Hydrogel Spacer Prospective Multicenter Randomized Controlled Pivotal Trial: Dosimetric and Clinical Effects of Perirectal Spacer Application in Men Undergoing Prostate Image Guided Intensity Modulated Radiation Therapy

Complications and Influential Perioperative Factors Associated with SpaceOAR Hydrogel Placement

Objective

To examine one academic institution's experiences with SpaceOAR placement, its associated complications, and periprocedural characteristics that affect outcomes for the purpose of quality improvement.

Materials and Methods

We conducted a retrospective review of 233 patients who received SpaceOAR from four surgeons and one radiation oncologist between 2018 and 2021. Variables such as demographics, oncologic parameters, radiation plan, and radiographic assessment of hydrogel placement were recorded. The Charlson Comorbidity Index (CCI) was used to assess comorbidity risk. Mann-Whitney and Fisher's exact tests were performed to compare patients with and without complications.

Results

Of the 233 patients who received SpaceOAR, 24 (10.3%) experienced toxicity. All complications were Clavien I or II, such as pelvic pain postplacement, pelvic fullness, bleeding, and lower urinary tract symptoms. 16 patients (6.9%) had some portion of the hydrogel injected into the rectal wall, but it was never clinically significant. The average CCI was 3.2 ± 0.95 for patients who experienced complications; the average CCI was 3.6 ± 1.6 (p=0.48) in the group without complications. Of the physicians with higher procedure volumes, Physician #1 had the highest rate of patient-reported complications at 11 out of 68 (16.2%) and Physician #2 had the lowest rate of complications at 4 out of 96 placements (4.2%). Multivariate analysis found that patients who had received hormone therapy previously had less odds of reporting complications after SpaceOAR placement.

Conclusions

The listed attending on the procedure had a significant correlation to complications with SpaceOAR placement on univariate analysis, and hormone therapy had some benefits to the tolerance for the procedure on multivariate analysis. Overall, the hydrogel placement was well tolerated with low incidence of mild and transient procedure-related toxicity.

Proton therapy toxicity outcomes for localized prostate cancer: Long-term results at a comprehensive cancer center

Background

Proton therapy (PT) has unique biologic properties with excellent clinical outcomes for the management of localized prostate cancer. Here, we aim to characterize the toxicity of PT for patients with localized prostate cancer and propose mitigation strategies using a large institutional database.

Methods

We reviewed medical records of 2772 patients with localized prostate cancer treated with definitive PT between May 2006 through January 2020. Disease risk was stratified according to National Comprehensive Cancer Network guidelines as low [LR, n = 640]; favorable-intermediate [F-IR, n = 849]; unfavorable-intermediate [U-IR, n = 851]; high [HR, n = 315]; or very high [VHR, n = 117]. Descriptive statistics and Kaplan-Meier estimates assessed toxicity and freedom from biochemical relapse (FFBR).

Results

Median follow-up was 7.0 years. The median dose was 78 Gy(RBE)(range: 72-79.2 Gy) in 2.0 Gy(RBE) fractions; 63 % of patients received 78 Gy(RBE) in 39 fractions, and 29 % received 76 Gy(RBE) in 38 fractions. Overall rates of late grade ≥3 GU and GI toxicity were 0.87 % and 1.01 %, respectively. Two patients developed grade 4 late GU toxicity and seven patients with grade 4 late GI toxicity. All patients experiencing severe late grade 4 toxicities were treated to 78 Gy(RBE) in 39 fractions with 80 Gy(RBE) dose to the anterior rectal wall and/or bladder neck. The 10-year FFBR rates for patients with LR to U-IR disease were compared between those treated with 76 and 78 Gy(RBE); the rates were 94.5 % (95 % confidence interval [CI] 92.4-96.0 %) and 93.2 % (95 % CI 91.3-95.7 %), respectively (log-rank p = 0.22).

Conclusions

Proton therapy is associated with low rates of late grade ≥3 GU and GI toxicity. While rare, late grade 4 toxicities occurred in nine (0.3 %) patients. De-escalation to a total dose of 76 Gy(RBE) yields excellent clinical outcomes for patients with LR to U-IR disease with the potential for significant reductions in grade ≥3 late toxicity.

Role of the gel spacer in safely delivering whole pelvic radiation therapy without central shielding in computed tomography-based image-guided adaptive brachytherapy for uterine cervical cancer patients

BACKGROUND

To protect the rectum and bladder from high dose exposure, the Japanese guidelines for managing uterine cervical carcinoma recommend pelvic irradiation with central shielding (CS). Conversely, the European Society for Radiotherapy and Oncology (ESTRO) and the American Brachytherapy Society (ABS) guidelines recommend delivering ≥85 Gy to high-risk clinical target volume D90 (CTVHR D90%). In this study, we investigated whether a gel spacer can enable the safe delivery of the ESTRO/ABS-recommended doses to the target while observing dose constraints for the OARs without using CS in external beam radiation therapy (EBRT).

MATERIALS AND METHODS

Twenty patients who received definitive radiation therapy without CS and were treated by brachytherapy with a gel spacer between 2017 and 2022 were retrospectively reviewed. The cumulative doses of EBRT and brachytherapy treatment outcomes and incidence of adverse events were also examined.

RESULTS

The median cumulative CTVHR D90%, rectum D2cm3, and bladder D2cm3 were 86.6 Gy, 62.9 Gy, and 72.0 Gy, respectively. The 2-year local control rate was 95%. There were no CTCAE ≥Grade 3 late gastrointestinal or genitourinary adverse events.

CONCLUSIONS

The use of gel spacer can enable ESTRO/ABS-recommended dose constraints even without using CS in EBRT, with favorable outcomes and low adverse event rates.

A Randomized Trial Comparing Quality of Life After Low-Dose Rate or High-Dose Rate Prostate Brachytherapy Boost With Pelvic External Beam Radiation Therapy

PURPOSE

To compare health-related quality of life (QoL) in urinary, bowel, and sexual domains after combined external beam radiation therapy (EBRT) and either low-dose rate (LDR) or high-dose rate (HDR) prostate brachytherapy (BT).

METHODS AND MATERIALS

Eligible men with intermediate or high-risk prostate cancer treated with combined pelvic EBRT and BT were randomly assigned to either HDR (15 Gy) or LDR (110 Gy) boost. International Prostate Symptom Score, Index of Erectile Function, and Expanded Prostate Cancer Composite were collected at baseline, 1, 3, 6, and 12 months, every 6 months to 3 years and then annually along with prostate-specific antigen/testosterone. Fisher's exact test compared categorical variables and the Mann-Whitney U test Expanded Prostate Cancer Index Composite (EPIC) domain scores.

RESULTS

From January 2014 to December 2019, a random number generator assigned 195 men: 108 to HDR and 87 to LDR. Median age was 71 years. Risk group was high in 57% and unfavorable intermediate in 43%. Androgen deprivation (used in 74%) began with 3 months neoadjuvant and continued for median 12 months. Baseline EPIC scores were similar for the LDR/HDR cohorts: 89 and 88 respectively for Genito-urinary; 92 and 93 for Gastro-intestinal. EPIC urinary scores decreased at 1 month for HDR but recovered promptly to a steady state by 6 months. LDR scores reached a nadir at 3 months with slow recovery to 18 months, after which urinary QoL was similar for HDR and LDR. Bowel QOL scores fell in both cohorts reaching respective nadirs at 12 months. HDR patients recovered close to baseline and maintained higher scores than LDR patients to 5 years. The decline for LDR patients remained more than the minimum clinically important difference out to 5 years.

CONCLUSIONS

The patient experience for combined EBRT and prostate BT is improved with HDR BT. Urinary QoL improves over time to be equivalent between the 2 modalities after 18 months, but LDR patients report lasting bowel symptoms.

Efficacy of a hydrogel spacer for improving quality of life in patients with prostate cancer undergoing low-dose-rate brachytherapy alone or in combination with intensity-modulated radiotherapy: An observational study using propensity score matching

BACKGROUND

It is unclear whether a hydrogel spacer can improve quality of life (QOL) in patients undergoing low-dose-rate brachytherapy (LDR-BT) alone or in combination with intensity-modulated radiotherapy (IMRT).

METHODS

We enrolled patients with prostate cancer who underwent LDR-BT alone with (n = 186) or without (n = 348) a hydrogel spacer, or underwent LDR-BT in combination with IMRT with (n = 70) or without (n = 217) a hydrogel spacer. QOL was evaluated using Expanded Prostate Cancer Index Composite (EPIC) questionnaires at baseline and 1, 3, 6, 12, and 24 months after implantation. The groups were compared using propensity score matching analysis.

RESULTS

Among patients who underwent LDR-BT alone, there were no differences regarding changes in urinary, bowel, sexual, or hormonal domain scores between the spacer and no-spacer groups; however, the dose at the bowel was significantly lower in the spacer group than in the no-spacer group. Among patients who underwent LDR-BT in combination with IMRT, there were no differences regarding changes in urinary, sexual, or hormonal domain scores between the spacer and no-spacer groups. However, the changes in the bowel domain score were significantly lower in the spacer group than in the no-spacer group (p < 0.001).

CONCLUSIONS

A hydrogel spacer may not improve impaired urinary, bowel, or sexual QOL in patients undergoing LDR-BT alone. However, in patients undergoing LDR-BT in combination with IMRT, a hydrogel spacer can improve impaired bowel QOL but not sexual or urinary QOL.

Radiation proctitis after iodine-125 low-dose-rate prostate brachytherapy utilizing SpaceOAR hydrogel

OBJECTIVE

We retrospectively evaluated the efficacy of combining the SpaceOAR (SOAR) hydrogel with prostate brachytherapy, using colonoscopy findings to assess for radiation proctitis.

METHODS

Among 731 patients undergoing iodine-125 low-dose-rate prostate brachytherapy (LDR-BT), SOAR was utilized in 394 patients (53.9%). Colonoscopy was performed for 97 patients (13.3%) to assess the presence, location, condition, and treatment of radiation proctitis. We also investigated treatment factors associated with the occurrence of radiation proctitis.

RESULTS

Radiation proctitis was observed in 57 patients (7.8%) and 17 (2.3%) were treated with argon plasma coagulation (APC). The incidence of radiation proctitis was 12.2% in the non-SOAR and 4.1% in the SOAR group (p < 0.001). In the non-SOAR group, the incidence of radiation proctitis was 6.6% for LDR-BT monotherapy and increased to 22.0% when combined with external beam radiation therapy (EBRT) (p = 0.001). However, in the SOAR group, these rates significantly decreased to 3.3% and 5.7% for monotherapy and combination therapy, respectively (p = 0.035, p < 0.001). With SOAR, inflammation was observed directly above the DL in most patients (87.5%), and only one patient (6.3%) required APC. The absence of SOAR (p < 0.001, HR = 0.29) and the concurrent use of EBRT (p = 0.018, HR = 2.87) were identified as significant risk factors for the occurrence of radiation proctitis.

CONCLUSION

The use of SOAR significantly reduced the incidence of radiation proctitis in patients undergoing LDR-BT monotherapy and combined EBRT. Inflammation primarily occurred directly above the DL; further examination is necessary to clarify its cause.

Rectal perforation following SpaceOAR placement combined with permanent prostate brachytherapy

Introduction

We report a case of rectal perforation following SpaceOAR placement utilized with iodine-125 low-dose-rate brachytherapy for prostate cancer.

Case presentation

A 65-year-old patient with localized prostate cancer underwent SpaceOAR placement following LDR-BT. No significant issues occurred with the SpaceOAR procedure, and no abnormalities were found on the next day's T2-weighted magnetic resonance imaging. Two weeks later, a colonoscopy was performed due to mucus stools revealing rectal perforation attributed to SpaceOAR. By maintaining Macrogol 4000 and a low residue diet, the perforation healed within 6 months.

Conclusion

Rectal ulcers and perforations are the most common severe adverse events from SpaceOAR placement. Effective management strategies are crucial since complications can't be entirely avoided, even with skilled surgeons.

The expanding role of radiation oncology across the prostate cancer continuum

Radiotherapy is used in the treatment of prostate cancer in a variety of disease states with significant reliance on imaging to guide clinical decision-making and radiation delivery. In the definitive setting, the choice of radiotherapy treatment modality, dose, and fractionation for localized prostate cancer is determined by the patient's initial risk stratification and other clinical considerations. Radiation is also an option as salvage therapy in patients with locoregionally recurrent disease after prior definitive radiation or surgery. In recent years, the role of radiation has expanded for patients with metastatic disease, including prostate-directed radiotherapy in de novo low volume metastatic disease, metastasis-directed therapy for oligorecurrent disease, and palliative management of symptomatic metastases in the advanced setting. Here we review the expanding role of radiation in the treatment of prostate cancer in the definitive, locoregionally recurrent, and metastatic settings, as well as highlight the role of imaging in clinical reasoning, radiation planning, and treatment delivery.

Overview of Radiation Therapy in the Management of Localized and Metastatic Prostate Cancer

PURPOSE OF REVIEW

The goal is to describe the evolution of radiation therapy (RT) utilization in the management of localized and metastatic prostate cancer.

RECENT FINDINGS

Long term data for a variety of hypofractionated definitive RT dose-fractionation schemes has matured, allowing patients and providers many standard-of-care options to choose from. Post-prostatectomy, adjuvant RT has largely been replaced by an early salvage approach. Multiparametric MRI and PSMA PET have enabled increasingly targeted RT delivery to the prostate and oligometastatic tumors. Areas of active investigation include determining the value of proton beam therapy and perirectal spacers, and optimally incorporate genomic tumor profiling and next generation hormonal therapies with RT in the curative setting. The use of radiation therapy to treat prostate cancer is rapidly evolving. In the coming years, there will be continued improvements in a variety of areas to enhance the value of RT in multidisciplinary prostate cancer management.

Long-term evaluation of the safety of a rectal-prostate spacer, the ProSpace® balloon, in patients treated with radiotherapy for prostate cancer

BACKGROUND

Due to the close proximity of the prostate and rectum, rectal toxicity remains a major problem in patient treated by radiotherapy for prostate adenocarcinoma. One method of increasing the distance between the prostate and the rectum is to use a spacer implanted into the rectoprostatic space. This report describes the long-term outcomes obtained with a new ballon spacer.

METHODS

Patients treated with curative radiotherapy for low- or intermediate-risk prostate adenocarcinoma, who underwent insertion of the ProSpace® (BioProtect Ltd, Tzur Yigal, Israel) rectal-prostate balloon spacer, were included. The main objective was to evaluate the dosimetric benefit of the spacer for OARs. The secondary objectives were to evaluate the feasibility and tolerability of ProSpace® balloon placement and to evaluate its long-term therapeutic efficacy and tolerance.

RESULTS

Between October 2013 and March 2015, 16 patients were enrolled in the Pasteur Clinic, Toulouse, France. The median follow-up was 85.5 months. From top to bottom, the space created was a mean of 16.3 mm (range: 11-20.5 mm) at the base of the prostate, 12.1 mm (range: 4-16 mm) at the middle and 8.9 mm at the apex (range: 5-15 mm). On average, rectal volumes receiving a dose of 70 Gy, 60 Gy and 50 Gy were significantly lower after balloon implantation: -4.81 cc (1.5 vs. 6.3; p < 0.0005), -8.08 cc (6.4 vs. 14.5; p = 0.002) and -9.06 cc (16.7 vs. 25.7; p = 0.003), respectively. There were significant differences in coverage after balloon implantation: Median V95% (p < 0.0005), median Dmin (p = 0.01) and median V98% (p < 0.001) were higher after balloon implantation. At 5 years, cumulative gastrointestinal toxicity was grade 1 in 6% (1/16 patients). No toxicity of grade 2 or higher was found. At 5 years, no urinary toxicity grade 3 or 4 toxicity was found. The QoL was not deteriorated.

CONCLUSIONS

The use of the ProSpace® balloon seems to be well accepted by patients, allowing a double dosimetric gain: a decrease in doses received by the rectum and an improvement in the coverage of the high-risk PTV. The long-term gastrointestinal toxicity remains low and QoL is preserved in all treated patients.

Correlation between dose-volume parameters and rectal bleeding after 12 fractions of carbon ion radiotherapy for prostate cancer

BACKGROUND

Carbon ion radiotherapy (CIRT) is currently used to treat prostate cancer. Rectal bleeding is a major cause of toxicity even with CIRT. However, to date, a correlation between the dose and volume parameters of the 12 fractions of CIRT for prostate cancer and rectal bleeding has not been shown. Similarly, the clinical risk factors for rectal bleeding were absent after 12 fractions of CIRT.

AIM

To identify the risk factors for rectal bleeding in 12 fractions of CIRT for prostate cancer.

METHODS

Among 259 patients who received 51.6 Gy [relative biological effectiveness (RBE)], in 12 fractions of CIRT, 15 had grade 1 (5.8%) and nine had grade 2 rectal bleeding (3.5%). The dose-volume parameters included the volume (cc) of the rectum irradiated with at least x Gy (RBE) (Vx) and the minimum dose in the most irradiated x cc normal rectal volume (Dx).

RESULTS

The mean values of D6cc, D2cc, V10 Gy (RBE), V20 Gy (RBE), V30 Gy (RBE), and V40 Gy (RBE) were significantly higher in the patients with rectal bleeding than in those without. The cutoff values were D6cc = 34.34 Gy (RBE), D2cc = 46.46 Gy (RBE), V10 Gy (RBE) = 9.85 cc, V20 Gy (RBE) = 7.00 cc, V30 Gy (RBE) = 6.91 cc, and V40 Gy (RBE) = 4.26 cc. The D2cc, V10 Gy (RBE), and V20 Gy (RBE) cutoff values were significant predictors of grade 2 rectal bleeding.

CONCLUSION

The above dose-volume parameters may serve as guidelines for preventing rectal bleeding after 12 fractions of CIRT for prostate cancer.

Prospective, Randomized Controlled Pivotal Trial of Biodegradable Balloon Rectal Spacer for Prostate Radiation Therapy

PURPOSE/OBJECTIVES

Rectal spacers have been shown to reduce rectal side effects in patients receiving prostate radiation. However, concerns remain regarding precise and reproducible gel injection. We evaluated efficacy and safety of a novel rectoprostatic spacer balloon that allows potential for controlled, adaptable deployment. This study tested co-primary hypotheses: (1) balloon spacer would result in ≥25% reduction of rectal V70 in >75% of subjects and (2) implantation procedure-related and rectal ≥grade 1 adverse events within 6 months (duration ≥2 days, Common Terminology Criteria for Adverse Events 4.0) would be noninferior in balloon versus control subjects.

METHODS AND MATERIALS

A total of 222 subjects were enrolled at 16 centers. All patients had T1-T3 prostate cancer without magnetic resonance imaging evidence of posterior extraprostatic invasion. Randomization was 2:1 (balloon: control) and subject-blinded. Patients underwent transperineal transrectal ultrasound axial and sagittal-guided fiducial placement ± balloon, followed by Intensity-Modulated Radiation Therapy (81 Gy in 1.8 Gy fractions or biologically equivalent hypofractionated dose). For efficacy comparisons, plans were generated by a central core lab on pre- and postimplant computed tomography scans.

RESULTS

The primary efficacy endpoint was met, with 97.9% of balloon subjects (139/142) having rectal V70 reduction >25% (P < .001). Mean V70 was 7.0 % pre- versus 1.1% postimplant. The primary safety endpoint was met with balloon subjects experiencing fewer ≥grade 1 events, 18% versus 23% (P < .001 for noninferiority). On predefined secondary endpoint of ≥grade 2 events, rates trended lower in balloon subjects (4.3% vs 6.5%, P = .527). Mean perirectal spacing was 19 ± 3.7 mm and maintained through radiation treatment (18 ± 3.9 mm). Balloon resorption was observed on 6-month computed tomography in 98.5% (133/135) of subjects. The Expanded Prostate Cancer Index quality of life instrument was collected throughout study, and did not differ statistically between the study arms.

CONCLUSIONS

Biodegradable rectal spacer balloon was effective in significantly reducing dose to rectum, and associated with decreased cumulative rectal plus implantation-related adverse events. Balloon resorption was consistently observed by 6 months.

Symmetry, separation, and stability: Physical properties for effective dosimetric space with a stabilized hyaluronic acid spacer

BACKGROUND

The proximity of the rectum to the prostate in radiation therapy (RT) for prostate cancer presents a significant dosimetric challenge, leading to high rectal doses and resulting in detrimental side effects. Perirectal tissue spacing reduces rectal dose and gastrointestinal toxicities by mechanically separating these organs. A variety of materials have been explored for use as rectal spacers, most recently, a stabilized hyaluronic acid (HA) gel, which can be formed into deliberate a shape, and retains the definition of that shape, while remaining flexible, unlike polyethylene glycol (PEG) hydrogels.

PURPOSE

This study evaluates the dosimetric impact of the spacer, including shape symmetry, the degree of separation at different locations, and the temporal stability of the space. Our goal is to provide physics-informed guidance on the optimal use of this sculptable spacer.

METHODS

A secondary analysis was performed on data from a 13-center prospective randomized trial (NCT04189913), involving 136 patients with centrally-reviewed treatment plans conducted on CT/MR simulation scans before and after receiving HA spacer implants. Patients were treated with 60 Gy in 20 fractions to the prostate. For this study, python software was utilized for automated processing of DICOM RTstruct and RTdose files, facilitating detailed analysis of the spacer's impact on anatomical displacement and dosimetric outcomes. Complete dose-volume histograms (DVHs) were reconstructed, and combined into composite population DVHs before and after implant, verified against trial-reported dose points. Patients were divided into similar groups of separation and symmetry, and differences in their composite DVHs were tested for significance. Stability of the spacer was studied by comparing serial MRI images and by computing the distance between contours at four axial planes, at simulation and 3-month follow-up, post RT.

RESULTS

The introduction of the HA spacer significantly enhanced rectal sparing, as evidenced by a reduction in the mean rectal integral dose by over 6 Gy. High rates of implant symmetry (>95%) were observed, indicating nearly optimal lateral spacer placement. In superior-inferior coverage, this study like many others, saw the spacing largest at the superior extent but becoming more variable inferiorly at the level of the prostate apex. This allowed study of the apex as a specific area for dosimetric concern. Stability assessments confirmed that the spacer maintained its position and dimensions between the simulation and the 3-month post-RT, implying stable geometry during treatment, with only minimal separation changes observed. Statistical analysis using the Kruskal-Wallis test revealed significant correlations of larger separations at the inferior and apical planes with improved dosimetric outcomes, including rV30Gy.

CONCLUSION

The use of a stabilized HA spacer in prostate RT effectively enhances prostate-rectum separation, leading to significant rectal sparing without undesirable dose compromises. This study underscores the role of strategic placement and shape, specifically including > 1 cm separation from the base down to the prostate apex. When combined with the treatment planning techniques used in the trial to create a steep dosimetric gradient across the spacer, these findings elucidate the dosimetric outcomes that can be expected in the clinical implementation of HA spacer. This is particularly relevant in the evolution of hypofractionated treatment regimens for prostate cancer therapy.

EUS-guided hydrogel injection to separate pancreatic head carcinoma from duodenum for enhanced radiotherapy: Multi-site feasibility study

Background and study aims The proximity of a pancreas head tumor to the duodenum often limits delivery of an ablative dose of radiation therapy. This study evaluated the feasibility and safety of using an injectable polyethylene glycol (PEG) hydrogel between the head of the pancreas and duodenum. Patients and methods In a multi-site feasibility cohort study of patients with localized pancreatic cancer, PEG hydrogel was injected under endoscopic ultrasound guidance to temporarily position the duodenum away from the pancreas. Procedure characteristics were recorded, including hydrogel volume and space created. Patients were monitored for adverse events (AEs) and radiotherapy toxicity. Results In all six intent-to-treat patients (four with borderline resectable, two with locally advanced disease), the ability to place and visualize PEG hydrogel and create space between the duodenum and the head of the pancreas was successful. There were no procedure-related AEs resulting in radiotherapy delay. There were no device-related AEs and no reports of pancreatitis. Conclusions PEG hydrogel was successfully placed, created space between the duodenum and the head of the pancreas, and was not associated with major toxicity. Enhancing radiotherapy for pancreatic cancer by using PEG hydrogel to create peri-duodenal space could have beneficial implications for treatment and warrants more exploration.

A Multi-Institutional Safety and Feasibility Study Exploring the Use of Hydrogel to Create Spatial Separation between the Pancreas and Duodenum in Patients with Pancreatic Cancer

PURPOSE

The administration of dose-escalated radiation for pancreatic adenocarcinoma remains challenging because of the proximity of dose-limiting stomach and bowel, particularly the duodenum for pancreatic head tumors. We explore whether endoscopic injection of a temporary, absorbable hydrogel into the pancreatico-duodenal (PD) groove is safe and feasible for the purpose of increasing spatial separation between pancreatic head tumors and the duodenum.

METHODS AND MATERIALS

Six patients with localized pancreatic adenocarcinoma underwent endoscopic injection of hydrogel into the PD groove. Safety was assessed based on the incidence of procedure-related adverse events resulting in a delay of radiation therapy initiation. Feasibility was defined as the ability to create spatial separation between the pancreas and duodenum, as assessed on simulation CT.

RESULTS

All 6 patients were able to undergo endoscopic injection of hydrogel into the PD groove. No device-related events were experienced at any point in follow-up. Presence of hydrogel in the PD groove was apparent on simulation CT in all 6 patients. Mean space created by the hydrogel was 7.7 mm +/- 2.4 mm. In 3 patients who underwent Whipple resection, presence of hydrogel in the PD groove was pathologically confirmed with no evidence of damage to the duodenum.

CONCLUSIONS

Endoscopic injection of hydrogel into the PD groove is safe and feasible. Characterization of the dosimetric benefit that this technique may offer in the setting of dose-escalated radiation should also be pursued, as should the ability of such dosimetric benefit to translate into clinically improved tumor control.

Unexpected change in hydrogel spacer volume during external-beam radiation therapy

PURPOSE

To reduce the rectal radiation dose during local radiation therapy of prostate cancer, a hydrogel spacer is typically implanted between the prostate and rectum. However, the spacer volume can change during external beam radiation therapy (EBRT). Therefore, we used magnetic resonance imaging (MRI) to determine changes in the spacer volume during EBRT and analyzed the data to identify patient factors influencing this change.

MATERIALS AND METHODS

A hydrogel spacer was implanted in each enrolled patient diagnosed with prostate cancer (n = 22, age = 69-86 years) for EBRT with a total dose of 70 Gy over 35 fractions. T2-weighted MRI images were acquired before (median = 8 days) and during EBRT, when the radiation dose of 48 Gy (median) was given at 55 days (median) after implantation. MRI images were used to determine the spacer volume as well as the maximum and minimum distances between the prostate and anterior wall of the rectum at the middle height of the prostate. Scatterplots were created to determine whether correlations existed between changes in the spacer volume and these two distances, while uni- and multivariate analyses were conducted to determine if the spacer volume change was influenced by the following patient factors: age, body mass index, estimated glomerular filtration rate, and visceral fat areas at the umbilical and femoral head positions.

RESULTS

The spacer volume increased in all 22 patients, with the smaller spacer volume before EBRT increasing by a larger amount during EBRT. This increase in the spacer volume was unaffected by other patient factors. However, it correlated with the change in the maximum distance between the prostate and anterior wall of the rectum.

CONCLUSION

To avoid adverse changes in the rectal radiation dose during EBRT, hydrogel spacer volume should be monitored, especially if the pre-EBRT volume is small.

CT-guided hydrogel injection for brachytherapy in cervical cancer: A case report

Rectal toxicity is a significant concern in cervical cancer radiotherapy. Despite advancements in image-guided brachytherapy (IGBT), rectal morbidity remains a challenge. Injectable hydrogel showed promise in creating a space between the vagina and rectum, reducing rectal radiation dose; however, the traditional ultrasound-guided injection revealed some problems, such as the inadequate separation of the upper edge of the cervix, which can be mitigated through adopting CT-guided injection. This case report presents the successful use of computed tomography (CT)-guided hydrogel injection to limit rectal doses and improve treatment outcomes. A forty-year-old female with stage IIIC1r cervical cancer received external-beam radiotherapy and concurrent chemotherapy. Due to the proximity of the tumor to the rectum, a CT-guided hydrogel injection was performed to increase the distance between the cervix and rectum. Post-injection, magnetic resonance imaging (MRI) demonstrated increased distances between the cervix and rectum. Subsequent MRI-based IGBT achieved high clinical target volume doses while limiting rectal doses. During the six-month follow-up, the patient reported only mild adverse effects. CT-guided hydrogel injection offers advantages over ultrasound-guided injection in cervical cancer radiotherapy. The technique allows for better puncture position adjustment, reduced reliance on specialized ultrasound expertise, and shorter puncture distances. This case report highlights the potential of hydrogel injection as a viable method to reduce rectal morbidity and improve treatment outcomes in a broader range of cervical cancer patients. Further studies are warranted to validate these findings and explore its applicability in larger cohorts.

The role of a radiopaque peri-rectal hydrogel spacer in aiding accurate daily image-guidance for prostate stereotactic radiotherapy

Introduction

Precise patient positioning with image guidance (IGRT) is essential for safe prostate radiotherapy. We present the first report of utilizing a CT-visible hydrogel spacer, used to decrease rectal radiation dose, as a surrogate fiducial marker to aid in daily IGRT with cone-beam CT (CBCT) in stereotactic radiotherapy (SABR) for prostate cancer.

Materials and methods

Prior to CT simulation, patients underwent placement of three intraprostatic gold fiducial markers and radiopaque hydrogel spacer per standard practice. At treatment, after initial setup, a CBCT was acquired and fused to the planning CT based on 3-dimensional matching of the spacer. A second alignment was then performed based on the fiducial markers. The six directional shifts (three linear and three rotational) were recorded, and the differences compared.

Results

140 individual fractions across 41 consecutive patients were evaluated. Mean/median differences between hydrogel spacer-based and fiducial-based alignment in linear (vertical, longitudinal, lateral) and rotational (rotation, pitch, roll) shifts were 0.9/0.6mm, 0.8/0.5mm, and 0.6/0.4mm, and 0.38/0, 0.62/0, and 0.35/0 degrees, respectively. No difference was observed in 9.9%, 22.9%, and 22.14% of linear shifts, and 65.7%, 65%, and 66.4% rotational shifts, respectively. Significantly smaller differences were observed in the latter 70 fractions vs. the former, and results were consistent across evaluators.

Conclusions

For precise daily IGRT with CBCT for prostate SABR, alignment using a radiopaque hydrogel spacer was highly comparable to intraprostatic fiducial markers. This represents the first report supporting an additional indication of IGRT for a CT-visible hydrogel spacer, to further enhance treatment accuracy and potentially obviate the need for the additional fiducial marker procedure.

Conditional Risk and Predictive Factors Associated With Late Toxicity in Patients With Prostate Cancer Treated With External Beam Radiation Therapy Alone in the Randomized Trial RTOG 0126

PURPOSE

The objective of this study was to characterize the conditional risk of developing grade 2+ urinary or gastrointestinal (GI) toxicity for patients treated with external beam radiation therapy in Radiation Therapy Oncology Group 0126. A secondary objective was to analyze baseline patient and treatment characteristics and determine their relevance in predicting toxicity both at the time of trial enrollment and at later points of follow-up.

METHODS AND MATERIALS

One thousand five hundred thirty-two patients with localized prostate cancer were enrolled between March 2002 and August 2008, of whom 1499 were eligible and included in data analysis with a median follow-up of 8.4 years (range, 0.02-13 years). Patients were treated with either 3-dimensional conformal radiation therapy or intensity-modulated radiation therapy according to institutional practice without the addition of androgen deprivation and randomized to receive either standard-dose radiation therapy of 70.2 Gy or dose-escalated radiation therapy of 79.2 Gy of radiation therapy to the prostate only with standard fractionation. Univariate and multivariate analyses were performed to determine whether initial factors were predictive of late toxicity at the time of treatment and at later time points.

RESULTS

As patients proceed further from completion of radiation therapy without the development of toxicity, the subsequent risk of both grade 2+ genitourinary (GU) and GI toxicity decreases with time. At the time of enrollment, the risk of developing grade 2+ toxicity over the next 5 years was 9.57% and 17.89%, respectively. After 5 years of toxicity-free survival, the risk of developing grade 2+ GU or GI toxicity in the subsequent 5 years was 3.02% and 1.54%, respectively. Baseline treatment and patient-related factors predicted late toxicity both at trial enrollment and after 2 years of toxicity-free survivorship. Baseline urinary dysfunction and dose-escalated radiation therapy were associated with increased late GU toxicity. Acute GI toxicity and dose-escalated radiation therapy were associated with increased risk of late GI toxicity. Treatment with intensity-modulated radiation therapy was associated with reduced risk of either toxicity.

CONCLUSIONS

The conditional risk of grade 2+ toxicities decreases as patients proceed further from treatment, with most toxicities occurring in the first few years after treatment completion. Baseline patient and treatment characteristics remain relevant at both enrollment and later time points.

Major Complications and Adverse Events Related to Use of SpaceOAR Hydrogel for Prostate Cancer Radiotherapy

OBJECTIVE

To determine the prevalence and severity of SpaceOAR-related adverse events using the Manufacturer and User Facility Device Experience (MAUDE) database.

METHODS

We analyzed SpaceOAR-related adverse event reports in the Manufacturer and User Facility Device Experience (MAUDE) database from January 2015 to May 2023. For each report, the event type, associated device and patient problems, event description, event timing, and event severity stratified by the Common Terminology Criteria for Adverse Events version 5.0 (CTCAE) grading system were recorded.

RESULTS

From 2015 to 2022, 206,619 SpaceOAR devices were sold. From January 2015 to May 2023, we identified 981 reports describing 990 SpaceOAR-related adverse events. Malfunctions were the most common event type (N = 626), followed by patient injuries (N = 350) with few reported deaths (N = 5). Device positioning problems were the most frequent device issue (N = 686). Pain was the most reported patient problem (N = 216). Abscesses and fistulas related to the device were each reported in 91 events. A noteworthy portion of relevant adverse events occurred before the initiation of radiation (N = 35, 22.4%), suggesting the device, rather than the radiation, was responsible. In total, 470 (50.2%) and 344 (36.7%) of the adverse events were CTCAE grade 1 and 2, respectively. There were 123 (13.1%) events that were CTCAE grade ≥3.

CONCLUSION

We identified multiple reports of SpaceOAR-related adverse events, many of which are more serious than have been reported in clinical trials. While SpaceOAR use is common, suggesting these events are rare, these data highlight the need for continued postmarket surveillance.

Sexual Structure Sparing for Prostate Cancer Radiotherapy: A Systematic Review

CONTEXT

Erectile dysfunction represents a major side effect of prostate cancer (PCa) treatment, negatively impacting men's quality of life. While radiation therapy (RT) advances have enabled the mitigation of both genitourinary and gastrointestinal toxicities, no significant improvement has been showed in sexual quality of life over time.

OBJECTIVE

The primary aim of this review was to assess sexual structures' dose-volume parameters associated with the onset of erectile dysfunction.

EVIDENCE ACQUISITION

We searched the PubMed database and ClinicalTrials.gov until January 4, 2023. Studies reporting the impact of the dose delivered to sexual structures on sexual function or the feasibility of innovative sexual structure-sparing approaches were deemed eligible.

EVIDENCE SYNTHESIS

Sexual-sparing strategies have involved four sexual organs. The mean penile bulb doses exceeding 20 Gy are predictive of erectile dysfunction in modern PCa RT trial. Maintaining a D100% of ≤36 Gy on the internal pudendal arteries showed preservation of erectile function in 88% of patients at 5 yr. Neurovascular bundle sparing appears feasible with magnetic resonance-guided radiation therapy, yet its clinical impact remains unanswered. Doses delivered to the testicles during PCa RT usually remain <2 Gy and generate a decrease in testosterone levels ranging from -4.6% to -17%, unlikely to have any clinical impact.

CONCLUSIONS

Current data highlight the technical feasibility of sexual sparing for PCa RT. The proportion of erectile dysfunction attributable to the dose delivered to sexual structures is still largely unknown. While the ability to maintain sexual function over time is impacted by factors such as age or comorbidities, only selected patients are likely to benefit from sexual-sparing RT.

PATIENT SUMMARY

Technical advances in radiation therapy (RT) made it possible to significantly lower the dose delivered to sexual structures. While sexual function is known to decline with age, the preservation of sexual structures for prostate cancer RT is likely to be beneficial only in selected patients.

Biomaterials-mediated radiation-induced diseases treatment and radiation protection

In recent years, the intersection of the academic and medical domains has increasingly spotlighted the utilization of biomaterials in radioactive disease treatment and radiation protection. Biomaterials, distinguished from conventional molecular pharmaceuticals, offer a suite of advantages in addressing radiological conditions. These include their superior biological activity, chemical stability, exceptional histocompatibility, and targeted delivery capabilities. This review comprehensively delineates the therapeutic mechanisms employed by various biomaterials in treating radiological afflictions impacting the skin, lungs, gastrointestinal tract, and hematopoietic systems. Significantly, these nanomaterials function not only as efficient drug delivery vehicles but also as protective agents against radiation, mitigating its detrimental effects on the human body. Notably, the strategic amalgamation of specific biomaterials with particular pharmacological agents can lead to a synergistic therapeutic outcome, opening new avenues in the treatment of radiation- induced diseases. However, despite their broad potential applications, the biosafety and clinical efficacy of these biomaterials still require in-depth research and investigation. Ultimately, this review aims to not only bridge the current knowledge gaps in the application of biomaterials for radiation-induced diseases but also to inspire future innovations and research directions in this rapidly evolving field.

Feasibility estimation of injected hydrodissection before definitive radiotherapy of pancreatic adenocarcinoma

BACKGROUND

Pancreatic adenocarcinoma is often not diagnosed until an advanced stage, and so most patients are not eligible for resection. For patients who are inoperable, definitive radiotherapy is crucial for local disease control. However, the pancreas is located close to other vulnerable gastrointestinal organs, making it challenging to deliver an adequate radiation dose. The surgical insertion of spacers or injection of fluids such as hydrogel before radiotherapy has been proposed, however, no study has discussed which patients are suitable for the procedure.

METHODS

In this study, we reviewed 50 consecutive patients who received definitive radiotherapy at our institute to determine how many could have benefitted from hydrodissection to separate the pancreatic tumor from the adjacent gastrointestinal tract. By hypothetically injecting a substance using either computed tomography (CT)-guided or endoscopic methods, we aimed to increase the distance between the pancreatic tumor and surrounding hollow organs, as this would reduce the radiation dose delivered to the organs at risk.

RESULTS

An interventional radiologist considered that hydrodissection was feasible in 23 (46%) patients with a CT-guided injection, while a gastroenterologist considered that hydrodissection was feasible in 31 (62%) patients with an endoscopic injection. Overall, we found 14 (28%) discrepancies among the 50 patients reviewed. Except for 1 patient who had no available trajectory with a CT-guided approach but in whom hydrodissection was considered feasible with an endoscopic injection, the other 13 patients had different interpretations of whether direct invasion was present in the CT images.

CONCLUSION

Our results suggested that about half of the patients could have benefited from hydrodissection before radiotherapy. This finding could allow for a higher radiation dose and potentially better disease control.

Transient, Image-Guided Gel-Dissection for Percutaneous Thermal Ablation

Image-guided tumor ablative therapies are mainstay cancer treatment options but often require intra-procedural protective tissue displacement to reduce the risk of collateral damage to neighboring organs. Standard of care strategies, such as hydrodissection (fluidic injection), are limited by rapid diffusion of fluid and poor retention time, risking injury to adjacent organs, increasing cancer recurrence rates from incomplete tumor ablations, and limiting patient qualification. Herein, a "gel-dissection" technique is developed, leveraging injectable hydrogels for longer-lasting, shapeable, and transient tissue separation to empower clinicans with improved ablation operation windows and greater control. A rheological model is designed to understand and tune gel-dissection parameters. In swine models, gel-dissection achieves 24 times longer-lasting tissue separation dynamics compared to saline, with 40% less injected volume. Gel-dissection achieves anti-dependent dissection between free-floating organs in the peritoneal cavity and clinically significant thermal protection, with the potential to expand minimally invasive therapeutic techniques, especially across locoregional therapies including radiation, cryoablation, endoscopy, and surgery.

An optimal method of hydrogel spacer insertion for stereotactic body radiation therapy of prostate cancer

PURPOSE

This study aimed to explore an ideal method for hydrogel spacer insertion by analyzing the efficacy and safety of our originally developed apex expansion method.

MATERIALS AND METHODS

Overall, 100 patients with low- and intermediate-risk localized prostate cancer treated with stereotactic body radiation therapy were included. A hydrogel spacer was inserted in 64 and 36 patients using the conventional and apex expansion methods, respectively. For dosimetry, we trisected the rectum into the upper rectum, middle rectum, and lower rectum on the sagittal section of magnetic resonance imaging. We compared the dose to each part of the rectum between the two methods using dose-volume histograms. Genitourinary and gastrointestinal toxicity assessments were conducted until 3 months of follow-up.

RESULTS

The whole rectal dose in the apex expansion method group was lower than that in the conventional method group, which was significant in all dose regions (V5-V35). Similarly, in the apex expansion method group, the dose to the middle rectum was lower in the low- to high-dose region (V10-V35), and the dose to the lower rectum was lower in the middle- to high-dose region (V15-35). No Grade ≥ 3 toxicity or procedure-related complications were observed. Additionally, Grade 2 genitourinary and gastrointestinal toxicities during the treatment showed no significant differences between the two methods.

CONCLUSION

The apex expansion method may be safe and effective in achieving a more efficient rectal dose reduction by expanding the anterior perirectal space in the prostatic apex area.

SpaceOAR Complication Affecting the Treatment of Prostate Cancer

A 60-year-old male presented with an elevated prostate-specific antigen (PSA) of 10 ng/ml. A transrectal ultrasound-guided prostate biopsy showed prostate adenocarcinoma GS 4+3 (grade 3) with 5 out of 12 cores positive for malignancy. He initially planned to have prostate stereotactic body radiation therapy (SBRT) with SpaceOAR gel insertion in his rectoprostatic space to reduce radiation to the rectum. Magnetic resonance imaging (MRI) two months after SpaceOAR insertion showed evidence of infiltration of the SpaceOAR within the anterior rectal wall. This delayed his treatment and he was started on a short course of androgen deprivation therapy with Leuprolide while waiting for absorption of the gel. After completion of androgen deprivation therapy, the patient was treated with external beam radiation therapy (EBRT) to the prostate, seminal vesicles, and pelvis to a total dose of 6000 centigray (cGy) in 20 fractions at a dose per fraction of 300 cGy. He did well after treatment with minimal side effects.

Safe dose escalation and reduction of the fraction number of uterine cervical brachytherapy using a gel spacer in the rectovaginal and vesicouterine septum: A planning study

PURPOSE

To evaluate the possibility of dose escalation and reduction of fraction number in cervical brachytherapy using a gel spacer.

MATERIAL AND METHODS

Twenty patients with uterine cervical cancer treated with image-guided adaptive brachytherapy (IGABT) were selected. Hyaluronic acid gel injection (HGI) was performed in the rectovaginal and vesicouterine septum for 10 patients. The other ten patients were not with HGI. Both groups were treated with IGABT involving tandem/ovoid or cylindrical applicators along with additional interstitial needles. Dose distributions approved by radiation oncologists were retrospectively analyzed, and a dose summation of 45 Gy/25 of external beam radiation therapy and IGABT was performed. Dose constraints for D2cc of bladder, rectum, and sigmoid were 80, 70, and 70 Gy, respectively. Equivalent dose in 2-Gy fractions calculations used α/β = 10 Gy for high-risk clinical target volume (CTVHR) D90 and α/β = 3 Gy for organs at risks (OARs). As a planning study, dose distribution rescaling was conducted to deliver as much dose to CTVHR D90 as possible within the dose constraint limitation for OARs when IGABT was performed for four, three, and two fractions in both groups.

RESULTS

The median CTVHR D90 was >80 Gy in the non-HGI group and >85 Gy in the HGI group for virtual two and three fractions. Rectum D2cc was significantly lower in the HGI group for three fractions (p < 0.01).

CONCLUSIONS

In the HGI group, adequate dose delivery to CTVHR could be achieved with a reduced IGABT fraction number while meeting the dose constraints of OARs.

Use of rectal balloon spacer in patients with localized prostate cancer receiving external beam radiotherapy

Objective

To evaluate the efficacy of the balloon spacer when used to reduce the radiation dose delivered to the rectum in prostate cancer patients undergoing external beam radiotherapy.

Method

A single center retrospective analysis including 75 PC patients with localized T1-T3a disease who received balloon spacer followed by EBRT. Pre- and post-implantation computed tomography (CT) scans were utilized for treatment planning for standard EBRT (78-81 Gy in 1.8-2 Gy fractions). Rectal dosimetry was assessed using DVHs, and toxicities were graded with CTCAE v.4.

Results

A median (IQR) prostate-rectum separation resulted in 1.6 cm (1.4-2.0) post balloon spacer implantation. Overall, 90.6 % (68/75) of patients had a clinically significant 25 % relative reduction in the rectal with a median relative reduction of 91.8 % (71.2-98.6 %) at rV70. Three (4.0 %) patients reported mild procedural adverse events, anal discomfort and dysuria. Within 90 days post-implantation, five patients (6.67 %) and 1 patient (1.33 %) reported grade 1 and grade 2 rectal toxicities (anal pain, constipation, diarrhea and hemorrhoids). Genitourinary (GU) grade 1 toxicity was reported in 37 patients (49.33 %), with only one patient (1.33 %) experiencing grade 2 GU toxicity. No grade ≥ 3 toxicity was reported.

Conclusion

Balloon spacer implantation effectively increased prostate-rectum separation and associated with dosimetric gains EBRT for PC stage T1-T3a. Further controlled studies are required to ascertain whether this spacer allows for radiotherapy dose escalation and minimizes gastrointestinal (GI) toxicity.

Stereotactic Body Radiation Therapy: A Radiosurgery Society Guide to the Treatment of Localized Prostate Cancer Illustrated by Challenging Cases

Traditionally, external beam radiotherapy (EBRT) for localized prostate cancer (PCa) involved lengthy courses with low daily doses. However, advancements in radiation delivery and a better understanding of prostate radiobiology have enabled the development of shorter courses of EBRT. Ultrahypofractionated radiotherapy, administering doses greater than 5 Gy per fraction, is now considered a standard of care regimen for localized PCa, particularly for intermediate-risk disease. Stereotactic body radiotherapy (SBRT), a specific type of ultrahypofractionated radiotherapy employing advanced planning, imaging, and treatment technology to deliver in five or fewer fractions, is gaining prominence as a cost-effective, convenient, and safe alternative to longer radiotherapy courses. It is crucial to address practical considerations related to patient selection, fractionation scheme, target delineation, and planning objectives. This is especially important in challenging clinical situations where clear evidence for guidance may be lacking. The Radiosurgery Society endorses this case-based guide with the aim of providing a practical framework for delivering SBRT to the intact prostate, exemplified by two case studies. The article will explore common SBRT dose/fractionation schemes and dose constraints for organs-at-risk. Additionally, it will review existing evidence and expert opinions on topics such as SBRT dose escalation, the use of rectal spacers, the role of androgen deprivation therapy in the context of SBRT, SBRT in special patient populations (e.g., high-risk disease, large prostate, high baseline urinary symptom burdens, and inflammatory bowel disease), as well as new imaging-guidance techniques like Magnetic Resonance Imaging for SBRT delivery.

Validation of a Quality Metric Score to Assess the Placement of Hydrogel Rectal Spacer in Patients Treated With Prostate Stereotactic Radiation Therapy

Purpose

To evaluate the quality of the interspace between the prostate and rectum and assess the effect on the dose to the rectum by measuring the spacer quality score (SQS) before and after implanting a hydrogel rectal spacer.

Methods and Materials

Thirty patients with prostate cancer were treated with stereotactic ablative body radiation therapy as part of the SPORT clinical trial. Each patient had a 10 mL polyethylene glycol hydrogel spacer inserted transperineally. Computed tomography scans were acquired before and after spacer insertion, 10MV flattening filter free (FFF) stereotactic ablative body radiation therapy (SABR) treatment plans were generated using each image set. To calculate the SQS, the prostate-rectal interspace (PRI) was measured in the anterior-posterior orientation, parallel to the anatomic midline at the prostate base, apex, and midgland on the prespacer and postspacer computed tomography. Measurements were taken in 3 transverse positions between the prostate and the rectum, and PRI scores of 0, 1, and 2 were assigned if the interspace between prostate and rectum was <0.3, 0.3 to 0.9, or ≥1 cm, respectively. The overall SQS was the lowest of the PRI scores. Differences between prespacer and postspacer PRIs and SQS were investigated by performing Fisher's exact test and differences between doses to the rectum were investigated by performing the paired samples Wilcoxon rank-sum test and Student t test.

Results

Statistically significant differences between prespacer versus postspacer patients were found when grouping patients according to their overall SQS. The PRI summary score did not reach statistical significance between prespacer and postspacer at the base but was significantly higher for the prostate midline and apex. Statistically significant differences in some rectum dose-volume metrics were found when grouping patients according to their PRIs and SQS.

Conclusions

SQS before and after the spacer insertion was evaluated and was found to be correlated with pre- and postspacer rectal dosimetry. Sources of improvement of the SQS scoring metric and limitations are discussed.

One-year clinical outcomes of MR-guided stereotactic body radiation therapy with rectal spacer for patients with localized prostate cancer

BACKGROUND AND PURPOSE

This prospective study aimed to investigate adaptive magnetic resonance (MR)-guided stereotactic body radiation therapy (MRgSBRT) with rectal spacer for localized prostate cancer (PC) and report 1-year clinical outcomes.

MATERIALS AND METHODS

Thirty-four consecutive patients with low- to high-risk localized PC that underwent 5-fraction adaptive MRgSBRT with rectal spacer were enrolled. The dosimetric comparison was performed on a risk- and age-matched cohort treated with MRgSBRT but without a spacer at a similar timepoint. Clinician-reported outcomes were based on Common Terminology Criteria for Adverse Events. Patient-reported outcomes were based on the Expanded Prostate Cancer Index Composite (EPIC) questionnaire at baseline, acute (1-3 months), subacute (4-12 months), and late (> 12 months) phases.

RESULTS

The median follow-up was 390 days (range 28-823) and the median age was 70 years (range 58-82). One patient experienced rectal bleeding soon after spacer insertion that subsided before MRgSBRT. The median distance between the midline of the prostate midgland and the rectum after spacer insertion measured 7.8 mm (range 2.6-15.3), and the median length of the spacer was 45.9 mm (range 16.8-62.9) based on T2-weighted MR imaging. The use of spacer resulted in significant improvements in target coverage (V100% > 95% = 98.6% [range 93.4-99.8] for spacer vs. 97.8% [range 69.6-99.7] for non-spacer) and rectal sparing (V95% < 3 cc = 0.7 cc [range 0-4.6] for spacer vs. 4.9 cc [range 0-12.5] for non-spacer). Nine patients (26.5%) experienced grade 1 gastrointestinal toxicities, and no grade ≥ 2 toxicities were observed. During the 1-year follow-up period, EPIC scores for the bowel domain remained stable and were the highest among all other domains.

CONCLUSIONS

MRgSBRT with rectal spacer for localized PC showed exceptional tolerability with minimal gastrointestinal toxicities and satisfactory patient-reported outcomes. Improvements in dosimetry, rectal sparing, and target coverage were achieved with a rectal spacer. Randomized trials are warranted for further validation.

Application of a Radiopaque Viscous Hydrogel Spacer for Prostate Cancer Radiation Therapy: A Prospective Phase 2 Study

PURPOSE

The aim of this study was to evaluate the application of a radiopaque viscous spacer (RVS) for prostate cancer radiation therapy (RT), including injection procedure, toxicity, treatment planning, image guidance, and imaging results up to 12 months after RT.

METHODS AND MATERIALS

RVS (median, 10 mL) was injected between prostate and rectal wall in 30 patients. Cone beam computed tomography (CT) was performed during the course of RT, a magnetic resonance imaging 3 and 12 months after RT. Injection and treatment tolerability were analyzed. The resulting distribution was compared with a control group of 30 patients with an initially fluid spacer.

RESULTS

Procedure- or device-related adverse events were not observed. Signs of hydrogel migration were not found in any case. The volume decreased by 25% at 3 months after RT, and small residues were detected at 12 months after RT in 3 cases (10%). The median rectal volume percentage within the 90% isodose was 3.0% (interquartile range, 1.5%-4.5%). Acute and late gastrointestinal toxicities were found in 17% and 3%, respectively (all grade 1). The median distance between prostate and rectum at the base/midplane/apex was greater for RVS in comparison to initially fluid spacer (14/12/11 mm vs 12/10/10 mm, respectively), the gel symmetry (right vs left from midline) was comparable. The application was assessed to be easier to control by the users, and visibility in cone beam CT as good.

CONCLUSIONS

The injection of a radiopaque viscous hydrogel spacer resulted in a prostate-rectum distance of >10 mm in most cases. The resulting rectum volume within the high-dose region and RT toxicity were very low. Advantages in comparison to the conventional hydrogel spacer are predominantly an improved placement control during the injection process and good visibility on CT.

Real-World Complications of the SpaceOAR Hydrogel Spacer: A Review of the Manufacturer and User Facility Device Experience Database

OBJECTIVE

To characterize adverse events related to use of the perirectal spacing agent SpaceOAR, we examined the Manufacturer and User Facility Device Experience (MAUDE) database.

METHODS

The MAUDE database was queried for "SpaceOAR" and "Augmenix" from June 2015 (when SpaceOAR was approved by the Food and Drug Administration) to October 2022. Reports were reviewed for adverse events (AEs), operative procedures performed because of the AE, and changes to the radiation plan. AEs were categorized using Common Terminology Criteria for Adverse Events (CTCAE), version 5.0.

RESULTS

Six hundred fifty-four reports were reviewed. Eighty-four were excluded and 4 reports reviewed 2 separate cases of SpaceOAR administration. Five hundred seventy-four cases were ultimately included. Three deaths were reported (0.5% of all AEs). One point six percent of cases represented CTCAE grade 4 injuries (life-threatening consequences; urgent intervention indicated), 15.9% grade 3 (severe but not immediately life-threatening; hospitalization), 24.2% grade 2 (moderate; local/noninvasive intervention), and 57% of events were CTCAE grade 1 (mild; asymptomatic or mild symptoms). Bowel diversion occurred in 29 cases (9%).

CONCLUSION

Both asymptomatic (n = 311) and debilitating (n = 12) complications of SpaceOAR hydrogel use were identified. Death, gel embolization, anaphylaxis, rectal ulcerations, and infections requiring bowel or urinary diversions were among the complications reviewed. Providers should consider these potential complications before perirectal spacer administration and during patient counseling.

Gynecological technical notes for appropriate spacer injections

BACKGROUND

Despite its efficacy, if adherence to dose constraints for surrounding normal tissues proves unattainable, the risk of late radiation-related adverse events after primary radiotherapy involving brachytherapy remains a noteworthy concern. Some studies suggest that similar to prostate radiotherapy, spacers may potentially reduce doses to surrounding healthy rectal or bladder tissues. However, guidance on spacer injections for gynecologic brachytherapy is scarce, and the optimal anatomical location for spacer placement remains undefined. We discuss maximizing the effects of spacers from an anatomical perspective.

FINDINGS

As vesicovaginal and rectovaginal septa form part of the endopelvic fascia and are not uniform tissues, spacer injection resistance varies. In pelvic organ prolapse surgery, saline is injected into the anterior and posterior vaginal walls as a spacer, and the vagina, vesicovaginal septum, and bladder can be fluidly dissected. Relatively firm vesicovaginal septum tissue is used as a reconstructive organ, whereas rectovaginal septum tissue is less dense. Cervical cancer is invasive, involving surrounding fascia and ligaments. Ideally, the vesicovaginal and rectovaginal septa should be resected in radical hysterectomy. Here, spacer adaptation and the technical details of injection are described. When using ultrasound guidance for spacer injection, the target site should be adequately magnified, and the spacer ideally injected into the incision layer during radical hysterectomy. Finally, posthysterectomy, the intestinal tract may adhere to the vaginal cuffs. Therefore, artificial ascites may be useful; however, the spread depends on perioperative manipulation.

CONCLUSIONS

Anatomical and surgical viewpoints are advantageous for safe, therapeutic, and replicable spacer injection administration.

Effect of Transperineal Versus Transrectal Prostate Biopsy on the Quality of Hydrogel Spacer Placement in Men Prior to Radiation Therapy for Prostate Cancer

OBJECTIVE

To determine whether prostate biopsy type affects spacer placement quality using a large sample of patients treated in the ambulatory setting.

METHODS

A retrospective cohort study was conducted on patients diagnosed with prostate cancer who underwent hydrogel spacer placement before primary radiation treatment between 2018 and 2023 after transperineal (TP) or transrectal (TR) prostate biopsy. Study outcomes were Spacer Quality Score (SQS) (0-2, with greater values indicating better placement), Rectal Wall Infiltration (RWI) (0-3, with lower values indicating lack of RWI), and the occurrence of other hydrogel complications.

RESULTS

A total of 395 patients were included. A pre-hydrogel TR biopsy was performed in 273 patients (69.1%), while TP biopsy was performed in 122 (30.9%). A SQS ≥1 occurred in 308 (77.9%) patients. A greater proportion of TP patients had a favorable SQS (≥1) compared to those who underwent TR (87.7 vs 73.5%, P <.002). An RWI score ≥2 was found in 180 (45.6%) patients. The proportion of patients with an unfavorable RWI score (≥2) did not differ significantly by type of biopsy performed. Patients who had an interval of >70 days between biopsy and hydrogel placement had significantly decreased odds of an RWI score ≥2 (odds ratio = 0.42, 95% confidence interval: 0.21-0.83). Only one infection was found after hydrogel placement.

CONCLUSION

The quality of hydrogel placement was significantly better in men who had undergone TP biopsy. Rectal wall infiltration was more common than previously reported but did not differ between TP and TR biopsies.

Clinical Efficacy and Openness to New Challenges of Low Dose Rate Brachytherapy for Prostate Cancer

Over a century ago, low-dose-rate (LDR) brachytherapy was introduced to treat prostate cancer (PCa). Since then, it has been widely applied worldwide, including in East Asia. LDR brachytherapy has been performed in 88 institutes in Japan. Beneficial clinical outcomes of LDR brachytherapy for intermediate-to-high-risk PCa have been demonstrated in large clinical trials. These clinical outcomes were achieved through advances in methods, such as urological precise needle puncture and seed placement, and the quantitative decision making regarding radiological parameters by radiation oncologists. The combined use of LDR brachytherapy with other therapeutic modalities, such as external beam radiation and androgen deprivation therapy, for the clinical risk classification of PCa has led to better anticancer treatment efficacy. In this study, we summarized basic LDR brachytherapy findings that should remain unchanged and be passed down in urology departments. We also discussed the applications of LDR brachytherapy for PCa in various clinical settings, including focal and salvage therapies. In addition, we highlighted technologies associated with brachytherapy that are under development.

Cs-131 prostate brachytherapy boost and effect of hydrogel rectal spacer on long-term patient-reported rectal bleeding and bowel quality of life

PURPOSE

This study evaluates long-term patient-reported bowel quality of life (QOL), rectal bleeding, and bleeding bother in patients with prostate cancer treated with external beam radiation therapy (EBRT) and Cesium-131 LDR brachytherapy (LDR-BT) boost with and without hydrogel rectal spacer.

METHODS AND MATERIALS

This is a retrospective analysis of prostate cancer patients treated between 2007 and 2022 with 45 Gy EBRT followed by 85 Gy Cs-131 LDR-BT boost with or without hydrogel rectal spacer. Expanded Prostate Cancer Index Composite (EPIC) QOL questionnaires pre-treatment and at each follow-up were collected. Patient-reported rectal bleeding occurring more than "rarely" and bother from rectal bleeding occurring more than a "very small problem" were deemed clinically significant. Fisher's exact test was used to test the association of rectal spacer use and the incidence of clinically significant rectal bleeding and bleeding bother. Paired samples t-test was used to analyze mean bowel scores at each time point.

RESULTS

Three hundred and forty-one patients were included in the analysis. The rectal spacer was used in 108 patients. Overall median follow-up was 48 months (IQR, 24-72), with a median follow-up of 24 months (IQR, 12-37.5) for the hydrogel group and 60 months (IQR, 36-84) for the non-hydrogel group. EPIC questionnaire response rates at median follow-up were 33% and 37% for the hydrogel and non-hydrogel groups, respectively. A clinically significant decrease in mean bowel domain scores was seen in the bowel bother domain at 6 and 12 months for patients who did not receive a rectal spacer. At the last follow-up of 60 months, the prevalence of clinically significant rectal bleeding and bleeding bother were 2.2% and 2.2%, respectively. The cumulative incidence of clinically significant long-term rectal bleeding was 2.8% and 18.9% in the hydrogel group and non-hydrogel group, respectively (Fisher's exact test, p < 0.0001). The cumulative incidence of clinically significant long-term bowel bother was 4.6% and 19.7% in the hydrogel group and non-hydrogel group, respectively (Fisher's exact test, p < 0.001).

CONCLUSIONS

Use of hydrogel rectal spacer with EBRT and Cs-131 LDR-BT boost was significantly associated with a lower incidence of patient-reported rectal bleeding and bother from rectal bleeding, and better long-term bowel QOL. Cumulative incidence was 2.8% (hydrogel group) versus 18.9% (non-hydrogel group) and 4.6% (hydrogel group) versus 19.7% (non-hydrogel group) for clinically significant long-term rectal bleeding and long-term bleeding bother, respectively.

Increasing rectum-prostate distance using a hydrogel spacer to reduce radiation exposure during proton beam therapy for prostate cancer

SpaceOAR, a polyethylene-glycol hydrogel, reduces rectal radiation exposure during radiation therapy for prostate cancer. Previously, our group reported the modified technique of hydrogel insertion, which achieves greater separated distance at prostate-apex. This study aimed to investigate the impact of separated distance at prostate-apex and our modifier technique, on radiation exposure reduction during proton beam therapy (PBT). We included 330 patients undergoing PBT with the relative biological effectiveness (RBE) of 63 Gray (Gy) for localized prostate cancer, and categorized them into groups 0 (no spacer, n = 141), 1 (separated distance of spacer at the prostate-apex level < 7.5 mm, n = 81), and 2 (distance ≥ 7.5 mm, n = 108). The rectal volumes to receive 30-60 Gy (RBE), was estimated and described as Rectal V30-60 (ml) in 10 Gy increments. The Rectal V30-60 (ml) was significantly lower in group 2 than in group 1, and in group 1 than in group 0. After propensity score matching, the multivariate logistic regression analysis revealed that the most significant factor to reduce radiation exposure was our modified technique of hydrogel insertion. Therefore, using a hydrogel spacer to expand the prostate-rectum distance not only at prostate-mid to prostate-base level but also at the prostate-apex level can reduce the radiation exposure in PBT for prostate cancer.

Gender-Affirming Surgery and Cancer: Considerations for Radiation Oncologists for Pelvic Radiation in Transfeminine Patients

Access to gender-affirming surgery is increasing for many transgender and nonbinary people in the United States, and radiation oncologists must be equipped to care for patients who have undergone such surgery in the region of their planned radiation treatment field. There are no guidelines for radiation treatment planning after gender-affirming surgery, and most oncologists do not receive training in the unique needs of transgender people with cancer. We review common gender-affirming genitopelvic surgeries for transfeminine people, including vaginoplasty, labiaplasty, and orchiectomy, and summarize the existing literature on the treatment of cancers of the neovagina, anus, rectum, prostate, and bladder in these patients. We also describe our systematic treatment approach and rationale for pelvic radiation treatment planning.

Radiological evaluation of an iodised hydrogel for prostate radiotherapy applications

PURPOSE

Physical separation of healthy tissue and target volumes in prostate radiotherapy through the insertion of hydrogel can improve patient toxicity rates. An iodised hydrogel may provide anatomical separation of prostate and rectum while being easily visualised through radio-opacity. The aim of this study was to characterise SpaceOAR Vue™ in kilovoltage (kV) images and megavoltage (MV) radiotherapy treatment planning.

METHODS

Two cassettes were 3D-printed, one filled with water and the other with SpaceOAR Vue™. Transmission dose through each cassette was measured in slab phantom geometry and compared for 6MV and 10MV photon energies. The SpaceOAR Vue™ slab phantom setup was simulated using computed tomography (CT) and a treatment plan created. The plan was calculated with the hydrogel segmented and material assignment set to water, and the resultant dose compared to corresponding measurement doses. The first 5 patients treated with SpaceOAR Vue™ were assessed with the volume and Hounsfield units (HU) of the hydrogel evaluated in CT and cone beam computed tomography (CBCT) imaging.

RESULTS

Transmission through Water and SpaceOAR Vue™ agreed to within 0.5% for both photon energies. Furthermore, the segmentation of SpaceOAR Vue™ and material assignment to water, resulted in a plan dose that agreed to measurement to within 0.5%. Clinically, the SpaceOAR Vue™ volume and HU did not vary over patient treatment course, however was found to display differently on different kV imaging modalities.

CONCLUSIONS

SpaceOAR Vue™ was found to be radio-opaque on kV images, but dosimetrically behaved similarly to water in MV treatment beams, making it suitable for clinical use.

Multicenter, dual fractionation scheme, single core lab comparison of rectal volume dose reduction following injection of two biodegradable perirectal spacers

PURPOSE

A multicenter, double-arm, central core lab, retrospective study was performed to compare the rectal dosimetry of patients implanted with two injectable, biodegradable perirectal spacers, in conventional fractionation (CF), as well as ultrahypofractionation (UH) treatment plans.

METHODS AND MATERIALS

Fifty-nine patients were enrolled into the study in five centers: two centers in Europe, which implanted a biodegradable balloon spacer in a total of 24 subjects and three centers in the US, which implanted the SpaceOAR in 35 subjects. Anonymized CTs (pre and post-implantation) were reviewed by the central core lab. For VMAT CF plans rectal V50, V60, V70, and V80 were calculated. For UH plans, a corresponding rectal V22.6, V27.1, V31.37, and V36.25 were established representing 62.5%, 75%, 87.5%, and 100% of the 36.25 Gy prescribed dose.

RESULTS

For CF VMAT, a comparison between the balloon spacer and the SpaceOAR revealed a significant difference of 33.4% decrease in mean rectal V50 (71.9% vs. 38.5%, p < 0.001), 27.7% in mean rectal V60 (79.6% vs. 51.9%, p < 0.001), 17.1% difference in mean rectal V70 (84.1% vs. 67.0%, p = 0.001), and a significant difference of 3.0% (p = 0.019) in mean rectal V80 (87.2% vs. 84.2%). With UH analysis, the mean rectal dose reduction for the balloon spacer compared to the SpaceOAR was 79.2% and 53.3% for V27.1 (p < 0.001), 84.1% and 68.1% for V31.71 (p = 0.001), and 89.7% and 84.8% for V36.25 (p = 0.012), respectively.

CONCLUSION

Rectal dosimetry is more favorable for treatment with the balloon spacer compared with SpaceOAR. Further research, particularly in the context of a prospective randomized clinical trial design, is needed to assess the acute and late toxicity experience as well as physician satisfaction with achieving symmetrical implantation, and ease of use in light of increasing clinical use.

Quality rectal hydrogel placement allows for gel-enabled dose-escalated EBRT (GEDE-EBRT) without rectal interference in prostate cancer

Multiple trials have shown that dose-escalation of radiation for prostate cancer provides a biochemical progression-free survival benefit (bPFS); however, rectal constraints are often limiting. In this dosimetric study, we hypothesized that a well-placed rectal hydrogel (RH) would permit improved dose-escalation and target coverage. We selected patients with good-quality RH and created plans with and without RH, prescribing 70 Gy in 28 fractions to the prostate and proximal seminal vesicles (PSV), and a peripheral zone (PZ) boost to 84 Gy, 98 Gy, or 112 Gy. We then compared plans with and without RH, prescribing a 112 Gy boost to 1 to 2 cm simulated dominant intraprostatic lesions (DIL). In the 18 plans created with a PZ boost, the PTV_boost D95% was higher in RH plans compared to non-RH plans (median 98.5 Gy vs 75.53 Gy, p < 0.01). The PSV planning target volume (PTV_PSV) D95% was also marginally higher with RH (71.87 Gy vs 71.04 Gy, p < 0.01). All rectal metrics were improved with RH. For the 32 plans created for simulated DILs treated to 112 Gy, the PTV_boost coverage (median D95% 112.48 Gy vs 102.63 Gy, p < 0.01) and rectal metrics were improved with RH. Four non-RH plans with at least a 4 mm rectal-PTV_boost gap achieved D95% > 98% of the prescription dose for the PTV_boost. Our study showed that placement of a high-quality RH allowed for GEDE-EBRT up to 112 Gy in 28 fractions (EQD2 160 Gy with α/β = 2.5). This concept should be tested prospectively, particularly to assess for increases in nonrectal toxicities.

A dosimetric analysis of rectal hydrogel spacer use in patients with recurrent prostate cancer undergoing salvage high-dose-rate brachytherapy

PURPOSE

We hypothesize rectal hydrogel spacer (RHS) improves rectal dosimetry in patients undergoing salvage high-dose-rate brachytherapy (HDR-BT) for intact, recurrent prostate cancer (PC).

METHODS AND MATERIALS

A prospectively collected institutional database was queried for recurrent PC patients treated with salvage HDR-BT from September 2015 to November 2021. Patients were offered RHS beginning June 2019. Dosimetric variables were compared between RHS and no-RHS groups for the average of two fractions using Wilcoxon rank-sum tests. Primary outcomes were rectal volume receiving 75% of prescription dose (V75%) and prostate volume receiving 100% of prescription dose (V100%). Generalized estimating equation (GEE) model was used to evaluate the association between other planning variables and rectal V75%.

RESULTS

Forty-one PC patients received salvage HDR-BT, of whom 20 had RHS. All patients received 2400cGy in 2 fractions. Median RHS volume was 6.2cm3 (Standard deviation [SD]: ± 3.5cm3). Median follow-up was 4 months and 17 months in the RHS and no-RHS groups, respectively. Median rectal V75% with and without RHS were 0.0cm3 (IQR: 0.0-0.0cm3) and 0.06cm3 (IQR: 0.0-0.14cm3), respectively (p<0.001). Median prostate V100% with and without RHS were 98.55% (IQR: 97.86-99.22%) and 97.78% (IQR: 97.50-98.18%), respectively (p = 0.007). RHS, rectum, and prostate volumes did not significantly affect rectal V75% per GEE modeling. There was 10% G1-2 and 5% G3 rectal toxicity in RHS group. There was 9.5% G1-2 and no G3+ rectal toxicities in the no-RHS group.

CONCLUSIONS

Absolute improvement in rectal V75% and prostate V100% was significant with RHS in PC patients undergoing salvage HDR-BT, but clinical benefit is marginal.

MucoUp® as a spacer in brachytherapy for uterine cervical cancer: A first-in-human experience

We first used MucoUp®, a hyaluronic acid used in endoscopic resection, as a spacer in brachytherapy. In five cervical cancer patients, MucoUp® insertion increased a 90% dose of the high-risk CTV to over 80 Gy while decreasing the dose of organs at risk. No related adverse events were observed.

The oncologic and safety outcomes of low-dose-rate brachytherapy for the treatment of prostate cancer

Around 40 years have passed since a modern low-dose-rate (LDR) brachytherapy for prostate cancer was introduced. LDR brachytherapy has become one of the definitive treatment options besides radical prostatectomy (RP) and external beam radiation therapy (EBRT). LDR brachytherapy has several advantages over EBRT such as a higher prescribed dose to the prostate gland while avoiding unnecessary irradiation of organs at risk, a precipitous dose gradient, a brief treatment time, and a short hospital stay. Previous reports revealed that the long-term oncologic outcomes of LDR brachytherapy are superior to those of EBRT. The oncologic outcomes of low- to intermediate-risk patients are equivalent to those of RP using the recurrence definition of surgery of prostate specific antigen (PSA) >0.2 ng/mL, while the oncologic outcomes of LDR brachytherapy as tri-modality (combined EBRT and androgen deprivation therapy) for high-risk patients is superior to that of RP using the recurrence definition of surgery. In respect of toxicity, urinary disorders such as urgency and frequency are often observed after the acute phase of treatment, but these events usually resolve, while the quality of life of urinary continence is well preserved for a long time. Erectile function decreases yearly, but is relatively preserved compared to RP. In conclusion, the most noteworthy strength of LDR brachytherapy for low- to intermediate-risk patients is the "brief treatment time" that provides long recurrence-free survival, while that for high-risk patients who received LDR brachytherapy (tri-modality) is "excellent disease control."