Radiotherapy For Prostate Cancer Research Articles

Utilization of machine learning methods for prediction of acute and late rectal toxicity due to curative prostate radiotherapy.

Rectal toxicity is one of the primary dose-limiting side effects of prostate cancer radiotherapy, and consequential impairment on quality of life in these patients with long survival is an important problem. In this study, we aimed to evaluate the possibility of predicting rectal toxicity with artificial intelligence model which was including certain dosimetric parameters. One hundred and thirty-seven patients with a diagnosis of prostate cancer who received curative radiotherapy for prostate +/- pelvic lymphatics were included in the study. The association of the clinical data and dosimetric data between early and late rectal toxicity reported during follow-up was evaluated. The sample size was increased to 274 patients by synthetic data generation method. To determine suitable models, 15 models were studied with machine learning algorithms using Python 2.3, Pycaret library. Random forest classifier was used with to detect active variables. The area under the curve and accuracy were found to be 0.89-0.97 and 95%-99%, respectively, with machine learning algorithms. The sensitivity values for acute and toxicity were found to be 0.95 and 0.99, respectively. Early or late rectal toxicity can be predicted with a high probability via dosimetric and physical data and machine learning algorithms of patients who underwent prostate +/- pelvic radiotherapy. The fact that rectal toxicity can be predicted before treatment, which may result in limiting the dose and duration of treatment, makes us think that artificial intelligence can enter our daily practice in a short time in this sense.

Poor prognosis among radiation associated bladder cancer is defined by clinicogenomic features.

Radiation therapy (RT) for prostate cancer has been associated with an increased risk for the development of bladder cancer. We aimed to integrate clinical and genomic data to better understand the development of RT-associated bladder cancer. A retrospective analysis was performed to identify control (CTRL; n= 41) and RT-associated (n=41) bladder cancer patients. RT and CTRL specific features were then identified through integration and analysis of the genomic sequencing data and clinical variables. RT-associated bladder tumors were significantly enriched for alterations in KDM6A and ATM, while CTRL tumors were enriched for CDKN2A mutation. Globally, there was an increased number of variants within RT tumors, albeit at a lower variant allele frequency. Mutational signature analysis revealed three predominate motif patterns, with similarity to SBS2/13 (APOBEC3A), SBS5 (ERCC2/Smoking) and SBS6/15 (MMR). Poor prognostic factors in the RT cohort include, a short tumor latency, smoking status, the presence of the smoking and XRT mutational signatures, and CDKN2A copy number loss. Based on the clinical and genomic findings, we suggest, at least two potential pathways leading to RT-associated bladder cancer; the first, occurs in the setting of field cancerization, related to smoking or pre-existing genetic alterations and leads to the development of more aggressive bladder tumors, and the second, in which RT initiates the oncogenic process in otherwise healthy urothelium, leading to a longer latency and less aggressive disease.

Long-term evaluation of the safety of a rectal-prostate spacer, the ProSpace® balloon, in patients treated with radiotherapy for prostate cancer

BackgroundDue to the close proximity of the prostate and rectum, rectal toxicity remains a major problem in patient treated by radiotherapy for prostate adenocarcinoma. One method of increasing the distance between the prostate and the rectum is to use a spacer implanted into the rectoprostatic space. This report describes the long-term outcomes obtained with a new ballon spacer.MethodsPatients treated with curative radiotherapy for low- or intermediate-risk prostate adenocarcinoma, who underwent insertion of the ProSpace® (BioProtect Ltd, Tzur Yigal, Israel) rectal-prostate balloon spacer, were included. The main objective was to evaluate the dosimetric benefit of the spacer for OARs. The secondary objectives were to evaluate the feasibility and tolerability of ProSpace® balloon placement and to evaluate its long-term therapeutic efficacy and tolerance.ResultsBetween October 2013 and March 2015, 16 patients were enrolled in the Pasteur Clinic, Toulouse, France. The median follow-up was 85.5 months. From top to bottom, the space created was a mean of 16.3 mm (range: 11–20.5 mm) at the base of the prostate, 12.1 mm (range: 4–16 mm) at the middle and 8.9 mm at the apex (range: 5–15 mm). On average, rectal volumes receiving a dose of 70 Gy, 60 Gy and 50 Gy were significantly lower after balloon implantation: -4.81 cc (1.5 vs. 6.3; p < 0.0005), -8.08 cc (6.4 vs. 14.5; p = 0.002) and -9.06 cc (16.7 vs. 25.7; p = 0.003), respectively. There were significant differences in coverage after balloon implantation: Median V95% (p < 0.0005), median Dmin (p = 0.01) and median V98% (p < 0.001) were higher after balloon implantation. At 5 years, cumulative gastrointestinal toxicity was grade 1 in 6% (1/16 patients). No toxicity of grade 2 or higher was found. At 5 years, no urinary toxicity grade 3 or 4 toxicity was found. The QoL was not deteriorated.ConclusionsThe use of the ProSpace® balloon seems to be well accepted by patients, allowing a double dosimetric gain: a decrease in doses received by the rectum and an improvement in the coverage of the high-risk PTV. The long-term gastrointestinal toxicity remains low and QoL is preserved in all treated patients.

Deep-learning-based segmentation using individual patient data on prostate cancer radiation therapy.

Organ-at-risk segmentation is essential in adaptive radiotherapy (ART). Learning-based automatic segmentation can reduce committed labor and accelerate the ART process. In this study, an auto-segmentation model was developed by employing individual patient datasets and a deep-learning-based augmentation method for tailoring radiation therapy according to the changes in the target and organ of interest in patients with prostate cancer. Two computed tomography (CT) datasets with well-defined labels, including contoured prostate, bladder, and rectum, were obtained from 18 patients. The labels of the CT images captured during radiation therapy (CT2nd) were predicted using CT images scanned before radiation therapy (CT1st). From the deformable vector fields (DVFs) created by using the VoxelMorph method, 10 DVFs were extracted when each of the modified CT and CT2nd images were deformed and registered to the fixed CT1st image. Augmented images were acquired by utilizing 110 extracted DVFs and spatially transforming the CT1st images and labels. An nnU-net autosegmentation network was trained by using the augmented images, and the CT2nd label was predicted. A patient-specific model was created for 18 patients, and the performances of the individual models were evaluated. The results were evaluated by employing the Dice similarity coefficient (DSC), average Hausdorff distance, and mean surface distance. The accuracy of the proposed model was compared with those of models trained with large datasets. Patient-specific models were developed successfully. For the proposed method, the DSC values of the actual and predicted labels for the bladder, prostate, and rectum were 0.94 ± 0.03, 0.84 ± 0.07, and 0.83 ± 0.04, respectively. We demonstrated the feasibility of automatic segmentation by employing individual patient datasets and image augmentation techniques. The proposed method has potential for clinical application in automatic prostate segmentation for ART.

Risk factors for secondary bladder cancer following prostate cancer radiotherapy.

This review investigates the complex landscape of secondary bladder cancer (SBC) after radiotherapy for prostate cancer (PCa). External beam radiotherapy (EBRT) poses an increased risk for SBC, while brachytherapy seems to be associated with smaller increased risks for SBC due to its targeted radiation delivery, sparing the surrounding bladder tissue. Secondary cancers in the bladder are the most frequently diagnosed secondary cancers in the PCa patient population treated with radiotherapy. Patient-related factors are pivotal, with age emerging as a dual-edged factor. While advanced age is a recognized risk for bladder cancer, younger PCa patients exhibit higher susceptibility to radiation-induced cancers. Smoking, a well-established bladder cancer risk factor, increases this vulnerability. Studies highlight the synergistic effect of smoking and radiation exposure, amplifying the likelihood of genetic mutations and SBC. The latency period of SBC, which spans years to decades, remains a critical aspect. There is a strong dose-response relationship between radiation exposure and SBC risk, with higher doses consistently being associated with a higher SBC risk. While specific models for therapeutic radiation-induced SBC are lacking, insights from related studies, like the Atomic Bomb survivor research, emphasize the bladder's sensitivity to radiation-induced cancer. Chemotherapy in combination with radiotherapy, although infrequently used in PCa, emerges as a potential risk for bladder cancer. Bladder cancer's complex epidemiology, encompassing risk factors, treatment modalities, and cancer types, provides a comprehensive backdrop. As research refines understanding, we hope that this review contributes to guide clinicians, inform patient care, and shape preventive strategies on SBC.

Automated contouring of CTV and OARs in planning CT scans using novel hybrid convolution-transformer networks for prostate cancer radiotherapy

Purpose objective(s)Manual contouring of the prostate region in planning computed tomography (CT) images is a challenging task due to factors such as low contrast in soft tissues, inter- and intra-observer variability, and variations in organ size and shape. Consequently, the use of automated contouring methods can offer significant advantages. In this study, we aimed to investigate automated male pelvic multi-organ contouring in multi-center planning CT images using a hybrid convolutional neural network-vision transformer (CNN-ViT) that combines convolutional and ViT techniques.Materials/methodsWe used retrospective data from 104 localized prostate cancer patients, with delineations of the clinical target volume (CTV) and critical organs at risk (OAR) for external beam radiotherapy. We introduced a novel attention-based fusion module that merges detailed features extracted through convolution with the global features obtained through the ViT.ResultsThe average dice similarity coefficients (DSCs) achieved by VGG16-UNet-ViT for the prostate, bladder, rectum, right femoral head (RFH), and left femoral head (LFH) were 91.75%, 95.32%, 87.00%, 96.30%, and 96.34%, respectively. Experiments conducted on multi-center planning CT images indicate that combining the ViT structure with the CNN network resulted in superior performance for all organs compared to pure CNN and transformer architectures. Furthermore, the proposed method achieves more precise contours compared to state-of-the-art techniques.ConclusionResults demonstrate that integrating ViT into CNN architectures significantly improves segmentation performance. These results show promise as a reliable and efficient tool to facilitate prostate radiotherapy treatment planning.

In Silico Comparison of Three Different Beam Arrangements for Intensity-Modulated Proton Therapy for Postoperative Whole Pelvic Irradiation of Prostate Cancer

Background and purpose: Proton therapy has been shown to provide dosimetric benefits in comparison with IMRT when treating prostate cancer with whole pelvis radiation; however, the optimal proton beam arrangement has yet to be established. The aim of this study was to evaluate three different intensity-modulated proton therapy (IMPT) beam arrangements when treating the prostate bed and pelvis in the postoperative setting. Materials and Methods: Twenty-three post-prostatectomy patients were planned using three different beam arrangements: two-field (IMPT2B) (opposed laterals), three-field (IMPT3B) (opposed laterals inferiorly matched to a posterior–anterior beam superiorly), and four-field (IMPT4B) (opposed laterals inferiorly matched to two posterior oblique beams superiorly) arrangements. The prescription was 50 Gy radiobiological equivalent (GyE) to the pelvis and 70 GyE to the prostate bed. Comparisons were made using paired two-sided Wilcoxon signed-rank tests. Results: CTV coverages were met for all IMPT plans, with 99% of CTVs receiving ≥ 100% of prescription doses. All organ at risk (OAR) objectives were met with IMPT3B and IMPT4B plans, while several rectum objectives were exceeded by IMPT2B plans. IMPT4B provided the lowest doses to OARs for the majority of analyzed outcomes, with significantly lower doses than IMPT2B +/− IMPT3B for bladder V30–V50 and mean dose; bowel V15–V45 and mean dose; sigmoid maximum dose; rectum V40–V72.1, maximum dose, and mean dose; femoral head V37–40 and maximum dose; bone V40 and mean dose; penile bulb mean dose; and skin maximum dose. Conclusion: This study is the first to compare proton beam arrangements when treating the prostate bed and pelvis. four-field plans provided better sparing of the bladder, bowel, and rectum than 2- and three-field plans. The data presented herein may help inform the future delivery of whole pelvis IMPT for prostate cancer.

Correlation between dose-volume parameters and rectal bleeding after 12 fractions of carbon ion radiotherapy for prostate cancer.

Carbon ion radiotherapy (CIRT) is currently used to treat prostate cancer. Rectal bleeding is a major cause of toxicity even with CIRT. However, to date, a correlation between the dose and volume parameters of the 12 fractions of CIRT for prostate cancer and rectal bleeding has not been shown. Similarly, the clinical risk factors for rectal bleeding were absent after 12 fractions of CIRT. To identify the risk factors for rectal bleeding in 12 fractions of CIRT for prostate cancer. Among 259 patients who received 51.6 Gy [relative biological effectiveness (RBE)], in 12 fractions of CIRT, 15 had grade 1 (5.8%) and nine had grade 2 rectal bleeding (3.5%). The dose-volume parameters included the volume (cc) of the rectum irradiated with at least x Gy (RBE) (Vx) and the minimum dose in the most irradiated x cc normal rectal volume (Dx). The mean values of D6cc, D2cc, V10 Gy (RBE), V20 Gy (RBE), V30 Gy (RBE), and V40 Gy (RBE) were significantly higher in the patients with rectal bleeding than in those without. The cutoff values were D6cc = 34.34 Gy (RBE), D2cc = 46.46 Gy (RBE), V10 Gy (RBE) = 9.85 cc, V20 Gy (RBE) = 7.00 cc, V30 Gy (RBE) = 6.91 cc, and V40 Gy (RBE) = 4.26 cc. The D2cc, V10 Gy (RBE), and V20 Gy (RBE) cutoff values were significant predictors of grade 2 rectal bleeding. The above dose-volume parameters may serve as guidelines for preventing rectal bleeding after 12 fractions of CIRT for prostate cancer.

Radiation therapy and IRreversible electroporation for intermediate risk prostate cancer (RTIRE)

IntroductionRadiation Therapy and IRreversible Electroporation for Intermediate Risk Prostate Cancer (RTIRE) is a phase II clinical trial testing combination of radiation therapy and irreversible electroporation for intermediate risk prostate cancerBackgroundPCa is the most common non-cutaneous cancer in men and the second leading cause of cancer death in men. PCa treatment is associated with long term side effects including urinary, sexual, and bowel dysfunction. Management of PCa is based on risk stratification to prevent its overtreatment and associated treatment-related toxicity. There is increasing interest in novel treatment strategies, such as focal therapy, to minimize treatment associated morbidity. Focal therapy alone has yet to be included in mainstream guidelines, given ongoing concerns with potentially higher risk of recurrence. We hypothesize combining focal therapy with whole gland, reduced dose radiotherapy will provide acceptable oncologic efficacy with minimal treatment associated morbidity. RTIRE is a phase II single institution, investigator-initiated study combining a local ablative technique though local irreversible electroporation (IRE) with MR guided RT (MRgRT) to treat the entire prostate. The goal is to provide excellent oncologic outcomes and minimize treatment related side effects through leveraging benefits of locally ablative therapy with established radiation treatment techniques.MethodsA total of 42 men with intermediate risk PCa per NCCN guidelines and focal grade group (GG) 2 or 3, Gleason Score (GS) 3 + 4 or GS 4 + 3, cancer in an MRI target will be enrolled. Patients with MRI visible foci of GG2/GG3 will undergo focal therapy with IRE of this lesion. Following successful focal therapy, patients will then undergo a course of reduced dose, whole gland MRgRT with either 32.5 Gy in 5 Fractions or 22 Gy in 2 fractions. The primary objective of the study is to determine safety. Secondary outcomes include evaluation of oncologic efficacy (as measured by the proportion of patients free of clinically significant cancer as defined as > Grade Group 1 at 1-year follow-up biopsy), imaging characteristics of patients pre and post RTIRE, impact on quality of life (QoL), and PSA kinetics.DiscussionCombining IRE with a reduced dose radiotherapy may offer a new treatment paradigm for PCa by both reducing treatment effects of full dose radiotherapy and minimizing the risk of recurrence observed with focal therapy.Trial RegistrationClinicaltrials.gov identifier: NCT05345444. Date of registration: April 25, 2022. Protocol Version: 6.0, July 7, 2023.

The Association between Patient Characteristics and Biochemical Recurrence after Radical Prostatectomy.

Background: Biochemical recurrence (BCR) represents the rise of prostate-specific antigen (PSA) levels after treatment with curative radical prostatectomy (RP) or radiation for prostate cancer. The objective of the current study was to test for the association between patient characteristics, namely age, body mass index (BMI), as well as prostate volume at surgery, and BCR after RP. Material and Methods: Within a tertiary care database, patients with prostate cancer treated with RP between January 2014 and June 2023 were included. Kaplan-Meier survival analyses and Cox regression models addressed BCR after RP according to patient characteristics. Results: Of 821 patients, the median age was 66 years (interquartile range [IQR] 61-71 years), BMI was 26.2 kg/m2 (IQR 24.3-28.8 kg/m2), and prostate volume was 40 cm3 (IQR 30-55 cm3). Median follow-up was 20 months. In survival analyses, the three-year BCR-free survival rates were 81 vs. 84 vs. 81% in patients aged ≤60 vs. 61-69 vs. 70 years (p = 0.1). In patients with BMI < 25.0 vs. 25.0-29.9 vs. ≥30.0 kg/m2, the three-year BCR-free survival rates were 84 vs. 81 vs. 84% (p = 0.7). In patients with prostate volume ≤40 vs. >40 cm3, the three-year BCR-free survival rates were 85 vs. 80% (p = 0.004). In multivariable Cox regression models accounting for patient and pathologic tumor characteristics and adjuvant radiation therapy, a higher prostate volume independently predicted BCR as continuous (hazard ratio 1.012, 95% confidence interval 1.005-1.019; p < 0.001), as well as categorized the variable based on the median (hazard ratio 1.66, 95% confidence interval 1.17-2.36; p = 0.005). Conversely, neither age nor BMI were significantly associated with BCR after RP. Conclusions: The higher prostate volume independently predicted BCR after RP, but not age or BMI at surgery. Consequently, patients with an elevated prostate volume should be considered for closer postoperative follow-up.

Acute toxicity and early PSA response after two-fraction stereotactic radiotherapy 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 two-fraction stereotactic radiotherapy (SABR) with optional MRI-based focal boost, using peri-rectal spacing, for localized prostate cancer. This represents the initial report from the phase-I non-randomized cohort. Materials and methods: Subjects had favorable intermediate risk (FIR) or low risk (LR) prostate adenocarcinoma, and gland volume <80cc. All underwent radiopaque hydrogel spacer and fiducial marker placement prior to simulation (CT and 3-tesla T2 MRI). The clinical target volume included the entire prostate, and in FIR patients, 1-2cm of seminal vesicle (SV). A 2mm 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-SV, with an optional 30 Gy simultaneous boost (SIB) to an MRI-defined dominant lesion. Primary endpoint was 3-month patient-reported changes in quality of life based on the EPIC-26, IPSS, and SHIM questionnaires. Secondary endpoints were 6-month quality of life, acute toxicity (using CTCAEv5) and early PSA response. Results: Among the 20 patients in the phase-I cohort, 95% had FIR disease, and 50% received an SIB. 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 IPSS and decrease of 1.8±6.5 in SHIM scores. Rates of grade 2 urinary and bowel toxicity 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 two-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.

Results with radical conformal radiotherapy in prostate cancer

Results with radical conformal radiotherapy in prostate cancer

Comparing the lifespan of virgin artificial urinary sphincters in radiated patients: transcorporal vs. standard placement.

To compare the lifespan of first transcorporal cuff(TC) placement of an artificial urinary sphincter (AUS) versus standard placement(SP) in patients with prior radiotherapy (RT) for prostate cancer(PCa). We reviewed first (virgin) AUS placements from two high-volume care centers between 1/2011 and 1/2021, including PCa patients with RT history. AUS lifespan was assessed via the hazard ratio of device explantation and/or revision within a ten-year timeframe for the TC vs. SP approaches. Chi-square, Fisher's exact, and t-tests compared clinicodemographic variables. Kaplan-Meier curve compared TC and SP lifespan. 85/314 men with AUS met inclusion criteria, with 38.8%(33/85) in the TC group and 61.2%(52/85) in the SP group. Median ages were 69.8(IQR = 65.2-73.6) and 67.1(61.6-72.9), respectively, p = 0.17. Over a median follow up of 51.9 (15.8-86.1) and 80.4(28.1-128.3) months for the TC and SP, overall, 12(36.4%) TC devices were removed (four[12.1%] due to mechanical failures; eight[24.2%] erosions, and two[6.1%] infections) vs. 29(55.8%) in the SP group (14[26.9%] mechanical failures; 11[21.1%] erosions, and five[9.6%] infections). No statistically significant differences were observed between the two approaches, with HR = 0.717, 95% CI 0.37-1.44, p = 0.35. The calculated device survival probabilities for the TC vs. SP at one, five, and 10 years were 78.8% vs. 76.9%, 69.3% vs. 58.7%, and 62.1% vs. 46.7%, respectively. TC cuff insertion for the first AUS implantation in pre-radiated patients showed to be comparable to SP when it comes to device survival, with comparable complication rates. Current guidance for approach selection is primarily based on patient selection and surgeon preference.

Symmetry, separation, and stability: Physical properties for effective dosimetric space with a stabilized hyaluronic acid spacer.

The proximity of the rectum to the prostate in radiation therapy (RT) for prostate cancer presents a significant dosimetric challenge, leading to high rectal doses and resulting in detrimental side effects. Perirectal tissue spacing reduces rectal dose and gastrointestinal toxicities by mechanically separating these organs. A variety of materials have been explored for use as rectal spacers, most recently, a stabilized hyaluronic acid (HA) gel, which can be formed into deliberate a shape, and retains the definition of that shape, while remaining flexible, unlike polyethylene glycol (PEG) hydrogels. This study evaluates the dosimetric impact of the spacer, including shape symmetry, the degree of separation at different locations, and the temporal stability of the space. Our goal is to provide physics-informed guidance on the optimal use of this sculptable spacer. A secondary analysis was performed on data from a 13-center prospective randomized trial (NCT04189913), involving 136 patients with centrally-reviewed treatment plans conducted on CT/MR simulation scans before and after receiving HA spacer implants. Patients were treated with 60Gy in 20 fractions to the prostate. For this study, python software was utilized for automated processing of DICOM RTstruct and RTdose files, facilitating detailed analysis of the spacer's impact on anatomical displacement and dosimetric outcomes. Complete dose-volume histograms (DVHs) were reconstructed, and combined into composite population DVHs before and after implant, verified against trial-reported dose points. Patients were divided into similar groups of separation and symmetry, and differences in their composite DVHs were tested for significance. Stability of the spacer was studied by comparing serial MRI images and by computing the distance between contours at four axial planes, at simulation and 3-month follow-up, post RT. The introduction of the HA spacer significantly enhanced rectal sparing, as evidenced by a reduction in the mean rectal integral dose by over 6Gy. High rates of implant symmetry(>95%) were observed, indicating nearly optimal lateral spacer placement. In superior-inferior coverage, this study like many others, saw the spacing largest at the superior extent but becoming more variable inferiorly at the level of the prostate apex. This allowed study of the apex as a specific area for dosimetric concern. Stability assessments confirmed that the spacer maintained its position and dimensions between the simulation and the 3-month post-RT, implying stable geometry during treatment, with only minimal separation changes observed. Statistical analysis using the Kruskal-Wallis test revealed significant correlations of larger separations at the inferior and apical planes with improved dosimetric outcomes, including rV30Gy. The use of a stabilized HA spacer in prostate RT effectively enhances prostate-rectum separation, leading to significant rectal sparing without undesirable dose compromises. This study underscores the role of strategic placement and shape, specifically including>1cm separation from the base down to the prostate apex. When combined with the treatment planning techniques used in the trial to create a steep dosimetric gradient across the spacer, these findings elucidate the dosimetric outcomes that can be expected in the clinical implementation of HA spacer. This is particularly relevant in the evolution of hypofractionated treatment regimens for prostate cancer therapy.

Stereotactic body radiation therapy for prostate cancer: a dosimetric comparison of IMRT and VMAT using flattening filter and flattening filter-free beams.

This retrospective study was performed to evaluate plan quality and treatment delivery parameters of stereotactic body radiation therapy (SBRT) for prostate cancer. The study utilized different isocentric modulated techniques: intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) using 6 MV flattening filter (FF) and 10 MV flattening filter-free beams (FFF). Fifteen retrospective prostate cancer patients were selected for this study. Sixty plans were created with an SBRT-prescribed dose of 36.25Gy delivered in five fractions. Planning target volume (PTV) coverage, plan quality indices, doses delivered to organs at risk (OARs), and treatment delivery parameters were compared for all plans. It turned out that VMAT plans, particularly those using the FFF beam, provided superior target conformality and a steeper dose gradient as compared to IMRT plans. Additionally, VMAT plans showed better OARs sparing compared to IMRT plans. However, IMRT plans delivered a lower maximum dose to the target than VMAT plans. Importantly, the VMAT plans resulted in reduced treatment delivery parameters, including beam on time (BOT), monitor unit (MU), and modulation factor (MF), compared to IMRT plans. Furthermore, a statistically significant difference was observed in BOT and mean body dose between FF and FFF beams, with FFF beams showing superior performance. Considering all results, VMAT using 10 MV (FFF) is suggested for treating prostate cancer patients with SBRT. This offers the fastest delivery in addition to maintaining the highest plan quality.

611 Hydrogel Vue Spacer in Prostate Cancer Radiotherapy for Patients with Inflammatory Bowel Disease (IBD): Pilot Study

Abstract Introduction Patients with Inflammatory Bowel Disease and those with previous rectal surgery may have challenges when undergoing prostate radiotherapy due to increased rectal toxicity after radiotherapy which may preclude them from having radiotherapy for their prostate cancer. We need solutions that can minimize rectal toxicity while maintaining the efficacy of radiotherapy for patients. We report on our experience using SpaceOAR Hydrogel Spacer as a solution to minimize the radiation dose to the rectum and reduce toxicities. Aim To assess the benefits of SpaceOAR Hydrogel spacers following radiotherapy in patients who are at risk than average of rectal toxicity. Method We collected data from patients with IBD or previous rectal/bowel surgery who received radical radiotherapy with SpaceOAR Vue™ Hydrogel from period between Sep/2021 and Sep/2022. Data was collected including age, stage, baseline PSA, Gleason score, number of endoscopic assessment required and need for any surgical/medical intervention within one-year after completion of their radiotherapy. Results 16 patients were included in the study with one year follow up. The range of age is (62-82 years), the dose of radiotherapy varies between 6000-7400Gy and the initial PSA range was (6.1-89). 8 patients required endoscopic assessment within 1 year of treatment (As a part of their normal follow-up). was normal in all patients except in 3 patients who has mild colitis. Biochemical control at one year was excellent. Conclusions Results demonstrated that the use of Hydrogel spacer in patients with IBD or previous bowel surgery undergoing radical prostate cancer radiotherapy is safe and is a reasonable strategy.

Urinary Organs at Risk for Prostate Cancer External Beam Radiation Therapy: Contouring Guidelines on Behalf of the Francophone Group of Urological Radiation Therapy

PurposeOccurrence of genitourinary (GU) toxicity is a common adverse event observed after external beam radiotherapy (EBRT) for prostate cancer (PCa). Recent findings suggest that the dose delivered to specific urinary organs-at-risk (OARs) such as ureters, bladder trigone, and urethra is involved in the development of GU toxicity. Methods and materialsA multidisciplinary task force including three radiation oncologists, a uroradiologist, and a urologist was created in 2022. First, OARs potentially involved in GU toxicity were identified and discussed. A literature review was performed, addressing several questions relative to urinary OARs: anatomical and radiological definition, radiation-induced injury, dose-volume parameters. Secondly, results were presented and discussed with a panel of radiation oncologists, members of the “Francophone Group of Urological Radiation Therapy” (GFRU). Thereafter, GFRU experts were asked to answer a dedicated questionnaire, including 35 questions on the controversial issues related to the delineation of urinary OARs. ResultsThe following structures were identified as critical for PCa EBRT: ureters, bladder, bladder neck, bladder trigone, urethra (intraprostatic, membranous, spongious), striated sphincter, and post-enucleation or post-transurethral resection of the prostate (TURP) cavity. A consensus was obtained for 32 out of 35 items. ConclusionThis consensus highlights contemporary urinary structures in both upper and lower urinary tract to be considered for EBRT treatment planning of PCa. The current recommendations also propose a standardized definition of urinary OARs, for both daily practice and future clinical trials.

Helical Tomotherapy versus Three-Dimensional Conformal Radiotherapy in High Risk Prostate Cancer: A Phase III Randomized Controlled Trial

We present long-term outcomes from a phase III randomized controlled trial that compared helical tomotherapy with three-dimensional conformal radiotherapy (3D-CRT) in the treatment of high-risk prostate cancer (PCa). Newly diagnosed patients with high-risk PCa were randomly allocated to receive radical radiotherapy using 3D-CRT or helical tomotherapy. In both arms, patients received an initial dose of 46 Gy in 23 fractions to the prostate and pelvic lymph nodes followed by additional boost to the prostate of 32 Gy in 16 fractions. Radiotherapy was combined with 3 years of adjuvant androgen deprivation. The primary endpoint was late (>90 days since RT initiation) rectal toxicity. Overall,123 patients were randomly assigned to either the 3D-CRT (n=60) or tomotherapy (n=63) arms. Median follow-up was 161 months. Overall, the proportion of patients with grade ≥2 late rectal toxicity was 8.3% (95% CI: 3.1 to 19.1; n=5) in the 3D-CRT arm and 11.1% (95% CI: 5.0 to 22.2; n=7) in the tomotherapy arm with no significant between-arm difference (p=0.83). There was no significant difference (p=0.17) in the proportion of patients with late grade ≥2 genitourinary toxicity:10.0% (95% CI: 4.1-21.2) in the 3D-CRT arm and 20.6% (95% CI: 11.9-33.0) in the tomotherapy arm. There was no significant difference in the hazard of biochemical progression or death between the two groups (HR for the tomotherapy arm: 0.72; 95% CI: 0.46-1.15, p=0.17). In this phase III trial, the overall incidence of grade ≥2 rectal toxicity was low and was not significantly different between the two arms. There was non-significant evidence of improved biochemical progression-free survival in patients treated with tomotherapy. These findings should be interpreted considering the possibility of type II errors due to limited sample size and low event rates. NCT00326638.

The impact of baseline health factors on second primary cancer risk after radiotherapy for prostate cancer.

In evaluating second primary cancers (SPCs) following External Beam Radiotherapy (EBRT), the role of lifestyle factors is frequently not considered due to data limitations. We investigated the association between smoking, comorbidities, and SPC risks within EBRT-treated patients for localized prostate cancer (PCa). The study included 1,883 PCa survivors aged 50-79, treated between 2006 and 2013, with intensity-modulated radiotherapy (IMRT) or three-dimensional conformal radiotherapy (3D-CRT). Clinical data were combined with SPC and survival data from the Netherlands Cancer Registry with a 12-month latency period. Standardized Incidence Ratios (SIRs) were calculated comparing the EBRT cohort with the general Dutch population. To explore the effect of patient and treatment characteristics on SPCs we conducted a Cox regression analysis. Lastly, we estimated cumulative incidences of developing solid SPC, pelvis SPC, and non-pelvis SPC using a competing risk analysis. Significantly increased SIRs were observed for all SPC (SIR = 1.21, 95% confidence interval [CI]: 1.08-1.34), pelvis SPC (SIR = 1.46, 95% CI: 1.18-1.78), and non-pelvis SPC (SIR = 1.18, 95% CI [1.04-1.34]). Smoking status was significantly associated with pelvic and non-pelvic SPCs. Charlson comorbidity index (CCI) ≥ 1 (Hazard Ratio [HR] = 1.45, 95% CI: 1.10-1.91), cardiovascular disease (HR = 1.41, 95% CI: 1.05-1.88), and chronic obstructive pulmonary disease (COPD) (HR = 1.91, 95% CI: 1.30-2.79) were significantly associated with non-pelvis SPC. The proportion of active smoking numbers in the cohort was similar to the general population. We conclude that the presence of comorbidities in the EBRT population might be a relevant factor in observed excess non-pelvis SPC risk, but not for excess pelvis SPC risk.

Internal urethral sphincter reconstruction with anterior bladder neck tube for robotic and laparoscopic radical prostatectomy: improving early return of continence.

In recent years, despite several surgical techniques having been applied, the early incontinence rate after radical prostatectomy (RP) remains high. In this study, we reconstructed an internal urethral sphincter (IUS) with anterior bladder neck tube (ABNT) to improve early return of continence and find a more effective technique for early urinary incontinence after RP. In this study, 96 previous patients who did not receive an ABNT between October 2018 and May 2020 were compared as historical controls (the control group). A total of 210 consecutive patients underwent robotic or laparoscopic RP with ABNT between May 2020 and February 2023 (the ABNT group). The inclusion criteria included Eastern Cooperative Oncology Group (ECOG) score 0-1 and localized prostate cancer (clinical stages cT1-3, cN0, cM0). The exclusion criteria included patients with diabetes, neurologic diseases, previous pelvic operations, symptoms of urinary incontinence, prior radiation, focal therapy, or androgen deprivation therapy for prostate cancer. ABNT was reconducted with a U-shaped flap from the anterior wall of the bladder neck, and was then anastomosed with the urethra. In the control group, the bladder outlet was directly anastomosed with the urethra. Continence, as defined if 0 pads were used per day and International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF) score ≤6, was assessed at 1, 4, 8, 12, and 24 weeks after catheter removal. At 2 weeks after catheter removal, urethral pressure profilometry (UPP) and upright urethrography were performed to evaluate the function of ABNT in the ABNT group. More patients in the ABNT group were continent than those in the control group at 1 week (85.2% vs. 22.9%, P<0.001), 4 weeks (91.4% vs. 27.1%, P<0.001), 8 weeks (95.2% vs. 40.6%, P<0.001), 12 weeks (100% vs. 71.9%, P<0.001), and at 24 weeks (100% vs. 87.5%, P<0.001) after catheter removal. Stricture was presented in 5.2% and 2.1% (P=0.34) in the ABNT group and control group, respectively. UPP showed that a functional IUS was reconstructed with ABNT. Upright urethrography showed that the ABNT was filled with contrast medium in the urination period and with no contrast medium during the storage period and interruption of urination. The ABNT technique significantly improved early return of continence in comparison with the no ABNT technique, especially the immediate continence. The ABNT technique reconstructed the functional IUS with acceptable urethral stricture. The limitations of the present study include that the comparison was conducted retrospectively with a historical cohort and lack of randomization, and the single center setting. A prospective, randomized, and multicenter evaluation is expected.