scholarly journals Intrafractional stability of MR-guided online adaptive SBRT for prostate cancer

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
J. Schaule ◽  
M. Chamberlain ◽  
L. Wilke ◽  
M. Baumgartl ◽  
J. Krayenbühl ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Linear Accelerator ◽  
Stereotactic Body Radiation Therapy ◽  
Organs At Risk ◽  
Target Coverage ◽  
Healthy Male ◽  
Mr Images ◽  
Full Compensation ◽  
Online Adaptation ◽  
The Stability

Abstract Background MR-guided online adaptive stereotactic body radiation therapy (SBRT) for prostate cancer aims to reduce toxicity by full compensation of interfractional uncertainties. However, the process of online adaptation currently takes approximately 45 min during which intrafractional movements remain unaccounted for. This study aims to analyze the dosimetric benefit of online adaptation and to evaluate its robustness over the duration of one treatment fraction. Methods Baseline MR-scans at a MR-linear accelerator were acquired for ten healthy male volunteers for generation of mock-prostate SBRT plans with a dose prescription of 5 × 7.25 Gy. On a separate day, online MR-guided adaptation (ViewRay® MRIdian) was performed, and thereafter MR images were acquired every 15 min for 1 h to assess the stability of the adapted plan. Results A dosimetric benefit of online MR-guided adaptive re-planning was observed in 90% of volunteers. The median D95CTV- and D95PTV-coverage was improved from 34.8 to 35.5 Gy and from 30.7 to 34.6 Gy, respectively. Improved target coverage was not associated with higher dose to the organs at risk, most importantly the rectum (median D1ccrectum baseline plan vs. adapted plan 33.3 Gy vs. 32.3 Gy). The benefit of online adaptation remained stable over 45 min for all volunteers. However, at 60 min, CTV-coverage was below a threshold of 32.5 Gy in 30% of volunteers (30.6 Gy, 32.0 Gy, 32.3 Gy). Conclusion The dosimetric benefit of MR-guided online adaptation for prostate SBRT was robust over 45 min in all volunteers. However, intrafractional uncertainties became dosimetrically relevant at 60 min and we therefore recommend verification imaging before delivery of MR-guided online adapted SBRT.

scholarly journals Gantry-Mounted Linear Accelerator–Based Stereotactic Body Radiation Therapy for Low- and Intermediate-Risk Prostate Cancer

2020 ◽  
Vol 5 (3) ◽  
pp. 404-411 ◽  
Author(s):  
Audrey T. Dang ◽  
Rebecca G. Levin-Epstein ◽  
David Shabsovich ◽  
Minsong Cao ◽  
Christopher King ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Radiation Therapy ◽  
Linear Accelerator ◽  
Stereotactic Body Radiation Therapy ◽  
Intermediate Risk ◽  
Stereotactic Body Radiation ◽  
Risk Prostate Cancer

scholarly journals A comparison of robotic arm versus gantry linear accelerator stereotactic body radiation therapy for prostate cancer

2016 ◽  
Vol Volume 8 ◽  
pp. 145-158 ◽  
Author(s):  
Nicholas Zaorsky ◽  
Vladimir Avkshtol ◽  
Yanqun Dong ◽  
Shelly Hayes ◽  
Mark Hallman ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Radiation Therapy ◽  
Linear Accelerator ◽  
Stereotactic Body Radiation Therapy ◽  
Robotic Arm ◽  
Stereotactic Body Radiation

scholarly journals Cone beam CT-based dose accumulation and analysis of delivered dose to the dominant intraprostatic lesion in primary radiotherapy of prostate cancer

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Jörg Tamihardja ◽  
Sinan Cirsi ◽  
Patrick Kessler ◽  
Gary Razinskas ◽  
Florian Exner ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
At Risk ◽  
Organs At Risk ◽  
Peripheral Zone ◽  
Planning System ◽  
Treatment Planning System ◽  
Cone Beam ◽  
Target Coverage ◽  
Dose Accumulation ◽  
Delivered Dose

Abstract Background Evaluation of delivered dose to the dominant intraprostatic lesion (DIL) for moderately hypofractionated radiotherapy of prostate cancer by cone beam computed tomography (CBCT)-based dose accumulation and target coverage analysis. Methods Twenty-three patients with localized prostate cancer treated with moderately hypofractionated prostate radiotherapy with simultaneous integrated boost (SIB) between December 2016 and February 2020 were retrospectively analyzed. Included patients were required to have an identifiable DIL on bi-parametric planning magnetic resonance imaging (MRI). After import into the RayStation treatment planning system and application of a step-wise density override, the fractional doses were computed on each CBCT and were consecutively mapped onto the planning CT via a deformation vector field derived from deformable image registration. Fractional doses were accumulated for all CBCTs and interpolated for missing CBCTs, resulting in the delivered dose for PTVDIL, PTVBoost, PTV, and the organs at risk. The location of the index lesions was recorded according to the sector map of the Prostate Imaging Reporting and Data System (PIRADS) Version 2.1. Target coverage of the index lesions was evaluated and stratified for location. Results In total, 338 CBCTs were available for analysis. Dose accumulation target coverage of PTVDIL, PTVBoost, and PTV was excellent and no cases of underdosage in DMean, D95%, D02%, and D98% could be detected. Delivered rectum DMean did not significantly differ from the planned dose. Bladder mean DMean was higher than planned with 19.4 ± 7.4 Gy versus 18.8 ± 7.5 Gy, p < 0.001. The penile bulb showed a decreased delivered mean DMean with 29.1 ± 14.0 Gy versus 29.8 ± 14.4 Gy, p < 0.001. Dorsal DILs, defined as DILs in the posterior medial peripheral zone of the prostate, showed a significantly lower delivered dose with a mean DMean difference of 2.2 Gy (95% CI 1.3–3.1 Gy, p < 0.001) compared to ventral lesions. Conclusions CBCT-based dose accumulation showed an adequate delivered dose to the dominant intraprostatic lesion and organs at risk within planning limits. Cautious evaluation of the target coverage for index lesions adjacent to the rectum is warranted to avoid underdosage.

scholarly journals Stereotactic Body Radiation Therapy (SBRT) for prostate cancer: Preliminary results of toxicity

2021 ◽  
Vol 93 (3) ◽  
pp. 370-372
Author(s):  
Asmaa Naim ◽  
Safae Mansouri ◽  
Kamal Saidi ◽  
Abdeljalil Heddat ◽  
Younes Elhoury ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Lung Cancer ◽  
Stereotactic Body Radiation Therapy ◽  
Therapeutic Option ◽  
Organs At Risk ◽  
Target Organ ◽  
Localized Prostate Cancer ◽  
External Radiotherapy ◽  
Fractionated Irradiation ◽  
Common Cancer

To the Editor, Prostate cancer is the second most common cancer in men in Morocco after lung cancer. External radiotherapy (RTE) is a curative therapeutic option for localized prostate cancer, However the conventional RTE remains a long treatment (7- 8 weeks, 5 days a week) which is demanding for patients and make difficult to manage the waiting lists. The development of imaging and irradiation techniques over the last decades has allowed a high precision in the delivery of the dose to the target organ and a better protection of the organs at risk (OAR), which has encouraged the hypo fractionated irradiation of localized prostate cancer, especially after the results of radiobiology studies that suggested a low report a/b for the prostate.

scholarly journals Ultra-Hypofractionated Proton Therapy in Localized Prostate Cancer: Passive Scattering versus Intensity-Modulated Proton Therapy

2021 ◽  
Vol 11 (12) ◽  
pp. 1311
Author(s):  
Dorota Maria Borowicz ◽  
Konstantin N. Shipulin ◽  
Gennady V. Mytsin ◽  
Agnieszka Skrobała ◽  
Piotr Milecki ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Proton Therapy ◽  
Organs At Risk ◽  
Localized Prostate Cancer ◽  
Conformity Index ◽  
High Dose ◽  
Target Coverage ◽  
Intensity Modulated Proton Therapy ◽  
Intensity Modulated ◽  
Passive Scattering

Few studies have directly compared passive scattering (PS) to intensity-modulated proton therapy (IMPT) in the delivery of ultra-hypofractionated proton beams to the localized prostate cancer (PCa). In this preliminary study involving five patients previously treated with CyberKnife, treatment plans were created for PS and IMPT (36.25 CGE in five fractions with two opposing fields) to compare the dosimetric parameters to the planning target volume (PTV) and organs-at-risk (OAR: rectum, bladder, femoral heads). Both plans met the acceptance criteria. Significant differences were observed in the minimum and maximum doses to the PTV. The mean dose to the PTV was lower for PS (35.62 ± 0.26 vs. 37.18 ± 0.14; p = 0.002). Target coverage (D98%) was better for IMPT (96.79% vs. 99.10%; p = 0.004). IMPT resulted in significantly lower mean doses to the rectum (16.75 CGE vs. 6.88 CGE; p = 0.004) and bladder (17.69 CGE vs. 5.98 CGE p = 0.002). High dose to the rectum (V36.25 CGE) were lower with PS, but not significantly opposite to high dose to the bladder. No significant differences were observed in mean conformity index values, with a non-significant trend towards higher mean homogeneity index values for PS. Non-significant differences in the gamma index for both fields were observed. These findings suggest that both PS and IMPT ultra-hypofractionated proton therapy for PCa are highly precise, offering good target coverage and sparing of normal tissues and OARs.

scholarly journals Dosimetric comparison of MR-linac-based IMRT and conventional VMAT treatment plans for prostate cancer

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Vanessa Da Silva Mendes ◽  
Lukas Nierer ◽  
Minglun Li ◽  
Stefanie Corradini ◽  
Michael Reiner ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Target Volume ◽  
Planning System ◽  
Treatment Planning System ◽  
Target Coverage ◽  
Treatment Delivery ◽  
Ptv Margin ◽  
Delivery Times ◽  
Low Field ◽  
Treatment Plans

Abstract Background The aim of this study was to evaluate and compare the performance of intensity modulated radiation therapy (IMRT) plans, planned for low-field strength magnetic resonance (MR) guided linear accelerator (linac) delivery (labelled IMRT MRL plans), and clinical conventional volumetric modulated arc therapy (VMAT) plans, for the treatment of prostate cancer (PCa). Both plans used the original planning target volume (PTV) margins. Additionally, the potential dosimetric benefits of MR-guidance were estimated, by creating IMRT MRL plans using smaller PTV margins. Materials and methods 20 PCa patients previously treated with conventional VMAT were considered. For each patient, two different IMRT MRL plans using the low-field MR-linac treatment planning system were created: one with original (orig.) PTV margins and the other with reduced (red.) PTV margins. Dose indices related to target coverage, as well as dose-volume histogram (DVH) parameters for the target and organs at risk (OAR) were compared. Additionally, the estimated treatment delivery times and the number of monitor units (MU) of each plan were evaluated. Results The dose distribution in the high dose region and the target volume DVH parameters (D98%, D50%, D2% and V95%) were similar for all three types of treatment plans, with deviations below 1% in most cases. Both IMRT MRL plans (orig. and red. PTV margins) showed similar homogeneity indices (HI), however worse values for the conformity index (CI) were also found when compared to VMAT. The IMRT MRL plans showed similar OAR sparing when the orig. PTV margins were used but a significantly better sparing was feasible when red. PTV margins were applied. Higher number of MU and longer predicted treatment delivery times were seen for both IMRT MRL plans. Conclusions A comparable plan quality between VMAT and IMRT MRL plans was achieved, when applying the same PTV margin. However, online MR-guided adaptive radiotherapy allows for a reduction of PTV margins. With a red. PTV margin, better sparing of the surrounding tissues can be achieved, while maintaining adequate target coverage. Nonetheless, longer treatment delivery times, characteristic for the IMRT technique, have to be expected.

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