The value of a bladder-filling protocol for patients with prostate cancer who receive post-operative radiation: results from a prospective clinical trial

A Smart Water Bottle and Companion App (HidrateSpark 3) to Improve Bladder-Filling Compliance in Patients With Prostate Cancer Receiving Radiotherapy: Nonrandomized Trial of Feasibility and Acceptability

BACKGROUND

Patients with prostate cancer undergoing radiation therapy (RT) need comfortably full bladders to reduce toxicities during treatment. Poor compliance is common with standard of care written or verbal instructions, leading to wasted patient value (PV) and clinic resources via poor throughput efficiency (TE).

OBJECTIVE

Herein, we assessed the feasibility and acceptability of a smartphone-based behavioral intervention (SBI) to improve bladder-filling compliance and methods for quantifying PV and TE.

METHODS

In total, 36 patients with prostate cancer were enrolled in a single-institution, closed-access, nonrandomized feasibility trial. The SBI consists of a fully automated smart water bottle and smartphone app. Both pieces alert the patient to empty his bladder and drink a personalized volume goal, based on simulation bladder volume, 1.25 hours before his scheduled RT. Patients were trained to adjust their volume goal and notification times to achieve comfortably full bladders. The primary end point was met if qualitative (QLC) and quantitative compliance (QNC) were >80%. For QLC, patients were asked if they prepared their bladders before daily RT. QNC was met if bladder volumes on daily cone-beam tomography were >75% of the simulation's volume. The Service User Technology Acceptability Questionnaire (SUTAQ) was given in person pre- and post-SBI. Additional acceptability and engagement end points were met if >3 out of 5 across 4 domains on the SUTAQ and >80% (15/18) of patients used the device >50% of the time, respectively. Finally, the impact of SBI on PV and TE was measured by time spent in a clinic and on the linear accelerator (linac), respectively, and contrasted with matched controls.

RESULTS

QLC was 100% in 375 out of 398 (94.2%) total treatments, while QNC was 88.9% in 341 out of 398 (85.7%) total treatments. Of a total score of 5, patients scored 4.33 on privacy concerns, 4 on belief in benefits, 4.56 on satisfaction, and 4.24 on usability via SUTAQ. Further, 83% (15/18) of patients used the SBI on >50% of treatments. Patients in the intervention arm spent less time in a clinic (53.24, SEM 1.71 minutes) compared to the control (75.01, SEM 2.26 minutes) group (P<.001). Similarly, the intervention arm spent less time on the linac (10.67, SEM 0.40 minutes) compared to the control (14.19, SEM 0.32 minutes) group (P<.001).

CONCLUSIONS

This digital intervention trial showed high rates of bladder-filling compliance and engagement. High patient value and TE were feasibly quantified by shortened clinic times and linac usage, respectively. Future studies are needed to evaluate clinical outcomes, patient experience, and cost-benefit.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04946214; https://www.clinicaltrials.gov/study/NCT04946214.

Target coverage and organs at risk dose in hypofractionated salvage radiotherapy after prostatectomy

Background and purpose

Introducing moderately hypofractionated salvage radiotherapy (SRT) following prostatectomy obligates investigation of its effects on clinical target volume (CTV) coverage and organ-at-risk (OAR) doses. This study assessed interfractional volume and dose changes in OARs and CTV in moderately hypofractionated SRT and evaluated the 8-mm planning target volume (PTV) margin.

Materials and methods

Twenty patients from the PERYTON-trial were included; 10 received conventional SRT (35 × 2 Gy) and 10 hypofractionated SRT (20 × 3 Gy). OARs were delineated on 539 pre-treatment Cone Beam CT (CBCT) scans to compare interfractional OAR volume changes. CTVs for the hypofractionated group were delineated on 199 CBCTs. Dose distributions with 4 and 6 mm PTV margins were generated using voxel-wise minimum robustness evaluation of the original 8-mm PTV plan, and dose changes were assessed.

Results

Median volume changes for bladder and rectum were -26 % and -10 %, respectively. OAR volume changes were not significantly different between the two treatment schedules. The 8-mm PTV margin ensured optimal coverage for prostate bed and vesicle bed CTV (V95 = 100 % in >97 % fractions). However, bladder V60 <25 % was not achieved in 5 % of fractions, and rectum V60 <5 % was unmet in 33 % of fractions. A 6-mm PTV margin resulted in CTV V95 = 100 % in 92 % of fractions for prostate bed, and in 86 % for vesicle bed CTV.

Conclusions

Moderately hypofractionated SRT yielded comparable OAR volume changes to conventionally fractionated SRT. Interfractional changes remained acceptable with a PTV margin of 6 mm for prostate bed and 8 mm for vesicle bed.

Influence of air mapping errors on the dosimetric accuracy of prostate CBCT-guided online adaptive radiation therapy

PURPOSE

CBCT-guided online adaptive radiotherapy (oART) plans presently utilize daily synthetic CTs (sCT) that are automatically generated using deformable registration algorithms. These algorithms may have poor performance at reproducing variable volumes of gas present during treatment. Therefore, we have analyzed the air mapping error between the daily CBCTs and the corresponding sCT and explored its dosimetric effect on oART plan calculation.

METHODS

Abdominopelvic air volume was contoured on both the daily CBCT images and the corresponding synthetic images for 207 online adaptive pelvic treatments. Air mapping errors were tracked over all fractions. For two case studies representing worst case scenarios, dosimetric effects of air mapping errors were corrected in the sCT images using the daily CBCT air contours, then recalculating dose. Dose volume histogram statistics and 3D gamma passing rates were used to compare the original and air-corrected sCT-based dose calculations.

RESULTS

All analyzed patients showed observable air pocket contour differences between the sCT and the CBCT images. The largest air volume difference observed in daily CBCT images for a given patient was 276.3 cc, a difference of more than 386% compared to the sCT. For the two case studies, the largest observed change in DVH metrics was a 2.6% reduction in minimum PTV dose, with all other metrics varying by less than 1.5%. 3D gamma passing rates using 1%/1 mm criteria were above 90% when comparing the uncorrected and corrected dose distributions.

CONCLUSION

Current CBCT-based oART workflow can lead to inaccuracies in the mapping of abdominopelvic air pockets from daily CBCT to the sCT images used for the optimization and calculation of the adaptive plan. Despite the large observed mapping errors, the dosimetric effects of such differences on the accuracy of the adapted plan dose calculation are unlikely to cause differences greater than 3% for prostate treatments.

Based on 0.35 T magnetic resonance-guided radiotherapy, what are the nonisotropic PTV margins required for conventional prostate radiotherapy?

This study aims to calculate planning target volume (PTV) margins for the prostate and seminal vesicles (SVs) from the use of magnetic resonance-guided radiation therapy (MRgRT). And whether nonisotropic PTV margins are beneficial for these structures. Organ motion is linked to the displacement of the prostate and SVs. From the use of MRgRT, the nearby organs at risk (OAR) can be visualized both inter- and intrafraction. This study looked to determine if there is a correlation between interfractional OAR changes and displacements to the prostate and SVs. Inter- and intrafractional data from 20 consecutive prostate cancer patients treated using extreme hypofractionated 0.35 T MRgRT indicated prostate and SV motion during treatment. Tracking points (TPs) on 2D sagittal cine-MRI enabled assessment of this intrafractional motion. To determine a correlation between rectal changes and target displacements, the rectal diameter (RD) changes were compared against the displacement differences (DDs) at the prostate and SVs. Eighty percent of patients required intrafractional imaging corrections during radiotherapy, including 16/100 fractions due to rectal volume increases and 24/100 fractions due to bladder volume increases. The frequency of ≥3 mm intrafraction displacement was considerably greater in TPs in the SV than in the prostate. A moderate positive correlation (R² = 0.417) was shown between RD changes and DDs at the level of the prostate and SVs. The PTV margins required for 90% of the patient cohort for prostate and SVs are nonuniform in different directions, and the margin is larger for SVs. Organ motion contributed toward prostate and SV displacements and showed the importance of a robust bladder and rectal-filling protocol.

Highly hypofractionated schedules for localized prostate cancer: Recommendations of the GETUG radiation oncology group

Stereotactic body radiotherapy (SBRT) has become treatment option for localized prostate cancer but the evidence base remains incomplete. Several clinical studies, both prospective and retrospective, have been published. However, treatment techniques, target volumes and dose constraints lack consistency between studies. Based on the current available literature, the French Genito-Urinary Group (GETUG) suggests that.

Bladder volume reproducibility after water consumption in patients with prostate cancer undergoing radiotherapy: A systematic review and meta-analysis

BACKGROUND

To minimize toxicity due to radiotherapy in patients with prostate cancer, high bladder volume reproducibility is essential. Water consumption is often used to increase bladder volume reproducibility, but the optimal amount of water required to be consumed remains unclear. We aimed to analyzed the relationship between water consumption and bladder volume reproducibility in patients undergoing radiotherapy for prostate cancer.

METHODS

We conducted a systematic review and meta-analysis of randomized controlled trials and cohort studies that assessed bladder volume change after water consumption in patients with prostate cancer undergoing radiotherapy. MEDLINE, Embase, and Cochrane Central Register of Controlled Trials were searched for relevant studies published from database inception up until July 4, 2020. The Newcastle-Ottawa Scale was used to evaluate the risk of bias in the included studies. The outcome was the mean difference (MD) of bladder volume after water consumption, evaluated through meta-analysis using a random-effects model.

RESULTS

Ten cohort studies and one randomized controlled trial with a total of 417 patients were included. For 300-400 ml water consumption, the bladder volume MD between during treatment and at computer tomography-simulation (95% confidence interval [CI]) was -11.97 (-51.68 to 27.74), was -45.99 (-82.85 to -9.13) for 500-540 ml water consumption and -45.92 (-78.86 to -12.98) for water consumption until full-bladder sensation was reached.

CONCLUSION

Consuming 300-400 ml of water potentially leads to the best bladder volume reproducibility; moreover, the higher the water consumption volume, the lower the bladder volume reproducibility.

Maintaining consistent bladder filling during external beam radiotherapy for prostate cancer

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Radiation for prostate cancer is preferably provided with a full urinary bladder.

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There are discrepancies how well current methods achieve consistent bladder filling.

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A urinary catheter with a check-valve controlled by a float is under development.

Radiation therapy for patients with prostate cancer is preferably provided with a full urinary bladder. Full bladder can potentially move the small intestine out of the radiation treatment regions, and results in decreased small bowel radiation dose and gastrointestinal toxicity. Maintaining consistent bladder filling during computerized tomography simulation scan used for treatment planning and at daily radiation treatments is challenging. Here we present an in-development urinary catheter with a floating balloon that drains the bladder only when urine reaches to a prespecified level, and review current methods used in clinic to ensure consistent bladder filling. These includes bladder filling protocols, ultrasound scanning and biofeedback techniques.

Influence of different urinary bladder filling levels and controlling regions of interest selection on deformable image registration algorithms

PURPOSE

Evaluation of Raystation ANAtomically CONstrained Deformation Algorithm (ANACONDA) performance to different urinary bladder filling levels in male pelvis anatomic site varying the controlling Regions Of Interest (ROIs).

METHODS

Different image datasets were obtained with ImSimQA (Oncology System Limited, Shrewsbury, UK) to evaluate ANACONDA performances (RaySearch Laboratories, Stockholm, Sweden). Deformation vector fields were applied to a synthetic man pelvis and a real patient computed tomography (CT) dataset (reference CTs) resulting in deformed CTs (target CTs) with various bladder filling levels. Different deformable image registrations (DIRs) were generated between each target CTs and reference CTs varying the controlling ROIs subset. Deformed ROIs were mapped from target CT to reference CT and then compared to reference ROIs. Evaluation was performed by Dice Similarity Coefficient (DSC), Correlation Coefficient (CC), Mean Distance to Agreement (MDA), maximum Distance to Agreement (maxDA) and with the introduction of global DSC (global_DSC) and global CC (global_CC) parameters.

RESULTS

In both synthetic and real patient CT cases, DSC scored less than 0.75 and MDA greater than 3 mm when no ROIs or only bladder were exploited as controlling ROI. DSC and CC increased by increasing the number of controlling ROIs selected whereas, an opposite behavior was observed for MDA and maxDA.

CONCLUSIONS

ANACONDA performances can be influenced by bladder filling fluctuation if no controlling ROIs are selected. Global_DSC and global_CC are useful parameters to quantitatively compare DIR algorithms. DIR performances improve by increasing the number of controlling ROIs selected, reaching a saturation level after a defined ROIs subset selection.

Three-dimensional MRI evaluation of the effect of bladder volume on prostate translocation and distortion

Background The accuracy of any radiation therapy delivery is limited by target organ translocation and distortion. Bladder filling is one of the recognised factors affecting prostate translocation and distortion. The purpose of our study was to evaluate the effect of bladder volume on prostate translocation and distortion by using detailed three-dimensional prostate delineation on MRI. Patients and methods Fifteen healthy male volunteers were recruited in this prospective, institutional review board-approved study. Each volunteer underwent 4 different drinking preparations prior to imaging, with MR images acquired pre- and post-void. MR images were co-registered by using bony landmarks and three-dimensional contouring was performed in order to assess the degree of prostate translocation and distortion. According to changes in bladder or rectum distention, subdivisions were made into bladder and rectal groups. Studies with concomitant change in both bladder and rectal volume were excluded. Results Forty studies were included in the bladder volume study group and 8 in the rectal volume study group. The differences in rectal volumes yielded higher levels of translocation (p < 0.01) and distortion (p = 0.02) than differences in bladder volume. Moderate correlation of prostate translocation with bladder filling was shown (r = 0.64, p < 0.01). There was no important prostate translocation when bladder volume change was < 2-fold (p < 0.01). Moderate correlation of prostate distortion with bladder filling was shown (r = 0.61, p < 0.01). Conclusions Bladder volume has a minimal effect on prostate translocation and effect on prostate distortion is negligible. Prostate translocation may be minimalised if there is < 2-fold increase in the bladder volume.