Spacer application for prostate cancer radiation therapy

Iodine-125 low-dose rate prostate brachytherapy

Robotic-assisted laparoscopic radical prostatectomy and intensity-modulated radiation therapy are the most common radical treatments for localized prostate cancer, and brachytherapy (BT) also plays a role in this field. Iodine-125 (I-125) low-dose rate (LDR) prostate BT is an established treatment. However, it remains controversial. Specifically, there are a variety of issues, such as indications for combined treatment with external beam radiotherapy and androgen deprivation therapy, prostate-specific antigen follow-up, the significance of postimplant biopsy, the usefulness of salvage BT and focal therapy, reduction of toxicities, and bladder cancer after BT. In this review, we summarize the recent developments in I-125 LDR BT.

Dose-escalated radiotherapy to 82 Gy for prostate cancer following insertion of a peri-rectal hydrogel spacer: 3-year outcomes from a phase II trial

BACKGROUND

Dose-escalation to above 80 Gy during external beam radiotherapy for localised prostate cancer leads to improved oncological outcomes but also substantially increased rectal toxicity. The aim of this study was to demonstrate the safety and efficacy of escalating the dose to 82 Gy following insertion of a peri-rectal hydrogel spacer (HS) prior to radiotherapy.

METHODS

This was a single arm, open-label, prospective study of men with localised prostate cancer who were prescribed a course of intensity modulated radiotherapy escalated to 82 Gy in 2 Gy fractions following insertion of the SpaceOAR™ HS (Boston Scientific, Marlborough, MA). Patients were prescribed a standard course of 78 Gy in 2 Gy fractions where rectal dose constraints could not be met for the 82 Gy plan. The co-primary endpoints were the rate of grade 3 gastrointestinal (GI) and genitourinary (GU) adverse events (CTCAE, v4), and patient-reported quality of life (QoL) (EORTC QLQ-C30 and PR25 modules), up to 37.5 months post-treatment.

RESULTS

Seventy patients received treatment on the study, with 64 (91.4%) receiving an 82 Gy treatment course. The median follow-up time post-treatment was 37.4 months. The rate of radiotherapy-related grade 3 GI and GU adverse events was 0% and 2.9%, respectively. There were 2 (2.9%) grade 3 adverse events related to insertion of the HS. Only small and transient declines in QoL were observed; there was no clinically or statistically significant decline in QoL beyond 13.5 months and up to 37.5 months post-treatment, compared to baseline. No late RTOG-defined grade ≥ 2 GI toxicity was observed, with no GI toxicity observed in any patient at 37.5 months post-treatment. Nine (12.9%) patients met criteria for biochemical failure within the follow-up period.

CONCLUSIONS

Dose-escalation to 82 Gy, facilitated by use of a hydrogel spacer, is safe and feasible, with minimal toxicity up to 37.5 months post-treatment when compared to rates of rectal toxicity in previous dose-escalation trials up to 80 Gy. Trials with longer follow-up of oncological and functional outcomes are required to robustly demonstrate a sustained widening of the therapeutic window. Trial registration Australian New Zealand Clinical Trials Registry, ACTRN12621000056897 , 22/01/2021. Retrospectively registered.

Rationale for Utilization of Hydrogel Rectal Spacers in Dose Escalated SBRT for the Treatment of Unfavorable Risk Prostate Cancer

In this review we outline the current evidence for the use of hydrogel rectal spacers in the treatment paradigm for prostate cancer with external beam radiation therapy. We review their development, summarize clinical evidence, risk of adverse events, best practices for placement, treatment planning considerations and finally we outline a framework and rationale for the utilization of rectal spacers when treating unfavorable risk prostate cancer with dose escalated Stereotactic Body Radiation Therapy (SBRT).

An injectable double-crosslinking iodinated composite hydrogel as a potential radioprotective spacer with durable imaging function

Prostate cancer is one of the leading causes of cancer incidence among males worldwide. Radiotherapy can achieve similar oncological outcomes to those of radical prostatectomy. One concern is, however, radiation damage to the rectum because of the extreme proximity between the two organs. Inserting a biomaterial to separate the prostate and rectum is a promising strategy, and an injectable hydrogel is regarded to be the preferred spacer after screening of various materials. Nevertheless, there exist shortcomings for the currently available injectable hydrogel that cannot fully meet the unique requirements in clinical practice. In this work, a novel injectable hydrogel spacer based on carboxymethyl chitosan (CMC), aldehyde guar gum (AG), and aldehyde iohexol (DHQ) with an imaging function is fabricated. Contrast agent DHQ is chemically attached to CMC-AG network to form a double-crosslinking network to obtain a controlled degradation rate and high strength as well as durable CT imaging function. The hydrogel is injected subcutaneously into rats, where rapid gelation occurs and it serves as a hydrogel spacer. During the month-long in vivo studies, the spacer exhibits remarkable radiation dose attenuation and sustainable imaging function, as well as excellent toxicity profiles. This novel hydrogel shows excellent potential in the protection of critical organs during prostate cancer radiotherapy.

Ano-rectal wall dose-surface maps localize the dosimetric benefit of hydrogel rectum spacers in prostate cancer radiotherapy

BACKGROUND AND PURPOSE

To evaluate spatial differences in dose distributions of the ano-rectal wall (ARW) using dose-surface maps (DSMs) between prostate cancer patients receiving intensity-modulated radiation therapy with and without implantable rectum spacer (IMRT+IRS; IMRT-IRS, respectively), and to correlate this with late gastro-intestinal (GI) toxicities using validated spatial and non-spatial normal-tissue complication probability (NTCP) models.

MATERIALS AND METHODS

For 26 patients DSMs of the ARW were generated. From the DSMs various shape-based dose measures were calculated at different dose levels: lateral extent, longitudinal extent, and eccentricity. The contiguity of the ARW dose distribution was assessed by the contiguous-DSH (cDSH). Predicted complication rates between IMRT+IRS and IMRT-IRS plans were assessed using a spatial NTCP model and compared against a non-spatial NTCP model.

RESULTS

Dose surface maps are generated for prostate radiotherapy using an IRS. Lateral extent, longitudinal extent and cDSH were significantly lower in IMRT+IRS than for IMRT-IRS at high-dose levels. Largest significant differences were observed for cDSH at dose levels >50 Gy, followed by lateral extent at doses >57 Gy, and longitudinal extent in anterior and superior-inferior directions. Significant decreases (p = 0.01) in median rectal and anal NTCPs (respectively, Gr 2 late rectal bleeding and subjective sphincter control) were predicted when using an IRS.

CONCLUSIONS

Local-dose effects are predicted to be significantly reduced by an IRS. The spatial NTCP model predicts a significant decrease in Gr 2 late rectal bleeding and subjective sphincter control. Dose constraints can be improved for current clinical treatment planning.

The role of radioprotective spacers in clinical practice: a review

The delivery of high dose radiotherapy to tumors is often limited by the proximity of the surrounding radiosensitive normal tissues, even using modern techniques such as intensity modulated radiation therapy (IMRT). Previous studies have reported that placement of a spacer can effectively displace normal tissues. So that they are some distance away from the lesion, thus allowing for the safe delivery of high-dose radiation. The application of radioprotective spacers was first reported 30 years ago regarding radiotherapy of tongue and abdominal cancers; more recently, they are increasingly being used in prostate cancer. This review focuses on the published data concerning the features of different types of spacers and their application in various tumor sites. Placement-related complications and the cost-effectiveness of the spacers are also discussed. With the increasing use of high-precision radiotherapy in clinical practice, especially the paradigm-changing stereotactic body radiotherapy (SBRT), more robust studies are warranted to further establish the role of radioprotective spacers through materials development and novel placement techniques.

Implantation of a biodegradable rectum balloon implant: tips, Tricks and Pitfalls

Introduction:

A rectum balloon implant (RBI) is a new device to spare rectal structures during prostate cancer radiotherapy. The theoretical advantages of a RBI are to reduce the high radiation dose to the anterior rectum wall, the possibility of a post-implant correction, and their predetermined shape with consequent predictable position.

Objective:

To describe, step-by-step, our mini-invasive technique for hands-free transperineal implantation of a RBI before start of radiotherapy treatment.

Materials and Methods:

We provide step-by-step instructions for optimization of the transperineal implantation procedure performed by urologists and/or radiation oncologists experienced with prostate brachytherapy and the use of the real-time bi-plane transrectal ultrasonography (TRUS) probe. A RBI was performed in 15 patients with localised prostate cancer. Perioperative side-effects were reported.

Results:

We provide ‘tips and tricks’ for optimizing the procedure and proper positioning of the RBI. Please watch the animation, see video in https://vimeo.com/205852376/789df4fae4.

The side-effects included mild discomfort to slight pain at the perineal region in 8 out of 15 patients. Seven patients (47%) had no complaints at all. Two patients developed redness of the skin, where prompt antibiotic regimen was started with no further sequelae. One patient revealed a temporary urine retention, which resolved in a few hours following conservative treatment. Further no perioperative complications occurred.

Conclusion:

This paper describes in detail the implantation procedure for an RBI. It is a feasible, safe and very well-tolerated procedure.

Use of hydrogel spacer for improved rectal dose-sparing in patients undergoing radical radiotherapy for localized prostate cancer: First Canadian experience

We describe the initial experience using a hydrogel spacer (SpaceOAR) to separate the prostate-rectum interspace in patients planned to undergo radical hypofractionated, image-guided, intensity-modulated radiotherapy (IG-IMRT). We depict and discuss the impact of SpaceOAR in the context of hypofractionated IG-IMRT, and the particular considerations for its applications in the Canadian setting.

Dynamics of rectal balloon implant shrinkage in prostate VMAT : Influence on anorectal dose and late rectal complication risk

PURPOSE

To assess the effect of a shrinking rectal balloon implant (RBI) on the anorectal dose and complication risk during the course of moderately hypofractionated prostate radiotherapy.

METHODS

In 15 patients with localized prostate cancer, an RBI was implanted. A weekly kilovolt cone-beam computed tomography (CBCT) scan was acquired to measure the dynamics of RBI volume and prostate-rectum separation. The absolute anorectal volume encompassed by the 2 Gy equieffective 75 Gy isodose (V_75Gy) was recalculated as well as the mean anorectal dose. The increase in estimated risk of grade 2-3 late rectal bleeding (LRB) between the start and end of treatment was predicted using nomograms. The observed acute and late toxicities were evaluated.

RESULTS

A significant shrinkage of RBI volumes was observed, with an average volume of 70.4% of baseline at the end of the treatment. Although the prostate-rectum separation significantly decreased over time, it remained at least 1 cm. No significant increase in V_75Gy of the anorectum was observed, except in one patient whose RBI had completely deflated in the third week of treatment. No correlation between mean anorectal dose and balloon deflation was found. The increase in predicted LRB risk was not significant, except in the one patient whose RBI completely deflated. The observed toxicities confirmed these findings.

CONCLUSIONS

Despite significant decrease in RBI volume the high-dose rectal volume and the predicted LRB risk were unaffected due to a persistent spacing between the prostate and the anterior rectal wall.

Prostate Cancer Radiation Therapy: What Do Clinicians Have to Know?

Radiotherapy (RT) for prostate cancer (PC) has steadily evolved over the last decades, with improving biochemical disease-free survival. Recently population based research also revealed an association between overall survival and doses ≥ 75.6 Gray (Gy) in men with intermediate- and high-risk PC. Examples of improved RT techniques are image-guided RT, intensity-modulated RT, volumetric modulated arc therapy, and stereotactic ablative body RT, which could facilitate further dose escalation. Brachytherapy is an internal form of RT that also developed substantially. New devices such as rectum spacers and balloons have been developed to spare rectal structures. Newer techniques like protons and carbon ions have the intrinsic characteristics maximising the dose on the tumour while minimising the effect on the surrounding healthy tissue, but clinical data are needed for confirmation in randomised phase III trials. Furthermore, it provides an overview of an important discussion issue in PC treatment between urologists and radiation oncologists: the comparison between radical prostatectomy and RT. Current literature reveals that all possible treatment modalities have the same cure rate, but a different toxicity pattern. We recommend proposing the possible different treatment modalities with their own advantages and side-effects to the individual patient. Clinicians and patients should make treatment decisions together (shared decision-making) while using patient decision aids.

Interdisciplinary consensus statement on indication and application of a hydrogel spacer for prostate radiotherapy based on experience in more than 250 patients

Background

The aim of the study was to reach a consensus on indication and application of a hydrogel spacer based on multicentre experience and give new users important information to shorten the learning curve for this innovative technique.

Methods

The interdisciplinary meeting was attended by radiation oncologists and urologists, each with experience of 23 – 138 hydrogel injections (SpaceOAR®) in prostate cancer patients before dose-escalated radiotherapy. User experience was discussed and questions were defined to comprise practical information relevant for successful hydrogel injection and treatment. Answers to the defined key questions were generated. Hydrogel-associated side effects were collected to estimate the percentage, treatment and prognosis of potential risks.

Results

The main indication for hydrogel application was dose-escalated radiotherapy for histologically confirmed low or intermediate risk prostate cancer. It was not recommended in locally advanced prostate cancer. The injection or implantation was performed under transrectal ultrasound guidance via the transperineal approach after prior hydrodissection. The rate of injection-related G2-toxicity was 2% (n = 5) in a total of 258 hydrogel applications. The most frequent complication (n = 4) was rectal wall penetration, diagnosed at different intervals after hydrogel injection and treated conservatively.

Conclusions

A consensus was reached on the application of a hydrogel spacer. Current experience demonstrated feasibility, which could promote initiation of this method in more centres to reduce radiation-related gastrointestinal toxicity of dose-escalated IGRT. However, a very low rate of a potential serious adverse event could not be excluded. Therefore, the application should carefully be discussed with the patient and be balanced against potential benefits.

Chronic radiation proctitis: tricks to prevent and treat

OBJECTIVE

The purpose of this study was to give an overview of the measures used to prevent chronic radiation proctitis (CRP) and to provide an algorithm for the treatment of CRP.

METHODS

Medical literature databases including PubMed and Medline were screened and critically analyzed for relevance in the scope of our purpose.

RESULTS

CRP is a relatively frequent late side effect (5-20%) and mainly dependent on the dose and volume of irradiated rectum. Radiation treatment (RT) techniques to prevent CRP are constantly improving thanks to image-guided RT and intensity-modulated RT. Also, newer techniques like protons and new devices such as rectum spacers and balloons have been developed to spare rectal structures. Biopsies do not contribute to diagnosing CRP and should be avoided because of the risk of severe rectal wall damage, such as necrosis and fistulas. There is no consensus on the optimal treatment of CRP. A variety of possibilities is available and includes topical and oral agents, hyperbaric oxygen therapy, and endoscopic interventions.

CONCLUSIONS

CRP has a natural history of improving over time, even without treatment. This is important to take into account when considering these treatments: first be conservative (topical and oral agents) and be aware that invasive treatments can be very toxic.

Can Anorectal Manometry Findings Predict Subsequent Late Gastrointestinal Radiation Toxicity in Prostate Cancer Patients?

PURPOSE

The purpose of this study is to investigate the influence of radiotherapy (RT) on anorectal function and radiation-induced toxicity in patients with prostate cancer.

MATERIALS AND METHODS

Fifty-four patients who were treated with RT for prostate cancer (T1c-4N0-1M0) were evaluated. To assess the changes in anorectal function, two consecutive anorectal manometry readings were performed in patients, before and after 4-6 months of RT. Late gastrointestinal (GI) toxicity was defined as symptoms occurring more than 6 months after RT. The median radiation dose was 70.0 Gy (range, 66.0 to 74.0 Gy). Whole pelvis field RT was performed in 16 patients (29.6%). Grade of late radiation toxicity was defined in accordance to the severity of symptoms (Gulliford's scoring system).

RESULTS

The median follow-up period was 60 months. Resting anal pressure (p=0.001), squeeze pressure (p < 0.001), and urge to defecate volume (p=0.025) were significantly reduced after RT. Fourteen patients (25.9%) experienced late GI toxicities. Among them, nine (16.7%) showed severe (grade ≥ 2) late toxicities. Elevated resting and squeeze external anal sphincter pressure prior to RT and large urge to defecate volumes after RT were associated with the occurrence of late GI toxicities.

CONCLUSION

RT caused symptomatic anorectal dysfunction and resulted in a weakened anal sphincter. Increased urge to defecate volumes after RT were related to late GI toxicities. Elevated resting and squeeze anal sphincter pressure prior to RT rodcan be used to identify patients with an increased risk of late GI toxicities.

A review of rectal toxicity following permanent low dose-rate prostate brachytherapy and the potential value of biodegradable rectal spacers

Permanent radioactive seed implantation provides highly effective treatment for prostate cancer that typically includes multidisciplinary collaboration between urologists and radiation oncologists. Low dose-rate (LDR) prostate brachytherapy offers excellent tumor control rates and has equivalent rates of rectal toxicity when compared with external beam radiotherapy. Owing to its proximity to the anterior rectal wall, a small portion of the rectum is often exposed to high doses of ionizing radiation from this procedure. Although rare, some patients develop transfusion-dependent rectal bleeding, ulcers or fistulas. These complications occasionally require permanent colostomy and thus can significantly impact a patient's quality of life. Aside from proper technique, a promising strategy has emerged that can help avoid these complications. By injecting biodegradable materials behind Denonviller's fascia, brachytherpists can increase the distance between the rectum and the radioactive sources to significantly decrease the rectal dose. This review summarizes the progress in this area and its applicability for use in combination with permanent LDR brachytherapy.

Rectal ulcer associated with SpaceOAR hydrogel insertion during prostate brachytherapy

We present a case of rectal ulceration associated with SpaceOAR hydrogel insertion during low-dose-rate (LDR) brachytherapy in a patient with prostate cancer.