 to 2.0 Gy). However, the gain in tumor equivalent dose in 2‐Gy fractions (EQD2) is accompanied by the increased uncertainty in delivereddose due to inter‐fractional variations. The purpose of this study is to evaluate how this trade‐off is affected by the uncertainty of the tumor alpha/beta. Methods: We used serial CTimages acquired from two prostate cancer patients. Target and normal organs were contoured on the simulation and daily images. A 3D conformal proton plan was designed based on standard fractionation (78 Gy in 39 fractions) and renormalized for hypofractionation (between 5 and 28 fractions). The fraction size of the hypofractionated protocols was adjusted so as to maintain the maximum rectal dose at 78 Gy‐EQD2 (alpha/beta = 3 Gy). The fractional dose, calculated on each daily CT, was mapped to the simulation geometry via deformable registRation. The worst‐case‐scenario PTV dose for a hypofractionated protocol was estimated by summing the fractions (e.g., 28) with the lowest D97%. The target dose (e.g., D100%) was evaluated for alpha/beta of 1.2 to 2.0 Gy. Results: The dosedelivery uncertainty due to inter‐fractional motion increased as the treatment became more hypofractionated. D100% was 1.25, 1.46, 1.68 and 1.84 Gy, respectively. At alpha/beta of 2 Gy (1.2 Gy), D99% ranged from ∼79 (81) to 85 (98) Gy‐EQD2 for treatments in 28 to 5 fractions. Below D97%, the target dose was predominantly determined by alpha/beta, and the motion impact was minimal. Conclusions: In prostate treatments, the impact of inter‐fractional motion on tumordose escalation is small for alpha/beta

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Yi Wang – One of the best experts on this subject based on the ideXlab platform.

  • MO-A-213AB-09: Hypofractionated Proton Therapy of the Prostate: The Impact of the Uncertainties in Dose Delivery and Alpha/Beta Ratio on Tumor Dose Escalation.
    Medical physics, 2012
    Co-Authors: Yi Wang, Alexei Trofimov

    Abstract:

    Hypofractionation is expected to improve therapeutic Ratio for prostate radiotherapy, due to the relatively low alpha/beta Ratio of the prostate tumor (∼1.2 to 2.0 Gy). However, the gain in tumor equivalent dose in 2-Gy fractions (EQD2) is accompanied by the increased uncertainty in delivered dose due to inter-fractional variations. The purpose of this study is to evaluate how this trade-off is affected by the uncertainty of the tumor alpha/beta.
    We used serial CT images acquired from two prostate cancer patients. Target and normal organs were contoured on the simulation and daily images. A 3D conformal proton plan was designed based on standard fractionation (78 Gy in 39 fractions) and renormalized for hypofractionation (between 5 and 28 fractions). The fraction size of the hypofractionated protocols was adjusted so as to maintain the maximum rectal dose at 78 Gy-EQD2 (alpha/beta = 3 Gy). The fractional dose, calculated on each daily CT, was mapped to the simulation geometry via deformable registRation. The worst-case-scenario PTV dose for a hypofractionated protocol was estimated by summing the fractions (e.g., 28) with the lowest D97%. The target dose (e.g., D100%) was evaluated for alpha/beta of 1.2 to 2.0 Gy.
    The dose delivery uncertainty due to inter-fractional motion increased as the treatment became more hypofractionated. D100% was<78 Gy-EQD2 for protocols with 28, 26, 23 and 20 fractions when alpha/beta was >1.25, 1.46, 1.68 and 1.84 Gy, respectively. At alpha/beta of 2 Gy (1.2 Gy), D99% ranged from ∼79 (81) to 85 (98) Gy-EQD2 for treatments in 28 to 5 fractions. Below D97%, the target dose was predominantly determined by alpha/beta, and the motion impact was minimal.
    In prostate treatments, the impact of inter-fractional motion on tumor dose escalation is small for alpha/beta <2.0 Gy, and is of minimal concern to hypofractionated proton therapy. This study was supported by the Federal Share of program income earned by Massachusetts General Hospital on C06-CA059267, Proton Therapy Research and Treatment Center.
    © 2012 American Association of Physicists in Medicine.

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  • MO-A-213AB-09: Hypofractionated Proton Therapy of the Prostate: The Impact of the Uncertainties in Dose Delivery and Alpha/Beta Ratio on Tumor Dose Escalation.
    Medical Physics, 2012
    Co-Authors: Yi Wang, Alexei Trofimov

    Abstract:

    Purpose: Hypofractionation is expected to improve therapeutic Ratio for prostate radiotherapy, due to the relatively low alpha/beta Ratio of the prostate tumor (∼1.2 to 2.0 Gy). However, the gain in tumor equivalent dose in 2‐Gy fractions (EQD2) is accompanied by the increased uncertainty in delivereddose due to inter‐fractional variations. The purpose of this study is to evaluate how this trade‐off is affected by the uncertainty of the tumor alpha/beta. Methods: We used serial CTimages acquired from two prostate cancer patients. Target and normal organs were contoured on the simulation and daily images. A 3D conformal proton plan was designed based on standard fractionation (78 Gy in 39 fractions) and renormalized for hypofractionation (between 5 and 28 fractions). The fraction size of the hypofractionated protocols was adjusted so as to maintain the maximum rectal dose at 78 Gy‐EQD2 (alpha/beta = 3 Gy). The fractional dose, calculated on each daily CT, was mapped to the simulation geometry via deformable registRation. The worst‐case‐scenario PTV dose for a hypofractionated protocol was estimated by summing the fractions (e.g., 28) with the lowest D97%. The target dose (e.g., D100%) was evaluated for alpha/beta of 1.2 to 2.0 Gy. Results: The dosedelivery uncertainty due to inter‐fractional motion increased as the treatment became more hypofractionated. D100% was 1.25, 1.46, 1.68 and 1.84 Gy, respectively. At alpha/beta of 2 Gy (1.2 Gy), D99% ranged from ∼79 (81) to 85 (98) Gy‐EQD2 for treatments in 28 to 5 fractions. Below D97%, the target dose was predominantly determined by alpha/beta, and the motion impact was minimal. Conclusions: In prostate treatments, the impact of inter‐fractional motion on tumordose escalation is small for alpha/beta

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Joost J. M. E. Nuyttens – One of the best experts on this subject based on the ideXlab platform.

  • predicting high grade esophagus toxicity after treating central lung tumors with stereotactic radiation therapy using a normal tissue complication probability model
    International Journal of Radiation Oncology Biology Physics, 2020
    Co-Authors: Marloes Duijm, Noelle C Van Der Voort Van Zyp, Paul Van De Vaart, Esther Oomende Hoop, Mirjam E Mast, Mischa S Hoogeman, Joost J. M. E. Nuyttens

    Abstract:

    PURPOSE: The treatment of central lung tumors with stereotactic body radiation therapy (SBRT) is challenged by the risk of excessive esophageal toxicity. To improve clinical decision making, we aimed to derive normal tissue complication probability (NTCP) models in a patient cohort with central lung tumors treated with SBRT and to evaluate the currently used esophagus dose constraints. METHODS AND MATERIALS: Patients with a central lung tumor who received SBRT (8 fractions of 7.5 Gy or 12 fractions of 5 Gy) were included. Doses were recalculated to an equivalent dose of 2 Gy with an alpha/beta-Ratio of 10 Gy for acute and 3 Gy for late toxicity (the cut-off was 3 months). The esophagus was manually delineated. NTCP modeling based on logistic regression was used to relate dose-volume histogram parameters (Dmax, D1cc, D2cc, D5cc) to acute and late toxicity. Parameters with a P < .05 were included in the model. Based on the NTCP models, we determined the probability of toxicity for the currently used dose constraints: D1cc

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