Urethra-Sparing Stereotactic Body Radiation Therapy for Prostate Cancer: Quality Assurance of a Randomized Phase 2 Trial

Jaccard, Maud; Zilli, Thomas; Dubouloz, A.; Escudé, L.; Jorcano, S.; Linthout, Nadine; Bral, Samuel; Verbakel, Wilko F.A.R.; Bruynzeel, A.; Björkqvist, M.; Minn, Heikki; Tsvang, L.; Symon, Zvi; Lencart, Joana; Oliveira, Â.; Özen, Z.; Abacıoğlu, Ufuk; Pérez-Moreno, Juan María; Rubio, Carmen; Rouzaud, Michel; Miralbell, Raymond

doi:10.1016/j.ijrobp.2020.06.002

Cited by 17 publications

(11 citation statements)

References 42 publications

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“…The alternative approach of placing an IDC is also sometimes deployed for ultrahypofractionated regimens, with some protocols exploring cooling of the urethra. 13 That said, the rate of moderate‐to‐severe GU toxicity appears to be low with RT doses <40 Gy in 5 fractions delivered without any specific urethral sparing. 26 , 27 As such, the main advantages of such an approach are likely to be in emerging indications such as boosting of the dominant intraprostatic nodule (DIL), prostate re‐irradiation and further dose escalation such as on virtual HDR boost protocols.…”

Section: Discussionmentioning

confidence: 99%

“…[10][11][12] With modern intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques combined with online and real-time image-guided radiation therapy (IGRT), the distribution of dose can be controlled so that maximum dose regions do not fall within the prostatic urethral volume whilst still maintaining the minimum therapeutic dose to the entire prostate gland. 13 Historically, the urethra has been a difficult OAR to accurately define for radiotherapy planning purposes. Ultrasound-based studies have shown the cranio-caudal urethral path and prostatic urethral angle can demonstrate considerable anatomical variations between subjects.…”

Section: Introductionmentioning

confidence: 99%

“… 10 , 11 , 12 With modern intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques combined with online and real‐time image‐guided radiation therapy (IGRT), the distribution of dose can be controlled so that maximum dose regions do not fall within the prostatic urethral volume whilst still maintaining the minimum therapeutic dose to the entire prostate gland. 13 …”

Section: Introductionmentioning

confidence: 99%

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Visualising the urethra for prostate radiotherapy planning

Richardson

Skehan

Wilton

et al. 2021

J of Medical Radiation Sci

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Introduction:The prostatic urethra is an organ at risk for prostate radiotherapy with genitourinary toxicities a common side effect. Many external beam radiation therapy protocols call for urethral sparing, and with modulated radiotherapy techniques, the radiation dose distribution can be controlled so that maximum doses do not fall within the prostatic urethral volume. Whilst traditional diagnostic MRI sequences provide excellent delineation of the prostate, uncertainty often remains as to the true path of the urethra within the gland. This study aims to assess if a high-resolution isotropic 3D T2 MRI series can reduce inter-observer variability in urethral delineation for radiotherapy planning. Methods: Five independent observers contoured the prostatic urethra for ten patients on three data sets; a 2 mm axial CT, a diagnostic 3 mm axial T2 TSE MRI and a 0.9 mm isotropic 3D T2 SPACE MRI. The observers were blinded from each other's contours. A Dice Similarity Coefficient (DSC) score was calculated using the intersection and union of the five observer contours vs an expert reference contour for each data set. Results: The mean DSC of the observer vs reference contours was 0.47 for CT, 0.62 for T2 TSE and 0.78 for T2 SPACE (P < 0.001). Conclusions: The introduction of a 0.9 mm isotropic 3D T2 SPACE MRI for treatment planning provides improved urethral visualisation and can lead to a significant reduction in inter-observer variation in prostatic urethral contouring.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Visualising the urethra for prostate radiotherapy planning

Richardson

Skehan

Wilton

et al. 2021

J of Medical Radiation Sci

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“…Electronic submission of DICOM files is requested in order to assess the contouring (target and OAR) and the treatment plan quality, with treatment delivery that can only start after approval [15]. Various studies have shown that protocol deviations occur even in randomized controlled trials [41][42][43]. Worse outcomes have been associated with such deviations [44][45][46][47][48], and well-established RTQA programs help in preventing them [42,49].…”

Section: Discussionmentioning

confidence: 99%

Single-fraction prostate stereotactic body radiotherapy: Dose reconstruction with electromagnetic intrafraction motion tracking

Jaccard

Ehrbar

Miralbell

et al. 2021

Radiotherapy and Oncology

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To reconstruct the dose delivered during single-fraction urethra-sparing prostate stereotactic body radiotherapy (SBRT) accounting for intrafraction motion monitored by intraprostatic electromagnetic transponders (EMT). Methods: We analyzed data of 15 patients included in the phase I/II ''ONE SHOT" trial and treated with a single fraction of 19 Gy to the planning target volume (PTV) and 17 Gy to the urethra planning risk volume. During delivery, prostate motion was tracked with implanted EMT. SBRT was interrupted when a 3mm threshold was trespassed and corrected unless the offset was transient. Motion-encoded reconstructed (MER) plans were obtained by splitting the original plans into multiple sub-beams with isocenter shifts based on recorded EMT positions, mimicking prostate motion during treatment. We analyzed intrafraction motion and compared MER to planned doses. Results: The median EMT motion range (±SD) during delivery was 0.26 ± 0.09, 0.22 ± 0.14 and 0.18 ± 0. 10 cm in the antero-posterior, supero-inferior, and left-right axes, respectively. Treatment interruptions were needed for 8 patients because of target motion beyond limits in the antero-posterior (n = 6) and/or supero-inferior directions (n = 4). Comparing MER vs. original plan there was a median relative dose difference of À1.9% (range, À7.9 to À1.0%) and of +0.5% (À0.3-1.7%) for PTV D 98% and D 2% , respectively. The clinical target volume remained sufficiently covered with a median D 98% difference of À0.3% (À1.6-0.5%). Bladder and rectum dosimetric parameters showed significant differences between original and MER plans, but mostly remained within acceptable limits. Conclusions: The dosimetric impact of intrafraction prostate motion was minimal for target coverage for single-fraction prostate SBRT with real-time electromagnetic tracking combined with beam gating.

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“…Currently, the risk of GI toxicities is further reduced by transperineal insertion of a hydrogel spacer between the rectum and prostate gland [4] , [5] ; however, it is difficult to physically distance the prostatic urinary tract and prostate gland. Thus, urethra-sparing radiation therapy (USRT) using image-guided intensity-modulated radiation therapy (IG-IMRT) may minimize GU toxicities [6] , [7] , [8] . Shimizu et al demonstrated that USRT using IG-IMRT with a small safety margin through a real-time tumor-tracking radiation therapy system achieved a very low incidence of GU toxicities [8] .…”

Section: Introductionmentioning

confidence: 99%