Feasibility of abdominal fat quantification on MRI and impact on effectiveness of abdominal compression for radiotherapy motion management

The impact of fat on abdominal compression effectiveness in abdominal cancers was determined using magnetic resonance imaging (MRI). Visceral and subcutaneous fat were delineated on T2W 3D MRI, and motion change with compression was measured on 2D cine MRI. Results from 16 participants showed no correlation between fat percentage, body mass index (BMI), and motion change. Median BMI was 28.7 (SD, 4.9). Mean motion reduction was 7.8 mm (IQR, 5.0; p = 0.001) with compression. While no direct link was found between fat, BMI, and compression effectiveness, abdominal compression remains crucial for motion management in radiotherapy planning, providing dosimetric benefits.

Co-enrichment of cancer-associated bacterial taxa is correlated with immune cell infiltrates in esophageal tumor tissue

Esophageal carcinoma (ESCA) is a leading cause of cancer-related death worldwide, and certain oral and intestinal pathogens have been associated with cancer development and progression. We asked if esophageal microbiomes had shared alterations that could provide novel biomarkers for ESCA risk. We extracted DNA from tumor and non-tumor tissue of 212 patients in the NCI-MD case control study and sequenced the 16S rRNA gene (V3-4), with TCGA ESCA RNA-seq (n = 172) and WGS (n = 123) non-human reads used as validation. We identified four taxa, Campylobacter, Prevotella, Streptococcus, and Fusobacterium as highly enriched in esophageal cancer across all cohorts. Using SparCC, we discovered that Fusobacterium and Prevotella were also co-enriched across all cohorts. We then analyzed immune cell infiltration to determine if these dysbiotic taxa were associated with immune signatures. Using xCell to obtain predicted immune infiltrates, we identified a depletion of megakaryocyte-erythroid progenitor (MEP) cells in tumors with presence of any of the four taxa, along with enrichment of platelets in tumors with Campylobactor or Fusobacterium. Taken together, our results suggest that intratumoral presence of these co-occurring bacterial genera may confer tumor promoting immune alterations that allow disease progression in esophageal cancer.

Outcomes in Locally Advanced Non-Metastatic Prostate Cancer Presenting with Low PSA at Diagnosis

PURPOSE/OBJECTIVE(S)

Men with low serum prostate-specific antigen (PSA) and high Gleason grade group (GGG) are thought to have poor outcomes compared to high PSA secretors. However, there is limited outcome data to support this. We report clinical outcomes from a single-institutional cohort of men presenting with locally advanced prostate cancer but low serum PSA.

MATERIALS/METHODS

Data from electronic database of a UK tertiary cancer center was acquired for men with histological diagnosis of prostate adenocarcinoma, GGG 4 or 5, stage ≥cT3a, and PSA <10ug/L at diagnosis. Men with metastatic disease, or prior androgen deprivation therapy (ADT) were excluded. Biochemical progression was defined as per Phoenix criteria (PSA > nadir+2) for primary radiotherapy, or PSA >0.2 ug/L after primary prostatectomy (and post-operative radiotherapy, if received). Overall survival (OS, from date of diagnosis to death), metastasis-free survival (MFS, from diagnosis to first recorded metastasis or death), and biochemical progression free survival (bPFS, from diagnosis to biochemical progression or death) were estimated by Kaplan Meier method, and multivariable analysis performed using Cox proportional hazards method.

RESULTS

Medical records of 7,200 men presenting with non-metastatic prostate cancer from 2013 to 2021 were screened, of which 270 men satisfying the eligibility criteria were included for this study. Initial analysis of 123 men shows median PSA at presentation 7.1 ug/L (IQR 5.6-8.5), and median age 70 years (IQR 65-75). Histology was GGG 4 in 47.6% and 5 in 52.4%. Tumor stage was cT3a in 56.6%, cT3b in 36.9%, and T4 in 6.6%. Pelvic nodes were involved in 5% patients. Majority (83.7%) were treated with radical radiotherapy (external beam alone 64.2%, brachytherapy boost 19.5%), with 24 months ADT; 11.4% underwent radical prostatectomy, and 4.9% received ADT alone. Three men (2.4%) received docetaxel, and one received abiraterone. At a median follow up of 66 months (IQR 27-77), 36 (29.3%) patients had biochemical failure. Total 23 (18.6%) patients had metastases at recurrence, which were visceral in 4%, bone-only in 10%, and nodal-only in 4%. Total 38 (30.6%) patients had died, 23% with prostate cancer and 11% due to other causes. Five-year bPFS was 65.9%, MFS 69.0%, and OS was 77.4%. GGG 5 (versus 4) was associated with significantly worse 5-year bPFS (59.4% vs 73.9%, HR 1.8, 95% CI 1.0-3.2, p = 0.05) and MFS (59.2% vs 81.6%, HR 2.2, 1.2-4.2, p = 0.02). On multivariable analysis including age and PSA at diagnosis, only GGG 5 was associated with worse bPFS (HR 1.8, 1.0-3.3, p = 0.05) and MFS (HR 2.42, 1.25-4.67, p = 0.009).

CONCLUSION

Men with low secreting but high Gleason grade group prostate cancer are a relatively rare group with poor clinical outcomes despite being non-metastatic. Ongoing work (expected completion June 2023) will analyze remaining cases, and compare outcomes within an expanded multicentric cohort with matched controls having elevated PSA at presentation.

Quality of Life in Prostate Cancer Patients Undergoing Daily Adaptive Versus Non-Adaptive Radiation Therapy Utilizing A 1.5 Tesla MR-Linac

PURPOSE/OBJECTIVE(S)

Using adaptive radiation therapy (ART) physicians can re-contour normal organs (such as bladder and rectum) before each fraction. While ART may result in more reliable dosimetry to regional organs at risk, the process is time consuming and more expensive than non-ART. We evaluated differences in patient reported quality of life (PR-QOL) between daily ART and non- ART.

MATERIALS/METHODS

Patients with prostate cancer from 3 centers in the Netherlands and United States were treated using a 1.5 Tesla MR Linear accelerator. Patients consented to the Multiple Outcome Evaluation of Radiation Therapy Using the MR-Linac Study (MOMENTUM, NCT04075305) between 2019 and 2022. PR-QOL was prospectively collected using the EORTC QLQ-C30 and PR-25 at baseline (before RT), and at 3 and 6 months after RT. Patients without complete QOL data were excluded. QOL differences were compared between patients undergoing daily ART vs. non-ART. A linear mixed effect model was performed to account for repeated measurements. Analyses were performed using R Studio.

RESULTS

One hundred thirty-six patients underwent RT with QOL were analyzed. Median follow up was 13 months (6-26 months). Patients were treated without daily ART (n = 94) or with daily ART (n = 42). The median age was 70 (range 53-83) years and 65.4% had intermediate risk disease, 35% of patients received hormonal therapy. Fractionation schedules included 36 Gy/6 (n = 16), 36.25 Gy/5 (n = 103), 60 Gy/20 (n = 6), 62 Gy/20 (n = 8), and 70 Gy/28 (n = 3). Compared to baseline scores, EORTC QLQ C30 diarrhea scores at 6 months post-treatment were significantly worse for patients treated without daily ART compared to those treated with daily ART (p < 0.05). Other QLQ PR25 bowel scores were not significantly different at 3 or 6 months. Both PR25 urinary and treatment-related symptoms were improved with daily ART compared to non-ART at the 3 (p < 0.001 and p < 0.01, respectively) and 6 (p < 0.01 and p < 0.001, respectively) month time points. Magnitude of improvements can be found in Table 1.

CONCLUSION

Among prostate cancer patients treated using 1.5 Tesla MRI-guided RT, daily ART was associated with improved PR-QOL in urinary and bowel domains compared to non-ART. These hypotheses generating preliminary results provide the first indications (to our knowledge) that adapting contours to daily anatomy may improve short-term urinary and bowel PR-QOL. Updated results will be presented at ASTRO 2023.

Validation of Hypoxia Detection Sequences on the MR Linac

PURPOSE/OBJECTIVE(S)

Magnetic resonance linear accelerator (MRL) systems permit acquisition of novel imaging at the time of radiotherapy. A validated MR hypoxia imaging biomarker could select patients for adaptive radiotherapy with hypoxia modification or dose escalation. The aims of this study were (1) to develop a protocol for quantitative hypoxia sensitive MRI (2) to validate these in prostate cancer (PCa) against pimonidazole-stained prostatectomy sections.

MATERIALS/METHODS

Blood oxygen level dependent (BOLD), intravoxel incoherent motion (IVIM), oxygen-enhanced (OE) and dynamic contrast enhanced (DCE) MRI were used. Sequences were developed on a diagnostic 1.5 T MR (MRD) and MRL with healthy volunteers and PCa patients. The Hyprogen trial includes men with localized PCa scheduled for prostatectomy. Imaging is acquired twice prior to surgery and oral pimonidazole is taken 8-16 hours before surgery. Whole prostate (WP) and dominant prostatic lesion (DIL) were outlined on T2-weighted (T2W) images and a 'normal prostate' (NP) volume created by subtracting DIL from WP. Contours were applied to parametric maps from the quantitative MRI, with median and IQR extracted. Patient-specific 3D-printed prostate molds were created from WP volumes and used to guide prostate whole organ dissection.

RESULTS

Three of 20 patients recruited to date. MRI data were acquired successfully. A personalized prostate mold was produced for each patient and facilitated dissection of the prostatectomy specimen in a matching plane to MRI to validate hypoxia detection of the MR protocol. Correlation with pimonidazole staining is underway. Imaging parameter median values for NP and DIL acquired on MRD and MRL for the first patient are shown (Table 1). The expected differences between NP and DIL for T1 and D are seen and median values for T2* are consistent with reported values in the literature.

CONCLUSION

The MR hypoxia protocol can be acquired safely and is well-tolerated on the MRL. Once validated against pimonidazole staining adaptive radiotherapy protocols will be developed to use this information.

Real World Multi-Institutional Outcomes of Bladder Carbogen and Nicotinamide (BCON) in Muscle-Invasive Bladder Cancer (MIBC)

PURPOSE/OBJECTIVE(S)

Bladder carbogen and nicotinamide (BCON), combined with radiotherapy, is a standard of care in the bladder-preserving treatment of muscle-invasive bladder cancer (MIBC). UK national guidelines recommend neoadjuvant chemotherapy (NAC) before bladder preservation. However, patients did not receive NAC in the definitive phase III BCON trial. This study assessed tolerability and real-world outcomes of BCON alone or with NAC (NAC-BCON).

MATERIALS/METHODS

With institutional approval, demographics and clinical information were obtained for a retrospective cohort study of BCON patients (2017-2021) across 3 UK centers. Clinician-reported toxicity was assessed using RTOG grading during radiotherapy, 6 weeks and 12 months after. Cross-sectional imaging and cystoscopy determined local control, metastasis-free survival (MFS), and cancer-specific survival (CSS). Subgroup differences were compared using T and χ2 tests. Survival was analyzed by Kaplan-Meier, log-rank, and multivariate Cox proportional hazard regression. Statistical analysis was conducted using R version 4.2.1 (R Core Team (2022)).

RESULTS

A total of 317 patients were treated with BCON; 75 (24%) received NAC-BCON. Median follow-up was 29 months (4-63m). Patient characteristics are shown in Table 1. NAC-BCON patients were younger (median 72 vs 78 years, p<0.05), with better PS (p<0.05) and ACE-27 (p<0.05), with no statistical difference in T-staging and histopathology. 298 (94%) completed BCON, whilst 59/75 (79%) completed ≥3 cycles of NAC. There was no significant increased grade 3 acute or late bowel or bladder toxicity with NAC. 3-month cystoscopy post radiotherapy demonstrated complete response in 282/317 (89%). 121 (38%) developed metastases, and 112 (35%) died of MIBC. 5-year BCON MFS was 62% and 49% for NAC-BCON (HR 0.69, 95% CI 0.98- 2.51, p = 0.064); 5-year BCON CSS was 55% and 52% for NAC-BCON (HR 0.83, 95% CI 0.79-1.83, p = 0.39). This remained after adjusting for clinical factors in a multivariate Cox model for both MFS (p = 0.22) and CSS (p = 0.37).

CONCLUSION

Our real-world data compares favorably to published BCON 5-year relapse-free survival (41%) and OS (49%). NAC-BCON has no increased toxicity with comparable treatment completion rates to BCON alone. No significant improvement in survival outcomes was seen with NAC, possibly due to small numbers and patient selection in a non-randomized cohort. Further analysis is planned with additional center input.

Evolution of the MOMENTUM Study for Evidence-Based Implementation of MR-Guided Radiotherapy Using the 1.5 Tesla MR-Linac

PURPOSE/OBJECTIVE(S)

The international prospective 'Multiple Outcome Evaluation of Radiation Therapy Using the MR-Linac' (MOMENTUM) study (NCT04075305) was initiated in 2019 by seven hospitals and industry partner precision radiation medicine company, with the aim to facilitate evidence-based implementation of magnetic resonance (MR) guided radiotherapy using the 1.5 Tesla (T) MR-linear accelerator (Linac). Over the last four years, MOMENTUM has expanded to other institutions and the design and organization of MOMENTUM have evolved. Herein, we give an overview of the current status of MOMENTUM and study innovations that have been implemented to accelerate development and assessment of the 1.5T MR-Linac.

MATERIALS/METHODS

We summarized operational outputs of MOMENTUM, including site participation, data aggregation, academic output, and study design elements that have been introduced since 2019.

RESULTS

As of January 2023, 17 sites have joined and 10 sites are actively enrolling patients in MOMENTUM. The MOMENTUM infrastructure, which consists of prospectively collected clinical and technical patient data and patient reported outcomes, is increasingly being used for predicate studies, technical development studies, safety and early clinical evaluation, and hypothesis testing studies according to R-IDEAL. Over 3500 patients who received treatment for 33 different tumor sites have provided informed consent for using their data for scientific research and product development. The technical database currently includes over 190.000 items, including approximately 98,000 MRI scans and 33,800 dose plans. A total of 38 data requests have been accepted (2019: n = 1; 2020: n = 5; 2021: n = 10; 2022: n = 22), including technical studies focused on algorithmic development. The MOMENTUM infrastructure is also hosting prospective clinical studies, including the randomized HERMES trial (NCT04595019) and prospective UNITED study (NCT04726397). Recently, the 'Trials within Cohorts' (TwiCs) design has been implemented, which is well suited to perform pragmatic randomized trials. MOMENTUM has partnered with Kaiku Health, an electronic patient-reported outcomes application, to facilitate collection of patient reported toxicity.

CONCLUSION

Over the past four years, the MOMENTUM study has evolved into a unique platform, whose infrastructure is increasingly being used by clinicians, researchers, physicists and industry. Continuous efforts are being made to encourage the participation of new sites and the development of innovative tools to facilitate the conduct of well-designed trials that are expected to transform daily clinical practice.

Single Institution Preliminary Evaluation of a National Study for the Development of Daily Online Magnetic Resonance Image Guided Radiotherapy

PURPOSE/OBJECTIVE(S)

A 4-stage non-comparative prospective feasibility study to assess and develop imaging protocols for MRIgRT was opened at the first two centers using MR Linac technology in the UK. The primary aims of this study were to determine a) the acceptability of MR images for target and organ at risk delineation and registration; b) inter/intra observer registration and delineation variation. This work reports on the initial results from a single center.

MATERIALS/METHODS

In June 2019, following ethical and regulatory approvals the 2nd UK centre began study recruitment as follows: Stage A: non-patient volunteer imaging to determine sequence suitability for normal tissue in 6 anatomical sites (head & neck (H&N), chest wall/breast, lung/esophagus, abdomen, male and female pelvis). Volunteers were recruited in cohorts of 3 participants per region, and image quality was assessed by 3 independent observers using a visual guidance assessment tool (VGA). Stage B: the most suitable sequences defined in stage A used to assess the visibility of targets/normal tissues in patient volunteers using the same methods as in stage A. Stage C: patient volunteers were imaged using sequences selected from stage B to determine inter and intra observer segmentation and registration variation. Stage D recruitment of patient and non-patient volunteers for further image develop and refinement of MRIgRT workflows. All participants completed experience questionnaires to optimize workflows. Participants were asked to undergo 1-12 imaging sessions, lasting no more than 60.

RESULTS

To date 151 participants (61 non-patients; 90 patients) have undergone 231 imaging sessions. From stage B, vendor provided, in-workflow sequences have been agreed from 47 completed VGAs by prioritizing high scores in either the tumor (e.g., lung) or organs at risk (e.g., cervix). T2w 3D sequences scored best in cervix, pancreas, prostate, bladder, liver, soft-tissue metastases and rectal cancers; T1w 3D sequences for H&N, and patient a specific approach for lung. No suitable sequences have been selected for partial breast. Research sequences (e.g., diffusion weighted or motion corrected imaging) have been agreed or are in development in stages C & D for H&N, cervix, bladder and prostate cancers. The mean interobserver (n = 8) vector variation in 5 H&N patients was largest (3.6mm) using T1-CT boney registrations and smallest (2.1mm) using T1-T1 soft-tissue registrations (mean observer match confidence 3.7/5). Analyses using MR to CT, MR to MR and CT to CT registrations in lung, pancreas, cervix, bladder, and prostate have also been completed. Interobserver delineation studies are on-going.

CONCLUSION

Using a 4-stage non-comparative prospective feasibility study has facilitated clinical implementation MRIgRT of multiple treatment sites at our institution.

Acute Toxicity of Hypofractionated and Conventionally Fractionated (Chemo)Radiotherapy Regimens for Bladder Cancer: An Exploratory Analysis from the RAIDER Trial

AIMS

Adding concurrent (chemo)therapy to radiotherapy improves outcomes for muscle-invasive bladder cancer patients. A recent meta-analysis showed superior invasive locoregional disease control for a hypofractionated 55 Gy in 20 fractions schedule compared with 64 Gy in 32 fractions. In the RAIDER clinical trial, patients undergoing 20 or 32 fractions of radical radiotherapy were randomised (1:1:2) to standard radiotherapy or to standard-dose or escalated-dose adaptive radiotherapy. Neoadjuvant chemotherapy and concomitant therapy were permitted. We report exploratory analyses of acute toxicity by concomitant therapy-fractionation schedule combination.

MATERIALS AND METHODS

Participants had unifocal bladder urothelial carcinoma staged T2-T4a N0 M0. Acute toxicity was assessed (Common Terminology Criteria for Adverse Events) weekly during radiotherapy and at 10 weeks after the start of treatment. Within each fractionation cohort, non-randomised comparisons of the proportion of patients reporting treatment emergent grade 2 or worse genitourinary, gastrointestinal or other adverse events at any point in the acute period were carried out using Fisher's exact tests.

RESULTS

Between September 2015 and April 2020, 345 (163 receiving 20 fractions; 182 receiving 32 fractions) patients were recruited from 46 centres. The median age was 73 years; 49% received neoadjuvant chemotherapy; 71% received concomitant therapy, with 5-fluorouracil/mitomycin C most commonly used: 44/114 (39%) receiving 20 fractions; 94/130 (72%) receiving 32 fractions. The acute grade 2+ gastrointestinal toxicity rate was higher in those receiving concomitant therapy compared with radiotherapy alone in the 20-fraction cohort [54/111 (49%) versus 7/49 (14%), P < 0.001] but not in the 32-fraction cohort (P = 0.355). Grade 2+ gastrointestinal toxicity was highest for gemcitabine, with evidence of significant differences across therapies in the 32-fraction cohort (P = 0.006), with a similar pattern but no significant differences in the 20-fraction cohort (P = 0.099). There was no evidence of differences in grade 2+ genitourinary toxicity between concomitant therapies in either the 20- or 32-fraction cohorts.

CONCLUSION

Grade 2+ acute adverse events are common. The toxicity profile varied by type of concomitant therapy; the gastrointestinal toxicity rate seemed to be higher in patients receiving gemcitabine.

Outcome of percutaneous transhepatic biliary interventions in the management of biliary enteric anastomotic strictures with hepatolithiasis

AIM

To evaluate percutaneous transhepatic biliary interventions (PTBI) using the ADDFREE (Access-Drain-Dilate-Flush-REpeat periodically-Evaluate and remove) technique and its outcomes in patients with biliary enteric anastomotic strictures (BEAS) and hepatolithiasis.

MATERIAL AND METHODS

A retrospective review was undertaken of patients having hepatolithiasis with BEAS who underwent PTBI with a therapeutic intent (from January 2010 to January 2021) was performed. The technical and clinical successes of PTBI were analysed. Technical success was divided into duct access, crossing of BEAS, stricture resolution, and calculi clearance. Improvement of liver function tests, resolution of leucocytosis and presenting complaints were considered as clinical success. The patients were followed-up for a minimum duration of 6-months.

RESULTS

Eighteen patients received PTBI in form of the ADDFREE technique. Hepatolithiasis was bilobar (44.4%), unilobar in multiple ducts (unilobar-m; 27.8%) and unilobar in a single duct (unilobar-s; 27.8%) along with anastomotic stricture. The average number of sessions of stone clearance for bilobar, unilobar-m, and unilobar-s was 4.4 (±1.6), 3.6 (±2.4), and 1.5 (±0.5), respectively. Clinical success was observed in 14 (77.8%), while one patient had recurrence of calculi and received repeat treatment. Bile culture was positive for bacterial organisms in 17 (94.4%) patients. No major complication were seen while minor complication were seen in five patients consisting of self-limiting haemobilia (n=1), per-catheter bile leak (n=2) and aggravation of cholangitis (n=2).

CONCLUSION

PTBI, consisting of bile duct access, cholangioplasty, and calculi clearance, is a safe and effective technique for the treatment of patients having hepatolithiasis secondary to BEAS.

Shockwave intravascular lithotripsy (IVL) for calcified coronary lesions; a real world multicentre European study with long term follow up

Background

The presence of calcium in atherosclerotic plaques is a challenge for successful angioplasty and is an independent risk factor for restenosis and stent thrombosis. Despite conventional tools (non-compliant, scoring and cutting balloons and rotational atherectomy), cracking calcium can still be challenging and incomplete. Intra-vascular lithotripsy (IVL) has shown promising results, although long-term data on safety and efficacy from real-world is lacking.

Purpose

This study was undertaken to report long-term outcomes following use of IVL from a European multi-centre experience.

Methods

This was a multicentre, retrospective observational study in which we enrolled all patients treated with shockwave lithotripsy from November 2018 to June 2021. Procedural success, complications and in hospital events were evaluated. The clinical outcomes during follow-up included cardiac death, target vessel myocardial infarction (TVMI), target lesion revascularisation (TLR), and major adverse cardiac event (MACE) (composite of cardiac death, TVMI, and TVR).

Result

A total of 272 patients were treated with IVL, with a mean age of 72 9.1 years and 78.5% (n=216) were male. Forty percent (n=110) were diabetic while 16% (n=45) had chronic kidney disease. Acute coronary syndrome was the presentation in 36% (n=99) while 51% (n=141) had stable angina. De novo lesions accounted for 78% (n=215) of the cases and the remainder were in-stent restenosis (21%; n=58). The LAD was the commonest artery treated 50% (n=139) followed by RCA 24% (n=68). Intracoronary imaging was performed in 33% of cases. Upfront IVL strategy was adopted in 37% (n=101) while 63% (n=171) were bail out procedures due to inadequate pre dilatation. Adjuvant rotational atherectomy was used on 31 (11.4%) cases. Procedural success was achieved in 96% (260) cases with major complications in 8 cases (perforation requiring covered stent in 3 patients) but there was no in-hospital mortality. Clinical outcomes over the median follow up of 641 days are shown in the table.

Conclusion

This is the largest multicentre registry with long term follow up. It has demonstrated that IVL appears to be safe with high success rates, low rates of complication and no in-hospital mortality. The long-term follow-up show promising results with low rates of hard-endpoints and revascularization rates.

Funding Acknowledgement

Type of funding sources: None.

Determinants of neointimal strut coverage in bio-degradable polymer coated ultrathin strut stent

Introduction

Incomplete strut coverage (ISC) is the most important morphometric determinant of stent thrombosis. Determinants of ISC have been studied in thick and thin strut stents.

Purpose

To identify morphometric factors causing ISC in the biodegradable polymer-coated ultra-thin strut drug eluting stent (BP-UTS-DES) that are designed to encourage better strut coverage.

Methods

Patients undergoing implantation of a 65μm BP-UTS-DES had opportunistic OCT during staged PCI to assess strut coverage at 90 days. Images were analysed offline by experienced operators blinded to patient and procedural data. Neointimal thickness (NIT, μm) was measured as the minimum endoluminal distant between the strut and lumen border. All malapposed struts were considered uncovered. ISC was defined as &lt;100% covered struts in a frame. Stepwise logistic regression using multiple morphometric variables was used to identify independent determinants of ISC including markers of circumferential distribution of neointimal growth (CVS,NUS,RUS), symmetry of stent expansion (SEI, AVS, MAS) in each cross section and the geographical location of the frame along the axis of the stent.

Results

We analysed 11652 frames of 65 stents (1976 mm) in 46 arteries of 40 patients. All stents were post dilated. 95.6% arteries had &gt;20mm stents, 39.1% were overlapped and 15.2% were chronic total occlusions. Malapposition was seen in 2.6% of all struts and 39.2% of uncovered struts. The proportion of covered struts decreased as indices of circumferential uniformity of distribution of neointimal hyperplasia increased (CVS: r=0.37, p&lt;0.001; RUS: r=0.36, p&lt;0.001; NUS: r=0.52, p&lt;0.001). As uniformity of stent expansion improved (SEI increased) strut coverage and circumferential uniformity of neointimal hyperplasia increased (CVS, NUS and RUS decreased) suggesting that distribution of neointimal growth becomes homogeneous as uniformity of stent expansion improves (Fig. 1). Determinants ISC is shown in Table 1.

Conclusion

SEI but not AVS or MAS determines ISC. Compared to the distal third of the stent frames in the middle third had lower and the proximal third had high risk of ISC.

Funding Acknowledgement

Type of funding sources: None.

Using Real-world Data to Define a Validated Nomogram for Advanced Bladder Cancer Patients Who Respond to Immunotherapy

AIMS

Immune checkpoint inhibitors (ICIs) are used in incurable urothelial cancers, both in chemo-naïve and platinum-refractory patients. Efficacy and toxicity data published outside controlled clinical trials are limited. We report overall survival, progression-free survival and toxicities of ICIs in locally advanced (LABC) or metastatic bladder cancer (MBC). We aimed to develop and validate a prognostic model for these patients.

MATERIALS AND METHODS

A multicentre real-world individual patient-level data study (n = 272) evaluating ICIs in the first-line platinum-ineligible or platinum-refractory setting for LABC/MBC between March 2017 and February 2020 was undertaken. Cox regression analyses evaluated the association of prognostic factors with overall survival. Data were split to create a training (n = 208) and validation (n = 64) cohort. The backward elimination method with a P-value cut-off of 0.05 was used to develop a reduced prognostic model using the training data set. The concordance index and assessment of observed versus predicted survival probabilities were used to evaluate the final model.

RESULTS

The median follow-up was 18.9 (15.8-21.5) months. The median overall survival and progression-free survival in the training cohort were 9.2 (95% confidence interval 7.4-10.5) and 4.5 months (3.5-5.7), respectively. The most common grade 1/2 adverse events recorded were fatigue (47.8%) and infection (19.9%). Five key prognostic factors found in the training set were low haemoglobin, high neutrophil count, choice of immunotherapy favouring pembrolizumab, presence of liver metastasis and steroid use within 30 days of treatment. The concordance index for the training and validation cohorts was 0.66 (standard error = 0.05) and 0.64 (standard error = 0.04), respectively, for the final model. A nomogram was developed to calculate the expected survival probabilities based on risk factors.

CONCLUSIONS

Real-world data were used to produce a validated prognostic model for overall survival in LABC/MBC treated with ICIs. This model could assist in patient stratification, interpreting and framing future trials incorporating PD-1/PD-L1 inhibitors in LABC/MBC.

Effect of Race and Ethnicity on Risk of Radiotherapy Toxicity and Implications for Radiogenomics

AIMS

Patient factors affect the risk of radiotherapy toxicity, but many are poorly defined. Studies have shown that race affects cancer incidence, survival, drug response, molecular pathways and epigenetics. Effects on radiosensitivity and radiotherapy toxicity are not well studied. The aim of the present study was to identify the effects of race and ethnicity on the risk of radiotherapy toxicity.

MATERIALS AND METHODS

A systematic review was carried out of PubMed, Ovid Medline and Ovid Embase with no year limit. PRISMA 2020 guidelines were followed. Two independent assessors reviewed papers.

RESULTS

Of 607 papers screened, 46 fulfilled the inclusion criteria. Papers were published between 1996 and 2021 and involved 30-28,354 individuals (median 433). Most involved patients with prostate (33%), breast (26%) and lung (9%) cancer. Both early and late toxicities were studied. Some studies reported a higher risk of toxicity in White men with prostate cancer compared with other races and ethnicities. For breast cancer patients, some reported an increased risk of toxicity in White women compared with other race and ethnic groups. In general, it was difficult to draw conclusions due to insufficient reporting and analysis of race and ethnicity in published literature.

CONCLUSIONS

Reporting of race and ethnicity in radiotherapy studies must be harmonised and improved and frameworks are needed to improve the quality of reporting. Further research is needed to understand how ancestral heritage might affect radiosensitivity and risk of radiotherapy toxicity.

495 Virtual Reality Simulation Training in Hip Surgery Versus Traditional Surgical Education Method: A Systematic Review of Randomised Controlled Trials

Aim

The purpose of this study was to perform a systematic review of the effects of orthopaedic virtual reality simulators on surgical skills across randomised controlled trials.

Method

The authors searched PubMed, CINAHL, MEDLINE, AMED, Eric, Embase, Cochrane Central Register of Controlled Trials, TRIP database and grey literature from 1946 to November 2020. Inclusion criteria were all level one studies, specifically randomised controlled trials with orthopaedic training simulators in hip surgery and clear evaluation of skills attained after virtual reality simulation (VR) training. The primary outcome was the reported quantitative assessment of operative skills acquisition. The Jadad scale was used as a tool in order to appraise the methodological quality of the included trials. The data collected were not amenable for meta-analysis as they were too heterogenous and were analysed and presented using a narrative analysis and the Synthesis Without Meta-analysis (SWiM) reporting guideline.

Results

A total of 1095 articles were identified. Four level I studies, all randomised controlled trials, including 86 participants were eligible for the final analysis. There were significant differences in the types of simulators, training structure, validity types, performance scores and outcome measures described in each study. In three out of four studies (75%) the use of VR training simulators led to improved surgical skills acquisition compared to other traditional teaching methods.

Conclusions

Overall, this review showed that the use of VR simulation training is a potential tool that can enhance surgical skills acquisition in hip surgery procedures compared to traditional education methods.

Translation of Prognostic and Pharmacodynamic Biomarkers from Trial to Non-trial Patients with Metastatic Castration-resistant Prostate Cancer Treated with Docetaxel

AIMS

We conducted a pooled analysis of four randomised controlled trials and a non-trial retrospective dataset to study the changes in serum prostate-specific antigen (PSA) concentrations during treatment and its impact on survival in men treated with docetaxel for metastatic castration-resistant prostate cancer. We also compared the outcomes and pre-treatment prognostic factors between trial and non-trial patients.

MATERIALS AND METHODS

Data were obtained from four randomised controlled trials and a non-trial cohort from a tertiary cancer centre. The PSA kinetics covariates chosen were absolute value (PSAT), best percentage change (BPCH) and tumour growth rate (K). The association between the covariates collected and overall survival was assessed within a Cox proportional hazards model. How well a covariate captured the difference between trial and non-trial patients was assessed by reporting on models with or without trial status as a covariate.

RESULTS

We reviewed individual datasets of 2282 patients. The median overall survival for trial patients was 20.4 (95% confidence interval 19.6-22.2) months and for the non-trial cohort was 12.4 (10.7-14.7) months (P < 0.001). Of the pre-treatment factors, we found that only lactate dehydrogenase fully captured the difference in prognosis between the trial and non-trial cohorts. All PSA kinetic metrics appeared to be prognostic in both the trial and non-trial patients. However, the effect size was reduced in non-trial versus trial patients (interaction P < 0.001). Of the time-dependent covariates, we found that BPCH best captured the difference between trial and non-trial patient prognosis.

CONCLUSIONS

The analysis presented here highlights how data from open-source trial databases can be combined with emerging clinical practice databases to assess differences between trial versus non-trial patients for particular treatments. These results highlight the importance of developing prognostic models using both pre-treatment and time-dependent biomarkers of new treatments.