Intensity-modulated fractionated radiotherapy versus stereotactic body radiotherapy for prostate cancer (PACE-B): acute toxicity findings from an international, randomised, open-label, phase 3, non-inferiority trial

Hypofractionation/Ultra-hypofractionation for Prostate Cancer Radiotherapy

Prostate cancer is the most commonly diagnosed cancer in men worldwide. Radiotherapy is an integral component for the treatment of localized prostate cancer. Radiobiologically, prostate cancer is sensitive to an increased dose of radiotherapy delivered per fraction, called "hypofractionation", due to intrinsic differences in the rate of cancer cell growth and repair of DNA damage. Hypofractionation delivers planned treatment over fewer radiotherapy sessions compared to conventional fractionation and has been shown to be noninferior to conventional fractionation with an acceptable toxicity profile. Ultra-hypofractionation, often delivered via stereotactic body radiotherapy (SBRT), further reduces the number of treatments by using even larger doses per fraction and has shown promising results with high biochemical control rates and low rates of late toxicity. The adoption of hypofractionated and ultra-hypofractionated schedules improves resource utilization in radiation oncology without compromising patient safety or efficacy. Ongoing research continues to refine patient selection, fractionation schemes, and incorporates advanced imaging, precise treatment planning, and motion management techniques to help mitigate toxicity and optimize outcomes in localized intermediate and high-risk disease.

Challenges and opportunities to minimize the dose in the neurovascular bundles during prostate radiotherapy

BACKGROUND AND PURPOSE

Radiation damage to the neurovascular bundles (NVB) has been linked to erectile dysfunction after prostate cancer radiotherapy (PCa). NVB sparing using coplanar and non-coplanar automated treatment planning is presented here in two settings: (1) without compromising target coverage, (2) allowing target coverage compromise.

MATERIAL AND METHODS

20 previously treated patients with localized PCa. Based on a MRI-CT match, the NVB were retrospectively delineated. All treatment plans (5 × 7.25 Gy) were automatically generated using Erasmus-iCycle (in-house automated treatment planning algorithm). Non-NVB sparing (non-NVBsparing) plans and NVB sparing plans in two settings were generated: (1) uncompromised NVB sparing (u-NVBsparing; maintaining target coverage) (2) and compromised NVB sparing (c-NVBsparing; allowing target underdosage). Coplanar and non-coplanar beam arrangements were compared. U-NVBsparing was compared to non-NVBsparing. C-NVBsparing plans were visualized in Pareto fronts. Statistical significance (p-value < 0.05) was determined by Wilcoxon signed-rank test.

RESULTS

u-NVBsparing compared to non-NVBsparing plans showed statistically significant median reductions in NVB D0.1 cc (38.9 vs 42.6 Gy for coplanar; 38.9 vs 43.3 Gy for non-coplanar) and Dmean (25.6 vs 30.0 Gy for coplanar; 24.7 vs 30.2 Gy for noncoplanar). Further lowering NVB D0.1 cc in c-NVBsparing plans clearly correlated to lower target coverage. Non-coplanar c-NVBsparing plans maintained significantly higher target coverages for similar NVB D0.1 cc values, compared to coplanar plans.

CONCLUSION

NVB sparing without compromising target coverage is feasible. No clinically relevant benefit was found for non-coplanar compared to coplanar NVB sparing plans, although overall statistically superior. Further sparing of the NVB comes at the cost of target coverage, for which a Pareto front could be used as a tool in clinical practise.

Acute toxicity and quality of life after margin reduction using a sub-fractionation workflow for stereotactic radiotherapy of localized prostate cancer on a 1.5 Tesla MR-linac

BACKGROUND AND PURPOSE

A sub-fractionation workflow to correct for intrafraction motion in localized prostate cancer radiotherapy was implemented at our center, allowing for PTV margin reduction from isotropic 5 mm to 2 mm in cranio-caudal and left-right directions and 3 mm in the anterior-posterior direction. The purpose of this study was to assess differences in acute toxicity before and after margin reduction.

MATERIALS AND METHODS

Included patients were treated with 36.25 Gy in five fractions on a 1.5 T MR-linac, with PTV margins of 5 mm (standard margins) or 2-3 mm (tight margins). The primary endpoint was acute (90 days post-RT) toxicity. Physician-reported toxicity was measured by maximum CTCAE version 5.0 genitourinary (GU) and gastrointestinal (GI) scores. Patient reported toxicity was a secondary endpoint, assessed through EPIC-26 urinary and bowel domain scores. Groups were balanced through propensity score matching after multiple imputation using chained equations. Pearson's Chi-squared tests were used to analyze CTCAE scores and Wilcoxon rank sum tests to analyze EPIC-26 scores.

RESULTS

299 eligible patients were identified (193 and 106 in the tight and standard margin groups, respectively). After matching, 212 patients (106 per treatment group) were available for assessment. No statistically significant between-group differences in physician-reported toxicity were observed at any follow-up point. Patient-reported urinary irritative/obstructive quality of life was statistically, but not clinically, significantly higher after one month. Overall, scores declined during treatment and one month post-RT, but returned to baseline levels three months post-RT.

CONCLUSION

Margin reduction below 5 mm did not seem to reduce acute toxicity after radiotherapy with a stereotactic body radiotherapy (SBRT) treatment schedule in localized prostate cancer. The introduction of real-time comprehensive motion management with prostate gating could further lower GU and GI toxicity and ameliorate treatment related quality of life.

HERMES: Randomised trial of 2-fraction or 5-fraction MRI-guided adaptive prostate radiotherapy

OBJECTIVE

To demonstrate safety and feasibility of 2-fraction stereotactic body radiotherapy (SBRT) for prostate cancer.

METHODS

This single centre, non-comparative, phase II/R-IDEAL2b trial randomised 46 patients with intermediate/lower high-risk prostate cancer with visible gross tumour volume (GTV) on multiparametric magnetic resonance imaging (MRI) to receive 36.25Gy in 5 fractions over 10 days or 24Gy in 2 fractions with a GTV boost up to 27Gy over 8 days. All treatment was delivered on an MR-linac with daily adaptive replanning. The primary endpoint was acute grade ≥2 (G2+) genitourinary (GU) toxicity (CTCAEv5). Secondary endpoints include gastrointestinal (GI) toxicity and patient reported outcomes.

RESULTS

G2+GU acute toxicity was observed in 6/22 (27.3%; 95% CI (0.11-0.50) of patients in the 2-fraction group and 7/24 (29.2%; 95% CI (0.13-0.50) in the 5-fraction group. There were no grade 3(G3) GU toxicities. G2+ urinary frequency rose from 4.5% (1/22) at week 2 to 13.6% (3/22) at week 4 in 2-fraction SBRT. G2+ urinary frequency peaked earlier in 5-fraction SBRT at 16.7% (4/24) in week 2, falling to 12.5% (3/24) at week 4. At 12 weeks, median EPIC-26 urinary-incontinence score was 85.5, IQR 75-100) for 2-fraction SBRT and 100, IQR 93.8-100) for 5-fraction SBRT. Urinary irritative-obstructive scores were higher at 12 weeks in the 2-fraction group (93.8, IQR 87.5-100) and 87.5, IQR 81.3-93.8 in the 5-fraction group. Peak IPSS score was lower in the 2-fraction group (8, IQR 4-11) and 13.5, IQR 10-17) in the 5-fraction group. G2+ GI acute toxicity occurred in 3/24 (6.8%) after 5-fraction SBRT, but none after 2-fraction SBRT.

CONCLUSIONS

Acceptable acute GU toxicity was seen after 2-fraction SBRT. Acute GI toxicity was low. Randomised trials are warranted to explore late toxicity and biochemical control.

PSMA MRI Guided Prostate SABR ARGOS-CLIMBER Phase I/II Trial: A Primary Endpoint Analysis

PURPOSE

The XXXXX trial is a multi-institutional phase I/II study utilizing a combined PSMA PET/MRI approach to treat dominant intraprostatic lesions (DILs) and affected lymph nodes in unfavorable intermediate and high-risk prostate cancer using a five fraction SABR and simultaneous in-field boost (SIB) technique. Here we report on the primary endpoint of toxicity within 6 months of treatment.

METHODS AND MATERIALS

SIB volumes were defined utilizing a PET/MRI acquired using 18F-PSMA 1007. Five fraction SABR was planned to deliver doses (maximum SIB) to prostate 35 Gy (50 Gy), SV 25 Gy (50 Gy) and lymph nodes 25 Gy (35 Gy) while respecting OAR's. Toxicity and QOL were assessed according to CTCAE 5.0 and EPIC-26 during radiation, at 6 weeks post-treatment and at 6 months post treatment.

RESULTS

In total 50 patients were treated, 23 patients had unfavorable intermediate risk disease, 23 were high risk, and 4 were very high-risk prostate cancer. Median prostate SIB of 41.6 Gy (IQR: 39.3-44.8 Gy) was delivered to a median of 1 intra-prostatic lesion. Eighteen patients received nodal treatment. There was a single acute grade 3 GI toxicity of diarrhea and a single late grade 4 GI toxicity of bleeding. With a median follow-up of 12 months, the EPIC-26 scale showed an increase in urinary irritation (p < 0.001) and no differences for urinary incontinence (p=0.12) and GI QOL (p=0.65) and a decrease in hormonal/sexual QOL (p < 0.001 and p < 0.001). Mean ± SD PSA, maximum SUV on PET and maximum MRI PiRADS scores at baseline to 6 months were 15.4 ± 10.3 to 0.18 ± 0.40 ng/mL, 25.5 ± 19.5 to 4.5 ± 7.7, and 4.7 ± 0.6 to 2.9 ± 1.5 respectively.

CONCLUSIONS

XXXXX demonstrated acceptable toxicity using 5 fraction SABR with PET/MRI directed SIB to prostate and lymph nodes.

Longitudinal stability of HyperSightTM-CBCT based radiomic features in patients with CT guided adaptive SBRT for prostate cancer

CT-guided adaptive radiotherapy (aRT) based on HyperSightTM-CBCT provides high-quality imaging, allowing quantitative radiomic feature analysis as a monitoring tool. This study comprehensively evaluates the stability of radiomic features, as potential imaging biomarkers, in pelvic structures of prostate cancer patients treated with adaptive stereotactic body radiation therapy (SBRT). Between December 2023 and July 2024, 32 patients with localized prostate cancer underwent adaptive SBRT at the Ethos® linear accelerator (Varian, Siemens Healthineers) with HyperSight-CBCT imaging. Longitudinal stability was assessed by intraclass correlation coefficient (ICC) over five fractions of aRT for target structures and non-hollow organs at risk. In pooled organs at risk, 93.0% of features showed very high stability (ICC > 0.9) compared to 67.4% in pooled target structures, indicating significantly lower stability for target structures (p = 0.00009129). Second-order features demonstrated greater stability than conventional and shape-based features (p = 0.0433, p = 0.0252). Fraction number significantly affected longitudinal prostate feature variability (p = 0.0135). This study comprehensively analyzed HyperSight-CBCT imaging to evaluate longitudinal stability of radiomic features during adaptive SBRT for prostate cancer. The trends observed will provide a framework for future CT-guided aRT studies, facilitating quantitative imaging analysis of radiological biomarkers for clinical translation and improving personalized treatment.

Implementation of a comprehensive clinical quality assurance system in radiation oncology

OBJECTIVE

The objective of this project was to develop and evaluate a comprehensive clinical quality assurance system for radiation oncology, and assess the system using definitive radiation therapy for prostate cancer as a first use case.

METHODS

The Zurich Clinical Quality Assurance System in Radiation Oncology (ZH-CLASSIC) was initiated to allow for continuous quality assurance in radiation oncology with respect to indication for radiation therapy, practice of radiation therapy and patient outcome. Data from the sources of the hospital information system, the Radiation Oncology Record and Verify System and a dedicated follow-up database were automatically retrieved, and combined using a unique patient-ID. Data aggregation, continuous analysis and reporting was performed using ten distinct patient care pathways as the basis which covers all aspects of radiation therapy treatments and indications as well as the different follow-up schemes (in-clinic, telemedicine, and external follow-up). The follow-up system was validated through analysis of patients with prostate cancer (≥ 18 years, cT1-3 cN0 cM0) who underwent curative, primary stereotactic radiation therapy. Survival, treatment effectiveness, tumor control, acute and late toxicity, and performance status were analyzed.

RESULTS

Since May 2021, a total of 4,515 individual patients were being managed in ZH-CLASSIC. Personal resources amounted to 0.75 full time equivalent (FTE) project manager for one year prior to implementation, 0.13 FTE physician and 1.00 FTE follow-up manager as ongoing expenses. Compliance with respect to reporting data into ZH-CLASSIC by the physicians increased from a mean of 54% in 2021 to 92% in 2024. For all patients, follow-up was performed as in-clinic visits (51%), via telephone (7%) or as an external query (43%), with missing information (5%) originating from external requests in 96%. Instead of an intended first in-clinic follow-up visit, telemedicine appointments were conducted in 10% and external follow-ups were performed in 22%. Oncological outcomes and toxicities were evaluated for all prostate cancer patients (n = 209) treated with daily online-adaptive SBRT on the MRIdian using 5 × 7.25 Gy every other day or 5 × 7.5 Gy weekly. After a median follow-up of 15 months (range, 6-41 months), 208/209 patients were alive. Over this time period, reported CTCAE toxicities included genitourinary grade 2: 12%, grade 3: 1%, and gastrointestinal grade 2: 3%, grade 3: 0%.

CONCLUSIONS

The ZH-CLASSIC system allowed for automated and structured documentation and analysis of the quality with regards to the indication, treatment and outcome of radio-oncological cancer patients. Dedicated staff are needed in the start-up period but personal resources are expected to continuously decrease. Analyses of patients treated with SBRT for localized prostate cancer resulted in plausible results in agreement with reported values in the literature.

CLINICAL TRIAL NUMBER

Not applicable.

PSA reduction as predictor of biochemical relapse in low and favourable intermediate prostate cancer treated with radical radiotherapy

PURPOSE

Radiation therapy (RT) is standard treatment for localized prostate cancer (PCa). Prostate-specific antigen (PSA) kinetics, particularly PSA reduction (PSAr) after RT, are emerging as significant prognostic indicators for biochemical control. This retrospective multi-institutional study explores the correlation between PSAr and biochemical relapse-free survival (BRFS). This retrospective multi-institutional study explores the correlation between PSAr and biochemical relapse-free survival (BRFS).

METHODS

251 low-to-intermediate risk PCa patients treated with RT only were analyzed. Isoeffective RT schedules were: 39 fractions × 2 Gy, 28 × 2.55 Gy, 16 × 3.5 Gy, 5 × 7 Gy. Main objective was BRFS, defined as the time from PSA nadir (PSAn) to PSAn plus 2 ng/ml. PSAr was defined as the percentage of total PSA reduction from baseline. The optimal PSAr cut-off value was defined as 90%. Patients were stratified by PSAr, baseline PSA, Gleason Score (GS), and RT schedules.

RESULTS

GS was 3 + 3 in 120 (48%) patients and 3 + 4 in 131 (52%) patients. After a median follow-up of 36 months (30-48), 2 and 5-year BRFS were 97.3% and 95.2%, respectively, in patients with PSAr ≥ 90% and 89.5%, 61.5% in patients with PSAr < 90% (p = 0.00). In the responder population, median time to PSAr 90% was 24 months and the median time to PSAn was 28.7 months (20-38). At univariate and multivariate analyses, PSAr was the only significant predictor of BRFS [HR 6.519 (95% IC 1.9-22.2), p = 0.003].

CONCLUSIONS

PSAr could be a reliable prognostic factor for long-term biochemical control. This study underscores the potential of PSAr as a tool for risk stratification and personalized follow-up strategies in PCa management.

Severe Late Toxicities (Grade 3-5) with 13 Years of Follow-up after Hypofractionated Postprostatectomy Radiotherapy

BACKGROUND

We previously reported outcomes after hypofractionated postprostatectomy radiotherapy (HYPORT) with a median follow-up of 32 months. This was a primary citation supporting the fractionation selection for NRG-GU003, which showed noninferiority of HYPORT versus conventional radiotherapy.

METHODS

One hundred sixty-one consecutive patients with biochemically recurrent prostate cancer after prostatectomy underwent HYPORT from 2003 to 2013 at a single academic institution using image guided intensity modulated radiation therapy, with the majority (154 of 161) receiving 65 Gy in 26 fractions.

RESULTS

Median follow-up was 13.5 years. Forty-four patients (27.3%) experienced 58 late grade 3 to 5 toxicities (LTOX3) a median of 106 months after HYPORT. Fifty-five of 58 LTOX3 were genitourinary related. Higher-grade toxicities included 6 cystectomies and 3 deaths. At 2 years, only 2 patients had experienced an LTOX3. At 15 years, overall survival was 70%, freedom from biochemical recurrence was 52%, and the risk of LTOX3 was 34%.

CONCLUSIONS

Long follow-up is needed to fully capture severe toxicities after dose-escalated HYPORT. This should be considered prior to the broad adoption of similar regimens for this patient population with long survival potential.

Optimal Planning Target Volume Margins to Account for Intra-Fractional Prostate Motion Relative to Treatment Duration: A Study Using Real-Time Transperineal Ultrasound Guidance

INTRODUCTION

Prostate motion during external beam radiotherapy (EBRT) is common and typically managed using fiducial markers and cone beam CT (CBCT) scans for inter-fractional motion correction. However, real-time intra-fractional motion management is less commonly implemented. This study evaluated the extent of intra-fractional prostate motion using transperineal ultrasound (TPUS) and examined the impact of treatment time on prostate motion.

METHODS

Patients undergoing prostate EBRT with TPUS at a single institution from August 2016 to August 2021 were analysed. Pre-treatment daily CBCT corrected inter-fractional prostate shift. Continuous intra-fractional prostate motion was recorded at two frames per second in three dimensions, with three-dimensional (3D) displacement calculated as a vector. Motion data were modelled to determine the probability of the prostate remaining within pre-specified PTV margins relative to treatment delivery time.

RESULTS

The study analysed 3364 fractions delivered to 122 patients. The mean treatment delivery time was 3.8 min. The prostate remained within a 5 mm margin with high frequencies in the superior-inferior (SI) and left-right (LR) directions, 97.8% and 98.4% of fractions respectively while 5.5% of fractions had deviations greater than 5 mm in the anterior-posterior (AP) direction. By contrast, the 3D vector exceeded a 5 mm margin in 14.5% of fractions. Drift motion modelling indicated a 99% probability of the vector staying within a 3 mm margin for 2 min, while for a 5 mm margin, the duration extended to 3.4 min.

CONCLUSIONS

Intra-fractional prostate motion monitoring is increasingly important as SABR with reduced PTV margins are utilised in prostate radiotherapy. Smaller PTV margins and longer treatment time require real-time monitoring to avoid geographical miss.

PSMA-PET Guided Intraprostatic Boost in Prostate SBRT (PROBE): A Phase 2 Trial

PURPOSE

To assess the safety of using combined Gallium68-prostate-specific membrane antigen (PSMA)-positron emission tomography (PET)/computed tomography (CT) (68Ga-PSMA-PET/CT) and multiparametric magnetic resonance imaging (mpMRI) for planning dominant intraprostatic lesion (DIL) boost in prostate stereotactic radiation therapy (SBRT) for dose escalation (PROBE).

METHODS AND MATERIALS

Patients with intermediate- or high-risk prostate adenocarcinoma with DIL identified on mpMRI and 68Ga-PSMA-PET/CT and suitable for SBRT were enrolled in this phase 2 trial. 68Ga-PSMA-PET/CT was fused with mpMRI for gross tumor volume (GTV) delineation. Semiautomatic contouring of DIL was performed using 20% to 90% of the maximum standardized uptake value (SUVmax) (DILx%). Concordance metrics were used to select the DILx% matching closest to GTVMRI (GTVPET). Prostate (36.25 Gy), pelvic nodes (25 Gy), GTVunion: GTVPET ∪ GTVMRI (40 Gy), and GTVoverlap: GTVPET ∩ GTVMRI (42.5 Gy) were planned for 5-fraction SBRT. All patients received androgen deprivation therapy (ADT) for 6 months. The primary endpoint for the present analysis was concordance (volumetric and spatial) between GTVMRI and GTVPET. Secondary endpoints included the percentage SUVmax threshold for GTVPET contouring (%SUVGTV-PET) and cumulative acute (≤90 days) urinary and gastrointestinal toxicity using Common Terminology Criteria for Adverse Event (CTCAE) v5.0.

RESULTS

Thirty patients (54% intermediate risk, 46% high risk) were enrolled. GTVMRI and GTVPET showed strong volumetric correlation (Spearman correlation coefficient ρ = 0.817, 95% CI, 0.64-0.91; P < .001). The median Dice similarity coefficient, Jaccard index, and the mean Hausdorff distance for PET and magnetic resonance imaging boost volumes were 0.56, 0.37, and 2.2, respectively. The median %SUVGTV-PET was 48% (IQR, 40%-58%). There was an inverse correlation between DIL SUVmax and %SUVGTV-PET (Spearman correlation coefficient ρ = -0.598, 95% CI lower -0.79, upper -0.29; P < 0.001). Cumulative grade 2 acute urinary and GI toxicity were 13.3% and 6.6%, respectively, with no grade ≥3 toxicities.

CONCLUSION

Boost volumes on 68Ga-PSMA-PET/CT and mpMRI were volumetrically similar, however, with poor spatial concordance. The %SUVmax threshold for GTVPET contouring correlated inversely with DIL SUVmax and was a median of 48%. Based on the favorable acute toxicity profile, PSMA-PET guided intraprostatic boost is likely to be safe for dose escalation in prostate SBRT.

Perirectal spacers in radiotherapy for prostate cancer - a systematic review and meta-analysis

Introduction

Perirectal spacers reduce the radiotherapy (RT) dose delivered to the rectum, but their impact on treatment toxicity remains debated. We conducted a systematic review and meta-analysis to synthesise emerging data (PROSPERO: CRD42024506380).

Material and methods

MEDLINE, Embase, Scopus, and Google Scholar were searched through 2024/08/18 for prospective randomised (RCT) and non-randomised trials evaluating the clinical outcomes of perirectal spacing in prostate cancer (PCa) patients. Random effects generalised linear mixed models were used to pool odds ratios (OR) for rectal adverse events (AEs) from RCTs. Non-randomised trials were summarised qualitatively. The risk of bias was assessed using the RoB2 and ROBINS-I tools.

Results

Three RCTs (n = 645) were identified. The rates of grade ≥ 2 (G ≥ 2) rectal AEs in control groups were low, ranging 4.2-13.8% for early AEs and 0-1.4% for late AEs. Perirectal spacers were associated with decreased incidence of early G ≥ 2 rectal AEs (OR: 0.43; 95% CI: 0.19-0.96), but not of late G ≥ 2 rectal AEs (OR: 0.26; 95% CI: 0.02-2.91). Assuming a comparator risk of 7.1% and 1%, this corresponded to a number needed to treat of 26 patients to avoid one early AE, and 135 pa- tients to avoid one late G ≥ 2 AE, respectively. Randomised clinical trial were at moderate risk of bias due to concerns regarding the concealment of allocation.

Conclusions

There is evidence that perirectal spacers result in a small decrease in acute rectal toxicity. However, modern RT for clinically localised PCa is generally well-tolerated, and severe AEs are rare. Greater scrutiny of the risks and benefits associated with perirectal spacers is necessary.

Travel costs and ecologic imprint associated with different fractionation schedules in prostate cancer radiotherapy

Improving the sustainability and cost-effectiveness of healthcare systems has become increasingly relevant in times of climate change, energy transition, an aging population and skyrocketing social costs. The selection of an adequate fractionation schedule is of fundamental importance in the field of Radiation Oncology. We evaluated three internationally established fractionation schedules for definitive prostate cancer radiation therapy (RT) with respect to their ecological and health-economic impacts.We analyzed the data of 109 patients with prostate cancer, who underwent outpatient radiation therapy at Jena University Hospital in 2022. After determination of travel distances between their homes and the treatment facility, carbon dioxide (CO2)-emissions and taxi costs were calculated for normofractionated RT (39 fractions, A), moderately hypofractionated RT (20 fractions, B) and ultrahypofractionated RT (5 fractions, C).Travel distances of 1616 km (A), 848 km (B) and 242 km (C) were calculated with corresponding costs ranging from 638 € (C) to 4255 € (A). According to the 2024 German physician's fee schedule, 9,604 € would be invoiced for medical treatment and transportation in (A), with transportation costs accounting for 44% of total treatment costs in normofractionated RT. The travel distance, CO2-emissions and transportation costs could be reduced by up to 85% by hypofractionation.(Ultra-)hypofractionated radiation therapy for prostate cancer has great potential to lower healthcare costs and reduce environmental pollution. Given that and the non-inferiority of oncological outcome and toxicity, hypofractionation should appear beneficial from patient's and healthcare provider's point of view. Current reimbursement structures seem to be inappropriate regarding increased personnel and technical efforts required for highly precise dose application and might hinder comprehensive establishment of ultrahypofraktionated RT in Germany.

Bowel Disorder Incidence and Rectal Spacer Use in Patients With Prostate Cancer Undergoing Radiotherapy

Importance

The polyethylene glycol-based hydrogel spacer (PHS) system temporarily separates the rectum from the prostate in patients undergoing radiotherapy (RT) for prostate cancer (PCa).

Objective

To compare incidence of bowel disorders and related procedures in patients receiving RT with and without PHS.

Design, Setting, and Participants

This retrospective cohort study used 4 datasets: Medicare 5% Standard Analytic Files, Medicare 100% Standard Analytic Files, Merative MarketScan Commercial Database, and Premier Healthcare Database. Participants included adult patients with PCa undergoing RT from 2015 to 2021.

Exposure

Placement of PHS.

Main Outcomes

All-cause bowel disorders and related procedures, identified from diagnosis and procedure codes. Results were compared with age-matched male general population without PCa or RT.

Results

Of 261 906 patients with PCa included in the study, 25 167 (9.6%) received PHS (mean [SD] age, 70.7 [6.5] years) and 236 739 did not (mean [SD] age, 71.1 [7.5] years). One year prior to RT, patients who received PHS had a lower mean (SD) Charlson Comorbidity Index score than those who did not (2.48 [1.08] vs 3.14 [1.95]; P < .001). Stereotactic RT was more common in patients who received PHS (2743 [10.9%] vs 8810 [3.7%]; P < .001), while intensity-modulated RT was less common (12 755 [50.7%] vs 142 402 [60.2%]; P < .001). After 4 years post RT, patients who received PHS had a 25% lower hazard of bowel disorders (hazard ratio [HR], 0.75 [95% CI, 0.72-0.78]; P < .001) and a 46% lower hazard of related procedures (HR, 0.54 [95% CI, 0.47-0.62]; P < .001) than patients who did not receive PHS. Patients without PHS had higher hazard compared with an age-matched general population (disorders: 17.1% [95% CI, 17.3%-17.6%] vs 10.3% [95% CI, 10.1%-10.5%]; HR, 1.35 [95% CI, 1.32-1.37]; P < .001; procedures: 2.0% [95% CI, 1.9%-2.1%] vs 0.7% [95% CI, 0.7%-0.8%]; HR, 1.92 [95% CI, 1.79-2.06]; P < .001), while patients who received PHS did not (disorders: 12.4% vs 10.3%; HR, 1.00 [95% CI, 0.98-1.05]; P = .82; procedures: 1.1% [95% CI, 1.0%-1.3%] vs 0.7% [95% CI, 0.7%-0.8%]; HR, 1.11 [95% CI, 0.96-1.29]; P = .15). Common procedures included colonoscopy, sigmoidoscopy, and rectal resection.

Conclusions and Relevance

In this cohort study of patients with PCa receiving RT, those receiving a PHS had a significantly lower incidence of all-cause bowel disorders and related procedures compared with patients who did not receive a PHS over the 4-year follow-up. The incidence among patients with PHS was similar to the general population. These findings are consistent with prior phase 3 trial results, where patients receiving PHS experienced no decline in bowel quality of life.

Partial or focal brachytherapy for prostate cancer: a systematic review and meta-analysis

OBJECTIVES

Recent advances in image-guided brachytherapy have allowed for treatment volume reduction in the treatment of prostate cancer, with the aim to optimize disease control and reduce toxicities. This systematic review reports on the efficacy and safety of focal brachytherapy for treatment of patients with localized prostate cancer.

METHODS

Medline, Embase, Web of Science, and Cochrane were searched from inception to July 2023. Studies were included if they reported on focal brachytherapy, and described either dosimetry or clinical outcomes in the monotherapy or salvage setting. Meta-analysis was conducted to estimate biochemical control (BC) at 12-60 months. The review protocol was registered on PROSPERO (CRD42022320921).

RESULTS

Twenty-six studies reporting on 1492 patients were included in this review. Fourteen studies reported on monotherapy, 10 on salvage, and two on boost. The majority of studies used MRI and/or biopsy or PET for target identification, and MRI fusion and transrectal ultrasound (TRUS) for image guidance technique. BC for monotherapy was 97% (95% CI: 86%-99%) at 24 months and 82% (95% CI: 65%-92%) at 60 months. BC for salvage was 67% (95% CI: 62%-72%) at 24 months and 35% (95% CI: 17%-58%) at 60 months. Low rates of toxicity were reported across studies.

CONCLUSIONS

Focal brachytherapy has promising efficacy and safety profiles. Future studies may compare focal brachytherapy to whole-gland treatments, to investigate relative efficacy and safety.

ADVANCES IN KNOWLEDGE

In well-selected patients, partial or focal brachytherapy represents an evidence-based option with acceptable BC rates and a favourable toxicity profile.

Patient experience preparing for prostate cancer radiotherapy

Introduction

Bladder and rectal preparation regimes for prostate cancer (PCa) radiotherapy (RT) can heighten anxiety before and during RT. Patient's perception of RT preparation is under-represented in the literature. To address this gap, patient's experience of preparation with respect to understanding, comfort, anxiety, effectiveness and impact on daily life was examined.

Materials and methods

A novel patient preparation survey was created and validated, it contained 12 original questions related to general, bladder and rectal preparation. Plus, the Patient Health Questionnaire 4 (PHQ4) and question 15 of the Expanded Prostate Cancer Index Composite (EPIC).Eligible patients were individuals referred for prostate or prostate bed +/- pelvic lymph node RT from March-May 2024. Surveys were issued immediately after the patient's planning scan, those completing the survey at this timepoint were asked to repeat it in their first and final weeks of RT.

Results

The survey was completed by 103/125 eligible patients at their planning scan, 47/103 in the first and 52/103 in the final week of RT. Perception of preparation was largely positive. For general and bladder preparation positive question response rate ranged from 55 to 98 % and negative from 0 to 26 %. Rectal preparation response rate was 59-100 % positive and 0-35 % negative. Difficulty maintaining a full bladder and using enemas was greatest at the end of RT.No significant difference in experience was found for participants using or not using enemas for preparation. Anxiety and depression (PHQ4) affected 12-13 % of respondents, and significantly more patients reported bowel toxicity (EPIC), in the last week of RT compared to earlier timepoints.

Conclusion

The authors conclude that the preparation needs of their patients are well met. However, a considerable number did find preparation difficult, disruptive and ineffective, more so at the end of treatment. Further qualitative analysis of patient's experience is needed to better understand why individuals experience varies.

Geometric and dosimetric evaluation of CTV contour adaptations by radiation therapists for adaptive prostate radiotherapy on a 0.35 T MR-Linac

Background & purpose

Magnetic resonance guided adaptive radiotherapy (MRgART) enables hypofractionated prostate radiotherapy by daily contour adaptation. The MRgART workflow, however, is labour intensive and in many institutes still requires the presence of the radiation oncologist (RO). Transferring the online contour adaptation task to the radiation therapist (RTT) will release the clinician from attending each treatment fraction making MRgRT more efficient and cost effective. In this study we investigate the viability of RTT-led prostate MRgART on a low-field MR-linac, by assessing the interobserver variations of RTT- and RO-generated CTV contour adaptations as well as the resulting dosimetric effects.

Materials & methods

Four RTTs and four ROs performed CTV contour adaptations on first fraction data in ten patients. Delineations were compared against a gold standard contour using target volume, Dice similarity coefficient (DSC), and 95th percentile Hausdorff distance. In addition, a dosimetric evaluation was performed on all first fractions by performing plan adaptations based on all RTT contour adaptation and comparing these to the clinically delivered plan. Finally, a full-treatment simulation was performed in four patients to investigate the dosimetric effects of the RTTs' contour adaptations throughout an entire treatment.

Results

RTTs with no experience in prostate delineation prior to this study spent more time on CTV contour adaptations. The geometric and dosimetric analyses, however, showed no statistically significant differences between both groups.

Conclusions

This study confirmed that RTTs perform similarly to ROs in carrying out online contour adaptations. These results indicate the feasibility of initiating a transition in contour adaptation tasks from ROs to RTTs.

Hypofractionation Utilisation in Radiation Therapy: A Regional Department Evaluation

INTRODUCTION

There has been an uptake in hypofractionation radiotherapy schedules (> 2.45 Gy per fraction) worldwide over the last decade. The aim of this paper was to evaluate the change in fractionation schedules for patients undergoing radiotherapy in regional Queensland. The influence of treatment site, intent and patient social circumstances was assessed, identifying any current gaps in practice.

METHODS

This retrospective clinical audit, included patients who underwent radiotherapy in 2012, 2019 and 2022 at a large regional department. This allowed a 10-year analysis and an evaluation of any impact of COVID-19. Demographic data and treatment information was collected and analysed using descriptive statistics.

RESULTS

There was a notable trend favouring hypofractionation for patients treated for breast and prostate cancer. In 2012, 62.7% of breast cancer patients were treated with conventional fractionation and 37.3% were treated with hypofractionation, versus 2.4% and 92.1%, respectively, in 2022. Prostate cancer fractionation changed from 99.4% of patients treated with conventional fractionation and 0.6% with hypofractionation in 2012 to 23.2% and 74.1%, respectively, in 2022. The standard of care also shifted for palliative intent, with lung, brain and bone metastases in 2022 being treated with increased hypofractionated and ultra-hypofractionated radiotherapy (> 5 Gy per fraction). This coincides with more complex and modulated treatments being readily available, such as stereotactic radiotherapy and volumetric modulated arc therapy. Hypofractionated treatments, however, were not influenced by the social factors of patients, having no distinct relationship with Indigenous status, age and patients' distance to treatment.

CONCLUSION

This study has validated the increase in hypofractionated treatments over a range of cancer sites and treatment intents, with increased treatment complexity. This has a direct impact on both departmental resources and patient-centred care, offering value-based radiotherapy.

Stereotactic body radiotherapy (SBRT) as a treatment for localized prostate cancer: a retrospective analysis

BACKGROUND

External beam radiotherapy (EBRT) is a standard treatment for localized prostate cancer, with recent advancements favoring a reduced number of treatment sessions. Stereotactic body radiotherapy (SBRT) is a form of radiotherapy that delivers higher doses per fraction, typically in five or fewer sessions. This retrospective study aims to evaluate the implementation of the PACE-SBRT protocol for localized prostate cancer at our center by assessing the incidence and severity of toxicity, as well as biochemical relapse-free survival.

METHODS

We conducted a retrospective analysis of patients with localized prostate cancer treated with SBRT at the Iridium Network in Antwerp, Belgium, who were treated between January 1, 2020, and December 31, 2022. Data were extracted from electronic medical records and included descriptive information on patient outcomes. Acute and late genitourinary (GU) and gastrointestinal (GI) toxicities were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4.0. Acute toxicity was defined as events occurring within 90 days post-SBRT, whereas late toxicity was evaluated at 6 months, 1 year, 2 years, and 3 years post treatment. Biochemical recurrence was defined via the Phoenix criteria, as a rise in PSA levels of 2 ng/mL or more above the post treatment nadir.

RESULTS

A total of 267 patients met the eligibility criteria for this study. In total, 9% of patients were low risk, 51% were intermediate risk, and 40% were high risk. The cumulative incidence of Grade 2 or higher GU toxicity was 27%, and for GI toxicity, it was 2%. At 24 months, 11.5% (20/175) of patients experienced CTCAE grade 2 or higher GU toxicity, and 1.7% (3/175) experienced grade 2 or higher GI toxicity. Biochemical relapse occurred in 1.5% (4/267) of patients, leading to a 2-year biochemical relapse-free survival rate of 98.5%.

CONCLUSION

SBRT for localized prostate cancer has favorable oncological outcomes with a low incidence of Grade 2 or higher toxicity. The results of this study are consistent with findings from prospective trials, suggesting that SBRT is an effective treatment modality. Trial registration Retrospectively registered.

A simple plan strategy to optimize the biological effective dose delivered in robotic radiosurgery of vestibular schwannomas

Using the concept of biologically effective dose (BED), the effect of sublethal DNA damage repair (SLR) on the bio-efficacy of prolonged radiotherapy treatments can be quantified (BEDSLR). Such treatments, lasting more than 20 min, are typically encountered in stereotactic radiosurgery (SRS) applications using the CyberKnife (CK) and Gamma knife systems. Evaluating the plan data from 45 Vestibular Schwannoma (VS) cases treated with single fraction CK-SRS, this work demonstrates a statistically significant correlation between the marginal BEDSLRdelivered to the target (m-BEDSLR) and the ratio of the mean collimator size weighted by the fraction of total beams delivered with each collimator (wmCs), to the tumor volume (Tv). The correlation betweenm-BEDSLRandwmCsTvdatasets was mathematically expressed by the power functionm-BEDSLR=85.21 (±1.7%)⋅(wmCsTv)(0.05±7%) enabling continuousm-BEDSLRpredictions. Using this formula, a specific range ofm-BEDSLRlevels cana prioribe targeted during treatment planning through proper selection of collimator size(s) for a given tumor volume. Inversely, for a selected set of collimators, the optimization range ofm-BEDSLRcan be determined assuming that all beams are delivered with the smallest and largest collimator size. For single collimator cases or when the relative usage of each collimator size is known or estimated, a specificm-BEDSLRlevel can be predicted within 3% uncertainty. The proposed equation is valid for the fixed CK collimators and a physical dose prescription (Dpr) of 13 Gy. For alternateDprin the range of 11-14 Gy, a linear relationship was found between relative changes ofm-BEDSLR(Dpr) andDprwith respect tom-BEDSLR(13 Gy) and 13 Gy, respectively. The proposed methodology is simple and easy to implement in the clinical setting allowing for optimization of the treatment's bio-effectiveness, in terms of the delivered BED, during treatment planning.

Dose Recommendations for Prostrate-specific Membrane Antigen Positron Emission Tomography (PSMA PET) Guided Boost Irradiation to Lymphatic Tissue in Prostate Adenocarcinoma

AIMS

Prostrate-specific membrane antigen positron emission tomography (PSMA-PET) imaging has led to an increase in identifiable small volume metastatic disease in prostate adenocarcinoma. There is clinical equipoise in how to treat these using radiotherapy regimens. The aim of this study is to determine an adequate dosing regimen for small volume lymphatic metastases in prostate adenocarcinoma.

MATERIALS AND METHODS

The authors first estimated the cell count of small volume metastases in prostate adenocarcinoma and then used a Poisson distribution-based estimation of the tumour control probability distribution, the required doses for 95% and 99% probabilities of tumour sterilisation were calculated using the linear quadratic formula.

RESULTS

Lymph node metastases of 3, 5, and 10 mm diameter were estimated to harbour 1.4, 6.5, and 52.3 million clonogens, respectively. When attempting for a 95% tumour control probability, estimated BEDs of 116.5, 127.0, and 141.1Gy were required. This translated to doses of 26.0, 27.3, and 29.0Gy in 5 fraction regimens. When attempting for a 99% tumour control probability, estimated biological effective doses (BEDs) of 127.6, 138.1, and 152.2 Gy were required. This translated to doses of 27.4, 28.6, and 30.2 Gy in 5 fraction regimens.

CONCLUSION

In prostate cancers with small-volume metastatic disease, doses can be adjusted according to tumour size without likely to compromise tumour control. This would have positive implications on radiotherapy planning and possibly lead to decreased risks of toxicity in scenarios where planning difficulty is encountered. Clinical evaluation of efficacy and safety for these dose regimens is warranted.

First-in-Men Online Adaptive Robotic Stereotactic Body Radiation Therapy: Toward Ultrahypofractionation for High-Risk Prostate Cancer Patients

Purpose

Ultrahypofractionation presents challenges for a subset of high-risk prostate cancer patients due to the large planning target volume (PTV) margin required for the seminal vesicles. Online adaptive radiation therapy could potentially reduce this margin. This paper focuses on the development, preclinical validation, and clinical testing of online adaptive robotic stereotactic body radiation therapy for this patient group.

Methods and Materials

An online adaptive workflow was developed for the CyberKnife with integrated in-room CT-on-rails. Preclinical validation involved comparing deep learning-based auto-contouring with deformable or rigid contour propagation in terms of subsequent editing time. A fast treatment planning method was implemented and compared with the conventional method in terms of optimization time and adherence to planning constraints. Clinical testing was conducted in the first study patients of the UPRATE trial, which investigates the feasibility of seminal vesicle PTV margin reduction in low-volume metastasized prostate cancer patients. Treatment time and patient experience were recorded.

Results

Rigid registration for prostate and deep-learning auto-contouring for seminal vesicles and organs at risk were selected based on editing time and robustness for anatomic changes. The fast treatment planning method reduced the optimization time from 10 to 3.5 minutes (P = .005). No significant differences in dose parameters were observed compared with the conventional plans. During clinical testing, 53 of 60 fast treatment plans adhered to the planning constraints, and all 60 were clinically accepted and delivered. The average total treatment time was 67.7 minutes, showing a downward trend. The treatment was well-experienced overall.

Conclusions

Online adaptive stereotactic body radiation therapy using CyberKnife with integrated CT-on-rails is clinically feasible for prostate cancer patients with seminal vesicles included in the target volume. The UPRATE trial outcome will reveal the extent to which online adaptation can reduce the PTV margin of the seminal vesicles.

The Determinants of Toxicity in the Treatment of Prostate Cancer With a Focal, Intraprostatic "Microboost"

PURPOSE

A single-phase 3 trial has demonstrated that prostate radiation therapy with a focal, intraprostatic "microboost" can improve disease control without an overall increase in toxicity. It is unclear how these results generalize to other treatment schedules and protocols.

METHODS AND MATERIALS

A systematic search of PubMed and the Cochrane review was performed for studies published on or before September 1, 2023. A random-effects meta-analysis was used to pool the cumulative incidence of grade ≥2 (≥G2) acute and late genitourinary (GU) and gastrointestinal (GI) toxicity. Heterogeneity was assessed, and the association of trial-level covariates with toxicity was examined via the subgroup analyses and meta-regression. Odds ratios (ORs) for dose metrics were reported per Gy equivalent dose in 2Gy per fraction (EQD2).

RESULTS

Thirty-eight patient cohorts were included. The pooled estimate of the cumulative incidence of ≥G2 acute and late GU toxicity was 25.3% (95% CI, 19.1%-32.8%) and 21.1% (95% CI, 16.7%-26.3%), respectively. Late ≥G2 GI toxicity was less frequent, estimated at 5.6% (95% CI, 3.5%-8.7%) and 6.9% (95% CI, 4.6%-10.1%), respectively. Subgroup factors associated with at least one ≥G2 toxicity category were treatment technique, imaging used for boost volume definition, intrafraction motion management, trial phase, and toxicity grading. Rectal DMax was associated with acute ≥G2 GI toxicity (OR, 1.05; 95% CI, 1.02-1.08; P < .001). Additionally, urethral DMax was associated with late ≥G2 GU toxicity (OR, 1.02; 95% CI, 1.01-1.03; P < .001), and a stronger relationship was observed with the average plan urethral DMax (OR, 1.05; 95% CI, 1.03-1.07; P < .001). No association of toxicity with any bladder dose metric examined was observed.

CONCLUSIONS

The utilization of a microboost seems tolerable across treatment protocols; however, subgroup factors, including the use of intrafraction motion management and the type of imaging modality used, may influence the probability of toxicity. Attention to rectal DMax constraints and urethral DMax dose constraints may help to mitigate GI and GU toxicity, respectively. No association between toxicity and bladder dose constraints was observed.

Prostate motion in magnetic resonance imaging-guided radiotherapy and its impact on margins

PURPOSE

This study focused on reducing the margin for prostate cancer treatment using magnetic resonance imaging-guided radiotherapy by investigating the intrafractional motion of the prostate and different motion-mitigation strategies.

METHODS

We retrospectively analyzed intrafractional prostate motion in 77 patients with low- to intermediate-risk prostate cancer treated with five fractions of 7.25 Gy on a 1.5 T magnetic resonance linear accelerator. Systematic drift motion was observed and described by an intrafractional motion model. The planning target volume (PTV) margin was calculated in a cohort of 77 patients and prospectively evaluated for geometric coverage in a separate cohort of 24 patients.

RESULTS

The intrafractional model showed that the prostate position starts out of equilibrium for the anterior-posterior (-1.8 ± 3.1 mm) and superior-inferior (1.7 ± 2.6 mm) directions, with relaxation times of 12 and 15 min, respectively. Position verification scans are acquired at 30 min on average. At that time, the transient drift motion becomes indistinguishable from the residual random intrafractional motion. PTV margins can be reduced to 1.8 mm (left-right), 3.2 mm (anterior-posterior), and 2.9 mm (superior-inferior). Evaluation of the overlap with the clinical target volume (CTV) was performed for a total of 120 fractions of 24 patients. The overlap range between the CTV and the PTV was 93-100% and the applied 3‑mm PTV margin for the CTV had a 99.5% averaged geometric overlap for all patients.

CONCLUSION

A PTV margin reduction to 3 mm is feasible. A patient-specific approach could reduce the margins further.

Prognostic significance of the mEPE score in intermediate-risk prostate cancer patients undergoing ultrahypofractionated robotic SBRT

PURPOSE

This study aimed to evaluate the prognostic significance of magnetic resonance imaging (MRI) parameters on biochemical failure-free survival (BFS) in patients diagnosed with intermediate-risk prostate cancer and treated with robotic ultrahypofractionated stereotactic body radiotherapy (SBRT) without androgen deprivation therapy (ADT).

METHODS

A retrospective analysis was conducted in patients with intermediate-risk prostate cancer undergoing robotic SBRT delivered in five fractions with a total radiation dose of 35-36.25 Gy. The primary endpoint was biochemical failure as defined by the Phoenix criteria. Among other clinicopathological data, T stage, Prostate Imaging-Reporting and Data System (PI-RADS) score, and multiparametric magnetic resonance imaging-based extra-prostatic extension (mEPE) score were collected and analyzed using the log-rank test.

RESULTS

A total of 74 patients were eligible for analysis. Median age at treatment was 68.8 years and median prostate volume was 47.8 cm3. Fifty-four and 14 patients were diagnosed with Gleason scores 7a and 7b, respectively. In total, 40 patients were classified as having unfavorable intermediate-risk prostate cancer according to American Urological Association/American Society for Radiation Oncology/ Society of Urologic Oncology (AUA/ASTRO/SUO) guidelines. The median follow-up was 30 months (range: 4-91.2 months; interquartile range (IQR): 18.5-48 months). The 3‑year BFS was 92%. A total of 12 (16.2%) biochemical failures were reported. In univariate analysis, an mEPE score of 5, the delivered total radiation dose (35 Gy vs. 36.25 Gy), and a prostate-specific antigen (PSA) nadir >1 ng/ml were associated with lower BFS (mEPE-BFS: p < 0.001, total radiation dose-BFS: p = 0.04, PSA nadir-BFS: p =< 0.001).

CONCLUSION

Patients diagnosed with intermediate-risk prostate cancer with a high mEPE score are more likely to experience biochemical failure after SBRT. Treatment intensification measures, such as administration of concomitant ADT, should be considered.

Neurovascular bundle sparing in hypofractionated radiotherapy maintained with realistic treatment uncertainties

Background and purpose

Erectile dysfunction is a common side effect of radiotherapy for prostate cancer. To mitigate this toxicity, it has been suggested to limit the dose to critical nerves and vessels. We investigated the feasibility of sparing the neuro-vascular bundles (NVBs) in stereotactic body radiotherapy under the impact of realistic treatment uncertainties.

Materials and methods

Non-sparing and sparing NVB treatment plans, delivered in 5 × 7.25 Gy, were automatically generated for 20 patients. Polynomial Chaos Expansion (PCE) was used to fast and accurately model the dose against treatment errors. PCE enabled a robustness evaluation of 100.000 treatment scenarios per plan, allowing to derive scenario distributions of clinically relevant dose volume histogram parameters and population dose histograms.

Results

An average decrease of 3.7 Gy and 4.4 Gy in the medianD 0.1 c m 3 of the NVB was achieved in the patient population in the presence of realistic treatment uncertainties for non-coplanar (NC) and coplanar (C) plans respectively. Sparing NVBs decreased planning target volume coverage by 2.1 % inV 36.25 G y on average, however clinical target volume (CTV) dose remained adequate. Population dose histograms showed that, while sparing does impact dose volume histogram parameters of organs at risk (OARs), the probability of a scenario exceeding planning constraints was limited.

Conclusion

NVB sparing was maintained in the presence of treatment uncertainties without compromising CTV coverage or OAR dose. There was no significant difference in the achieved NVB dose between NC and C plans. The clinical impact of the achieved sparing is subject of ongoing clinical trials.

Full bladder, empty rectum? Revisiting a paradigm in the era of adaptive radiotherapy

BACKGROUND AND PURPOSE

Many patients find it challenging to comply with instructions regarding rectum and bladder filling during pelvic radiotherapy. With the implementation of online adaptive radiotherapy, the reproducibility of organ volumes is no longer a prerequisite. This study aims to analyze the sparing of the bladder and the posterior rectum wall (PRW) in conditions of full versus empty bladder and rectum.

METHODS

280 fractions from 14 patients with prostate cancer who underwent adaptive radiotherapy using the Varian Ethos system were analyzed post-hoc. Various metrics for the bladder and PRW were correlated with respect to organ volume.

RESULTS

Our analysis quantitatively confirms the advantage of a full bladder during radiotherapy, as metrics V48Gy and V40Gy significantly inversely correlate with bladder filling for each patient individually. While bladder volume did not show a gradual decrease over the course of radiotherapy, it was observed to be higher during planning CT scans compared to treatment sessions. A full rectum condition either significantly improved (in 2 out of 7 patients) or at least did not impair (in 5 out of 7 patients) PRW sparing, as represented by the V30Gy metric, when patients were compared individually. The average V30Gy across all patients demonstrated a significant improvement in PRW sparing for the full rectum condition, with a [Formula: see text]-value of 0.039.

CONCLUSION

Despite the implementation of adaptive therapy, maintaining a high bladder filling remains important. However, the recommendation for rectum filling can be abandoned, as reproducibility is not critical for adaptive radiotherapy and no dosimetric advantage per se is associated with an empty rectum. Patients may even be encouraged not to void their bowels shortly before treatment, as long as this is tolerated over the treatment session.

Moderate-Hypofractionated Radical Radiotherapy for Early-Stage Prostate Cancer: A Propensity Score Matching Analysis Comparing Dose Fractionation Patterns

IntroductionThis study evaluates the clinical outcomes, survival benefits, and toxicities of two moderate-hypofractionated radiotherapy (MHRT) patterns, 60 Gy in 20 fractions (60 Gy/20f) and 70 Gy in 28 fractions (70 Gy/28f), in early-stage prostate cancer patients.MethodsThis retrospective study analyzed data from 187 patients diagnosed between 2014 and 2023, using propensity score matching to ensure efficacy assessment accuracy. The primary endpoints reported were overall survival (OS) and disease-free survival (DFS), calculated using Kaplan-Meier analysis. Toxicity and side effects were evaluated using Criteria for Adverse Events v5.0, focusing on the urinary and gastrointestinal (GI) systems.ResultsAfter matching, each of the 60 Gy and 70 Gy groups included 73 patients. The median follow-up duration for all patients was 36.0 months. The OS rates for the 60 Gy and 70 Gy groups were 86.3% and 89.0%, respectively, with 3-year OS rates of 92.4% and 89.0% (P = 0.375). The 3-year DFS rates were 91.0% in the 60 Gy group and 81.0% in the 70 Gy group (P = 0.096), indicating no significant differences between the groups. The incidence of acute Grade 2 or higher urinary toxicities was comparable between the two groups (60 Gy group vs 70 Gy group: 9.6% vs 9.6%, P = 1.0), while the 70 Gy group demonstrated an advantage for late Grade 2 or higher toxicities (60 Gy group vs 70 Gy group: 12.3% vs 2.8%, P = .028). For the GI system, the incidence of acute toxicities was higher in the 60 Gy group, albeit not statistically significant (60 Gy group vs 70 Gy group: 11.0% vs 6.8%, P = .383), while late toxicities were equivalent between the groups (60 Gy group vs 70 Gy group: 1.4% vs 1.4%, P = 1.0).ConclusionBoth MHRT fractionation patterns demonstrate comparable survival outcomes and toxicities in early-stage prostate cancer, suggesting MHRT's viability as a primary treatment. The 60 Gy/20f pattern marginally favored survival, albeit not with statistical significance.

Acute Toxicity and Early Prostate Specific Antigen Response After Two-Fraction Stereotactic Radiation Therapy for Localized Prostate Cancer Using Peri-Rectal Spacing-Initial Report of the SABR-Dual Trial

PURPOSE

SABR-Dual is a phase-III trial with an initial phase-I safety cohort, of 2-fraction stereotactic radiotherapy (SABR) with optional magnetic resonance imaging (MRI)-based focal boost, using peri-rectal spacing, for localized prostate cancer. This represents the initial report from the phase-I non-randomized cohort.

METHODS AND MATERIALS

Subjects had favorable intermediate risk (FIR) or low risk prostate adenocarcinoma, and gland volume <80 cc. All underwent radiopaque hydrogel spacer and fiducial marker placement before simulation (computed tomography and 3-tesla T2 MRI). The clinical target volume included the entire prostate, and in FIR patients, 1-2 cm of seminal vesicle. A 2-mm expansion was applied for planning target volume (PTV), and a dose of 27 Gy was prescribed to the PTV-prostate, 23 Gy to the PTV-seminal vesicle, with an optional 30 Gy simultaneous boost to an MRI-defined dominant lesion. Primary endpoint was 3-month patient-reported changes in quality of life based on the Expanded Prostate Cancer Index Composite-26, International Prostate Symptom Score, and Sexual Health Inventory for Men questionnaires. Secondary endpoints were 6-month quality of life, acute toxicity (using Common Terminology Criteria for Adverse Events version 5.0) and early Prostate specific antigen (PSA) response.

RESULTS

Among the 20 patients in the phase-I cohort, 95% had FIR disease, and 50% received a simultaneous boost. At median follow-up of 8 months, a 3-month minimally clinically important change occurred in 1/20 (5%), 6/20 (30%), 2/20 (10%), 4/20 (20%), and 5/20 (25%) in urinary incontinence, urinary obstructive, bowel, sexual, and hormonal domains. There was a mean increase of 1 ± 5.4 in International Prostate Symptom Score and decrease of 1.8 ± 6.5 in Sexual Health Inventory for Men scores. Rates of grade 2 urinary and bowel toxicity were 10% and 0%, respectively, with no grade ≥3 toxicities. Mean PSA decrease at last follow-up was 70.4% ± 17.7%.

CONCLUSION

This generalizable protocol of 2-fraction prostate SABR using peri-rectal spacing is a safe approach for ultra-hypofractionated dose-escalation, with minimal acute toxicity. Longer-term outcomes and direct comparison with standard 5-fraction SABR are being studied in the phase-III randomized portion of SABR-Dual.

Ablative Radiation Therapy for Unfavorable Prostate Tumors (ABRUPT): Preliminary Analysis of Toxicity and Quality of Life from a Prospective Study

PURPOSE

To assess late gastrointestinal (GI) and genitourinary (GU) side effects in patients with organ-confined unfavorable prostate cancer (PCa) treated with single-dose ablative radiation therapy (SDRT).

METHODS AND MATERIALS

Thirty patients enrolled in a single-arm prospective trial received 24 Gy SDRT to the whole prostate with urethra-sparing and organ motion control delivered on a Linac platform with a 10 MV flattening filter-free single partial arc. Androgen deprivation therapy was prescribed as per standard of care. Treatment-related acute and late GU and GI toxicities (Common Terminology Criteria for Adverse Events_v5 scale) and quality of life (QoL) outcomes (European Organisation for Research and Treatment of Cancer [EORTC] QLQ-PR25/C30, International Prostate Symptom Score [IPSS]) were assessed at different time points. Minimal important difference (MID) was established as a change of >0.5 pooled standard deviations from baseline. Statistical analysis included analysis of variance and logistic regression.

RESULTS

Median follow-up was 18 months (range, 6-31 months), with no ≥G3 late side effects observed. G2 late GI and G2 late GU toxicities occurred in 1 and 2 patients, respectively. GI toxicity of any grade correlated with maximum rectal dose (P = .021). Lower baseline QoL score (P = .025), higher baseline IPSS score (P = .049), acute GU toxicity (P = .029), and acute urinary domain MID (P = .045) predicted GU toxicity of any grade. In multivariate analysis (MVA), only baseline QoL score (odds ratio [OR], 0.95, P = .031) and acute GU toxicity (OR, 8.4, P = .041) remained significant. Significant QoL change was observed only in the urinary domain (P = .005), with a median increase from 8 to 17. Late urinary MID correlated with acute urinary MID (P = .003), acute QoL MID (P = .029), acute GU toxicity (P = .030), and lower baseline urinary score (P = .033). In MVA, only acute urinary MID predicted late urinary MID (OR, 9.7, P = .035).

CONCLUSIONS

Our findings provide promising data on the feasibility and safety of 24 Gy whole-gland SDRT with urethra-sparing and organ motion control, in association with androgen deprivation therapy and an adequate prophylactic medication, in organ-confined unfavorable PCa. Long-term follow-up is needed to confirm these results.

Stereotactic Body Radiation Adoption Impacts Prostate Cancer Treatment Patterns

OBJECTIVE

To investigate stereotactic body radiation (SBRT) adoption for prostate cancer. As evidence supporting SBRT mounts, its utilization and impact relative to other prostate cancer treatments is unknown.

METHODS

We used SEER-Medicare to identify patients diagnosed with localized prostate cancer from 2008 to 2017. We then identified physician networks by identifying the primary treating physician of each patient based on primary treatment, then linking each physician to a practice. We examined trends in prostate cancer treatment between networks performing SBRT or not using chi-squared tests and logistic regression models.

RESULTS

There were 35,972 patients who received treatment for prostate cancer at 234 physician networks. Of these patients, 30,635 were treated in a non-SBRT network (n = 190), while 5337 received treatment in a SBRT network (n = 44). Patients who received care in an SBRT network were more likely to live in metropolitan areas ≥1 million (70% vs 46%, P <.001), have a higher median income >$60,000 (62% vs 42%, P <.001), and live in the northeast (35% vs 12%) or west (40% vs 38%, P <.001) compared to non-SBRT networks. In SBRT networks, more patients received IMRT (31% vs 23%), and fewer patients received prostatectomy (16% vs 23%) or active surveillance (15% vs 19%) compared to non-SBRT networks. Black men were 45% less likely to receive SBRT (OR=0.55, CI: 0.36-0.85) compared to White men.

CONCLUSION

SBRT utilization is increasing relative to other prostate cancer treatments. Prostate cancer treatment mix is different in networks that offer SBRT, and SBRT is less available to some patient groups, raising concern for novel treatment inequity.

Radical Prostatectomy Versus Stereotactic Radiotherapy for Clinically Localised Prostate Cancer: Results of the PACE-A Randomised Trial

BACKGROUND AND OBJECTIVE

Randomised data on patient-reported outcomes (PROs) for stereotactic body radiotherapy (SBRT) and prostatectomy in localised prostate cancer are lacking. PACE-A compared patient-reported health-related quality of life after SBRT with that after prostatectomy.

METHODS

PACE is a phase 3 open-label, randomised controlled trial. PACE-A randomised men with low- to intermediate-risk localised prostate cancer to SBRT or prostatectomy (1:1). Androgen deprivation therapy (ADT) was not permitted. The coprimary outcomes were the Expanded Prostate Index Composite (EPIC-26) number of absorbent urinary pads required daily and bowel domain score at 2 yr. The secondary endpoints were clinician-reported toxicity, sexual functioning, and other PROs.

KEY FINDINGS AND LIMITATIONS

In total, 123 men were randomised (60 undergoing prostatectomy and 63 SBRT) from August 2012 to February 2022. The median follow-up time was 60.7 mo. The median age was 65.5 yr and the median prostate-specific antigen (PSA) value 7.9 ng/ml; 92% had National Comprehensive Cancer Network (NCCN) intermediate-risk disease. Fifty participants received prostatectomy and 60 received SBRT. At 2 yr, 16/32 (50%) prostatectomy and three of 46 (6.5%) SBRT participants used one or more urinary pads daily (p < 0.001; 15 and two, respectively, used one pad daily); the estimated difference was 43% (95% confidence interval [CI]: 25%, 62%). At 2 yr, bowel scores were better for prostatectomy (median [interquartile range] 100 [100-100]) than for SBRT (87.5 [79.2-100]; p < 0.001), with an estimated mean difference of 8.9 between these (95% CI: 4.2, 13.7); sexual scores were worse for prostatectomy (18 [13.8-40.3]) than for SBRT (62.5 [32.0-87.5]). The limitations were slow recruitment and incomplete 2-yr PRO response rates.

CONCLUSIONS AND CLINICAL IMPLICATIONS

SBRT was associated with less patient-reported urinary incontinence and sexual dysfunction, and slightly more bowel bother than prostatectomy. These randomised data should inform treatment decision-making for patients with localised, intermediate-risk prostate cancer.

Current State of Stereotactic Body Radiation Therapy for Genitourinary Malignancies

ABSTRACT

Stereotactic body radiation therapy (SBRT) involves the delivery of high-dose, highly precise radiation therapy to focal sites of gross tumor involvement. Recent advances in radiation planning and image guidance have facilitated rapid growth in the evidence for and use of SBRT, particularly for genitourinary malignancies, where the underlying radiobiology often suggests greater tumor sensitivity to SBRT than to conventionally fractionated radiation. Here, we review the evolution of SBRT for patients with prostate adenocarcinoma and renal cell carcinoma. We discuss state-of-the-art trials, indications, and future directions in the SBRT-based management of both localized and metastatic disease. With rapidly growing enthusiasm and evidence, clinical and translational research efforts on the biology and outcomes of SBRT over the coming decade will be crucial to refining the indications, technical approach, and synergistic combinations of SBRT with highly active systemic therapies and improve the efficacy and quality-of-life outcomes for patients with genitourinary malignancies.

Japanese clinical practice guidelines for prostate cancer 2023

This fourth edition of the Japanese Clinical Practice Guidelines for Prostate Cancer 2023 is compiled. It was revised under the leadership of the Japanese Urological Association, with members selected from multiple academic societies and related organizations (Japan Radiological Society, Japanese Society for Radiation Oncology, the Department of EBM and guidelines, Japan Council for Quality Health Care (Minds), Japanese Society of Pathology, and the patient group (NPO Prostate Cancer Patients Association)), in accordance with the Minds Manual for Guideline Development (2020 ver. 3.0). The most important feature of this revision is the adoption of systematic reviews (SRs) in determining recommendations for 14 clinical questions (CQs). Qualitative SRs for these questions were conducted, and the final recommendations were made based on the results through the votes of 24 members of the guideline development group. Five algorithms based on these results were also created. Contents not covered by the SRs, which are considered textbook material, have been described in the general statement. In the general statement, a literature search for 14 areas was conducted; then, based on the general statement and CQs of the Japanese Clinical Practice Guidelines for Prostate Cancer 2016, the findings revealed after the 2016 guidelines were mainly described. This article provides an overview of these guidelines.

The impact of rectal spacers in MR-guided adaptive radiotherapy

Background and purpose

The use of stereotactic ablative radiotherapy (SABR) for prostate cancer has increased significantly. However, SABR can elevate the risk of moderate gastrointestinal (GI) side effects. Rectal spacers mitigate this risk by reducing the rectal dose. This study evaluates the impact of rectal spacers in MR-guided adaptive radiotherapy (MRgART) for prostate SABR.

Materials and methods

A retrospective analysis was conducted on twenty patients with localised prostate cancer treated on the Unity MR-Linac at a single centre. Half of the cohort (n = 10) had rectal spacers placed before treatment. The adapt-to-shape strategy was used for online MRgART, and non-adapted plans were later generated offline for comparison. Dosimetric assessments were made between spacer and no-spacer cohorts, and between online adapted and non-adapted plans. Clinician-reported outcomes for genitourinary (GU) and GI toxicity were assessed at 3-, 6-, and 12-months post-treatment using Common Terminology Criteria for Adverse Events v.5.0.

Results

No grade 2 or higher toxicity was observed in either cohort. Overall, the dosimetric analysis showed comparable results between the cohorts for target volumes, with D95% of 36.3 Gy in the spacer cohort and 36.0 Gy in the no-spacer cohort (p = 0.08). The spacer cohort demonstrated significant benefits in all rectal dose objectives (p < 0.0001) and in some bladder objectives (V40, p = 0.03; V36, p = 0.03). Failure rates for achieving planning objectives were similar between spacer and no-spacer groups for online adapted plans, with most rates ranging from 0 % to 4 % in both groups.

Conclusion

The findings from this cohort suggest that MRgART is safe and effective for prostate SABR, with comparable toxicity rates in both spacer and no-spacer cohorts. While rectal spacers offer dosimetric advantages, the adaptive nature of MRgART can mitigate some dosimetric disparities, potentially reducing the need for invasive spacer placement. However, further studies with larger patient populations are needed to confirm these results.

Adapting outside the box: Simulation-free MR-guided stereotactic ablative radiotherapy for prostate cancer

BACKGROUND AND PURPOSE

Magnetic resonance (MR)-guided radiotherapy (MRgRT) enhances treatment precision and adaptive capabilities, potentially supporting a simulation-free (sim-free) workflow. This work reports the first clinical implementation of a sim-free workflow using the MR-Linac for prostate cancer patients treated with stereotactic ablative radiotherapy (SABR).

MATERIALS AND METHODS

Fifteen patients who had undergone a prostate-specific membrane antigen positron emission tomography/CT (PSMA-PET/CT) scan as part of diagnostic workup were included in this work. Two reference plans were generated per patient: one using PSMA-PET/CT (sim-free plan) and the other using standard simulation CT (simCT plan). Dosimetric evaluations included comparisons between simCT, sim-free, and first fraction plans. Timing measurements were conducted to assess durations for both simCT and sim-free pre-treatment workflows.

RESULTS

All 15 patients underwent successful treatment using a sim-free workflow. Dosimetric differences between simCT, sim-free, and first fraction plans were minor and within acceptable clinical limits, with no major violations of standardised criteria. The sim-free workflow took on average 130 min, while the simCT workflow took 103 min.

CONCLUSION

This work demonstrates the feasibility and benefits of sim-free MR-guided adaptive radiotherapy for prostate SABR, representing the first reported clinical experience in an ablative setting. By eliminating traditional simulation scans, this approach reduces patient burden by minimising hospital visits and enhances treatment accessibility.

Physician reported toxicities and patient reported quality of life of transperineal ultrasound-guided radiotherapy of prostate cancer

Purpose

This study aims to address therapy-related toxicities and quality of life in prostate cancer patients undergoing transperineal ultrasound (TPUS) guided radiotherapy (RT).

Methods

Acute and late gastrointestinal (GI) and genitourinary (GU) toxicities were assessed by physicians using CTCAE v5.0. Patient-reported quality of life outcomes were evaluated using EORTC QLQ-C30, -PR25 and IPSS. We utilized Volumetric Modulated Arc Therapy (VMAT) or intensity modulated radiation therapy (IMRT) as the RT technique for this study. The assessments were carried out before RT, at RT end, 3 months after RT and subsequently at 1-year intervals. Prostate-specific antigen (PSA) was also evaluated at each follow-up.

Results

In this study, a total of 164 patients were enrolled, while among them, 112 patients delivered quality-of-life data in a prospective evaluation. The median pre-treatment PSA was 7.9 ng/mL (range: 1.8-169 ng/ml). At the median follow-up of 19 months (3-82 months), the median PSA decreased to 0.22 ng/ml. Acute grade II GI and GU toxicities occurred in 8.6 % and 21.5 % patients at RT end. Regarding late toxicities, 2.2 % patients experienced grade II GI toxicities at 27 months and only one patient at 51 months, whereas no grade II GU late toxicities were reported at these time points. Quality of life scores also indicated a well-tolerated treatment. Patients mainly experienced acute clinically relevant symptoms of fatigue, pain, as well as deterioration in bowel and urinary symptoms. However, most symptoms normalized at 3 months and remained stable thereafter. Overall functioning showed a similar decline at RT end but improved over time.

Conclusion

The outcomes of TPUS-guided RT demonstrated promising results in terms of minimal physician-reported toxicities and satisfactory patient-reported QoL.

French AFU Cancer Committee Guidelines - Update 2024-2026: Prostate cancer - Diagnosis and management of localised disease

OBJECTIVE

The aim of the Oncology Committee of the French Urology Association is to propose updated recommendations for the diagnosis and management of localized prostate cancer (PCa).

METHODS

A systematic review of the literature from 2022 to 2024 was conducted by the CCAFU on the elements of diagnosis and therapeutic management of localized PCa, evaluating references with their level of evidence.

RESULTS

The recommendations set out the genetics, epidemiology and diagnostic methods of PCa, as well as the concepts of screening and early detection. MRI, the reference imaging test for localized cancer, is recommended before prostate biopsies are performed. Molecular imaging is an option for disease staging. Performing biopsies via the transperineal route reduces the risk of infection. Active surveillance is the standard treatment for tumours with a low risk of progression. Therapeutic methods are described in detail, and recommended according to the clinical situation.

CONCLUSION

This update of French recommendations should help to improve the management of localized PCa.

Enhancing Delivery Efficiency on the Magnetic Resonance-Linac: A Comprehensive Evaluation of Prostate Stereotactic Body Radiation Therapy Using Volumetric Modulated Arc Therapy

PURPOSE

Long treatment sessions are a limitation within magnetic resonance imaging guided adaptive radiation therapy (MRIgART). This work aims for significantly enhancing the delivery efficiency on the magnetic resonance linear accelerator (MR-linac) by introducing dedicated optimization and delivery techniques for volumetric modulated arc therapy (VMAT). VMAT plan and delivery quality during MRIgART is compared with step-and-shoot intensity-modulated radiation therapy (IMRT) for prostate stereotactic body radiation therapy.

METHODS AND MATERIALS

Ten patients with prostate cancer previously treated on a 1.5T MR-linac were retrospectively replanned to 36.25 Gy in 5 fractions using step-and-shoot IMRT and the clinical Hyperion optimizer within Monaco (Hyp-IMRT), the same optimizer with a VMAT technique (Hyp-VMAT), and a research-based optimizer called optimal fluence levels and pseudo gradient descent with VMAT (OFL+PGD-VMAT). The plans were then adapted onto each daily magnetic resonance imaging data set using 2 different optimization strategies to evaluate the adapt-to-position workflow: "optimize weights" (IMRT-Weights and VMAT-Weights) and "optimize shapes" (IMRT-Shapes and VMAT-Shapes). Treatment efficiency was evaluated by measuring optimization time, delivery time, and total time (optimization+delivery). Plan quality was assessed by evaluating organ at risk sparing. Ten patient plans were measured using a modified linac control system to assess delivery accuracy via a gamma analysis (2%/2 mm). Delivery efficiency was calculated as average dose rate divided by maximum dose rate.

RESULTS

For Hyp-VMAT and OFL+PGD-VMAT, the total time was reduced by 124 ± 140 seconds (P = .020) and 459 ± 110 seconds (P < .001), respectively, as compared with the clinical Hyp-IMRT group. Speed enhancements were also measured for adapt-to-position with reductions in total time of 404 ± 55 (P < .001) for VMAT-Weights as compared with the clinical IMRT-Shapes group. Bladder and rectum dosimetric volume histogram (DVH) points were within 1.3% or 0.8 cc for each group. All VMAT plans had gamma passing rates greater than 96%. The delivery efficiency of VMAT plans was 89.7 ± 2.7 % compared with 50.0 ± 2.2 % for clinical IMRT.

CONCLUSIONS

Incorporating VMAT into MRIgART will significantly reduce treatment session times while maintaining equivalent plan quality.

Phase 3 Trial of Stereotactic Body Radiotherapy in Localized Prostate Cancer

BACKGROUND

Whether stereotactic body radiotherapy (SBRT) is noninferior to conventionally or moderately hypofractionated regimens with respect to biochemical or clinical failure in patients with localized prostate cancer is unclear.

METHODS

We conducted a phase 3, international, open-label, randomized, controlled trial. Men with stage T1 or T2 prostate cancer, a Gleason score of 3+4 or less, and a prostate-specific antigen (PSA) level of no more than 20 ng per milliliter were randomly assigned (in a 1:1 ratio) to receive SBRT (36.25 Gy in 5 fractions over a period of 1 or 2 weeks) or control radiotherapy (78 Gy in 39 fractions over a period of 7.5 weeks or 62 Gy in 20 fractions over a period of 4 weeks). Androgen-deprivation therapy was not permitted. The primary end point was freedom from biochemical or clinical failure, with a critical hazard ratio for noninferiority of 1.45. The analysis was performed in the intention-to-treat population.

RESULTS

A total of 874 patients underwent randomization at 38 centers (433 patients in the SBRT group and 441 in the control radiotherapy group) between August 2012 and January 2018. The median age of the patients was 69.8 years, and the median PSA level was 8.0 ng per milliliter; the National Comprehensive Cancer Network risk category was low for 8.4% of the patients and intermediate for 91.6%. At a median follow-up of 74.0 months, the 5-year incidence of freedom from biochemical or clinical failure was 95.8% (95% confidence interval [CI], 93.3 to 97.4) in the SBRT group and 94.6% (95% CI, 91.9 to 96.4) in the control radiotherapy group (unadjusted hazard ratio for biochemical or clinical failure, 0.73; 90% CI, 0.48 to 1.12; P = 0.004 for noninferiority), which indicated the noninferiority of SBRT. At 5 years, the cumulative incidence of late Radiation Therapy Oncology Group (RTOG) grade 2 or higher genitourinary toxic effects was 26.9% (95% CI, 22.8 to 31.5) with SBRT and 18.3% (95% CI, 14.8 to 22.5) with control radiotherapy (P<0.001), and the cumulative incidence of late RTOG grade 2 or higher gastrointestinal toxic effects was 10.7% (95% CI, 8.1 to 14.2) and 10.2% (95% CI, 7.7 to 13.5), respectively (P = 0.94).

CONCLUSIONS

Five-fraction SBRT was noninferior to control radiotherapy with respect to biochemical or clinical failure and may be an efficacious treatment option for patients with low-to-intermediate-risk localized prostate cancer as defined in this trial. (Funded by Accuray and others; PACE-B ClinicalTrials.gov number, NCT01584258.).

Sustainability in radiation oncology: opportunities for enhancing patient care and reducing CO2 emissions in breast cancer radiotherapy at selected German centers

BACKGROUND AND OBJECTIVE

Radiotherapy often entails a substantial travel burden for patients accessing radiation oncology centers. The total travel distance for such treatments is primarily influenced by two factors: fractionation schedules and the distances traveled. Specific data on these aspects are not well documented in Germany. This study aims to quantify the travel distances for routine breast cancer patients of five radiation oncology centers located in metropolitan, urban, and rural areas of Germany and to record the CO2 emissions resulting from travel.

METHODS

We analyzed the geographic data of breast cancer patients attending their radiotherapy treatments and calculated travelling distances using Google Maps. Carbon dioxide emissions were estimated assuming a standard 40-miles-per-gallon petrol car emitting 0.168 kg of CO2 per kilometer.

RESULT

Addresses of 4198 breast cancer patients treated between 2018 and 2022 were analyzed. Our sample traveled an average of 37.2 km (minimum average: 14.2 km, maximum average: 58.3 km) for each radiation fraction. This yielded an estimated total of 6.2 kg of CO2 emissions per visit, resulting in 156.2 kg of CO2 emissions when assuming 25 visits (planning, treatment, and follow-up).

CONCLUSION

Our study highlights the environmental consequences associated with patient commutes for external-beam radiotherapy, indicating that reducing the number of treatment fractions can notably decrease CO2 emissions. Despite certain assumptions such as the mode of transport and possible inaccuracies in patient addresses, optimizing fractionation schedules not only reduces travel requirements but also achieves greater CO2 reductions while keeping improved patient outcomes as the main focus.

Acute toxicity patterns and their management after moderate and ultra- hypofractionated radiotherapy for prostate cancer: A prospective cohort study

Objective

Hypofractionation has become the new clinical standard for prostate cancer. We investigated the management of acute toxicity in patients treated with moderate hypofractionation (MHF) or Ultrahypofractionation (UHF).

Methods

In a prospective cohort setting, patients (N=316) received either MHF (20 fractions of 3/3.1 Gy, 5 fractions per week, N=156) or UHF (7 fractions of 6.1 Gy, 3 fractions per week, N=160) to the prostate +/- (base of the) seminal vesicles between 2019 and 2023. UHF was not indicated in case of significant lower urinary tract symptoms (LUTS) or T3b disease. Patient-reported outcomes (PRO) were online distributed at baseline, end of treatment (aiming at last fraction +/- 3 days), 3 months. Acute toxicity rates, management, and associations with baseline factors were analysed using Chi-square test and logistic regression. CTCAE scores (version 5) were calculated.

Results

Treatment for acute urinary complaints was prescribed in 46 % (MHF) and 29 % (UHF). Taking into consideration baseline LUTS, MHF and UHF showed similar rates of PROs and management. Medication for acute gastrointestinal (GI) symptoms was prescribed for 21.1 % (MHF) and 14.1 % (UHF) with more loperamide for diarrhea in MHF (9.0 %) vs UHF (1.9 %, p = 0.005). Grade ≥ 2 (MHF / UHF) was scored in 40 % / 28 % for GI (p = 0.03) and 50 % / 31 % for GU (p < 0.01). PROs for GI reported after last fraction of UHF were significantly worse compared to before last fraction.

Conclusion

UHF was safe with respect to acute toxicity risks in the selected population. MHF is associated with risks of significant diarrhea which needs further investigation. Furthermore, optimal registration of acute toxicity for UHF requires measurements up to 1-2 weeks after the last fraction.

The Proteogenomics of Prostate Cancer Radioresistance

Prostate cancer is frequently treated with radiotherapy. Unfortunately, aggressive radioresistant relapses can arise, and the molecular underpinnings of radioresistance are unknown. Modern clinical radiotherapy is evolving to deliver higher doses of radiation in fewer fractions (hypofractionation). We therefore analyzed genomic, transcriptomic, and proteomic data to characterize prostate cancer radioresistance in cells treated with both conventionally fractionated and hypofractionated radiotherapy. Independent of fractionation schedule, resistance to radiotherapy involved massive genomic instability and abrogation of DNA mismatch repair. Specific prostate cancer driver genes were modulated at the RNA and protein levels, with distinct protein subcellular responses to radiotherapy. Conventional fractionation led to a far more aggressive biomolecular response than hypofractionation. Testing preclinical candidates identified in cell lines, we revealed POLQ (DNA Polymerase Theta) as a radiosensitizer. POLQ-modulated radioresistance in model systems and was predictive of it in large patient cohorts. The molecular response to radiation is highly multimodal and sheds light on prostate cancer lethality.

SIGNIFICANCE

Radiation is standard of care in prostate cancer. Yet, we have little understanding of its failure. We demonstrate a new paradigm that radioresistance is fractionation specific and identified POLQ as a radioresistance modulator.

Simultaneous Focal Boost With Stereotactic Radiation Therapy for Localized Intermediate- to High-Risk Prostate Cancer: Primary Outcomes of the SPARC Phase 2 Trial

PURPOSE

Dose-escalated radiation therapy is associated with better biochemical control at the expense of toxicity. Stereotactic body radiation therapy (SBRT) with dose escalation to the dominant intraprostatic lesion (DIL) provides a logical approach to improve outcomes in high-risk disease while limiting toxicity. This study evaluated the toxicity and quality of life (QoL) with CyberKnife-based SBRT and simultaneous integrated boost in localized prostate cancer.

METHODS AND MATERIALS

Eligible participants included newly diagnosed, biopsy-proven unfavorable intermediate- to high-risk localized prostate cancer (at least 1 of the following: Gleason ≥4+3, magnetic resonance imaging(MRI)-defined T3a N0, prostate-specific antigen ≥20) with up to 2 MRI-identified DILs. Participants received 36.25 Gy in 5 fractions on alternative days with a simultaneous boost to DIL up to 47.5 Gy as allowed by organ-at-risk constraints delivered by CyberKnife. All participants received androgen deprivation therapy. The primary outcome measure was acute grade 2+ genitourinary toxicity. Acute and late genitourinary and gastrointestinal toxicity using Radiation Therapy Oncology Group scoring, biochemical parameters, International Prostate Symptom Score, International Index of Erectile Function 5, and EQ-5D QoL outcomes were assessed.

RESULTS

Between 2013 and 2023, 20 participants were enrolled with a median follow-up of 30 months. The median D95 dose to DIL was 47.43 Gy. Cumulative acute grade 2+ genitourinary and gastrointestinal toxicity were 25% and 30%, respectively. One patient developed acute grade 3 genitourinary toxicity (5%). There is no late grade 3 genitourinary or gastrointestinal toxicity to date. International Prostate Symptom Score and urinary QoL scores recovered to baseline by 6 months. Patient-reported outcomes showed no significant change in EQ-5D QoL scores at 12 weeks and 1 year. There are no cases of biochemical relapse reported to date.

CONCLUSIONS

CyberKnife SBRT-delivered dose of 36.25 Gy to the prostate with a simultaneous integrated boost up to 47.5 Gy is well tolerated. Acute and late genitourinary and gastrointestinal toxicity rates are comparable to other contemporary SBRT trials and series with focal boost.

Hypofractionated Radiation Therapy: A Cross-sectional Survey Study of US Radiation Oncologists

OBJECTIVES

For many malignancies, hypofractionated radiotherapy (HFRT) is an accepted standard associated with decreased treatment time and costs. United States provider beliefs regarding HFRT likely impact its adoption but are poorly studied. We surveyed US-based radiation oncologists (ROs) to gauge HFRT utilization rates for prostate (PC), breast (BC), and rectal cancer (RC) and to characterize the beliefs governing these decisions.

METHODS

From July to October 2021, an anonymized, online survey was electronically distributed to ROs actively practicing in the United States. Demographic and practice characteristic information was collected. Questions assessing rates of offering HFRT for PC, BC, and RC and perceived limitations towards using HFRT were administered.

RESULTS

A total of 203 eligible respondents (72% male, 72% White, 53% nonacademic practice, 69% with 11+ years in practice) were identified. Approximately 50% offered stereotactic body radiation therapy (SBRT) for early/favorable intermediate risk PC. Although >90% of ROs offered whole-breast HFRT for early-stage BC, only 33% offered accelerated partial-breast irradiation (APBI). Overall, 41% of ROs offered short-course neoadjuvant RT for RC. The primary reported barriers to HFRT utilization were lack of data, inexperience, and referring provider concerns.

CONCLUSIONS

HFRT is safe, effective, and beneficial, yet underutilized-particularly prostate SBRT, APBI, and short-course RT for RC. Skills retraining and education of ROs and referring providers may increase utilization rates.

Risk factors for the long-term persistent genitourinary toxicity after stereotactic body radiation therapy for localized prostate cancer: A single-center, retrospective study of 306 patients

OBJECTIVES

To identify risk factors for the long-term persistent genitourinary toxicity (GUT) after stereotactic body radiation therapy (SBRT) for localized prostate cancer (PCa).

METHODS

A total of 306 patients who underwent SBRT at our institution between March 2017 and April 2022 were retrospectively evaluated. SBRT was performed at 35 Gy in five fractions over 5 or 10 days. Factors related to the long-term persistence of acute GUT after SBRT were analyzed.

RESULTS

During the median follow-up period of 39.1 months, 203 (66%) patients experienced any grade of acute GUT, which remained in 78 (26%) patients 6 months after SBRT. Multivariate analysis revealed that age ≥75 years was consistently a significant independent risk factor for any grade of acute GUT 6, 12, and 24 months after SBRT (hazard ratio [HR] 2.31, p = 0.010; HR 2.84, p = 0001; and HR 3.05, p = 0.009, respectively). Older age was not a significant risk factor for the development of grade ≥2 acute GUT. The duration of acute GUT was significantly longer in the older group than in the nonolder group (median duration = 234 vs. 61 days, p < 0.001), and the incidence of persistent GUT was significantly more frequent in the older group beyond 6 months after SBRT.

CONCLUSIONS

Older age is a significant independent risk factor for the long-term persistent GUT after SBRT for localized PCa.

Clinical implementation of real time motion management for prostate SBRT: A radiation therapist's perspective

Background and purpose

The adoption of hypo-fractionated stereotactic body radiotherapy (SBRT) for treating prostate cancer has led to an increase in specialised techniques for monitoring prostate motion. The aim of this study was to comprehensively review a radiation therapist (RTT) led treatment process in which two such systems were utilised, and present initial findings on their use within a SBRT prostate clinical trial.

Materials and Methods

18 patients were investigated, nine were fitted with the Micropos RayPilotTM (RP) system (Micropos Medical, Gothenburg, SE) and nine were fitted with the Micropos Raypilot Hypocath TM (HC) system. 36.25 Gray (Gy) was delivered in 5 fractions over 7 days with daily pre- and post-treatment cone beam computed tomography (CBCT) images acquired. Acute toxicity was reported on completion of treatment at six- and 12-weeks post-treatment, using the Radiation Therapy Oncology Group (RTOG) grading system and vertical (Vrt), longitudinal (Lng) and lateral (Lat) transmitter displacements recorded.

Results

A significant difference was found in the Lat displacement between devices (P=0.003). A more consistent bladder volume was reported in the HC group (68.03 cc to 483.7 cc RP, 196.11 cc to 313.85 cc HC). No significant difference was observed in mean dose to the bladder, rectum and bladder dose maximum between the groups. Comparison of the rectal dose maximum between the groups reported a significant result (P=0.09). Comparing displacements with toxicity endpoints identified two significant correlations: Grade 2 Genitourinary (GU) at 6 weeks, P=0.029; and no toxicity, Gastrointestinal (GI) at 12 weeks P=0.013.

Conclusion

Both the directly implanted RP device and the urinary catheter-based HC device are capable of real time motion monitoring. Here, the HC system was advantageous in the SBRT prostate workflow.

Stereotactic Magnetic Resonance-Guided Daily Adaptive Radiation Therapy for Localized Prostate Cancer: Acute and Late Patient-Reported Toxicity Outcomes

Purpose

To report acute and late bowel, urinary, and sexual dysfunction patient-reported outcome measures, among patients with localized prostate cancer who underwent stereotactic magnetic resonance-guided daily adaptive radiation therapy (SMART).

Methods and Materials

All patients who completed a baseline 12-item Patient-Reported Outcomes Version of the Common Terminology Criteria for Adverse Events questionnaire, before undergoing SMART with 36.25 Gy in 5 fractions, were subsequently followed up with the same graded questionnaire at set time points. Latest prostate-specific antigen levels were recorded. The percentage of patients who reported no change from their baseline adverse event (AE) or reported a new ≥ "frequent or almost constant" or "severe grade or higher" AE grade during follow-up was calculated. The maximum 12-item Patient-Reported Outcomes Version of the Common Terminology Criteria for Adverse Events grade for each item was recorded for each patient. The percentage of toxicity levels for each separate AE item at set time points was calculated.

Results

The total number of patients was 69 with a median follow-up of 27 months. Median age of the cohort was 73 years (range, 54-85 years). The median pretreatment prostate-specific antigen level, T stage, and Gleason score were 7.5 mmol/L (range, 4.5-32 mmol/L), T2b (range, T2-T3b), and 7 (3 + 4; range, 6-9), respectively. No patient had biochemical failure during follow-up. Regarding bowel symptoms, >80% of men reported no change from baseline toxicity during follow-up. New ≥ frequent or almost constant diarrhea was reported in 9% of patients. "Almost constant" diarrhea peaked at 1 month but was absent at >33 months. Regarding urinary symptoms, increased urinary urgency was the most common complaint (39%). Twenty percent of men reported new ≥ frequent or almost constant urinary urgency incidence peaking at 1 month but absent at >33 months. New "severe" sexual dysfunction was seen in 26% of patients and was persistent at >33 months.

Conclusions

Our study is one the largest patient-reported outcomes study after prostate SMART. It shows acceptable levels of toxicity even up to 2 years after treatment.