Rectal Spacer Research Articles

Creating CT- and MRI-guided urethra planning-risk-volumes for urethra-sparing prostate stereotactic body radiotherapy

Dose-escalation in prostate cancer SBRT improves PSA nadir and negative post-treatment biopsy rates, but increases genitourinary toxicity. The definition of the urethra PRV (uPRV) is not standardized. A Foley-catheter based uPRV incorporates catheter-induced anatomic variability that is not reproduced during daily treatment without catheter, whereas anatomic uncertainty during MRI-CT registration is inherent to the MRI-based uPRV. We thus examined the urethra as delineated on CT and MRI to identify an optimal urethral PRV. The urethra was contoured on CT with catheter (uCT) and T2 MRI without catheter (uMRI) in 25 men with prostate cancer. Men received three intraprostatic gold fiducial markers for localization, and rectal spacer to reduce rectal toxicity. MRI was first registered to the CT (reg1) using automated rigid registration of fiducial markers; u_MRI in this position was labelled uMRI_1. MRI was rigidly registered to the CT again (reg2); this time manually to the posterior prostate/anterior rectal wall interface (a clinically relevant region of interest in delineating a hydrogel spacer for radiation planning without taking into account fiducial markers). The uMRI volume created from this manual MRI-CT registration was labeled uMRI_2. Urethral PRVs were created by uniform, and anterior-posterior (A-P) only, expansions in 1 mm increments around uCT. The proportion of uMRI_1, and uMRI_2 covered by each successive uPRV was measured, as was the decrement in the volume PTV-uPRV. Mean and standard deviation uCT and uMRI volumes were 1.72±0.58 and 1.01±0.51 cc, respectively. Automated MRI-CT registration (reg1) with fiducial markers resulted, on average, in 0.2 mm translational separation of each fiducial marker on MRI to its intended fiducial marker target on CT. The translation and rotation matrix differences between reg1 and reg2 (manual) were: -1.1±2.47, -2.87±6.17 and 0.08±4.68 mm; and -0.16±8.29, 0.75±3.17 and 1.42±4.01 degrees. The smallest average urethra contour that would encompass uCT and uMRI_1 was 2.34±0.75 cc; that for uCT, uMRI_1 and uMRI_2 was 2.87±1.04 cc. The likelihood of urethra coverage and mean percent PTV-uPRV for a given uPRV are shown in the table. Uniform 3 mm uPRV encompassed 88% of uCT and uMRI_1, and 83% of uCT, uMRI_1 and uMRI_2, versus 82% and 75% with A-P only uPRV. Uniform and A-P 3 mm uPRVs are created at the expense of 7% and 4% of PTV, respectively. Three-quarters of potential urethra variability on CT and MRI are included in an A-P 3 mm PRV around a catheter. Additional uniform, or A-P, uPRV expansions for urethral protection must be weighed against clinically relevant declines in PTV-uPRV.Abstract 4128; TablePRV (mm)123456% of:uCT, uMRI_1 included in uniform PRV808588919395uCT, uMRI_1 included in A-P PRV768082848687uCT, uMRI_1 and uMRI_2 included in uniform PRV717883889193uCT, uMRI_1 and uMRI_2 included in A-P PRV677275788183PTV decrease by uniform PRV457101215PTV decrease by A-P PRV344567 Open table in a new tab

Polyethylene glycol-based hydrogel rectal spacers for prostate brachytherapy: a systematic review with a focus on technique

IntroductionRadiation dose to the rectum in prostate brachytherapy (PBT) can be reduced by the use of polyethylene glycol (PEG) hydrogel spacers. This reduces the rate of rectal toxicity and allows dose escalation to the prostate. Our objectives were to provide an overview of technique for injection of a PEG hydrogel spacer, reduction in rectal dosimetry, gastrointestinal toxicity and potential complications.MethodsWe systematically reviewed the role of PEG hydrogel spacers in PBT using the Cochrane and PRISMA methodology for all English-language articles from January 2013 to December 2019. Data was extracted for type of radiotherapy, number of patients, type of PEG-hydrogel used, mean prostate-rectum separation, rectal dosimetry, acute and late GI toxicity, procedure-related complications and the technique used for hydrogel insertion.ResultsNine studies (671 patients and 537 controls) met our inclusion criteria. Of these 4 used DuraSeal® and 5 used SpaceOAR®. The rectal spacing achieved varied between 7.7-16 mm. Failure of hydrogel insertion was seen only in 12 patients, mostly related to failure of hydrodissection in patients undergoing salvage PBT. Where reported, the rectal D2 cc was reduced by between 21.6 and 52.6% and the median rectal V75% cc was reduced by between 91.8–100%. Acute GI complications were mostly limited to grade 1 or 2 toxicity (n = 153, 33.7%) with low levels of grade 3 or 4 toxicity (n = 1, 0.22%). Procedure-related complications were limited to tenesmus (0.14%), rectal discomfort (1.19%), and bacterial prostatitis (0.44%).ConclusionsPEG hydrogel spacers are safe to insert. Gel insertion is easy, fast and has a low rate of failure. These studies convincingly demonstrate a significant reduction in rectal dosimetry. Although the results of spacers in reducing rectal toxicity is promising, these need to be confirmed in prospective randomised trial.

Impact of hydrogel peri-rectal spacer insertion on prostate gland intra-fraction motion during 1.5\u2009T MR-guided stereotactic body radiotherapy

BackgroundThe assessment of organ motion is a crucial feature for prostate stereotactic body radiotherapy (SBRT). Rectal spacer may represent a helpful device in order to outdistance rectal wall from clinical target, but its impact on organ motion is still a matter of debate. MRI-Linac is a new frontier in radiation oncology as it allows a superior visualization of the real-time anatomy of the patient and the current highest level of adaptive radiotherapy.MethodsWe present data regarding a total of 100 fractions in 20 patients who underwent MRI-guided prostate SBRT for low-to-intermediate risk prostate cancer with or without spacer. Translational and rotational shifts were computed on the pre- and post-treatment MRI acquisitions referring to the delivery position for antero-posterior, latero-lateral and cranio-caudal direction, and assessed using the Mann-Whitney U-Test.ResultsAll patients were treated with a five sessions schedule (35 Gy/5fx) using MRI-Linac for a median fraction treatment time of 50 min (range, 46–65). In the entire study sample, median rotational displacement was 0.1° in cranio-caudal, − 0.002° in latero-lateral and 0.01° in antero-posterior direction; median translational shift was 0.11 mm in cranio-caudal, − 0.24 mm in latero-lateral and − 0.22 mm in antero-posterior. A significant difference between spacer and no-spacer patients in terms of rotational shifts in the antero-posterior direction (p = 0.033) was observed; also for translational shifts a positive trend was detected in antero-posterior direction (p = 0.07), although with no statistical significance. We observed statistically significant differences in the pre-treatment planning phase in favor of the spacer cohort for several rectum dose constraints: rectum V32Gy < 5% (p = 0.001), V28 Gy < 10% (p = 0.001) and V18Gy < 35% (p = 0.039). Also for bladder V35 Gy < 1 cc, the use of spacer provided a dosimetric advantage compared to the no-spacer subpopulation (p = 0.04). Furthermore, PTV V33.2Gy > 95% was higher in the spacer cohort compared to the no-spacer one (p = 0.036).ConclusionIn our experience, the application of rectal hydrogel spacer for prostate SBRT resulted in a significant impact on rotational antero-posterior shifts contributing to limit prostate intra-fraction motion. Further studies with larger sample size and longer follow-up are required to confirm this ideally favorable effect and to assess any potential impact on clinical outcomes.

Prostate oncologic therapy while ensuring neurovascular conservation (POTEN-C): A phase II randomized controlled trial of stereotactic ablative body radiotherapy (SAbR) with or without neurovascular sparing for erectile function preservation in localized prostate cancer.

TPS381 Background: Radiotherapy (RT) associated sexual dysfunction occurs in half of men following treatment for localized prostate cancer. Proposed mechanisms include vascular injury of adjacent internal pudendal arteries (IPA), penile bulb (PB), corpora cavernosa (CC) or neurovascular bundles (NVB). Ability to spare these structures has been limited by a presumed need to treat the entire prostate gland, while also preventing rectal injury. Recent innovations have challenged this issue: a) precise dose delivery with stereotactic ablative RT (SAbR), b) improved spatial mapping of clinically significant disease with mpMRI, c) rectal avoidance with rectal spacer use. Methods: POTEN-C is a multi-center phase II randomized control trial, which includes men with a) low-intermediate risk prostate cancer eligible for SAbR without ADT, b) potent by sexual composite score ≥60 on EPIC patient-reported quality of life instrument, c) mpMRI delineated disease (PIRADS v2 score 3-5) ≥5mm to at least one ‘spared’ NVB. After placement of rectal spacer gel and CT/MRI simulation, men are randomized to standard SAbR to 40-45Gy/5fx or neurovascular-sparing SAbR. In the sparing experimental arm, the prostate PTV is given 30Gy/5fx excluding unilateral ‘spared’ NVB, while a 40-45Gy PTV further excludes a 5mm protective shell on the unilateral ‘spared’ NVB+IPA+PB+CC. Centralized rapid review of initial contours/plans and online training materials are integrated. The primary endpoint is 2-year patient-reported potency, measured by EPIC sexual composite score. We hypothesize that neurovascular sparing SAbR will reduce 2-year EPIC score decline from a control of 20 to 10 (corresponding to a MCID). Assuming standard deviation 20, two-sided significance level 0.10 with two-sample t-testing, and 15% attrition, we intend to enroll 120 patients to provide 80% power to detect this difference. Secondary endpoints include sexual medication/aid use, relapse rates, GU/GI toxicity. Enrollment is ongoing. Details: http://www.poten-c.org . Clinical trial information: 03525262.

Safety and outcome of stereotactic body radiation therapy (SBRT) with rectal hydrogel spacer for prostate cancer.

76 Background: Ultra-hypofractionated radiotherapy delivered using stereotactic body radiotherapy (SBRT) is a cost-effective treatment for localized prostate cancer. Optimal dosing remains unclear, as commonly used 30-40Gy/5fx regimens appear to overestimate hypofractionation’s control benefits. Here, we report the largest experience of 45Gy/5Fx of SBRT for prostate cancer patients treated with hydrogel peri-rectal spacer (‘hydrogel’). Methods: An IRB-approved retrospective protocol was used to conduct a registry search identifying all patients with prostate cancer who received 45Gy/5Fx between 2015-2019 with hydrogel. Genitourinary (GU) and gastrointestinal (GI) toxicities were defined using the NCI Common Toxicity Criteria for Adverse Events (CTCAE) v.5.0. The ASTRO-Phoenix failure definition of Nadir+2 ng/mL was used for biochemical failure. Results: We analyzed 250 low (9.2%), intermediate (85.2%), and high-risk (5.6%) prostate cancer patients with a median follow-up of 9.9 months (range: 0-45.7 months). Acute GU and GI grade ≥ II toxicities were noted in 15.2% and 7.2% of patients, respectively. Late GU grade II and III toxicities occurred in 24.0% and 1.2% of patients, respectively, while late GI grade II and III toxicities occurred in 4.0% and 0.4% of patients, respectively. In patients (N=44) with follow-up &gt;2 years, late GU and GI grade III toxicities occurred in 4.55% and 2.27% of patients, respectively. A significant correlation was noted for acute GI and GU toxicity predicting the respective late GI and GU toxicity (p-value &lt; 0.001 for both). Physician-reported Grade ≥ II new onset erectile dysfunction was 17.2%. A gradual decline in prostate-specific antigen with a mean nadir of 0.04 (95% CI: [0.018, 0.067]) at 36 months was noted. The actuarial freedom from biochemical failure was 96.33% at 3 years. Overall survival was 94.09% at 3 years with no deaths attributed to prostate cancer. Conclusions: SBRT treatment of 45Gy/5Fx with hydrogel is well tolerated with GU/GI toxicities comparable to those reported for conventional fractionation. Although short, the 3-year biochemical control rate is encouraging. Longer follow-up and prospective evaluation are warranted.

Rectal spacing, prostate coverage, and periprocedural outcomes after hydrogel spacer injection during low-dose-rate brachytherapy implantation

To analyze the dosimetric impact and periprocedural outcomes with a bioabsorbable hydrogel rectal spacer injected during low-dose-rate (LDR) prostate brachytherapy implants. A consecutive series of 80 patients implanted with stranded I-125 LDR brachytherapy seeds were evaluated, of which 40 underwent a transperineal injection of polyethylene glycol (5cc) in between the prostate and rectum. Same day CT-based dosimetry was compared between patients with and without hydrogel spacer to evaluate for differences in rectal and prostate dosimetry. Physician-reported toxicities were coded with Common Terminology Criteria for Adverse Events (CTCAE) v4. Baseline patient and implant characteristics were similar. There were no acute genitourinary or rectal toxicities attributed to the hydrogel spacer. Comparing patients with and without hydrogel, the mean separation between the prostate and rectum was 13.9±5.2mm vs. 6.5±5.0mm (p < 0.0001), respectively. The adjusted mean dose to 1cc, 2cc, and 5cc of the rectum relative to prescription dose was decreased by 32% (p < 0.01), 26% (p < 0.01), and 17% (p < 0.01), respectively. There were no statistically significant differences in prostate coverage: mean V100 (92% vs. 91%), V150 (45% vs. 48%), and D90 (106% vs. 106%), respectively. At 1month followup, grade 1 rectal toxicity was 12.5% vs. 17.5% (p= 0.35). No patients developed Grade ≥2 rectal toxicity with hydrogel, although one did without. Hydrogel rectal spacers significantly reduced rectal exposure to LDR brachytherapy seeds without an observable impact on prostate coverage or periprocedural side effects. These outcomes reflect only LDR implants that used stranded seeds.

Rectal Hydrogel Spacer Improves Late Gastrointestinal Toxicity Compared to Rectal Balloon Immobilization After Proton Beam Radiation Therapy for Localized Prostate Cancer: A Retrospective Observational Study

Our purpose was to compare dosimetric parameters and late gastrointestinal outcomes between patients treated with proton beam therapy (PBT) for localized prostate cancer with rectal balloon immobilization versus a hydrogel rectal spacer. Patients with localized, clinical stage T1-4 prostate adenocarcinoma were treated at a single institution using conventionally fractionated, dose-escalated PBT from 2013 to 2018. Patient-reported gastrointestinal toxicity was prospectively collected, and the incidence of rectal bleeding was retrospectively reviewed from patient records. One hundred ninety-two patients were treated with rectal balloon immobilization, and 75 were treated with a rectal spacer. Rectal hydrogel spacer significantly improved rectal dosimetry while maintaining excellent target coverage. The 2-year actuarial rate of grade 2+ late rectal bleeding was 19% and 3% in the rectal balloon and hydrogel spacer groups, respectively (P = .003). In univariable analysis, the probability of grade 2+ rectal bleeding was significantly correlated with increasing rectal dose. In multivariable analysis, only receipt of spacer hydrogel (hazard ratio, 0.145; P = .010) and anticoagulation use (hazard ratio, 5.019; P < .001) were significantly associated with grade 2+ bleeding. At 2-year follow-up, patient-reported Expanded Prostate Cancer Index Composite bowel quality of life composite scores were less diminished in the hydrogel spacer group (absolute mean difference, 5.5; P = .030). Use of rectal hydrogel spacer for prostate PBT is associated with a significantly lower incidence of clinically relevant, late rectal bleeding and lower decrement in long-term, patient-reported bowel quality of life compared with rectal balloon immobilization. Our results suggest that hydrogel spacer may improve rectal sparing compared with rectal balloon immobilization during PBT for prostate cancer.

Who Benefits From a Prostate Rectal Spacer? Secondary Analysis of a Phase III Trial

PurposePreviously a phase III trial of a hydrogel rectal spacer during prostate radiation therapy found decreased toxicity and a clinically significant improvement in bowel quality of life (QOL) at 3 years by the Expanded Prostate Cancer Index. We performed a secondary analysis to identify men less likely to benefit. Methods and MaterialsClinical and dosimetric data for the 222 patients enrolled on the SpaceOAR phase III trial were analyzed. The volume of rectum treated to 70 Gy (V70) and the quantitative analysis of normal tissue effects in the clinic (QUANTEC) rectal dose goals were used as surrogates for clinical benefit and plan quality. Mean bowel QOL was assessed at 15 and 36 months posttreatment and the likelihood of 1× (5 points) or 2× (10 points) minimally important difference changes were assessed. ResultsRectal V70 was correlated with physician scored toxicity (P = .033) and was used as a surrogate for plan quality. There was no correlation between prostate volume and rectal V70 (r = 0.077). Rectal V70 pre- and post-hydrogel was 13% and 3% for the smallest prostates (<40 mL) and 12% and 2% for the largest (>80 mL). The relative reduction in rectal V70 of 78% did not vary by prespacer V70, but the absolute reduction was greater for a higher V70. All spacer plans met the 5 QUANTEC rectal dose constraints, although 92% of control plans met all constraints. At 3 years, those not meeting all QUANTEC goals had a 15.0-point (standard deviation 15.1) decline, control patients meeting QUANTEC goals had a 4.0-point (9.5) decline, and spacer had >0.5 (7.6; P < .01). Previous surgery was not correlated with QOL (P = .8). Across prognostic groups, including age, body mass index, previous surgery, target volume, or quality of radiation plans, there was no statistically significant heterogeneity in the relative benefit of spacer in decreasing the risk of 1× or 2× the minimally important difference declines. ConclusionsThere was little heterogeneity in the likelihood of spacer reducing the risk of declines in bowel QOL across clinical and dosimetric variables. Even for the >95% of plans meeting QUANTEC rectal criteria, hydrogel spacer provided potentially meaningful benefits.

What is the quality of hydrogel spacer insertions? and which patients will benefit? A literature review

AbstractAim:To evaluate the quality of rectal hydrogel spacer (HS) insertions from literature in patients undergoing radical radiotherapy for prostate cancer. The secondary aim is to assess the benefit of HSs in patients with risk factors more likely to have rectal complications, such as non-conventional radiotherapy dose fractionations and high-risk disease.Method and materials:A literature search of peer-reviewed electronic articles was carried out using Boolean connectors and Medical Subject Headings in the databases. Databases searched included ScienceDirect, Medline and Cinahl. The articles were assessed using relevant critical appraisal skills programme tools.Results:From the 26 studies used, HS showed a clinically significant relative reduction in rectal planning dose volumes for both high- and low-risk prostate cancer patients in a range of radiotherapy treatment modalities including volumetric modulated arc therapy, intensity-modulated radiotherapy, intensity-modulated proton therapy, stereotactic ablative body radiotherapy and brachytherapy. Spacer placements were successfully inserted in 99% of patients. However, rectal wall infiltration occurrence was 6% and ≥2 cm unsymmetrical placements in 2%.Findings:A spacer scoring system based on the HS symmetry has provided evidence of the quality of the position inserted, which was visually aided by T2-wieghted MRIs. Despite optimal HS placements ranging from 62 to 72%, HS had a clinically significant reduction of ≥25% in planned rectal V70 dose in 97% of patients.

Early Tolerance and Tumor Control Outcomes with High-dose Ultrahypofractionated Radiation Therapy for Prostate Cancer

BackgroundStudies using stereotactic body radiotherapy (SBRT) dose escalation in in low- and intermediate-risk prostate cancer patients have indicated favorable outcomes. ObjectiveTo evaluate tolerance and tumor control outcomes in low- and intermediate-risk prostate cancer patients treated with high-dose SBRT following our phase 1 trial. Design, setting, and participantsA total of 551 patients with low- or intermediate-risk prostate cancer were treated with SBRT. InterventionTreatment with 37.5–40Gy SBRT in five fractions directed to the prostate and seminal vesicles. Outcome measurements and statistical analysisOutcome measurements included acute toxicities (<3 mo after radiotherapy [RT]) and late toxicities (>3 mo after RT) and tumor control evaluation (prostate-specific antigen [PSA] levels at 3–6-mo intervals and post-treatment prostate biopsy at 2yr). Results and limitationsAcute grade 2 gastrointestinal (GI) toxicities occurred in 1.8% of patients, and late grade 2 and 3 GI toxicities were observed in 3.4% and 0.4% of patients, respectively. Acute grade 2 genitourinary (GU) toxicities occurred in 10% of patients, and grade 3 acute GU toxicities were observed in 0.7% of patients. Late grade 2 and 3 GU toxicities were observed in 21.1% and 2.5% of patients, respectively. The use of a hydrogel rectal spacer was significantly associated with reduced late GI toxicity and lower odds of developing late GU toxicity. The median follow-up was 17 mo, and 53% of those with at least 2yr of follow-up (103/193) had a biopsy performed. The 5-yr cumulative incidence of PSA failure was 2.1%, and the incidence of a positive 2-yr treatment biopsy was 12%. Limitations to this report include its retrospective nature and short follow-up time. ConclusionsFavorable short-term outcomes were achieved with high-dose SBRT for low- and intermediate-risk disease. Severe late toxicities were observed and favorable tumor control was found. Patient summaryWe utilized stereotactic body radiotherapy, a form of external beam radiotherapy that delivers highly targeted high-dose treatment to the prostate, to treat over 500 localized prostate cancer patients in five sessions over 1.5 wk. Treatments were well tolerated without significant urinary or rectal side effects. Nearly 90% of those who underwent biopsies after treatment did not demonstrate residual active disease.

Deep learning-based auto-segmentation of targets and organs-at-risk for magnetic resonance imaging only planning of prostate radiotherapy.

Magnetic resonance (MR) only radiation therapy for prostate treatment provides superior contrast for defining targets and organs-at-risk (OARs). This study aims to develop a deep learning model to leverage this advantage to automate the contouring process. Six structures (bladder, rectum, urethra, penile bulb, rectal spacer, prostate and seminal vesicles) were contoured and reviewed by a radiation oncologist on axial T2-weighted MR image sets from 50 patients, which constituted expert delineations. The data was split into a 40/10 training and validation set to train a two-dimensional fully convolutional neural network, DeepLabV3+, using transfer learning. The T2-weighted image sets were pre-processed to 2D false color images to leverage pre-trained (from natural images) convolutional layers' weights. Independent testing was performed on an additional 50 patient's MR scans. Performance comparison was done against a U-Net deep learning method. Algorithms were evaluated using volumetric Dice similarity coefficient (VDSC) and surface Dice similarity coefficient (SDSC). When comparing VDSC, DeepLabV3+ significantly outperformed U-Net for all structures except urethra (P < 0.001). Average VDSC was 0.93 ± 0.04 (bladder), 0.83 ± 0.06 (prostate and seminal vesicles [CTV]), 0.74 ± 0.13 (penile bulb), 0.82 ± 0.05 (rectum), 0.69 ± 0.10 (urethra), and 0.81 ± 0.1 (rectal spacer). Average SDSC was 0.92 ± 0.1 (bladder), 0.85 ± 0.11 (prostate and seminal vesicles [CTV]), 0.80 ± 0.22 (penile bulb), 0.87 ± 0.07 (rectum), 0.85 ± 0.25 (urethra), and 0.83 ± 0.26 (rectal spacer). A deep learning-based model produced contours that show promise to streamline an MR-only planning workflow in treating prostate cancer.

Long-term Follow-up after Radiotherapy for Prostate Cancer with and without Rectal Hydrogel Spacer: A Pooled Prospective Evaluation of Sexual Function of Men with Good Baseline Sexual Function

Hydrogel spacers are a tool to improve dosimetry and overall quality of life with limited follow-up in men receiving radiotherapy for prostate cancer. This study is a pooled analysis of prospective cohorts with long-term quality of life (QOL) follow-up with or without a rectal spacer to minimize dose to rectum as well as other adjacent organs at risk. QOL was examined using the Expanded Prostate Cancer Index Composite (EPIC) and mean changes from baseline to EPIC domains were evaluated. A total of 126 patients with good pre-treatment sexual function (baseline EPIC >/=60) including 88 patients from a randomized multi-institutional trial of radiation with or without hydrogel rectal spacer with a QOL end-point were pooled with 38 non-randomized patients from a single institution with prospective QOL collection in patients with or without hydrogel spacer. The proportions of men with a predetermined minimally important differences (MIDs) relative to pre-treatment baseline (11 point decline from baseline = MIDx1 and 22 point decline from baseline = MIDx2) in sexual function were evaluated. A total of 126 men were evaluated (64% with spacer and 36% without) with QOL data being available for 68 men beyond 24 months of follow-up (median: 33 months, range: 2.5-69.4 months). MID was more common in men without a rectal spacer at 15 months (60.5% vs 44.4%) and at >/= 24 months (80% vs 55%). MIDX2 occurred at 15 months of 45% in men without rectal spacer vs 29% in men with rectal spacer and >/= 24months in 68% of men without rectal spacer vs 39% with rectal spacer. At >/= 24 months of follow up, men without spacer were more likely to have 1xMID in sexual QOL (11 point decline, p= 0.041, Fisher Exact) as well as 2xMID (22 point decline, p=0.025, Fischer Exact) declines. The use of rectal separation was associated with adequate erectile quality. In men with rectal spacer at late follow up, 63% of patients had firm enough erections for intercourse and 1% had no erectile function compared to 28% adequate erectile function for intercourse and 12% without any erectile function in patients without rectal spacer. In this pooled analysis of QOL after prostate radiotherapy with up to 5-years of follow-up, utilization of a hydrogel rectal spacer was associated with less MID per patient reported sexual QOL. This was especially important in patient reported adequate erectile function for intercourse.

Predictors of Intra-Fraction Prostate Motion during Stereotactic Body Radiation Therapy (SBRT)

The ultimate success and safety of prostate stereotactic body radiation therapy (SBRT) relies on adequate organ motion management. The hypothesis of this study is that there are patient clinical and anatomical variables that predict for prostate motion during treatment. Data were obtained on 52 prostate cancer patients treated with 5 or 6 fraction VMAT SBRT using simultaneous MV/kV imaging for intra-fraction fiducial marker monitoring. Patients were given strict instructions to have a full bladder and empty rectum for simulation and each treatment. 260 cone beam CTs (CBCTs) were used to measure pre-treatment bladder, rectal and gas volumes. Prostate motion end points included number of “beam-offs” and shifts from the position of the day. “Beam offs” occurred when therapists interrupted treatment due to fiducial makers tracking off by >1.5 mm from their reference for 12-15 seconds. Shifts in the lateral, ventral-dorsal and cranial-caudal directions, in addition to the three-dimensional vector from position of the day were measured at 35 MV/kV imaging control points during 2 minutes of treatment and averaged over each fraction. For each patient, urinary symptom score (IPSS), age and body mass index (BMI) were collected as well as the presence of rectal spacer and use of urinary dysfunction medications. Prostate motion data were evaluated per patient and per fraction. Statistical analysis included Spearman’s rank-order correlation, Wilcoxon Rank-Sum test and a Linear mixed model fit by restricted maximum likelihood. The average patient age, BMI and pre-treatment IPSS were 70 years old (range: 56-84), 30 kg/m2 (range:19-55), and 8 (range: 0-21), respectively. Most patients (48/52) had rectal spacers placed prior to SBRT. Data analysis for predictors of intrafraction prostate motion revealed that larger pre-treatment bladder and rectal volumes were associated with more beam offs per fraction (p = 0.018 and p = 0.014, respectively). In addition, there was a trend for larger bladder volumes to predict greater shifts in the ventral-dorsal direction (p= 0.052) and magnitude of the 3D vector (p = 0.051). Patients using urinary medications had fewer number of beam offs during their treatment course (p = 0.038). Patient age, BMI, baseline IPSS and pre-treatment gas volume did not correlate with prostate motion during treatment. Our results suggest that patient bladder and rectal volumes at the time of treatment can influence prostate motion during SBRT. We can conclude that rectal emptying prior to treatment is critical for rectal dose avoidance and prostate motion mitigation, however future studies will be needed to determine the optimal bladder volume during prostate SBRT.

Addition of Iodinated Contrast to Rectal Hydrogel Spacer to Facilitate MRI-Independent Target Delineation and Treatment Planning for Prostate Cancer

Rectal hydrogel spacers are increasingly used to reduce dose and thereby limit toxicity to the rectum during prostate radiotherapy. Commercially available products require magnetic resonance imaging (MRI) for hydrogel visualization and treatment planning, with only anecdotal reports of treatment planning with computed tomography (CT) alone. MRI-incompatible hardware, patient intolerance, and added cost provide incentives for MRI-independent alternatives for treatment planning. This case series evaluates the addition of iodinated contrast to spacer gel and assesses its impact on CT visualization. Three prostate cancer patients underwent contrasted rectal spacer placement in preparation for external beam radiotherapy. Standard low-osmolar iodinated contrast was added to a commercially available rectal hydrogel. 0.5cc of contrast was added to 4.5cc of accelerator and subsequently combined with 5cc of diluent. The resultant 10cc of hydrogel was injected into each patient as per standard procedure, utilizing transrectal ultrasound guidance. Two patients were simulated with MRI; a third with a non-MRI compatible pacemaker was planned with CT alone. CT was performed on the day of hydrogel placement within 2 hours of procedure and again 7-12 days later to account for fiducial migration and dissipation of injected air. The second CT was used for treatment planning. Hydrogel visibility was compared between CT and MRI through standardized symmetry scoring, volume calculation, and measurements taken at prostate base, mid-gland, and apex. Spacer contrast was visible only on the day of hydrogel placement by CT, allowing target delineation for treatment planning. On comparison to MRI delineation of spacer one week later, minimal changes in relevant spacer measurements were observed. In one patient, a significant amount of injected air dissipated between the time of hydrogel placement and repeat CT. CT visualization of rectal hydrogel with iodinated contrast on day of placement is feasible and allows MRI-independent treatment planning with spacer gel, but requires repeat CT on a subsequent day to allow for resolution of prostatic edema, fiducial migration, and air within the hydrogel spacer.Abstract 3673; Table 1PatientSimulation Type (Day)Spacer Volume (cc)CC Dimension (mm)AP Dimension (mm)TV Dimension (mm)Base Thickness (mm)Mid-gland Thickness (mm)Apex Thickness (mm)Symmetry Score1CT* (0)16.661.416.430.815.714.715.91CT (8)15.951.417.629.519.017.716.91MR (8)15.555.817.32616.516.816.212CT* (0)12.636.613.839.215.813.811.82CT (12)14.138.812.641.512.811.502MR (12)14.748.615.343.213.212.511.213CT* (0)18.1†58.7†11†40.5†11.8†12.3†15.7†3†CT (7)11.352.41030.411.910.59.52*Spacer contrast visible, †Includes injected air Open table in a new tab

Overview of patient preparation strategies to manage internal organ motion during radiotherapy in the pelvis

AbstractIntroduction:Pelvic internal organs change in volume and position during radiotherapy. This may compromise the efficacy of treatment or worsen its toxicity. There may be limitations to fully correcting these changes using online image guidance; therefore, effective and consistent patient preparation and positioning remain important. This review aims to provide an overview of the extent of pelvic organ motion and strategies to manage this motion.Methods and Materials:Given the breadth of this topic, a systematic review was not undertaken. Instead, existing systematic reviews and individual high-quality studies addressing strategies to manage pelvic organ motion have been discussed. Suggested levels of evidence and grades of recommendation for each strategy have been applied.Results:Various strategies to manage rectal changes have been investigated including diet and laxatives, enemas and rectal emptying tubes and rectal displacement with endorectal balloons (ERBs) and rectal spacers. Bladder-filling protocols and bladder ultrasound have been used to try to standardise bladder volume. Positioning the patient supine, using a full bladder and positioning prone with or without a belly board, has been examined in an attempt to reduce the volume of irradiated small bowel. Some randomised trials have been performed, with evidence to support the use of ERBs, rectal spacers, bladder-filling protocols and the supine over prone position in prostate radiotherapy. However, there was a lack of consistent high-quality evidence that would be applicable to different disease sites within the pelvis. Many studies included small numbers of patients were non-randomised, used less conformal radiotherapy techniques or did not report clinical outcomes such as toxicity.Conclusions:There is uncertainty as to the clinical benefit of many of the commonly adopted interventions to minimise pelvic organ motion. Given this and the limitations in online image guidance compensation, further investigation of adaptive radiotherapy strategies is required.

Stereotactic prostate focal reirradiation therapy for local recurrence: preliminary results of Hartmann Oncology Radiotherapy Group.

Objective:Our objective was to report our experience and to evaluate the feasibility and toxicity of focal salvage stereotactic body radiation therapy (SBRT) in patients with post-radiation local recurrence of prostate cancer.Methods:We retrospectively reviewed medical records of patients treated with Cyberknife ® between October 2014 and April 2017 at our institution for a focal reirradiation delivered to the prostate/prostatic bed for local recurrence after radical or adjuvant radiotherapy. All patients underwent prostate biopsies at recurrence at the time of fiducial markers placement, had choline PET/CT and pelvic MRI. The treatment consisted in 36 Gy in six fractions delivered every other day. Post reirradiation toxicities were assessed according to the CTCAE v4 (Common Terminology Criteria for Adverse Events).Results:42 patients were treated with followed with a median follow-up of 21 months (range 3 – 31). 34 patients had biopsy proven recurrence. The initial treatment was radical prostatectomy and radiation therapy for 9 patients and radiation therapy alone for 33 patients. 23 patients from the group of prostate reirradiation had placement of rectal spacers. No Grade 4 or 5 toxicity were observed. 27 acute urinary events were recorded: 18 patients experienced Grade 1, 9 patients experienced Grade 2 toxicity and 1 patient experienced Grade 3 urinary toxicity, namely cystitis and/or dysuria. No Grade 2 or more digestive toxicity was observed. Rectal doses were significantly lower with rectal spacers.Conclusion:Salvage focal Cyberknife ® seems feasible and show promising results.Advances in knowledge:SBRT for local prostate cancer recurrence after initial radiotherapy is well tolerated with short follow-up.

Risk-adapted moderate hypofractionation of prostate cancer

PurposeProstate cancer (PCA) is highly heterogeneous in terms of its oncologic outcome. We therefore aimed to tailor radiation treatment to the risk status by using three different hypofractionated radiation regimen differing in applied dose, use of rectum spacer, inclusion of pelvic lymph nodes (pLN) and use of androgen deprivation therapy (ADT). Here we report on acute toxicity, quality of life (QOL) and oncologic outcome at a median follow-up of 12 months.MethodsA total of 221 consecutive PCA patients received hypofractionated intensity-modulated radiotherapy (IMRT). Low-risk (LR) patients were planned to receive 60 Gy in 20 fractions (EQD2α/β1.5 = 77.1 Gy), intermediate-risk (IR) patients 63 Gy in 21 fractions (EQD2α/β1.5 = 81 Gy), and high-risk (HR) patients 67.5 Gy in 25 fractions (EQD2α/β1.5 = 81 Gy) to the prostate and 50 Gy in 25 fractions to the pLN. Acute rectal toxicity was assessed by endoscopy. In addition, toxicity was scored using CTC-AE 4.0 and IPSS score, while QOL was assessed using QLQ-PR25 questionnaires.ResultsAcute CTC reactions were slightly higher in the HR regimen but reverted to baseline at 3 months. GI G2 toxicity was 4%, 0% and 12% for the LR, IR and HR regimen. Compared to IR patients, the increase in toxicity in HR patients was statistically significant (p = 0.002) and mainly caused by a higher incidence of diarrhea presumably due to pelvic EBRT. QOL scores of all domains were worse for the HR regimen (not significant).ConclusionRisk-adapted moderate hypofractionation is associated with low GI/GU toxicity. Given the higher rate of pelvic metastases in HR patients, slightly higher transient acute reactions should be outweighed by possible oncological benefits.

Autologous fat as a rectal–prostate spacer for prostate brachytherapy: Results at 6 months

PurposeImplanted rectal spacers (IRS) have been developed to increase the distance between the prostate and the rectum, thus optimizing dose escalation. Cost is a disadvantage and there are still uncertainties as to their durability. We have developed an autologous fat transfer (AFT) technique to use as an IRS. We aim to present the feasibility and durability at 6 months of AFT placed immediately after the implant of the seeds in low-dose-rate brachytherapy (BT). Methods and MaterialsThirty-five patients underwent AFT (12 were treated with primary BT, 7 with a combined primary treatment of external beam radiotherapy + BT, 16 with salvage BT). The isodose used for primary BT was 14400 cGy, 11,000 cGy after 4600 cGy of external beam radiotherapy in the combined group, and 14400 cGy for the salvage group. Patients underwent a CT scan at 1, 3, and 6 months to measure the distance between the rectum and the prostate. ResultsAn average of 32.7 cc (20–40) of fat was transferred successfully in 100% of cases. The mean distance to the rectum at the level of the base, middle, and apex at 1 and 6 months were 11.2, 9.7, and 7.6 mm; 8.3, 8.1, and 5.9 mm, respectively. No rectal toxicity or major complications were reported. ConclusionsThe use of fat as an IRS seems to be a valid alternative to reduce rectal toxicity after BT, achieving equivalent distances to synthetic IRS. It is feasible, safe, and the loss of distance at 6 months is small. Cost is lower than other alternatives.

Dosimetric Analysis of Permanent Prostate Monotherapy with Prostate Rectal Spacer

Dosimetric Analysis of Permanent Prostate Monotherapy with Prostate Rectal Spacer

EP-2127 Hydrogel bladder and rectal spacer (TraceIT) for brachytherapy in locally advanced Cervical cancer

EP-2127 Hydrogel bladder and rectal spacer (TraceIT) for brachytherapy in locally advanced Cervical cancer