Purpose/Objective(s) Radiation therapy for prostate cancer may cause gastrointestinal (GI) toxicity as the rectum is an organ at risk. Stabilized hyaluronic acid (sHA) has recently been approved for use as a rectal spacer and reduces GI toxicity in this setting. It has several advantages, including its reversibility using hyaluronidase. This is particularly beneficial in cases of rectal wall infiltration (RWI). The use of non-reversible rectal spacers may lead to severe adverse outcomes such as mucosal ulceration, pelvic abscess and recto-prostatic fistula after RWI. As such, we aim to assess the outcomes of inadvertent RWI by sHA rectal spacers. Materials/Methods A retrospective analysis of patients who had inadvertent RWI following the use of sHA rectal spacers was conducted in Australia. More than 5000 patients have had sHA rectal spacing with the majority undergoing magnetic resonance imaging (MRI) simulation. Patients with RWI were identified based on post-procedural MRI. Data collection included patient demographics, delays in radiation therapy, grade of the RWI and symptoms, and management of the RWI. The patients were followed up during and post radiation therapy and assessed for rectal complications. Results A total of 16 prostate cancer patients were identified to have RWI after sHA spacer insertion. The grade of RWI as defined by Fischer Valuck criteria were as follows: Grade 1, N = 5; Grade 2, N = 6; and Grade 3, N = 5. The median volume of misplaced sHA was 2.8 cc from an average total of 9cc used. No post procedural GI symptoms were reported. A sigmoidoscopy was performed in 12 patients including all 5 with grade 3 RWI, and all of these showed intact rectal mucosa. Seven patients underwent targeted reversal procedures while 9 patients were monitored. Of those who underwent reversal procedures, the median (and mean) volume of misplaced hyaluronic acid is 4 mL (3.8mL), compared to 1.5 mL (2.1mL) in those who did not undergo reversal (Mann-Whitney U test, p = 0.1). All 7 who underwent reversal with hyaluronidase were successful. No post reversal complications were reported. One patient underwent successful reinsertion of sHA following reversal. Initiation of radiation therapy was delayed in 11 cases by a median of 3.2 months. All patients completed their RT as planned. No acute grade 2 or higher GI toxicity was reported in any of the 16 patients. Conclusion This case series presents the first evidence for the safety of sHA rectal spacer in cases of RWI, with an event rate of less than 0.03% We have proven the efficacy of hyaluronidase in reversal of RWI with HA with the majority of patients experiencing minimal delay in commencement of RT. No severe adverse complications were reported.

Purpose:Low-dose-rate (LDR) brachytherapy in young men remains controversial amongst urologists due to their concerns regarding long-term biochemical control and treatment-related toxicities. The purpose of this study was to evaluate the treatment outcomes of men under 60 years of age who underwent LDR brachytherapy with iodine-125 (125I) for clinically localized low- to intermediate-risk prostate cancer. Material and methods:All consecutive patients with clinically localized prostate cancer treated at our institution from 2003 to 2016 with 125I monotherapy were included in the study. Prescription dose was 145.0 Gy modified peripheral loading (MPD). All patients were assessed for biochemical progression-free survival using Phoenix definition (nadir +2 ng/ml), clinical progression-free survival, overall survival (OS), and any associated treatment toxicity. Results:A total of 161 patients were included, with a median follow-up of 6.8 years (range, 3-14.54 years). Median age at implant was 57 years (range, 53-59 years). Mean prostate specific antigen (PSA) level at diagnosis was 4.43 ng/ml (SD = 2.29). Majority of men had low-risk prostate cancer (70.2%). Biochemical progression-free survival at 8 years was 94% for the entire cohort. Median PSA at 4 years was 0.169 (IQR, 0.096-0.360), with 45% of patients having a PSA greater than 0.2. OS was 96.9%, with 5 deaths reported but only one was secondary to prostate cancer. Late grade > 2 genitourinary toxicities were reported in 18 patients (11.2%). Three patients (1.9%) developed secondary cancers, all considered unrelated to their LDR brachytherapy. Conclusions:With excellent long-term treatment outcomes and minimal associated toxicities, our results showed that LDR brachytherapy can be an effective treatment of choice in younger men.

Purpose/Objective(s) To assess implant quality using modified SQS (mSQS) and FV scores achieved in 100 men with localized prostate cancer (PCa) treated with moderately hypofractionated external beam radiotherapy (EBRT) who underwent stabilized HA rectal spacer (RS) implant, and its impact on acute and late GI toxicity. Materials/Methods This retrospective multi-institutional review involved 100 consecutive men with localized PCa treated with moderately hypofractionated EBRT (60Gy/62Gy in 20#) and underwent HA RS insertion, treated between June 2020 - September 2022. Statistical metrics were used to assess patient and disease characteristics. Acute and late GI toxicity were assessed using CTCAEv5. Implant quality was assessed using mSQS (recto-prostatic separation (RPS)), FV score (symmetry) and RS rectal wall infiltration (RWI) evaluated on post implant T2-weighted MRI axial slices. RWI was independently assessed by an MRI prostate specialist radiologist. SQS, RWI and FV scoring were performed according to prior publications by Grossman et al and Fischer-Valuck et al. mSQS scores were used to stringently account for our PTV expansions (mSQS score 2 = ≥10mm RPS, mSQS score 1 = 6-9mm RPS, mSQS score 0 = ≤5mm RPS). Results The mean age was 74.6 years (SD 6.0 y); 54 patients had unfavorable intermediate risk PCa, 33 had favorable intermediate risk PCa and 9 had low risk PCa. 88 patients were treated to 60Gy/20#, while 12 patients were treated to 62Gy/20#. Of the RS implants, 98% were deemed “very easy” by the injector and 2% were deemed “easy”. Overall mSQS score of 1 (“good”) was achieved in 74 patients, score of 2 (“excellent”) in 24 patients, and a score of 0 occurred in just 2 patients. 97% of the injectors successfully shaped HA to achieve symmetrical rectal spacing with FV score 1. Median rectal V36 was 13.2% (IQR 9.2-17.5), V42 was 8.4% (IQR 5.4-12.3), V48 was 5.1% (IQR 2.7-8.2), V54 was 2.1% (IQR 0.9-4.5) and V57 was 0.9% (IQR 0.2-2.3). Seven acute G1 and 5 late G1 GI toxicities were recorded. There was no ≥G2 acute or late GI toxicity. No statistically significant association was identified between FV and SQS scores with acute or late GI toxicity incidence. Only 1 patient experienced implant RWI and the RWI was reversed with hyaluronidase, with no significant sequelae reported. He was subsequently reimplanted successfully with HA RS and completed EBRT uneventfully. Median follow-up was 1.68 years (IQR: 1.28-2.23), with only one regional recurrence reported. Conclusion The majority (97%) of patients who underwent HA RS implant had easily achieved high quality RS (both modified SQS scores 1-2 and FV score 1). This translated to low rectal doses and low incidence of acute and late G1 GI toxicities. Stabilized HA RS may be considered in patients undergoing hypofractionated EBRT to the prostate.

Objectives: Our objective was to assess the rate of complications and gastrointestinal adverse effects of rectal spacer insertion for salvage post prostatectomy radiation therapy. Methods: A retrospective observational study was performed. Between September 2018 and March 2022, 64 post-radical prostatectomy patients who were planned for salvage radiation therapy received a rectal spacer. The selected patients were those who had nerve-sparing prostatectomy with intrafascial or interfascial dissections (where Denonvillier’s fascia is retained). Radiation dose to the rectal wall and gastrointestinal symptoms were assessed. Symptoms were graded using the National Cancer Center Institute Common Terminology Criteria for Adverse Events v4.0 grading scheme. A total of 39 patients had pre-spacer planning computer tomography (CT) scans, and the rectal dose before and after the spacer insertion was calculated. Comparisons were made using the Student’s t-test, with a p-value < 0.05 representing statistical significance. Finally, clinicians were surveyed to rate the ease of the procedure using a 5-point Likert scale of 1 to 5 (1: very difficult, 2: difficult, 3: moderate, 4: easy, 5: very easy). Results: A total of 64 patients successfully underwent rectal spacer insertion. The mean age was 64.4 years (standard deviation: 5.7 years). After a median of 14 months’ (range 6 to 35) follow up, acute grade 1 and above gastrointestinal (GI) toxicities were seen in 28% of patients (grade 2 in 1.5%), and late grade 1 and above GI toxicities were seen in 12% of patients (grade 2 in 1.5%). Amongst the 39 patients with pre-spacer planning CT images, the volume of the rectum receiving 60%, 70%, 80%, 90%, and 100% of the prescribed radiation dose was reduced by 25.9%, 34.2%, 35.4%, 43.7%, and 61.7%, respectively. All dose reductions were statistically significant. The procedure was rated as “easy” or “very easy” to perform in 56% of cases. Conclusions: The insertion of a rectal spacer in selected patients undergoing PPRT is feasible and safe and significantly improves rectal wall radiation dosimetry in salvage post prostatectomy radiation therapy. It was accomplished in >95% of patients, increasing vesico-rectal separation from ‘immediate vicinity’ to 11 mm without any post-operative complications in experienced hands. In addition, it achieved significant reduction in rectal radiation doses, leading to low rates of acute and late grade 2 toxicity.

Purpose:Insertion of a spacer between tumor and an adjacent organ at risk may improve the therapeutic ratio in gynecological cancer brachytherapy. The purpose of this review was to assess the available literature on the use of injectable bio-absorbable spacers in brachytherapy for gynecological cancers. Material and methods:Embase, PubMed, Medline, and Cochrane Central Register of Controlled Trials were searched until March 28, 2024. Studies reporting on injectable bio-absorbable spacers in gynecological cancer brachytherapy were included. Two independent reviewers completed screening, assessment for eligibility, and data extraction of included studies. Data were collected on spacer material, technique, safety, feasibility, spacer quality, dosimetric values, clinical outcomes, and cost-effectiveness. Results:Seventeen studies met inclusion criteria, with a total of 312 patients and 169 spacers. Clinical application was primarily in cervix cancer brachytherapy (47%) and spacer placement in the recto-vaginal space (88%). Eight different products were used, with no significant spacer-related adverse effects reported. Spacer insertion reduced rectal dose in eight studies, bladder dose in one study, sigmoid dose in four studies, and permitted tumor dose escalation in three studies. Five studies reported on tumor outcomes and eight studies on late toxicities. There were no studies evaluating patient-reported outcomes and cost-effectiveness. Conclusions:Injectable bio-absorbable spacers offer a promising approach for improving the therapeutic ratio in gynecological cancer brachytherapy. There is low certainty evidence available in the literature for their use, and rigorous prospective studies are needed to provide evidence on outcomes.

The hybrid magnetic resonance image (MRI) scanner and radiation therapy linear accelerator (MR-Linac) has the potential to enhance clinical outcomes for anal cancer (AC) patients with improved soft tissue visualization and daily plan adaption but has planning and delivery limitations due to the incorporation of MRI. We aimed to identify if Elekta Unity MR-Linac-based radiation therapy is feasible for anal cancer. Ten prospectively enrolled AC patients treated with radical chemoradiotherapy were replanned for MR-Linac treatment using departmental planning criteria. For comparison, and to reduce interobserver variability, volumetric modulated arc radiation therapy (VMAT) plans were also created for each patient by the same single senior radiation therapist. Plans were compared using departmental dosimetric plan criteria, as well as conformity and homogeneity indices, monitor units (MUs) and measured plan delivery (beam-on) time. Results were deemed clinically acceptable. Target and organ at risk (OAR) doses were comparable between MR-Linac plans and VMAT plans, although PTV45Gy D98% coverage was compromised in 3 of 10 MR-Linac plans due to caudocranial length exceeding the limits of the MR-Linac. MR-Linac plans had lower MUs, median of 689.1 vs 849.65 (p = 0.002), but took over twice as long to deliver, 529.5s vs 224s (p = <0.0001) as VMAT plans. MR-Linac planning and treatment of AC is feasible for a subset of patients. The current physical limitations of the Elekta Unity system mean patients with large caudocranial elective PTV45Gy target volumes may not be covered dosimetrically to the required clinical standard. Longer image verification and treatment delivery times of the MR-Linac also mean patient selection and intrafractional IGRT are likely to be integral to ensuring high quality clinical outcomes in this rare cancer.

Gastrointestinal stromal tumors (GISTs) are mesenchymal neoplasms representing just 1% to 2% of primary gastrointestinal malignancies. The rectum is an uncommon primary site representing 5% of all GISTs.1 In view of the targetable c-kit mutation found in the majority of tumors, the mainstay of systemic therapy is tyrosine kinase inhibitors (TKIs). Although durable responses to TKI therapy are common, most patients subsequently develop resistance. Nonsurgical procedures rather than commencement of a subsequent line of systemic therapy can be considered in cases of focal progression.

PURPOSE:The TOPGEAR phase 3 trial hypothesized that adding preoperative chemoradiation therapy (CRT) to perioperative chemotherapy will improve survival in patients with gastric cancer. Owing to the complexity of gastric irradiation, a comprehensive radiation therapy quality assurance (RTQA) program was implemented. Our objective is to describe the RTQA methods and outcomes. METHODS AND MATERIALS:RTQA was undertaken in real time before treatment for the first 5 patients randomized to CRT from each center. Once acceptable quality was achieved, RTQA was completed for one-third of subsequent cases. RTQA consisted of evaluating (1) clinical target volume and organ-at-risk contouring and (2) radiation therapy planning parameters. Protocol violations between high- (20+ patients enrolled) and low-volume centers were compared using the Fisher exact test. RESULTS:TOPGEAR enrolled 574 patients, of whom 286 were randomized to receive preoperative CRT and 203 (71%) were included for RTQA. Of these, 67 (33%) and 136 (67%) patients were from high- and low-volume centers, respectively. The initial RTQA pass rate was 72%. In total, 28% of cases required resubmission. In total, 200 of 203 cases (99%) passed RTQA before treatment. Cases from low-volume centers required resubmission more often (44/136 [33%] vs 13/67 [18%]; P = .078). There was no change in the proportion of cases requiring resubmission over time. Most cases requiring resubmission had multiple protocol violations. At least 1 aspect of the clinical target volume had to be adjusted in all cases. Inadequate coverage of the duodenum was most common (53% major violation, 25% minor violation). For the remaining cases, the resubmission process was triggered secondary to poor contour/plan quality. CONCLUSIONS:In a large multicenter trial, RTQA is feasible and effective in achieving high-quality treatment plans. Ongoing education should be performed to ensure consistent quality during the entire study period.

ABSTRACT:Prostate cancer (PCa) is a multifaceted, heterogeneous disease (with 7 molecular subtypes), which can metastasize to common sites, such as bone, lymph nodes, liver, and lungs. However, with PSMA PET imaging, rare sites of metastasis are increasingly discovered. We report 5 cases of unusual metastases in patients with castrate-sensitive PCa: solitary right inguinal nodal metastasis, solitary abdominal wall metastasis, penile shaft metastases, solitary perineum metastasis, and pleural metastases. These cases further support the use of PSMA-PET imaging in PCa monitoring, with the ability to detect solitary, small volume, and rare sites of metastases, which may not be apparent on conventional imaging.

Introduction Image guidance with gold fiducials improves outcomes of prostate radiotherapy. However, gold produces artefact on CT imaging, interfering with contouring and verification. The purpose of this study was to compare polymer to standard gold fiducials using radiotherapy imaging modalities to assess the visibility and artefact. Methods Twenty eight patients with locally advanced prostate cancer were enrolled, half had three polymer fiducials implanted into the prostate and half underwent insertion of gold fiducials. Patients were imaged with CT, T2 weighted MRI, cone-beam CT (CBCT) and planar KV images. Fiducials were scored for visibility and assessed for CT artefact in surrounding prostate tissue. The artefact was quantified from Hounsfield number histograms and separated into percentile ranges and proportion of voxels in HU normal tissue range of a 2cm sphere surrounding the fiducial. Results Gold and polymer fiducials were sufficiently visible for CT and CBCT verification. The gold fiducials could be visualized well on KV planar imaging; however, the polymer markers were obscured by pelvic bones. Neither polymer nor gold fiducials could be visualized on MRI. The polymer fiducial produced less artefact than gold on CT, having less voxel spread for the HU percentile ranges and a greater proportion of voxels in the normal tissue range. Conclusions Polymer fiducials are a more suitable fiducial than gold for CT/CBCT in prostate cancer radiotherapy, demonstrating minimal artefact and good visibility on CT. However, they were not well seen on MRI or KV imaging and thus not suitable for co-registration or planar KV verification.

Supplementary Table S1 from Pretreatment Transcriptional Profiling for Predicting Response to Neoadjuvant Chemoradiotherapy in Rectal Adenocarcinoma

OBJECTIVES:To report on the usability, safety, symmetry, and effectiveness of hyaluronic acid (HA) injected between the prostate and the rectum for patients undergoing treatment for prostate cancer with external beam radiotherapy (EBRT), and present a novel definition of rectal spacer symmetry that is reproducible and independent of patient anatomy. PATIENTS AND METHODS:102 consecutive patients with clinical stage of T1c-3b prostate cancer underwent general anaesthesia for fiducial marker insertion and injection of HA into the perirectal space before EBRT. HA safety, symmetry, separation, and usability based on user experience were assessed. RESULTS:HA insertion was completed with a 100% success rate independent of user experience, rated as 'easy' or 'very easy' in all cases. There were no postoperative complications reported. The mean (SD) recto-prostatic separation for all patients at the base, midgland and apex were 12 (±2) mm, 11 (±2) mm, and 9 (±1) mm respectively. The mean sagittal length of the implant was 43 (±5) mm. The implant was rated as symmetrical in 98% of cases. The mean rV70Gy was 1.6% (IQR 0.8-3.3%) for patients receiving 78-80Gy. The mean rV53Gy was 2.8% (IQR 1.2-4.8%) for patients receiving 60-62Gy. The median prostate size was 43.5 cc (IQR 32-57). CONCLUSION:Injection of HA was able to achieve highly symmetrical recto-prostatic separation, with new users able to produce excellent separation, particularly at the apex, achieving similar dosimetry outcomes as competent and experienced users. HA is safe, easy to use, and significantly reduced mean rV70Gy and rV53Gy compared to non-spacer patients.

You have accessJournal of UrologyCME1 May 2022V09-05 NOVEL TECHNIQUE FOR INJECTION OF LIPIODOL AS FIDUCIAL MARKER FOR RADIOTHERAPY TREATMENT IN BLADDER CANCER Aoife McVey, Elvira Polo Alonso, Olivia Fraser, Daryl Lim Joon, and Gregory Jack Aoife McVeyAoife McVey More articles by this author , Elvira Polo AlonsoElvira Polo Alonso More articles by this author , Olivia FraserOlivia Fraser More articles by this author , Daryl Lim JoonDaryl Lim Joon More articles by this author , and Gregory JackGregory Jack More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002617.05AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Radiotherapy for the primary treatment of bladder cancer is becoming increasingly common. Several studies have shown that fiducial marking of the site of the primary tumour can assist with radiotherapy planning and reduce dosimetry to surrounding benign bladder tissue. Lipiodol, which is Iodinated contrast agent can be injected cystoscopically and serve as a fiducial marker to demarcate the primary bladder tagets for radiotherapy. Few studies have looked at the ideal technique and dose of lipiodol injection. Furthermore those study is typically advise 5 mL of concentrated lipiodol injected in 1mL aliquats through a rigid cystoscope with a williams cystoscopic needle, which tends to lead to excessive urothelial migration of the lipiodol. We described a novel technique of 100uL injections of 1:3 dilute lipiodol performed via flexible cystoscopy under local anaesthesia. METHODS: After obtaining patient consent, we video-recorded a case of cystoscopic injection of Lipiodol in a patient selected for image guided radiotherapy treatment (IGRT). Using iMovie editing software we prepared a video describing this technique. RESULTS: This technique for injection has been successfully implemented at our single centre and has allowed effective delivery of targeted radiotherapy treatment using Lipiodol as a fiducial marker. CONCLUSIONS: This is a simple, reproducible, and easily performed office procedure with durable results and minimal lipiodol migration. Source of Funding: None © 2022 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 207Issue Supplement 5May 2022Page: e806 Advertisement Copyright & Permissions© 2022 by American Urological Association Education and Research, Inc.MetricsAuthor Information Aoife McVey More articles by this author Elvira Polo Alonso More articles by this author Olivia Fraser More articles by this author Daryl Lim Joon More articles by this author Gregory Jack More articles by this author Expand All Advertisement PDF downloadLoading ...

Purpose/Objective(s)To report the feasibility, post-operative complications and recto-prostatic separation achieved with hyaluronic acid (HA) inserted into the perirectal fat before definitive prostate radiotherapy (RT).Materials/MethodsFifty-seven patients with clinical stage T1-3 prostate cancer underwent transrectal ultrasound guided transperineal insertion of fiducial markers and HA into the perirectal space before volumetric arc RT between 7/2020 to 7/2021. Post insertion computerized tomography (CT) and magnetic resonance imaging (MRI) scans were obtained for treatment planning. HA feasibility, safety and recto-prostatic separation were assessed. The prescribed dose to the planning target volume (PTV) ranged from 60-62Gy in 20 fractions.ResultsThe mean age was 74.7 years. The median PSA was 8.1 [Interquartile range (IQR)6.2-10.0]. The majority of patients had ISUP 2 adenocarcinoma (60%). The rest had ISUP 1 (11%) and ISUP 3 (30%). The disease risk was staged as early in 11%, favorable intermediate in 30%, unfavorable intermediate in 58% and high in 2%. Androgen deprivation therapy was delivered in 63%. HA insertion was completed with a 100% success rate. This was rated as ‘easy' to ‘very easy' 100% of the time. There were no device related complications, rectal perforation, serious bleeding, infections or allergic reactions. The mean prostate size was 43cc (IQR 30-55cc). Recto-prostatic separation at the base (measured 5mm below the prostate base), mid gland and apex (measured 5mm above the prostate apex) were 12mm (0.2), 11mm (0.2) and 0.9mm (0.1) respectively. The HA was also symmetrically placed in breadth at the mid gland in all patients. The mean rectal volume receiving 53Gy (rV53) was 3.2% (IQR 1.3-5.5) for patients receiving 60-62Gy. The median follow up was 13.5 months (IQR 9.5-17.5). The risk of any acute GU toxicity was 81%. The majority had grade 1 GU toxicity at 67% with urinary frequency, urgency and obstruction being the commonest reported side effects. The risk of any grade 2 GU toxicity was 14% with urinary obstruction (13%) and urgency (7%). The risk of any acute GI toxicity was 2%. Only 1 patient developed grade 1 GI toxicity with diarrhea. The risk of any late GU toxicity was 43%. The majority had grade 1 GU toxicity at 32% with urinary frequency, urgency and obstruction. The risk of any grade 2 GU toxicity was 11% with urinary obstruction (5%), urgency (5%) and incontinence (2%). The risk of any late GI toxicity was 2%. Only 1 patient had grade 1 GI toxicity with diarrhea.ConclusionHA was successfully inserted in all patients and was well tolerated. Recto-prostatic separation was symmetrical in length from the base to the apex and in breadth at the midgland. The risk of developing any acute GI toxicity was minimal at 2% with the use of HA. In addition, the risk of late GI toxicity was 2%, albeit with short follow up.

Purpose/Objective(s)To report single institutional feasibility of recto-vesical hyaluronic acid or hydrogel spacer insertion for patients undergoing post prostatectomy radiotherapy (PPRT).Materials/MethodsSpacer insertion was considered in patients referred for PPRT following an intra or interfascial radical prostatectomy who had no radiological evidence of local recurrence (based on prostate specific membrane antigen positron emission tomography). The spacer was inserted into the perirectal fat between the bladder and anterior rectal wall using a transperineal approach under transrectal ultrasound guidance. Two gold seed fiducial markers were also inserted at the level of the vesico-urethral anastomosis for image guided radiation therapy as per institutional practice. Pre and post spacer computerized tomography planning scans, together with post spacer magnetic resonance imaging scans, were acquired for dosimetric comparison. The prostate bed clinical target volume (CTV) was delineated according to Australian guidelines and the CTV was uniformly expanded by 7mm to create the planning target volume (PTV). The prescribed dose to the prostate bed was 70.2Gy in 1.8 Gy fractions using volumetric arc radiation therapy. The PTV and rectal dosimetry for the two sets of planning scans (PTV 7mm/pre spacer and PTV 7mm/post spacer) were compared.ResultsSixty-one patients were recruited between 9/18 to 10/21. Fifty-eight patients successfully underwent rectal spacer insertion without postoperative complications. We did not attempt spacer insertion in 3 patients as we were unable to hydrodissect the perirectal fat plane. Only 33 patients had pre spacer planning scans available for dosimetric comparison. The distance between the bladder and rectal wall was increased from ≤1mm to a median of 11mm (9-13) at its greatest extent. The rectal volume for all patients (N=61) receiving 42.2Gy (rV60%), 49.1Gy (rV70%), 56.2 Gy (rV80%), 63.2Gy (rV90%) and 70.2Gy (rV100%)] were 28.1%, 23%, 17.9%, 12.5% and 3.8% respectively. With spacing, a statistically significant reduction was seen on all rectal volume end points from rV60% to rV100% in the 33 patients with both pre and post planning scans (see Table 1). The median follow up was 10.5 months (3-31). The risk of any grade acute GI toxicity was 28% (grade 1 26% and grade 2 2%). The risk of late GI toxicity was 7% (all grade 1 proctitis).ConclusionMore than 90% of our selected PPRT patients were able to achieve recto-vesical separation, with no surgical complications, resulting in a 43.7% reduction in rV90%. The reduction in acute and late grade 2 GI toxicity is of notable significance, albeit with short follow up. Table 1 Pre and Post Spacer Rectal Dosimetry

AbstractIntroductionAnal cancer (AC) is 18F‐FDG‐PET avid and has been used to evaluate treatment response several months after chemoradiotherapy. This pilot study aimed to assess the utility of semi‐automated contouring methods and quantitative measures of treatment response using 18F‐FDG‐PET imaging at the early time point of 1‐month post‐chemoradiotherapy.MethodsEleven patients with AC referred for chemoradiotherapy were prospectively enrolled into this study, with 10 meeting eligibility requirements. 18F‐FDG‐PET imaging was obtained pre‐chemoradiotherapy (TP1), and then 1‐month (TP2), 3–6 months (TP3) and 9–12 months (TP4) post‐chemoradiotherapy. Manual and semi‐automated (Threshold) contouring methods were used to define the primary tumour on all 18F‐FDG‐PET images. Resultant contours from each method were interrogated using quantitative measures, including volume, response index (RI), total lesion glycolysis (TLG), SUVmax, SUVmedian and SUVmean. Response was assessed quantitatively as reductions in these measures and also qualitatively against established criteria.ResultsNine patients were qualitatively classified as complete metabolic responders at TP2 and all 10 at TP3. All quantitative measures demonstrated significant (P < 0.05) reductions at TP2 for both Manual and Threshold methods. All reduced further at TP3 and again at TP4 for Threshold methods. TLG showed the highest reduction at all post‐chemoradiotherapy time points and classified the most responders for each method at each time point. All patients are recurrence‐free at minimum 4‐year follow‐up.ConclusionBased on our small sample size, semi‐automated methods of disease definition using 18F‐FDG‐PET imaging are feasible and appear to facilitate quantitative response classification of AC as early as 1‐month post‐chemoradiotherapy. Early identification of treatment response may potentially improve disease management.

Purpose Clinician inexperience, intra–observer and inter–observer variations in tumour definition may affect staging, radiotherapy target definition, and treatment outcomes, particularly in rare cancers. The purpose of this study was to assess the correlation between semi–automated methods of primary anal cancer (AC) definition and our current clinical standard of manual clinician definition using 18F–FDG–PET imaging and to provide recommendations for clinical use. Methods All patients referred for chemoradiotherapy for AC between 2012 and 2016 were prospectively enrolled, with all 18F–FDG–PET imaging acquired within one year of chemoradiotherapy collected. Three methods of primary AC definition were performed on all PET datasets. Manual definition by an experienced radiologist was considered the clinical standard for comparison of volume and coincidence (Dice coefficient) in our study. Semi–automated techniques assessed included a gradient–based SUV (SUV–gradient) method and a SUV threshold method with a range of thresholds relative to SUVmax (40 (T40), 50 (T50) and 60% (T60)). Results Ten patients were enrolled with 33 PET study sets available for analysis. While all methods created contours on pre– and post–treatment scans, manual definition of PET–avid disease was only necessary on 11 of the 33 study sets. SUV–gradient and T40 defined contours were not statistically different in volume to the clinical standard (p = 0.83 & 0.72 respectively). The observed Dice coefficient relative to the manual clinician contours were 0.75 and 0.73 for the SUV–gradient and T40 methods respectively. Conclusions It is possible to define gross AC using SUV–based methods, with the SUV–gradient–based method followed by the T40 method most closely correlating with our current clinical standard. The SUV–gradient–based method studied is housed within a proprietary clinical system. A semi–automated approach that uses a vendor neutral T40 method and the clinician’s knowledge and skill appears optimal in defining AC. With this approach AC may be defined reliably to enhance efficiencies in radiotherapy and nuclear medicine processes, and to support clinicians in identifying and defining this rare disease. Trial registration ANZCTR, ACTRN12620000066987. Registered 28 January 2020–Retrospectively registered, https://www.anzctr.org.au/ACTRN12620000066987.aspx

Introduction: Guidelines recommend that the proximal seminal vesicles (PrSV) should be included in the clinical target volume for locally advanced prostate cancer patients undergoing radiotherapy. Verification and margins for the prostate may not necessarily account for PrSV displacement. The purpose was to determine the inter-fraction displacement of the PrSV relative to the prostate during radiotherapy. Methods: Fiducials were inserted into the prostate, and right and left PrSV (RSV and LSV) in 30 prostate cancer patients. Correctional shifts for the prostate, right and left PrSV and pelvic bones were determined from each patient's 39 daily orthogonal portal images relative to reference digitally reconstructed radiographs. Results: There was a significant displacement of the RSV relative to the prostate in all directions: on average 0.38 mm (95% confidence interval (CI) 0.26 to 0.50) to the left, 0.80-0.81 mm (CI 0.68 to 0.93) superiorly and 1.51 mm (CI 1.36 to 1.65) posteriorly. The LSV was significantly displaced superiorly to the prostate 1.09-1.13 mm (CI 0.97 to 1.25) and posteriorly 1.81 mm (CI 1.67 to 1.96), but not laterally (mean 0.06, CI -0.06 to 0.18). The calculated PTV margins (left-right, superior-inferior, posterior-anterior) were 4.9, 5.3-5.6 and 4.8 mm for the prostate, 5.2, 7.1-8.0 and 9.7 mm for the RSV, and 7.2, 7.5-7.6 and 8.6 mm for the LSV. Conclusion: There is a significant displacement of the PrSV relative to the prostate during radiotherapy. Greater margins are recommended for the PrSV compared to the prostate.

Purpose To report on rectal dosimetry and toxicity outcomes in men with prostate cancer (PCa) treated with iodine-125 low-dose-rate brachytherapy (LDR-BT) with or without polyethylene glycol hydrogel (HS) or hyaluronic acid (HA) rectal spacer (RS) insertion. Material and methods Seventy consecutive men treated with LDR-BT between December 2017 and July 2019 were included in this study, including twenty-eight (40%) men who had RS insertion according to the preference of referring urologist, compared to a group of forty-two men (60%) without RS. Descriptive statistics were used to compare RS safety, dosimetric effects on organs at risk (rectum and urethra), and gastrointestinal (GI) and genitourinary toxicities (GU) (assessed using the CTCAE v.4) between the two groups of patients. Results The median prostate-rectal separation with RS at mid prostate was 10 mm (IQR, 8-11.5 mm). The median follow-up was 23.5 months. There were no post-operative complications for RS insertion. There was significantly reduced rectal dosimetry in RS-group vs. non-RS group; the median RV100 was 0.0 cc (IQR, 0.0-0.0 cc) vs. 0.4 cc (IQR, 0.1-1.1 cc) (p < 0.001), respectively. The mean rectal D1cc and D2cc were 52.4% vs. 84.2% (p < 0.001) and 45.7% vs. 70.0% (p < 0.001) for RS and non-RS group, respectively. There were no statistically significant differences in the mean urethral D20, D5, and D1. There were significantly less grade 1 acute and late GI toxicities in RS-group when compared to non-RS group (0% vs. 24%, p = 0.004 for acute GI toxicity; 4% vs. 33%, p = 0.003 for late GI toxicity). There were no reported acute or late grade 2 or above GI toxicities. Conclusions Insertion of RS in men treated with LDR-BT is safe and resulted in a significant reduction in rectal dosimetry. The reduction in rectal dosimetry with RS insertion translates into significantly reduced acute and late GI toxicities.