Pembrolizumab with Chemoradiation as Treatment for Muscle-invasive Bladder Cancer: Analysis of Safety and Efficacy of the PCR-MIB Phase 2 Clinical Trial (ANZUP 1502)

BACKGROUND

Radiation may improve the efficacy of immune checkpoint inhibition. This study investigates the combination of pembrolizumab and chemoradiation (CRT) for muscle-invasive bladder cancer (MIBC).

OBJECTIVE

To assess the feasibility and safety of pembrolizumab combined with CRT for MIBC.

DESIGN, SETTING, AND PARTICIPANTS

A single-arm phase 2 trial was performed with 28 participants having cT2-T4aN0M0 MIBC (Eastern Cooperative Oncology Group performance status 0-1; estimated glomerular filtration rate ≥40 ml/min; no contraindications to pembrolizumab) suitable for CRT.

INTERVENTION

Whole bladder radiation therapy (RT; 64 Gy in 32 daily fractions, over 6.5 wk, combined with cisplatin (35 mg/m2 intravenously [IV] weekly, six doses) and pembrolizumab (200 mg IV q3 weeks, seven doses), both starting with RT. Surveillance cystoscopy/biopsy and computerised tomography scans performed 12 and 24 wk after CRT.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was feasibility, determined by a prespecified satisfactory low rate of grade 3 or worse nonurinary toxicity or completion of planned CRT according to defined parameters. Secondary endpoints were complete cystoscopic response, locoregional progression-free survival (LRPFS), distant metastasis-free survival (DMFS), and overall survival (OS).

RESULTS AND LIMITATIONS

Twenty-eight patients were enrolled with a 31-mo median follow-up. Six had Grade >3 nonurinary adverse events during/within 12 wk after treatment; three had more than one cisplatin dose reduction. The 24-wk post-CRT complete response (CR) rate was 88%. Eight patients developed metastatic disease, and three had nonmetastatic progression. The DMFS at 2 yr is 78% (95% confidence interval [CI] 54-90%), with LRPFS at 2 yr of 87% (95% CI 64-96%) and median OS of 39 mo (95% CI 17.1-not evaluable). Limitations are the single-arm design and sample size.

CONCLUSIONS

Combining pembrolizumab with CRT for MIBC was feasible, with manageable toxicity and promising CR rates.

PATIENT SUMMARY

Immunotherapy treats nonmetastatic/metastatic bladder cancer effectively. We combined pembrolizumab with chemotherapy and radiation to assess its safety and impact on treatment delivery. The combination was feasible with encouraging early activity. Further larger trials are warranted.

Robust Optimization for Prostate Radiation Therapy: Assessment of Delivered Dose by Incorporating Intrafraction Prostate Position Deviations

Purpose

To assess the robustness of the dose delivered to the clinical target volume (CTV) between planning target volume (PTV)-based and robust optimization planning approaches in localized prostate cancer radiation therapy.

Methods and Materials

Retrospective data of 20 patients with prostate cancer, including radiation therapy and real-time prostate position, were analyzed. Two sets of volumetric modulated arc therapy plans were generated per patient: PTV-based and robust optimization. PTV-based planning used a 7-mm CTV-PTV margin, whereas robust planning considered same-magnitude position deviations. Differences in CTV dose delivered to 99% volume (D99), PTV dose delivered to 95% volume (D95), and bladder and rectum V40 (volume receiving 40 Gy) and V60 (volume receiving 60 Gy) values were evaluated. The target position, determined by in-house position monitoring system, was incorporated for dose assessment with and without position deviation correction.

Results

In the robust optimization approach, compared with PTV-based planning, the mean (standard deviation) V40 and V60 values of the bladder were reduced by 5.2% (4.1%) and 5.1% (1.9%), respectively. Similarly, for the rectum, the reductions were 0.8% (0.5%) and 0.6% (0.6%). In corrected treatment scenarios, both planning approaches resulted in a mean (standard deviation) CTV D99 difference of 0.1 Gy (0.1 Gy). In the not corrected scenario, PTV-based planning reduced CTV D99 by 0.1 Gy (0.5 Gy), whereas robust planning reduced it by 0.2 Gy (0.6 Gy). There was no statistically significant difference observed in the planned and delivered rectum and bladder dose for both corrected and not corrected scenarios.

Conclusions

Robust optimization resulted in lower V40 and V60 values for the bladder compared with PTV-based planning. However, no difference in CTV dose accuracy was found between the 2 approaches.

Dose-effect Relationship of Kidney Function After Stereotactic Ablative Body Radiotherapy for Primary Renal Cell Carcinoma: Trog 15.03 Fastrack Ii

BACKGROUND

Stereotactic ablative body radiotherapy (SABR) is a novel option to treat primary renal cell carcinoma (RCC). However, a high radiation dose may be received by the treated kidney, which may affect its function post-treatment. This study investigates the dose-effect relationship of kidney SABR with posttreatment renal function.

METHODS

This was a prespecified secondary endpoint of the multicenter FASTRACK II clinical trial (NCT02613819). Patients received either 26 Gy in a single fraction (SF) for tumors with a maximal diameter of 4 cm or less, or 42 Gy in three fractions (multi-fraction (MF)) for larger tumors. To determine renal function change, 99mTc-DMSA SPECT/CT scans were acquired, and the glomerular filtration rate (GFR) was estimated at baseline, 12-, and 24-months post-treatment. Imaging datasets were rigidly registered to the planning CT where kidneys were segmented to calculate dose-response curves.

RESULTS

From 71 enrolled patients, data from 36 (51%) and 26 (37%) patients were included in this study based on availability of post-treatment data at 12- and 24-months, respectively. The ipsilateral kidney GFR decreased from baseline by 42% and 39% in the SF cohort, and by 45% and 62% in the MF cohort, at 12- and 24-months respectively (p-values < 0.03). The loss in renal function was 3.6±0.8% and 4.5±1.0% in the SF cohort, and 1.7±0.1% and 1.7±0.2% in the MF cohort, at 12- and 24-months respectively. The major loss in renal function occurred in high-dose regions, where dose-response curves converged to a plateau.

CONCLUSIONS

For the first time in a multicenter study, the dose-effect relationship at 12- and 24-months post-SABR treatment for primary RCC was quantified. Kidney function reduces linearly with dose up to 100 Gy BED3.

Evaluating the relationship between contouring variability and modelled treatment outcome for prostate bed radiotherapy

Objectives.Contouring similarity metrics are often used in studies of inter-observer variation and automatic segmentation but do not provide an assessment of clinical impact. This study focused on post-prostatectomy radiotherapy and aimed to (1) identify if there is a relationship between variations in commonly used contouring similarity metrics and resulting dosimetry and (2) identify the variation in clinical target volume (CTV) contouring that significantly impacts dosimetry.Approach.The study retrospectively analysed CT scans of 10 patients from the TROG 08.03 RAVES trial. The CTV, rectum, and bladder were contoured independently by three experienced observers. Using these contours reference simultaneous truth and performance level estimation (STAPLE) volumes were established. Additional CTVs were generated using an atlas algorithm based on a single benchmark case with 42 manual contours. Volumetric-modulated arc therapy (VMAT) treatment plans were generated for the observer, atlas, and reference volumes. The dosimetry was evaluated using radiobiological metrics. Correlations between contouring similarity and dosimetry metrics were calculated using Spearman coefficient (Γ). To access impact of variations in planning target volume (PTV) margin, the STAPLE PTV was uniformly contracted and expanded, with plans created for each PTV volume. STAPLE dose-volume histograms (DVHs) were exported for plans generated based on the contracted/expanded volumes, and dose-volume metrics assessed.Mainresults. The study found no strong correlations between the considered similarity metrics and modelled outcomes. Moderate correlations (0.5 <Γ< 0.7) were observed for Dice similarity coefficient, Jaccard, and mean distance to agreement metrics and rectum toxicities. The observations of this study indicate a tendency for variations in CTV contraction/expansion below 5 mm to result in minor dosimetric impacts.Significance. Contouring similarity metrics must be used with caution when interpreting them as indicators of treatment plan variation. For post-prostatectomy VMAT patients, this work showed variations in contours with an expansion/contraction of less than 5 mm did not lead to notable dosimetric differences, this should be explored in a larger dataset to assess generalisability.

Stereotactic ablative body radiotherapy for primary kidney cancer (TROG 15.03 FASTRACK II): a non-randomised phase 2 trial

BACKGROUND

Stereotactic ablative body radiotherapy (SABR) is a novel non-invasive alternative for patients with primary renal cell cancer who do not undergo surgical resection. The FASTRACK II clinical trial investigated the efficacy of SABR for primary renal cell cancer in a phase 2 trial.

METHODS

This international, non-randomised, phase 2 study was conducted in seven centres in Australia and one centre in the Netherlands. Eligible patients aged 18 years or older had biopsy-confirmed diagnosis of primary renal cell cancer, with only a single lesion; were medically inoperable, were at high risk of complications from surgery, or declined surgery; and had an Eastern Cooperative Oncology Group performance status of 0-2. A multidisciplinary decision that active treatment was warranted was required. Key exclusion criteria were a pre-treatment estimated glomerular filtration rate of less than 30 mL/min per 1·73 m2, previous systemic therapies for renal cell cancer, previous high-dose radiotherapy to an overlapping region, tumours larger than 10 cm, and direct contact of the renal cell cancer with the bowel. Patients received either a single fraction SABR of 26 Gy for tumours 4 cm or less in maximum diameter, or 42 Gy in three fractions for tumours more than 4 cm to 10 cm in maximum diameter. The primary endpoint was local control, defined as no progression of the primary renal cell cancer, as evaluated by the investigator per Response Evaluation Criteria in Solid Tumours (version 1.1). Assuming a 1-year local control of 90%, the null hypothesis of 80% or less was considered not to be worthy of proceeding to a future randomised controlled trial. All patients who commenced trial treatment were included in the primary outcome analysis. This trial is registered with ClinicalTrials.gov, NCT02613819, and has completed accrual.

FINDINGS

Between July 28, 2016, and Feb 27, 2020, 70 patients were enrolled and initiated treatment. Median age was 77 years (IQR 70-82). Before enrolment, 49 (70%) of 70 patients had documented serial growth on initial surveillance imaging. 49 (70%) of 70 patients were male and 21 (30%) were female. Median tumour size was 4·6 cm (IQR 3·7-5·5). All patients enrolled had T1-T2a and N0-N1 disease. 23 patients received single-fraction SABR of 26 Gy and 47 received 42 Gy in three fractions. Median follow-up was 43 months (IQR 38-60). Local control at 12 months from treatment commencement was 100% (p<0·0001). Seven (10%) patients had grade 3 treatment-related adverse events, with no grade 4 adverse events observed. Grade 3 treatment-related adverse events were nausea and vomiting (three [4%] patients), abdominal, flank, or tumour pain (four [6%]), colonic obstruction (two [3%]), and diarrhoea (one [1%]). No treatment-related or cancer-related deaths occurred.

INTERPRETATION

To our knowledge, this is the first multicentre prospective clinical trial of non-surgical definitive therapy in patients with primary renal cell cancer. In a cohort with predominantly T1b or larger disease, SABR was an effective treatment strategy with no observed local failures or cancer-related deaths. We observed an acceptable side-effect profile and renal function after SABR. These outcomes support the design of a future randomised trial of SABR versus surgery for primary renal cell cancer.

FUNDING

Cancer Australia Priority-driven Collaborative Cancer Research Scheme.

Development of Prostate Bed Delineation Consensus Guidelines for Magnetic Resonance Image-Guided Radiotherapy and Assessment of Its Effect on Interobserver Variability

PURPOSE

The use of magnetic resonance imaging (MRI) in radiotherapy planning is becoming more widespread, particularly with the emergence of MRI-guided radiotherapy systems. Existing guidelines for defining the prostate bed clinical target volume (CTV) show considerable heterogeneity. This study aimed to establish baseline interobserver variability (IOV) for prostate bed CTV contouring on MRI, develop international consensus guidelines, and evaluate its effect on IOV.

METHODS AND MATERIALS

Participants delineated the CTV on 3 MRI scans, obtained from the Elekta Unity MR-Linac, as per their normal practice. Radiation oncologist contours were visually examined for discrepancies, and interobserver comparisons were evaluated against simultaneous truth and performance level estimation (STAPLE) contours using overlap metrics (Dice similarity coefficient and Cohen's kappa), distance metrics (mean distance to agreement and Hausdorff distance), and volume measurements. A literature review of postradical prostatectomy local recurrence patterns was performed and presented alongside IOV results to the participants. Consensus guidelines were collectively constructed, and IOV assessment was repeated using these guidelines.

RESULTS

Sixteen radiation oncologists' contours were included in the final analysis. Visual evaluation demonstrated significant differences in the superior, inferior, and anterior borders. Baseline IOV assessment indicated moderate agreement for the overlap metrics while volume and distance metrics demonstrated greater variability. Consensus for optimal prostate bed CTV boundaries was established during a virtual meeting. After guideline development, a decrease in IOV was observed. The maximum volume ratio decreased from 4.7 to 3.1 and volume coefficient of variation reduced from 40% to 34%. The mean Dice similarity coefficient rose from 0.72 to 0.75 and the mean distance to agreement decreased from 3.63 to 2.95 mm.

CONCLUSIONS

Interobserver variability in prostate bed contouring exists among international genitourinary experts, although this is lower than previously reported. Consensus guidelines for MRI-based prostate bed contouring have been developed, and this has resulted in an improvement in contouring concordance. However, IOV persists and strategies such as an education program, development of a contouring atlas, and further refinement of the guidelines may lead to additional improvements.

Prostate Virtual High-dose-rate Brachytherapy Boost: 5-Year Results from the PROMETHEUS Prospective Multicentre Trial

BACKGROUND AND OBJECTIVE

Despite the high efficacy of high-dose-rate brachytherapy boost (HDRB) in the management of prostate cancer (PC), use of this approach is declining. Similar dosimetry can be achieved using stereotactic body radiotherapy or "virtual HDRB" (vHDRB). The aim of the multicentre, single-arm, phase 2 PROMETHEUS trial (ACTRN12615000223538) was to evaluate the safety and efficacy of vHDRB in patients with PC.

METHODS

Patients with intermediate-risk PC or selected patients with high-risk PC were eligible for inclusion. vHDRB was given as 19-20 Gy in two fractions, delivered 1 wk apart, followed by conventionally fractionated external beam radiotherapy (EBRT) at 46 Gy in 23 fractions or 36 Gy in 12 fractions. The primary endpoint was the biochemical/clinical relapse-free rate (bcRFR). Toxicity was graded using Common Terminology Criteria for Adverse Events version 4 and quality of life (QoL) data were collected used the Expanded Prostate Cancer Index Composite-26 questionnaire.

KEY FINDINGS AND LIMITATIONS

From March 2014 to December 2018, 151 patients (74% intermediate risk, 26% high risk) with a median age of 69 yr were treated across five centres. Median follow-up was 60 mo. The 5-yr bcRFR was 94.1% (95% confidence interval [CI] 90-98%) and the local control rate was 98.7%. Acute grade 2 gastrointestinal (GI) and genitourinary (GU) toxicity occurred in 6.6% and 23.2% of patients, respectively, with no acute grade 3 toxicity. At 60 mo after treatment, the prevalence of late grade ≥2 GI toxicity was 1.7% (95% CI 0.3-6.5%) and the prevalence of late grade ≥2 GU toxicity was 3.3% (95% CI 1.1-8.8%). Between baseline and 60 mo, QoL improved for urinary obstructive and hormonal domains, was stable for the bowel domain, and deteriorated slightly for the sexual and urinary incontinence domains.

CONCLUSIONS

Delivery of gantry-based vHDRB followed by conventionally fractionated EBRT is feasible in a multicentre setting, with high 5-yr bcRFR and low toxicity. This approach is being compared with prostate ultrahypofractionated radiotherapy in the TROG 18.01 NINJA randomised trial (ACTRN12618001806257).

PATIENT SUMMARY

The PROMETHEUS trial investigated noninvasive high-dose precision radiotherapy combined with conventional radiotherapy in patients with prostate cancer. We found that this new technique was well tolerated and resulted in better cancer control outcomes than historically reported.

TROG 15.03/ANZUP International Multicenter Phase II Trial of Focal Ablative STereotactic RAdiotherapy for Cancers of the Kidney (FASTRACK II)

PURPOSE/OBJECTIVE(S)

Stereotactic body radiotherapy (SBRT) is an emerging non-invasive alternative for primary renal cell cancer (RCC) in patients unsuitable for surgery. The objective of the FASTRACK II clinical trial was to investigate the efficacy of SBRT for primary RCC.

MATERIALS/METHODS

This non-randomized, intergroup multi-institutional phase II study was activated in 7 Australian centers and 1 Dutch center, through the Trans Tasman Radiation Oncology Group (TROG) and the Australian and New Zealand Urogenital and Prostate Cancer Trials Group (ANZUP). Eligible patients had biopsy confirmed diagnosis of primary RCC with a single lesion within a kidney, ECOG performance ≤2 and were medically inoperable, high risk or declined surgery. For tumors ≤4 cm a single fraction of 26 Gy was prescribed, for tumors > 4 cm, 42 Gy in three fractions was prescribed. The primary outcome of the study was to estimate the efficacy of SBRT for primary RCC, defined as local control based on RECIST criteria. The study was powered assuming that 1-year local control would be 90%, with the null hypothesis of ≤80% considered undesirable and not worthy of proceeding to a future randomized controlled trial.

RESULTS

Between July 2016 and February 2020, 70 patients were enrolled with a median follow-up of 42 months. Median age was 77 years. Forty-nine patients were male (70%), median BMI was 32 and median Charlson comorbidity score was 7. The median [IQR] RENAL complexity score was 8 [7-10]. Biopsy confirmation was 100%. Twenty-three patients (33%) had T1a disease. The median (interquartile range [IQR]) tumor size was 4.6cm [3.7-5.5]; it was 3.3cm [3.0-3.6] in those receiving single fraction (n = 23), and 5.3cm [4.6-6.0] in those receiving 3-fraction SBRT (n = 47). During real-time pre-treatment quality assurance review, 10 cases (14.3%) required resubmission for protocol deviation, 2119 variables were assessed at final review, and final protocol compliance was 99.3%. Seven (10%) patients experienced grade 3 treatment-related adverse events, with no grade 4 or 5 events observed. Eleven (16%) patients reported no adverse events. Local control was 100% throughout the lifetime of the trial (p<0.001). Cancer-specific survival was also 100% throughout the lifetime of the trial. Freedom from distant failure (95% CIs) at 1 and 3 years was 99% (90-100%). Overall survival (95% CIs) at 1 and 3 years was 99% (90-100%) and 82% (70-89%), respectively. Baseline mean eGFR (95% CI) was 61.1 mLs/min (56.6; 65.6) and reduced by -10.8 mLs/min (-13.0; -8.6) by 1-year, by -14.6 mLs/min (-17.0; -12.2) by 2-years and plateaued thereafter.

CONCLUSION

In the first multicenter prospective trial of a non-surgical primary RCC cohort, enrolling mostly T1b+ disease, SBRT was an effective treatment strategy with no observed local failures. We observed an acceptable side effect profile and renal function after SBRT. These outcomes support the design of a future randomized clinical trial of SBRT versus surgery for primary RCC. The trial was registered with ID: NCT02613819.

Clinical target volume delineation quality assurance for MRI-guided prostate radiotherapy using deep learning with uncertainty estimation

BACKGROUND AND PURPOSE

Previous studies on automatic delineation quality assurance (QA) have mostly focused on CT-based planning. As MRI-guided radiotherapy is increasingly utilized in prostate cancer treatment, there is a need for more research on MRI-specific automatic QA. This work proposes a clinical target volume (CTV) delineation QA framework based on deep learning (DL) for MRI-guided prostate radiotherapy.

MATERIALS AND METHODS

The proposed workflow utilized a 3D dropblock ResUnet++ (DB-ResUnet++) to generate multiple segmentation predictions via Monte Carlo dropout which were used to compute an average delineation and area of uncertainty. A logistic regression (LR) classifier was employed to classify the manual delineation as pass or discrepancy based on the spatial association between the manual delineation and the network's outputs. This approach was evaluated on a multicentre MRI-only prostate radiotherapy dataset and compared with our previously published QA framework based on AN-AG Unet.

RESULTS

The proposed framework achieved an area under the receiver operating curve (AUROC) of 0.92, a true positive rate (TPR) of 0.92 and a false positive rate of 0.09 with an average processing time per delineation of 1.3 min. Compared with our previous work using AN-AG Unet, this method generated fewer false positive detections at the same TPR with a much faster processing speed.

CONCLUSION

To the best of our knowledge, this is the first study to propose an automatic delineation QA tool using DL with uncertainty estimation for MRI-guided prostate radiotherapy, which can potentially be used for reviewing prostate CTV delineation in multicentre clinical trials.

Surgical Training in the United Kingdom's National Health Service: The Challenges for International Medical Graduates

BACKGROUND

The UK's National Health Service (NHS) is a hub that trainees from all over the world want to join. However, there are many challenges for International Medical Graduates (IMGs). The aim of this study is to raise awareness of these challenges and to attempt to identify areas for improvement in the surgical training experience for international graduates wishing to join the NHS and obtain a National Training Number (NTN).

METHODS

 A 33-question survey was designed and distributed to the surgical community via The Upper Gastrointestinal Surgery Society (TUGSS) and social media. Eighty-five respondents, IMGs from 25 countries, participated.

RESULTS

 The results showed that 43.5% of doctors had a Master's degree (MSc). Most IMGs joined as locally employed doctors at the senior house officer or registrar level. They all faced many challenges in the UK, including difficulties finding a job in the NHS, obtaining an NTN, and adapting to the differences between UK surgical practice and their home country. More than 50% of doctors did not have a named educational/clinical supervisor, and 63.2% of them felt that the supervisor helped them to become more familiar with the system. The support doctors received from the human resources department of the hospital they joined was poor. In addition, more than half of the IMGs changed their career plans after joining the NHS (56.4%) and would like to stay in the UK (52.9%). The majority of them (43.9%) plan to obtain an NTN.

CONCLUSIONS

This study showed that there is a need to support international doctors who wish to start or continue their training in the UK. Furthermore, IMGs should expect to face several challenges when applying to work in the UK NHS.

Patterns of practice regarding use of radiation therapy following radical prostatectomy: A survey of Radiation Oncologists and Urologists in Australia and New Zealand

INTRODUCTION

This study aimed to investigate the patterns of practices of radiation oncologists (ROs) and urologists in Australia and New Zealand with respect to the utilisation of post-prostatectomy radiation therapy (RT) and help guide the development of an update to the existing Faculty of Radiation Oncology Genito-Urinary Group post-prostatectomy guidelines.

METHODS

ROs and urologists with subspecialty practice in prostate cancer from Australia and New Zealand were invited to participate in an online survey comprised of clinical scenarios regarding post-prostatectomy RT.

RESULTS

Sixty-five ROs and 28 urologists responded to the survey. In the setting of low-risk biochemical relapse, the threshold for initiating RT was lower for ROs than urologists. ROs were more likely than urologists to recommend adjuvant RT for node-positive disease. When salvage RT was advised for a pT3N0R1 recurrence, there was no consensus amongst ROs on whether to add either ADT or nodal treatment over prostate bed RT alone. For a solitary PSMA-avid pelvic lymph node recurrence, whole pelvis RT with androgen deprivation therapy was the preferred treatment option (72% ROs, 43% urologists). Most ROs (92%) recommended conventionally fractionated RT to 66-70 Gy, with a boost to any PSMA PET avid recurrent disease.

CONCLUSION

This survey highlights the marked discordance in practice for the management of prostate cancer relapse post-prostatectomy. This is seen not only between specialties but also within the radiation oncology community. This emphasises the need for an updated evidence-based guideline to be produced.

Assessment of intrafraction motion and its dosimetric impact on prostate radiotherapy using an in-house developed position monitoring system

Purpose

To implement an in-house developed position monitoring software, SeedTracker, for conventional fractionation prostate radiotherapy, and study the effect on dosimetric impact and intrafraction motion.

Methods

Thirty definitive prostate radiotherapy patients with implanted fiducial markers were included in the study. All patients were treated with VMAT technique and plans were generated using the Pinnacle planning system using the 6MV beam model for Elekta linear accelerator. The target dose of 60 Gy in 20 fractions was prescribed for 29 of 30 patients, and one patient was treated with the target dose of 78 Gy in 39 fractions. The SeedTracker position monitoring system, which uses the x-ray images acquired during treatment delivery in the Elekta linear accelerator and associated XVI system, was used for online prostate position monitoring. The position tolerance for online verification was progressively reduced from 5 mm, 4 mm, and to 3 mm in 10 patient cohorts to effectively manage the treatment interruptions resulting from intrafraction motion in routine clinical practice. The delivered dose to target volumes and organs at risk in each of the treatment fractions was assessed by incorporating the observed target positions into the original treatment plan.

Results

In 27 of 30 patients, at least one gating event was observed, with a total of 177 occurrences of position deviation detected in 146 of 619 treatment fractions. In 5 mm, 4 mm, and 3 mm position tolerance cohorts, the position deviations were observed in 13%, 24%, and 33% of treatment fractions, respectively. Overall, the mean (range) deviation of -0.4 (-7.2 to 5.3) mm, -0.9 (-6.1 to 15.6) mm, and -1.7 (-7.0 to 6.1) mm was observed in Left-Right, Anterior-Posterior, and Superior-Inferior directions, respectively. The prostate CTV D99 would have been reduced by a maximum value of 1.3 Gy compared to the planned dose if position deviations were uncorrected, but with corrections, it was 0.3 Gy. Similarly, PTV D98 would have been reduced by a maximum value of 7.6 Gy uncorrected, with this difference reduced to 2.2 Gy with correction. The V60 to the rectum increased by a maximum of 1.0% uncorrected, which was reduced to 0.5%.

Conclusion

Online target position monitoring for conventional fractionation prostate radiotherapy was successfully implemented on a standard Linear accelerator using an in-house developed position monitoring software, with an improvement in resultant dose to prostate target volume.

Reducing the margin in prostate radiotherapy: optimizing radiotherapy with a general-purpose linear accelerator using an in-house position monitoring system

Purpose

To study the feasibility of optimizing the Clinical Target Volume to Planning Target Volume (CTV-PTV) margin in prostate radiotherapy(RT) with a general-purpose linear accelerator using an in-house developed position monitoring system, SeedTracker.

Methods

A cohort of 30 patients having definitive prostate radiotherapy treated within an ethics-approved prospective trial was considered for this study. The intrafraction prostate motion and the position deviations were measured using SeedTracker system during each treatment fraction. Using this data the CTV-PTV margin required to cover 90% of the patients with a minimum of 95% of the prescription dose to CTV was calculated using van Herk's formula. The margin calculations were performed for treatment scenarios both with and without applying the position corrections for observed position deviations. The feasibility of margin reduction with real-time monitoring was studied by assessing the delivered dose that incorporates the actual target position during treatment delivery and comparing it with the planned dose. This assessment was performed for plans generated with reduced CTV-PTV margin in the range of 7mm-3mm.

Results

With real-time monitoring and position corrections applied the margin of 2.0mm, 2.1mm and 2.1mm in LR, AP and SI directions were required to meet the criteria of 90% population to receive 95% of the dose prescription to CTV. Without position corrections applied for observed position deviations a margin of 3.1mm, 4.0mm and 3.0mm was required in LR, AP and SI directions to meet the same criteria. A mean ± SD reduction of 0.5 ± 1.8% and 3 ± 7% of V60 for the rectum and bladder can be achieved for every 1mm reduction of PTV margin. With position corrections applied, the CTV D99 can be delivered within -0.2 ± 0.3 Gy of the planned dose for plans with a 3mm margin. Without applying corrections for position deviations the CTV D99 was reduced by a maximum of 1.1 ± 1.1 Gy for the 3mm margin plan and there was a statistically significant difference between planned and delivered dose for 3mm and 4mm margin plans.

Conclusion

This study demonstrates the feasibility of reducing the margin in prostate radiotherapy with SeedTracker system without compromising the dose delivery accuracy to CTV while reducing dose to critical structures.

Virtual HDR Boost for Prostate Cancer: Rebooting a Classic Treatment Using Modern Tech

Prostate cancer (PC) is the most common malignancy in men. Internal radiotherapy (brachytherapy) has been used to treat PC successfully for over a century. In particular, there is level-one evidence of the benefits of using brachytherapy to escalate the dose of radiotherapy compared with standard external beam radiotherapy approaches. However, the use of PC brachytherapy is declining, despite strong evidence for its improved cancer outcomes. A method using external beam radiotherapy known as virtual high-dose-rate brachytherapy boost (vHDRB) aims to noninvasively mimic a brachytherapy boost radiation dose plan. In this review, we consider the evidence supporting brachytherapy boosts for PC and the continuing evolution of vHDRB approaches, culminating in the current generation of clinical trials, which will help define the role of this emerging modality.

Genitourinary quality of life comparison between urethral sparing prostate SBRT monotherapy and virtual HDRB boost

BACKGROUND AND PURPOSE

Although radiation dose escalation improves prostate cancer disease control, it can cause increased toxicity. Genitourinary (GU) symptoms after prostate radiotherapy impact patient health related Quality of Life (QoL). We compared patient-reported genitourinary QoL outcomes following two alternative urethral sparing SBRT (US-SBRT) regimens.

MATERIALS AND METHODS

EPIC-26 GU scores were compared between two US-SBRT trials. The SPARK trial prescribed a "Monotherapy" dose of 36.25 Gy in 5 fractions to the prostate. The PROMETHEUS trial prescribed two phases; a 19-21 Gy in 2 fraction "Boost" to the prostate, followed by 46 Gy in 23 fractions or 36 Gy in 12 fractions. The Biological Effective Dose (BED) for urethral toxicity was 123.9 Gy for Monotherapy, and 155.8-171.2 Gy for Boost. Mixed effects logistic regression models were utilised to estimate the difference in the odds of a Minimal Clinically Important Change (MCIC) from baseline EPIC-26 GU score between regimens at each follow-up.

RESULTS

46 Monotherapy and 149 Boost patients completed baseline EPIC-26 scoring. Mean EPIC-26 GU scores revealed statistically superior urinary incontinence outcomes for Monotherapy at 12 months (mean difference 6.9 [95% CI 1.6 - 12.1]; p = .01), and 36 months (mean difference 9.6 [95% CI 4.1 - 15.1]; p < .01). Monotherapy also revealed superior mean urinary irritative/obstructive outcomes at 12 months (mean difference 6.9 [95% CI 2.0 - 12.9] p < .01), and 36 months (mean difference 6.3 [95% CI 1.9 - 10.8] p < .01). For both domains, and at all time points, the absolute differences were <10%. There were no significant differences in the odds of reporting a MCIC between regimens at any time-point.

CONCLUSION

Even in the presence of urethral sparing, the higher BED delivered in the Boost schedule may have a small adverse impact on GU QoL compared with Monotherapy. However, this did not translate to statistically significant differences in Minimal Clinically Important Changes. Whether the higher BED of the boost arm offers an efficacy advantage is being investigated in the TROG 18.01 NINJA randomized trial.

Encouraging Patients to Ask Questions: Development and Pilot Testing of a Question Prompt List for Patients Undergoing a Biopsy for Suspected Prostate Cancer

This study assessed the acceptability and feasibility of a question prompt list (QPL) to facilitate informed treatment decision-making in men with suspected localised prostate cancer, which involves values-based choices between options with similar efficacy but different side effects. The QPL was developed through iterative consultation with consumers, clinicians and researchers. Acceptability was assessed using study-specific questions regarding QPL satisfaction and usefulness and qualitative interviews. Feasibility was determined via the proportion of men given the QPL according to medical records and the completion of standardised measures of decisional outcomes. Quantitative data were analysed using descriptive and univariate statistics. Qualitative data were thematically analysed. Fifty-two men consented; 34 provided data for analysis. The QPL recipients reported moderate-high content satisfaction (70.6%) and perceived usefulness in guiding appointments when receiving biopsy results (64.7%). Two main qualitative themes also indicated the QPL acceptability: (1) the freedom to ask-acceptable timing, flexible usage and usefulness of the QPL, and (2) satisfaction with the QPL content. However, only 18.4% of eligible men received the QPL, indicating limited feasibility. The QPL is safe and acceptable, but further research is needed regarding how to facilitate the uptake of the question prompt list in clinical practice.

Implementing online position monitoring for prostate radiotherapy using an in-house position monitoring system: User experience and impact on workforce

INTRODUCTION

To evaluate the feasibility of prostate intrafraction motion monitoring using the SeedTracker real-time image guidance system in order to improve targeting accuracy in prostate radiotherapy.

METHODS

SeedTracker was used to monitor prostate gold fiducial seeds with kV x-ray imaging during radiotherapy in 30 patients. Feedback from radiation therapists was collected via the use of a user evaluation form. The impact on treatment time was established by using a record and verify system. The effective dose and a risk of exposure-induced cancer death (REID) were estimated for a 60-year-old patient when using the SeedTracker system.

RESULTS

A total of 22 radiation therapists completed user evaluation forms. The time taken to prepare a reference data set for one patient varied with three (13.6%) radiation therapists taking less than 2 min, 10 (45.5%) between 2 and 4 min, eight (36.4%) between 4 and 6 min and one (4.5%) between 6 and 8 min. The useability of the SeedTracker system was reported as 'easy' by 21 (95.5%) radiation therapists and 'hard' by 1 (4.5%) radiation therapist. Mean treatment time changed from 6 to 7 min with prostate-only radiotherapy treatment and from 6.9 to 10.2 min with prostate and whole pelvis radiotherapy treatments. The maximum effective dose with the SeedTracker was 1.6276 mSv, and increase in REID was 0.007%.

CONCLUSION

The SeedTracker real-time image guidance system is a feasible tool to use in radiotherapy departments to monitor and correct for prostate intrafraction motion.

Automatic radiotherapy delineation quality assurance on prostate MRI with deep learning in a multicentre clinical trial

Volume delineation quality assurance (QA) is particularly important in clinical trial settings where consistent protocol implementation is required, as outcomes will affect future as well current patients. Currently, where feasible, this is conducted manually, which is time consuming and resource intensive. Although previous studies mostly focused on automating delineation QA on CT, magnetic resonance imaging (MRI) is being increasingly used in radiotherapy treatment. In this work, we propose to perform automatic delineation QA on prostate MRI for both the clinical target volume (CTV) and organs-at-risk (OARs) by using delineations generated by 3D Unet variants as benchmarks for QA. These networks were trained on a small gold standard atlas set and applied on a multicentre radiotherapy clinical trial dataset to generate benchmark delineations. Then, a QA stage was designed to recommend 'pass', 'minor correction' and 'major correction' for each manual delineation in the trial set by thresholding its Dice similarity coefficient to the network generated delineation. Among all 3D Unet variants explored, the Unet with anatomical gates in an AtlasNet architecture performed the best in delineation QA, achieving an area under the receiver operating characteristics curve of 0.97, 0.92, 0.89 and 0.97 for identifying unacceptable (major correction) delineations with a sensitivity of 0.93, 0.73, 0.74 and 0.90 at a specificity of 0.93, 0.86, 0.86 and 0.95 for bladder, prostate CTV, rectum and gel spacer respectively. To the best of our knowledge, this is the first study to propose automated delineation QA for a multicentre radiotherapy clinical trial with treatment planning MRI. The methods proposed in this work can potentially improve the accuracy and consistency of CTV and OAR delineation in radiotherapy treatment planning.

Low conflict and high satisfaction: Decisional outcomes after attending a combined clinic to choose between robotic prostatectomy and radiotherapy for prostate cancer

BACKGROUND

Decisional conflict and post-treatment decisional regret have been documented in men with localised prostate cancer (LPC). However, there is limited evidence regarding decisional outcomes associated with the choice between robotic-assisted radical prostatectomy (RARP) and radiotherapy, when both treatment options are available in the public health system. There is increasing support for multidisciplinary approaches to guide men with LPC in their decision-making process. This study assessed decisional outcomes in men deciding between RARP or radiotherapy treatment before and after attending a LPC combined clinic (CC).

METHODS

Quantitative longitudinal data were collected from 52 men who attended a LPC CC, where they saw both a urologist and radiation oncologist. Patients completed questionnaires assessing involvement in decision-making, decisional conflict, satisfaction and regret before and after the CC, three months, six months and 12 months post-treatment. Urologists and radiation oncologists also reported their perceptions regarding patients' suitability for, openness to, perceived preferences and appropriateness for each treatment. Data was analysed using paired/independent samples t-tests and McNemar's tests.

RESULTS

Most participants (n = 37, 71%) opted for RARP over radiotherapy (n = 14, 27%); one participant deferred treatment (2%). Urologists and radiation oncologists reported low agreement (κ = 0.26) regarding the most appropriate treatment for each patient. Participants reported a desire for high levels of control over their decision-making process (77.5% patient-led, 22.5% shared) and high levels of decisional satisfaction (M = 4.4, SD = 0.47) after the CC. Decisional conflict levels were significantly reduced (baseline: M = 29.3, SD = 16.9, post-CC: M = 16.3, SD = 11.5; t = 5.37, P < 0.001) after the CC. Mean decisional regret scores were 'mild' at three-months (M = 16.0, SD = 17.5), six-months (M = 18.8, SD = 18.7) and 12-months (M = 18.2, SD = 15.1) post-treatment completion.

CONCLUSION

This is the first Australian study to assess decisional outcomes when patients are offered the choice between RARP and radiotherapy in the public health system. A CC seems to support decision-making in men with LPC and positively impact some decisional outcomes. However, larger-scale controlled studies are needed to confirm these findings.

Measurements of human tolerance to horizontal rotation within an MRI scanner: Towards gantry-free radiation therapy

INTRODUCTION

Recent advances in image guidance and adaptive radiotherapy could enable gantry-free radiotherapy using patient rotation. Gantry-free radiotherapy could substantially reduce the cost of radiotherapy systems and facilities. MRI guidance complements a gantry-free approach because of its ability to visualise soft tissue deformation during rotation. A potential barrier to gantry-free radiotherapy is patient acceptability, especially when combined with MRI. This study investigates human experiences of horizontal rotation within an MRI scanner.

METHODS

Ten healthy human participants and nine participants previously treated with radiotherapy were rotated within an MRI scanner. Participants' anxiety and motion sickness was assessed before being rotated in 45-degree increments and paused, representing a multi-field intensity-modulated radiotherapy treatment. An MR image was acquired at each 45-degree angle. Following imaging, anxiety and motion sickness were re-assessed, followed by a comfort questionnaire and exit interview. The significance of the differences in anxiety and motion sickness pre- versus post-imaging was assessed using Wilcoxon signed-rank tests. Content analysis was performed on exit interview transcripts.

RESULTS

Eight of ten healthy and eight of nine patient participants completed the imaging session. Mean anxiety scores before and after imaging were 7.9/100 and 11.8/100, respectively (P = 0.26), and mean motion sickness scores were 5.3/100 and 13.7/100, respectively (P = 0.02). Most participants indicated likely acceptance of rotation if MRI were to be used in a hypothetical treatment. Physical discomfort was reported to be the biggest concern.

CONCLUSIONS

Horizontal rotation within an MRI scanner was acceptable for most (17/19) participants.

Pelvic organ motion and dosimetric implications during horizontal patient rotation for prostate radiation therapy

PURPOSE

Gantry-free radiation therapy systems utilizing patient rotation would be simpler and more cost effective than the conventional gantry-based systems. Such a system could enable the expansion of radiation therapy to meet global demand and reduce capital costs. Recent advances in adaptive radiation therapy could potentially be applied to correct for gravitational deformation during horizontal patient rotation. This study aims to quantify the pelvic organ motion and the dosimetric implications of horizontal rotation for prostate intensity-modulated radiation therapy (IMRT) treatments.

METHODS

Eight human participants who previously received prostate radiation therapy were imaged in a clinical magnetic resonance imaging (MRI) scanner using a bespoke patient rotation system (PRS). The patients were imaged every 45 degrees during a full roll rotation (0-360 degrees). Whole pelvic bone, prostate, rectum, and bladder motion were compared to the supine position using dice similarity coefficient (DSC) and mean absolute surface distance (MASD). Prostate centroid motion was compared in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) direction prior to and following pelvic bone-guided rigid registration. Seven-field prostate IMRT treatment plans were generated for each patient rotation angles under three adaption scenarios: No plan adaption, rigid planning target volume (PTV)-guided alignment to the prostate, and plan re-optimization. Prostate, rectum, and bladder doses were compared for each adaption scenario.

RESULTS

Pelvic bone motion within the PRS of up to 53 mm relative to the supine position was observed for some participants. Internal organ motion was greatest at the 180-degree PRS couch angle (prone), with prostate centroid motion range < 2 mm LR, 0 mm to 14 mm SI, and -11 mm to 4 mm AP. Rotation with no adaption of the treatment plan resulted in an underdose to the PTV -- in some instances up to 75% (D95%: 78 ± 0.3 Gy at supine to 20 ± 15.0 Gy at the 225-degree PRS couch angle). Bladder dose was reduced during the rotation by up to 98% (V60 Gy: 15.0 ± 9.4% supine to 0.3 ± 0.5% at the 225-degree PRS couch angle). In some instances, the rectum dose increased during rotation (V60Gy: 20.0 ± 4.5% supine to 25.0 ± 15.0% at the 135-degree PRS couch angle). Rigid PTV-guided alignment resulted in PTV coverage which, though statistically lower (P < 0.05 for all D95% values), was within 1 Gy of the supine plans. Plan re-optimization resulted in a statistically equivalent PTV coverage compared to the supine plans (P > 0.05 for all D95% metrics and all within ±0.4 Gy). For both rigid PTV-guided alignment and plan re-optimization, rectum dose volume metrics were reduced compared to the supine position between the 90- and 225-degree PRS couch angles (P < 0.05). Bladder dose volume metrics were not impacted by rotation.

CONCLUSION

Pelvic bone and internal organ motion are present during patient rotation. Rigid PTV-guided alignment to the prostate will be a requirement if prostate IMRT is to be safely delivered using patient rotation. Plan re-optimization for each PRS couch angle to account for anatomical deformations further improves the PTV coverage.

Adjuvant radiotherapy versus early salvage radiotherapy following radical prostatectomy (TROG 08.03/ANZUP RAVES): a randomised, controlled, phase 3, non-inferiority trial

BACKGROUND

Adjuvant radiotherapy has been shown to halve the risk of biochemical progression for patients with high-risk disease after radical prostatectomy. Early salvage radiotherapy could result in similar biochemical control with lower treatment toxicity. We aimed to compare biochemical progression between patients given adjuvant radiotherapy and those given salvage radiotherapy.

METHODS

We did a phase 3, randomised, controlled, non-inferiority trial across 32 oncology centres in Australia and New Zealand. Eligible patients were aged at least 18 years and had undergone a radical prostatectomy for adenocarcinoma of the prostate with pathological staging showing high-risk features defined as positive surgical margins, extraprostatic extension, or seminal vesicle invasion; had an Eastern Cooperative Oncology Group performance status of 0-1, and had a postoperative prostate-specific antigen (PSA) concentration of 0·10 ng/mL or less. Patients were randomly assigned (1:1) using a minimisation technique via an internet-based, independently generated allocation to either adjuvant radiotherapy within 6 months of radical prostatectomy or early salvage radiotherapy triggered by a PSA of 0·20 ng/mL or more. Allocation sequence was concealed from investigators and patients, but treatment assignment for individual randomisations was not masked. Patients were stratified by radiotherapy centre, preoperative PSA, Gleason score, surgical margin status, and seminal vesicle invasion status. Radiotherapy in both groups was 64 Gy in 32 fractions to the prostate bed without androgen deprivation therapy with real-time review of plan quality on all cases before treatment. The primary endpoint was freedom from biochemical progression. Salvage radiotherapy would be deemed non-inferior to adjuvant radiotherapy if freedom from biochemical progression at 5 years was within 10% of that for adjuvant radiotherapy with a hazard ratio (HR) for salvage radiotherapy versus adjuvant radiotherapy of 1·48. The primary analysis was done on an intention-to-treat basis. This study is registered with ClinicalTrials.gov, NCT00860652.

FINDINGS

Between March 27, 2009, and Dec 31, 2015, 333 patients were randomly assigned (166 to adjuvant radiotherapy; 167 to salvage radiotherapy). Median follow-up was 6·1 years (IQR 4·3-7·5). An independent data monitoring committee recommended premature closure of enrolment because of unexpectedly low event rates. 84 (50%) patients in the salvage radiotherapy group had radiotherapy triggered by a PSA of 0·20 ng/mL or more. 5-year freedom from biochemical progression was 86% (95% CI 81-92) in the adjuvant radiotherapy group versus 87% (82-93) in the salvage radiotherapy group (stratified HR 1·12, 95% CI 0·65-1·90; p_{non-inferiority}=0·15). The grade 2 or worse genitourinary toxicity rate was lower in the salvage radiotherapy group (90 [54%] of 167) than in the adjuvant radiotherapy group (116 [70%] of 166). The grade 2 or worse gastrointestinal toxicity rate was similar between the salvage radiotherapy group (16 [10%]) and the adjuvant radiotherapy group (24 [14%]).

INTERPRETATION

Salvage radiotherapy did not meet trial specified criteria for non-inferiority. However, these data support the use of salvage radiotherapy as it results in similar biochemical control to adjuvant radiotherapy, spares around half of men from pelvic radiation, and is associated with significantly lower genitourinary toxicity.

FUNDING

New Zealand Health Research Council, Australian National Health Medical Research Council, Cancer Council Victoria, Cancer Council NSW, Auckland Hospital Charitable Trust, Trans-Tasman Radiation Oncology Group Seed Funding, Cancer Research Trust New Zealand, Royal Australian and New Zealand College of Radiologists, Cancer Institute NSW, Prostate Cancer Foundation Australia, and Cancer Australia.

An assessment of the ExacTrac intrafraction imaging capabilities for flattening filter free prostate stereotactic body radiotherapy

The uncertainties associated with image matching using the ExacTrac® system (BrainLab, Munich, Germany) have been the subject of investigation in the literature for extra-cranial sites. However, the uncertainties involved in the use of ExacTrac in the presence of higher scatter conditions like that for intrafraction imaging of prostate stereotactic radiotherapy utilising unflattened beams is yet to be determined. A prostate phantom was created with 3 implanted gold fiducial markers. This phantom was shifted by 1 mm and 2 mm amounts in the translational planes and by 1° and 2° amounts in the rotational planes and subsequently imaged by ExacTrac during delivery of a clinical SBRT plan. ExacTrac auto-match results were compared to the known offsets with uncertainties calculated. Calculated shifts were shown to be accurate within one standard deviation of the known offsets. Uncertainties were found to vary considerably among the 6 dimensions with matching in the vertical and angle vertical directions having standard deviations of 0.7 mm and 1.3°, respectively. These results agreed with the literature cases for pre-treatment setup and lower scatter condition IMRT intrafraction delivery. Based on these values, probabilities of intrafraction inhibits were calculated based on patient movement and possible fusion tolerances. While the measured uncertainties are adequately defined in order to calculate appropriate target margins, their relatively large magnitudes made choice of intrafraction fusion tolerances problematic. A degree of compromise between the rate of false positives and false negatives is required when implementing ExacTrac into a SBRT prostate protocol.

Real-Time Image Guided Ablative Prostate Cancer Radiation Therapy: Results From the TROG 15.01 SPARK Trial

PURPOSE

Kilovoltage intrafraction monitoring (KIM) is a novel software platform implemented on standard radiation therapy systems and enabling real-time image guided radiation therapy (IGRT). In a multi-institutional prospective trial, we investigated whether real-time IGRT improved the accuracy of the dose patients with prostate cancer received during radiation therapy.

METHODS AND MATERIALS

Forty-eight patients with prostate cancer were treated with KIM-guided SABR with 36.25 Gy in 5 fractions. During KIM-guided treatment, the prostate motion was corrected for by either beam gating with couch shifts or multileaf collimator tracking. A dose reconstruction method was used to evaluate the dose delivered to the target and organs at risk with and without real-time IGRT. Primary outcome was the effect of real-time IGRT on dose distributions. Secondary outcomes included patient-reported outcomes and toxicity.

RESULTS

Motion correction occurred in ≥1 treatment for 88% of patients (42 of 48) and 51% of treatments (121 of 235). With real-time IGRT, no treatments had prostate clinical target volume (CTV) D98% dose 5% less than planned. Without real-time IGRT, 13 treatments (5.5%) had prostate CTV D98% doses 5% less than planned. The prostate CTV D98% dose with real-time IGRT was closer to the plan by an average of 1.0% (range, -2.8% to 20.3%). Patient outcomes showed no change in the 12-month patient-reported outcomes compared with baseline and no grade ≥3 genitourinary or gastrointestinal toxicities.

CONCLUSIONS

Real-time IGRT is clinically effective for prostate cancer SABR.

Stereotactic body radiotherapy boost toxicity for high and intermediate-risk prostate cancer: Report of a multi-institutional study

365

Background: External beam radiation therapy (EBRT) with androgen suppression (AS) and low dose rate (LDR)brachytherapy boost has been shown to improve biochemical progression free survival in unfavorable intermediate risk and high-risk prostate cancer (PC) compared to EBRT and AS. Excellent rates of local control in locally advanced prostate cancer with EBRT with high dose rate brachytherapy (HDR) boost. Prostate Stereotactic Radiosurgery (SBRT) may be an alternative to brachytherapy in patients with unfavorable intermediate and high-risk PC. Here we report the toxicity of pelvic lymph node/prostate EBRT and SBRT as the radiation boost in a large retrospective cohort. Methods: 473 patients with intermediate or high-risk PC, from the Radiosurgery Society Registry, Beth Israel Deaconess Medical Center, Georgetown University, and 5 Australian centers, were included. Patients received treatment from 3/2004- 9/2018 were the basis of this IRB approved retrospective study. The prostate and pelvis nodes were treated with between 36-50.4 Gy in 1.8/2.0 Gy fractions of radiation therapy EBRT. Patients received a SBRT boost to the prostate. Boost dose was 19-19.5 Gy (range 19-36.25 Gy). 274 and 199 patients presented with unfavorable or high-risk disease. The median follow-up was 33 months (IQR:18-63). Results: 33 deaths of 473 patients occurred in this cohort, 8 of which were caused by PC. There were 13.9% (n=66) acute Grade 1 or 2 GI toxicities (11.8% grade 1, 2.1% grade 2). There were 27.7% (n=131) acute Grade 1 or 2 GU toxicities (19.2% grade 1, 8.5% grade 2). No severe acute GU or GI toxicities were reported. There were 32 (6.8%) Grade 1 and 3 (0.6%) Grade 2 late GI toxicities. There were 9 (1.9%) Grade 3 and 1 (0.2%) Grade 4 late GI toxicities. There were 60 (12.7%) Grade 1 and 23 (4.9%) Grade 2 late GU toxicities. 15 (3.2%) Grade 3, but no Grade 4 late GU toxicity were reported. Conclusions: In this large multi-institutional retrospective cohort SBRT boost to pelvic/prostate EBRT had acceptable acute and late toxicities. The high dose per fraction of SBRT is similar to the dose delivered with HDR. This data raises the hypothesis that SBRT boost should be evaluated in additional clinical trials.

A Multi-center Prospective Study for Implementation of an MRI-Only Prostate Treatment Planning Workflow

Purpose: This project investigates the feasibility of implementation of MRI-only prostate planning in a prospective multi-center study.

Method and Materials: A two-phase implementation model was utilized where centers performed retrospective analysis of MRI-only plans for five patients followed by prospective MRI-only planning for subsequent patients. Feasibility was assessed if at least 23/25 patients recruited to phase 2 received MRI-only treatment workflow. Whole-pelvic MRI scans (T2 weighted, isotropic 1.6 mm voxel 3D sequence) were converted to pseudo-CT using an established atlas-based method. Dose plans were generated using MRI contoured anatomy with pseudo-CT for dose calculation. A conventional CT scan was acquired subsequent to MRI-only plan approval for quality assurance purposes (QA-CT). 3D Gamma evaluation was performed between pseudo-CT calculated plan dose and recalculation on QA-CT. Criteria was 2%, 2 mm criteria with 20% low dose threshold. Gold fiducial marker positions for image guidance were compared between pseudo-CT and QA-CT scan prior to treatment.

Results: All 25 patients recruited to phase 2 were treated using the MRI-only workflow. Isocenter dose differences between pseudo-CT and QA-CT were −0.04 ± 0.93% (mean ± SD). 3D Gamma dose comparison pass-rates were 99.7% ± 0.5% with mean gamma 0.22 ± 0.07. Results were similar for the two centers using two different scanners. All gamma comparisons exceeded the 90% pass-rate tolerance with a minimum gamma pass-rate of 98.0%. In all cases the gold fiducial markers were correctly identified on MRI and the distances of all seeds to centroid were within the tolerance of 1.0 mm of the distances on QA-CT (0.07 ± 0.41 mm), with a root-mean-square difference of 0.42 mm.

Conclusion: The results support the hypothesis that an MRI-only prostate workflow can be implemented safely and accurately with appropriate quality assurance methods.

TROG 18.01 phase III randomised clinical trial of the Novel Integration of New prostate radiation schedules with adJuvant Androgen deprivation: NINJA study protocol

INTRODUCTION

Stereotactic body radiotherapy (SBRT) is a non-invasive alternative to surgery for the treatment of non-metastatic prostate cancer (PC). The objectives of the Novel Integration of New prostate radiation schedules with adJuvant Androgen deprivation (NINJA) clinical trial are to compare two emerging SBRT regimens for efficacy with technical substudies focussing on MRI only planning and the use of knowledge-based planning (KBP) to assess radiotherapy plan quality.

METHODS AND ANALYSIS

Eligible patients must have biopsy-proven unfavourable intermediate or favourable high-risk PC, have an Eastern Collaborative Oncology Group (ECOG) performance status 0-1 and provide written informed consent. All patients will receive 6 months in total of androgen deprivation therapy. Patients will be randomised to one of two SBRT regimens. The first will be 40 Gy in five fractions given on alternating days (SBRT monotherapy). The second will be 20 Gy in two fractions given 1 week apart followed 2 weeks later by 36 Gy in 12 fractions given five times per week (virtual high-dose rate boost (HDRB)). The primary efficacy outcome will be biochemical clinical control at 5 years. Secondary endpoints for the initial portion of NINJA look at the transition of centres towards MRI only planning and the impact of KBP on real-time (RT) plan assessment. The first 150 men will demonstrate accrual feasibility as well as addressing the KBP and MRI planning aims, prior to proceeding with total accrual to 472 patients as a phase III randomised controlled trial.

ETHICS AND DISSEMINATION

NINJA is a multicentre cooperative clinical trial comparing two SBRT regimens for men with PC. It builds on promising results from several single-armed studies, and explores radiation dose escalation in the Virtual HDRB arm. The initial component includes novel technical elements, and will form an important platform set for a definitive phase III study.

TRIAL REGISTRATION NUMBER

ANZCTN 12615000223538.

Robot or radiation? A qualitative study of the decision support needs of men with localised prostate cancer choosing between robotic prostatectomy and radiotherapy treatment

OBJECTIVE

To understand how best to support men diagnosed with localised prostate cancer to decide which treatment option best suits their needs, when robotic prostatectomy and radiotherapy are equally appropriate to offer them.

METHODS

Twenty-five men recently diagnosed with localised prostate cancer completed semi-structured interviews asking about information/decision-making needs before and/or after attending a combined clinic in which they consulted a urologist and a radiation oncologist regarding treatment options. Data was transcribed verbatim and thematically analysed.

RESULTS

Most men preferred robotic prostatectomy pre-combined clinic and chose it afterwards. The thematic analysis revealed four themes: 1) trust in clinicians and the information they provide is critical for treatment choice, 2) perceived fit between treatment characteristics and personal circumstances, 3) additional considerations: specific side effects, socio-emotional and financial factors, and 4) need for tailored information delivery. Robotic prostatectomy was mistakenly believed to provide a more definitive cure than radiotherapy, which was seen as having a lesser lifestyle impact.

CONCLUSIONS

Treatment choice is largely dependent on clinicians' (mainly urologists') recommendations.

PRACTICE IMPLICATIONS

Patients need more balanced information about alternatives to robotic prostatectomy earlier in the treatment decision-making process. Referral to a radiation oncologist or combined clinic shortly after diagnosis is recommended.

Reduced motion and improved rectal dosimetry through endorectal immobilization for prostate stereotactic body radiotherapy

OBJECTIVE

PROMETHEUS (ACTRN12615000223538) is a multicentre clinical trial investigating the feasibility of 19 Gy in 2 fractions of stereotactic body radiotherapy (SBRT) as a boost technique for prostate cancer. The objective of this substudy was to evaluate intrafraction motion using cine MRI and assess the dosimetric impact of using a rectal displacement device (RDD).

METHODS

The initial 10 patients recruited underwent planning CT and MRI, with and without a RDD. Cine MRI images were captured using an interleaved T2 HASTE sequence in sagittal and axial planes with a temporal resolution of 5.2 s acquired over 4.3 min. Points of interest (POIs) were defined and a validated tracking algorithm measured displacement of these points over the 4.3 min in the anteroposterior, superior-inferior and left-right directions. Plans were generated with and without a RDD to examine the impact on dosimetry.

RESULTS

There was an overall trend for increasing displacement in all directions as time progressed when no RDD was in situ . points of interest remained comparatively stable with the RDD. In the sagittal plane, the RDD resulted in statistically significant improvement in the range of anteroposterior displacement for the rectal wall, anterior prostate, prostate apex and base. Dosimetrically, the use of a RDD significantly reduced rectal V16, V14 and D_max, as well as the percentage of posterior rectal wall receiving 8.5 Gy.

CONCLUSION

The RDD used in stereotactic prostate radiotherapy leads to reduced intrafraction motion of the prostate and rectum, with increasing improvement with time. It also results in significant improvement in rectal wall dosimetry.

ADVANCES IN KNOWLEDGE

It was found that the rectal displacement device improved prostate stabilization significantly, improved rectum stabilization and dosimetry significantly. The rectal displacement device did not improve target volume dosimetry.

Phase 2 Multicenter Study of Gantry-Based Stereotactic Radiotherapy Boost for Intermediate and High Risk Prostate Cancer (PROMETHEUS)

Objectives: To report feasibility, early toxicity, and PSA kinetics following gantry-based, stereotactic radiotherapy (SBRT) boost within a prospective, phase 2, multicenter study (PROMETHEUS: ACTRN12615000223538).

Methods: Patients were treated with gantry-based SBRT, 19–20 Gy in two fractions delivered 1 week apart, followed by conventionally fractionated IMRT (46 Gy in 23 fractions). The study mandated MRI fusion for RT planning, rectal displacement, and intrafraction image guidance. Toxicity was prospectively graded using the Common Terminology Criteria for Adverse Events version 4.0 (CTCAE v4).

Results: Between March 2014 and July 2018, 135 patients (76% intermediate, 24% high-risk) with a median age of 70 years (range 53–81) were treated across five centers. Short course (≤6 months) androgen deprivation therapy (ADT) was used in 36% and long course in 18%. Rectal displacement method was SpaceOAR in 59% and Rectafix in 41%. Forty-two and ninety-three patients were treated at the 19 Gy and 20 Gy dose levels, respectively. Median follow-up was 24 months. Acute grade 2 gastrointestinal (GI) and urinary toxicity occurred in 4.4 and 26.6% with no acute grade 3 toxicity. At 6, 12, 18, 24, and 36 months post-treatment the prevalence of late grade ≥2 gastrointestinal toxicity was 1.6, 3.7, 2.2, 0, and 0%, respectively, and the prevalence of late grade ≥2 urinary toxicity was 0.8, 11, 12, 7.1, and 6.3%, respectively. Three patients experienced grade 3 late toxicity at 12 to 18 months which subsequently resolved to grade 2 or less. For patients not receiving ADT the median PSA value pre-treatment was 7.6 ug/L (1.1–20) and at 12, 24, and 36 months post-treatment was 0.86, 0.36, and 0.20 ug/L.

Conclusions: Delivery of a gantry-based SBRT boost is feasible in a multicenter setting, is well-tolerated with low rates of early toxicity and is associated with promising PSA responses. A second transient peak in urinary toxicity was observed at 18 months which subsequently resolved. Follow-up is ongoing to document late toxicity, long-term patient reported outcomes, and tumor control with this approach.

Long-term outcomes in 1121 Australian prostate cancer patients treated with definitive radiotherapy

INTRODUCTION

Optimal definitive treatment of prostate cancer is controversial, especially in high-risk patients. We report the largest prospective cohort of Australian patients treated with radiotherapy for localised prostate cancer.

METHODS

One thousand, one hundred and twenty-one patients with prostate cancer were prospectively registered and treated to a dose of 70-74 Gy. Patients were classified as low, intermediate or high risk based on PSA, clinical staging and Gleason score. Intermediate-risk patients were treated with 0-6 months of hormonal therapy (ADT) and high-risk patients were offered neoadjuvant and adjuvant ADT. Overall survival (OS) and biochemical relapse-free survival (bNED) were calculated using the Kaplan-Meier method.

RESULTS

Median follow-up was 92 months. Eight-year OS and bNED were 78.4% and 68.1% respectively in the entire cohort. OS for the low, intermediate and high-risk groups was 84.5%, 78.4% and 68% respectively. For these risk groups, bNED was 80.3%, 65.7% and 53.7% respectively. In the intermediate and high-risk group, OS and bNED decreased with increasing number of risk factors.

CONCLUSION

Definitive radiotherapy is an effective treatment for prostate cancer, including in high-risk cases.

Radiotherapy for recurrent prostate cancer: 2018 Recommendations of the Australian and New Zealand Radiation Oncology Genito-Urinary group

The management of patients with biochemical, local, nodal, or oligometastatic relapsed prostate cancer has become more challenging and controversial. Novel imaging modalities designed to detect recurrence are increasingly used, particularly PSMA-PET scans in Australia, New Zealand and some European countries. Imaging techniques such as MRI and PET scans using other prostate cancer-specific tracers are also being utilised across the world. The optimal timing for commencing salvage treatment, and the role of local and/or systemic therapies remains controversial. Through surveys of the membership, the Australian and New Zealand Faculty of Radiation Oncology Genito-Urinary Group (FROGG) identified wide variation in the management of recurrent prostate cancer. Following a workshop conducted in April 2017, the FROGG management committee reviewed the literature and developed a set of recommendations based on available evidence and expert opinion, for the appropriate investigation and management of recurrent prostate cancer. These recommendations cover the role and timing of post-prostatectomy radiotherapy, the management of regional nodal metastases and oligometastases, as well as the management of local prostate recurrence after definitive radiotherapy.

PROstate Multicentre External beam radioTHErapy Using a Stereotactic boost: the PROMETHEUS study protocol

Background

High Dose Rate Brachytherapy (HDRB) boost is a well-established treatment for prostate cancer (PC). We describe the PROstate Multicentre External beam radioTHErapy Using Stereotactic boost (PROMETHEUS) study. Non-surgical stereotactic techniques are used to deliver similar doses to HDRB boost regimens with a dose escalation sub-study.

Methods

Eligible patients have intermediate or high risk PC. PROMETHEUS explores the safety, efficacy and feasibility of multiple Australian centres cooperating in the delivery of Prostate Stereotactic Body Radiotherapy (SBRT) technology. A SBRT boost component Target Dose (TD) of 19Gy in two fractions is to be delivered, followed by a subsequent EBRT component of 46Gy in 23 fractions. Once accrual triggers have been met, SBRT doses can be escalated in 1 Gy increments to a maximum of 22Gy in two fractions. Patient safety will also be measured with the rate of both acute and late moderate to severe Gastro-Intestinal (GI) and Genito-Urinary (GU) Common Terminology Criteria for Adverse Events (CTCAE) toxicities as well as patient reported quality of life. Efficacy will be assessed via biochemical control after 3 years.

Discussion

PROMETHEUS aims to generate evidence for a non-surgical possible future alternative to HDRB boost regimens, and introduce advanced radiotherapy techniques across multiple Australian cancer centres.

Trial registration

The study was retrospectively registered on the ANZCTR (Australian New Zealand Clinical Trials Registry) with trial ID: ACTRN12615000223538.

Rectal protection in prostate stereotactic radiotherapy: a retrospective exploratory analysis of two rectal displacement devices

INTRODUCTION

High rectal doses are associated with increased toxicity. A rectal displacement device (RDD) reduces rectal dose in prostate stereotactic body radiation therapy (SBRT). This study investigates any dosimetric difference between two methods of rectal displacement (Rectafix and SpaceOAR) for prostate SBRT.

METHODS

Rectal dosimetry of 45 men who received SBRT within the PROMETHEUS trial was retrospectively examined, across two radiation therapy centres using the two RDD's. Men received a total dose (TD) of 19 or 20 Gy in two fractions followed by 46 Gy in 23 fractions. Centre 1 contributed 16 Rectafix and 10 SpaceOAR patients. Centre 2 contributed 19 Rectafix patients. Rectal dose volume histogram (DVH) data were recorded as a TD percentage at the following volume intervals; V1%, V2%, V5%, V10% and then 10% increments to V80%. As only one centre employed both RDD's, three sequential rectal dosimetry comparisons were performed; (1) centre 1 Rectafix versus centre 1 SpaceOAR; (2) centre 1 Rectafix versus centre 2 Rectafix and (3) centre 1+ centre 2 Rectafix versus centre 1 SpaceOAR.

RESULTS

In comparison (1) Rectafix demonstrated lower mean doses at 9 out of 11 measured intervals (P = 0.0012). Comparison (2) demonstrated a moderate difference with centre 2 plans producing slightly lower rectal doses (P = 0.013). Comparison (3) further demonstrated that Rectafix returned lower mean doses than SpaceOAR (P < 0.001). Although all dose levels were in favour of Rectafix, in absolute terms differences were small (2.6-9.0%).

CONCLUSIONS

In well-selected prostate SBRT patients, Rectafix and SpaceOAR RDD's provide approximately equivalent rectal sparing.

Prostatectomy versus radiotherapy for early-stage prostate cancer (PREPaRE) study: protocol for a mixed-methods study of treatment decision-making in men with localised prostate cancer

BACKGROUND

Men diagnosed with localised prostate cancer (LPC) wanting curative treatment face a highly preference-sensitive choice between prostatectomy and radiotherapy, which offer similar cure rates but different side effects. This study aims to determine the information, decision-making needs and preferences of men with LPC choosing between robotic prostatectomy and standard external beam or stereotactic radiotherapy.

METHODS AND ANALYSIS

This study will be conducted at a large public teaching hospital in Australia offering the choice between robotic prostatectomy and radiotherapy from early 2017. Men (20-30) diagnosed with LPC who want curative treatment and meet criteria for either treatment will be invited to participate. In this mixed-methods study, patients will complete semistructured interviews before and after attending a combined clinic in which they consult a urologist and a radiation oncologist regarding treatment and four questionnaires (one before treatment decision-making and three after) assessing demographic and clinical characteristics, involvement in decision-making, decisional conflict, satisfaction and regret. Combined clinic consultations will also be audio-recorded and clinicians will report their perceptions regarding patients' suitability for, openness to and preferences for each treatment. Qualitative data will be transcribed verbatim and thematically analysed and descriptive statistical analyses will explore quantitative decision-making outcomes, with comparison according to treatment choice.

DISCUSSION

Results from this study will inform how to best support men diagnosed with LPC deciding which curative treatment option best suits their needs and may identify the need for and content required in a decision aid to support these men.

ETHICS AND DISSEMINATION

All participants will provide written informed consent. Data will be rigorously managed in accordance with national legislation. Results will be disseminated via presentations to both scientific and layperson audiences and publications in peer-reviewed scientific journals.