Comprehensive review of the use of hydrogel spacers prior to radiation therapy for prostate cancer

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.

SpaceOAR hydrogel complications in prostate cancer

SpaceOAR hydrogel, a novel biodegradable spacer, is increasingly used in managing prostate cancer patients undergoing radiation therapy to minimize rectal radiation dose and associated complications. However, its use has raised new concerns regarding its potential complications and impact on subsequent imaging interpretation. This article provides a pictorial review of the imaging complications of using SpaceOAR hydrogel in prostate cancer patients. We present multiple examples demonstrating the types of complications that can occur, potential underlying mechanisms, and their impact on patient outcomes and imaging interpretation. This review aims to provide radiologists and oncologists with an updated understanding of these complications, guiding better patient management and interpretation of imaging studies.

The march toward single-fraction stereotactic body radiotherapy for localized prostate cancer-Quo Vadimus?

PURPOSE

Stereotactic body radiotherapy (SBRT) is an emerging treatment option for localized prostate cancer. There is increasing interest to reduce the number of fractions for prostate SBRT.

METHODS

We provide a narrative review and summary of prospective trials of different fractionation schedules for prostate SBRT, focusing on efficacy, toxicities, and quality of life outcomes.

RESULTS

There are two randomized phase 3 trials comparing standard external beam radiotherapy with ultra-hypofractionated radiotherapy. HYPO-RT-PC compared 78 Gy in 39 fractions vs 42.7 Gy in 7 fractions (3D-CRT or IMRT) showing non-inferiority in 5-year biochemical recurrence-free survival and equivalent tolerability. PACE-B trial compared 78 Gy in 39-fraction or 62 Gy in 20-fraction vs 36.25 Gy in 5-fraction prostate SBRT, with no significant differences in toxicity outcomes at 2 years. Five-year efficacy data for PACE-B are expected in 2024. Five-fraction prostate SBRT is currently the most common and well-established fractionation schedule with multiple prospective phase 2 trials published to date. There is more limited data on 1-4 fraction prostate SBRT. All fractionation schedules had acceptable toxicity outcomes. Experience from a high-dose-rate brachytherapy randomized trial showed inferior efficacy with single-fraction compared to two-fraction brachytherapy. Hence, caution should be applied in adopting single-fraction prostate SBRT.

CONCLUSION

Two-fraction SBRT is likely the shortest fractionation schedule that maintains the therapeutic ratio. Several randomized trials currently recruiting will likely provide us with more definite answers about whether two-fraction prostate SBRT should become a standard-of-care option. Enrollment of eligible patients into these trials should be encouraged.

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.

Population-based patient-reported quality of life outcomes following low-dose-rate versus high-dose-rate brachytherapy monotherapy for low-intermediate risk prostate cancer

INTRODUCTION

To evaluate patient reported quality of life outcomes (QoL) following low-dose-rate brachytherapy (LDR-BT) and high-dose-rate brachytherapy (HDR-BT) monotherapy for prostate cancer at a population-based setting.

METHODS

The study comprised men with low-intermediate risk prostate cancer in the Prostate Cancer Outcomes Registry Victoria (PCOR-Vic), who were treated with LDR-BT or HDR-BT monotherapy between 2015 and 2020 and completed the Expanded Prostate Cancer Index Composite (EPIC-26) questionnaire 12-month post-treatment. Men who had ADT were excluded (n = 12). Differences in substantial symptoms (i.e. 'moderate' or 'big' problem on a 5-point Likert scale) between LDR-BT and HDR-BT arms were evaluated using Pearson's chi-squared test. Multivariable linear regressions were used to estimate differences in EPIC-26 urinary, bowel and sexual functional domain scores between LDR-BT and HDR-BT arms.

RESULTS

Overall, 198 men were included in this study, of which 167 (84%) had LDR-BT and 31 (16%) had HDR-BT. 9 (4.6%), 10 (5.1%) and 56 (28%) reported substantial symptoms for overall urinary, bowel and sexual function at 12-month post-treatment, with no significant difference between LDR-BT and HDR-BT arms. The adjusted mean differences in urinary incontinence, urinary obstructive, bowel and sexual function domain scores between LDR-BT and HDT-BT were: -3.53 (-8.21 to 1.14), -1.27 (-6.88 to 4.35), -0.01 (-5.63 to 5.63) and -8.68 (-21.44 to 4.07) respectively - these were not statistically significant and did not meet the minimal clinically important difference.

CONCLUSION

This is the first Australian population-based study comparing QoL in men who had LDR-BT and HDR-BT, with no statistically or clinically significant differences in QoL observed at 12-month post-treatment.

Sexual health and treatment-related sexual dysfunction in sexual and gender minorities with prostate cancer

Prostate cancer treatment has substantial effects on sexual health and function. Sexual function is a vital aspect of human health and a critical component of cancer survivorship, and understanding the potential effects of different treatment modalities on sexual health is crucial. Existing research has extensively described the effects of treatment on male erectile tissues necessary for heterosexual intercourse; however, evidence regarding their effects on sexual health and function in sexual and gender minority populations is minimal. These groups include sexual minority - gay and bisexual - men, and transgender women or trans feminine people in general. Such unique effects in these groups might include altered sexual function in relation to receptive anal and neovaginal intercourse and changes to patients' role-in-sex. Sexual dysfunctions following prostate cancer treatment affecting quality of life in sexual minority men include climacturia, anejaculation, decreased penile length, erectile dysfunction, and problematic receptive anal intercourse, including anodyspareunia and altered pleasurable sensation. Notably, clinical trials investigating sexual outcomes after prostate cancer treatment do not collect sexual orientation and gender identity demographic data or outcomes specific to members of these populations, which perpetuates the uncertainty regarding optimal management. Providing clinicians with a solid evidence base is essential to communicate recommendations and tailor interventions for sexual and gender minority patients with prostate cancer.

The Use of Hydrogel-Based Materials for Radioprotection

Major causes of the radiation-induced disease include nuclear accidents, war-related nuclear explosions, and clinical radiotherapy. While certain radioprotective drug or bioactive compounds have been utilized to protect against radiation-induced damage in preclinical and clinical settings, these strategies are hampered by poor efficacy and limited utilization. Hydrogel-based materials are effective carriers capable of enhancing the bioavailability of compounds loaded therein. As they exhibit tunable performance and excellent biocompatibility, hydrogels represent promising tools for the design of novel radioprotective therapeutic strategies. This review provides an overview of common approaches to radioprotective hydrogel preparation, followed by a discussion of the pathogenesis of radiation-induced disease and the current states of research focused on using hydrogels to protect against these diseases. These findings ultimately provide a foundation for discussions of the challenges and future prospects associated with the use of radioprotective hydrogels.

Patient-Reported Outcomes 12 Years after Localized Prostate Cancer Treatment

BACKGROUND: Long-term patient-reported outcomes are needed to inform treatment decisions for localized prostate cancer. METHODS: Patient-reported outcomes of 1643 randomly assigned participants in the ProtecT (Prostate Testing for Cancer and Treatment) trial were evaluated to assess the functional and quality-of-life impacts of prostatectomy, radiotherapy with neoadjuvant androgen deprivation, and active monitoring. This article focuses on the outcomes of the randomly assigned participants from 7 to 12 years using mixed effects linear and logistic models. RESULTS: Response rates exceeded 80% for most measures. Among the randomized groups over 7 to 12 years, generic quality-of-life scores were similar. Among those in the prostatectomy group, urinary leakage requiring pads occurred in 18 to 24% of patients over 7 to 12 years, compared with 9 to 11% in the active monitoring group and 3 to 8% in the radiotherapy group. In the prostatectomy group, 18% reported erections sufficient for intercourse at 7 years, compared with 30% in the active monitoring and 27% in the radiotherapy groups; all converged to low levels of potency by year 12. Nocturia (voiding at least twice per night) occurred in 34% in the prostatectomy group compared with 48% in the radiotherapy group and 47% in the active monitoring group at 12 years. Fecal leakage affected 12% in the radiotherapy group compared with 6% in the other groups by year 12. The active monitoring group experienced gradual age-related declines in sexual and urinary function, avoiding radical treatment effects unless they changed management. CONCLUSIONS: ProtecT provides robust evidence about continued impacts of treatments in the long term. These data allow patients newly diagnosed with localized prostate cancer and their clinicians to assess the trade-offs between treatment harms and benefits and enable better informed and prudent treatment decisions. (Funded by the UK National Institute for Health and Care Research Health Technology Assessment Programme projects 96/20/06 and 96/20/99; ISRCTN number, ISRCTN20141297; ClinicalTrials.gov number, NCT02044172.)