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MR-guided high dose rate (HDR) brachytherapy for focal GTV boost in prostate cancer radiotherapy is an established technique. However, this is resource-intense, invasive and may be contraindicated in some patients. Linear accelerators with integrated MRI allow visualization of the GTV within the prostate, facilitating the use of External Beam Radiation Therapy (EBRT) to deliver GTV boost. This study compared patient-reported quality of life for the first 20 patients treated with these two techniques. Twenty intermediate risk prostate cancer patients who were enrolled and treated between May 2022 and August 2023 in prospective clinical trials were included in this study. Patients were stratified based on patient preference; 10 patients received GTV boost fraction using HDR brachytherapy and 10 patients were treated with EBRT using a 1.5T MR-Linac. For HDR treatment patients were positioned supine under general anesthesia while transperineal catheters were inserted under MRI guidance. For EBRT treatment patients were positioned supine with minimal immobilization and an empty bladder. All patients received 1 × 15 Gy to the GTV followed within 1 week by 5 × 6 Gy (alternate days) to the whole prostate. Both groups received their subsequent whole gland prostate treatment on the MR-Linac. Patient-reported quality of life was captured using The Expanded Prostate Cancer Index Composite (EPIC) survey. The questionnaire was administered at baseline and at one month follow-up. Results were analyzed using descriptive statistics. All patients completed treatment as planned and had minimum follow up of 1 month (range 1-6). The mean score and standard deviation collected from EPIC for bladder and bowel subscales at 1-month follow up were similar between those who received HDR and EBRT with 81.1(29.7) and 94.1 (13.9) vs 85.2(23.1) and 93.9(15.0) respectively. There were also no statistically significant differences when looking further at additional subsets, urinary function was 87.7(13.1) vs 89.8(8.3), p=1.0 for HDR and EBRT and urinary bother 74.2(21.8) vs 81.63(11.0), p=0.71. Bowel function was 94.3(6.2) vs 92.9(8.3), p=1.0 for HDR and EBRT and bowel bother 93.9(7.5) vs 94.8(8.8), p=0.62. The mean change in score from baseline assessment was –5.7 for urinary incontinence and –6.1 urinary irritative/obstructive and 0.8 in rectal subscales for HDR patients compared to 1.0, -1.9 and 0.0 for EBRT patients. These changes from baseline only exceeded the minimally important difference (MID) reported in literature for the urinary irritative/obstructive subscale and only in HDR patients. MRL focal boost to GTV region of the prostate was found to have a similar patient-reported quality of life compared to HDR focal boost at 1 month following completion of treatment, although patients receiving HDR reported a MID from baseline in urinary irritative/obstructive symptoms. A larger sample size may confirm these preliminary findings translate into differences in QOL. [ABSTRACT FROM AUTHOR]

Delivery of a focal boost to the intraprostatic gross tumour volume (GTV) for prostate cancer patients has shown to improve biochemical disease-free survival and has been done via brachytherapy at our institution. However, brachytherapy has contraindications and patients may not want to undergo an invasive procedure. Onboard MR imaging enables visualization of gross disease and can guide treatment on a linear accelerator (linac). The purpose of this study was to describe the initial experience of delivering a focal boost to intraprostatic GTV(s) using MR-guidance on a 1.5T MR-Linac and determining the relevance of bladder preparation for this adaptive radiotherapy technique, because bladder filling may contribute to intrafraction motion. Between March 2023 and January 2024, 20 patients with prostate cancer were enrolled onto a prospective study involving the delivery of a 15 Gy in 1 focal boost to their GTV(s), followed by 30 Gy in 5 to the whole gland. GTV(s) were required to be less than 1/3 of the total prostate volume. Patients were treated using the 1.5T MR-Linac (Unity, Elekta). All patients were asked to empty their bladder prior to the treatment session. The first 10 patients were treated without additional hydration (no-prep), while the latter 10 were given 300mL of water to drink 10 minutes prior to entering the treatment room (prep). The margin expansion used to generate the planning target volume was 3mm in the left-right direction, and 4mm in all other directions from the contoured GTV volume. Daily online adaptive procedure used the full adapt-to-shape (ATS) workflow, including online recontouring and full inverse-replanning on the initial 3D T2-weighted localization image. Additional ATS or adapt-to-position (ATP) virtual-couch-shift procedures, and additional verification imaging were done when large intra-fraction motion was exhibited by the patient. If further large intra-fraction motion was observed after additional ATS or ATP procedure, the session would be aborted, and the patient rescheduled for treatment on a subsequent day. Treatment time, bladder volumes and frequency of additional adaption and aborting treatment were collected, and the student t-test was used for mean comparison. Delivery of the focal boost was completed for all 20 patients. Average treatment time was 55 minutes (sd = 9.8minutes). Bladder dose constraint D0.05cc<1800cGy was met for all patients. Mean bladder volumes on the initial localization scans were not statistically different between the two groups (no-prep: mean=87.4cc, SD=50.7cc vs prep: mean=134.8cc, SD=64.7cc, p = 0.0855). Of the 10 no-prep patients, additional adaptation was required for 4 patients and treatment was aborted for 3 due to large intrafraction motion that could not be rectified with a second adaptation. Although additional adaptation was performed for more patients treated with prep (n=6), all patients received treatment on the scheduled day. Whilst bladder volume between patients with and without prep were not statistically significantly different, based on the current data, bladder prep is still relevant to increase the likelihood of successful treatment delivery. Further investigation is required to understand what other factors may have contributed to the large intrafraction motion observed that led to treatments being aborted. [ABSTRACT FROM AUTHOR]

An integrated linear accelerator and magnetic resonance scanner (MR-linac) was implemented with a multidisciplinary model-of-care for daily online adaptive radiation therapy (ART). A potential disadvantage of this technique is the long patient treatment times within the enclosed MR-linac bore. This study evaluated patient-reported experiences with their overall hospital care as well as treatment in the MR-linac environment Patients pre-screened for MR-eligibility and claustrophobia were referred to simulation on a 1.5T MR-linac (Unity, Elekta AB). MR-linac simulation included assessment to determine suitability of MR-guided ART. Daily MR-guided ART procedure included patient set up, MR imaging, target and organ at risk contouring, treatment plan re-optimization and review by the team (3 Therapists, 1 Physicist, 1 Oncologist). All patients were approached for a single-institution, prospective, observational study to evaluate clinical outcomes, patient experiences and collect technical data for MR-linac research. Patient-reported experience measures were captured using two validated surveys. The 15-item MR-anxiety questionnaire (MR-AQ) was administered immediately after the first treatment to rate MR-related anxiety and relaxation as "not at all", "somewhat", "moderately" or "very much so". The 40-item satisfaction with cancer care questionnaire (EORTC PATSAT-C33 plus OUT-PATSAT7) was administered immediately after the last treatment using five-point Likert responses, with "very good" or "excellent" responses considered positive. Results were analyzed using descriptive statistics One hundred and forty patients consented to the study and completed questionnaires from 114 patients were included in this analysis. The median age was 70 (range 27-91). Treatments were 1-7 fractions (median 6) with an average patient time on the MR-linac couch of 50 minutes (range 31-114) per fraction. Treated sites were prostate (n=76), pancreas (n=14), liver (n=12), kidney (n=4) and other (n=8). All patients were positioned supine with arms by side or on chest and 29% had abdominal compression to limit breathing motion. Following MR-linac simulation, no patient discontinued treatment on MR-linac due to MR-related comfort or anxiety reasons. Patients rated MR-related anxiety scores as 86% "not at all", 12% "somewhat", 2% "moderately" and 0% as "very much so". Positive satisfaction responses ranged from 79-100% (median 95%) across all items. All of the MR-linac radiation therapist-specific items were rated as 97-100% including provision of information on treatment and symptoms, providing physical comfort and emotional support. The five lowest rated items (range 79-84%) were related to general provision of information and coordination by the team on supportive services, post-treatment care planning, communication with the team from home, and hospital access (e.g. parking, transportation). Overall hospital care was rated positively as 99% Despite lengthy treatments for ART, MR-linac treatment was well tolerated with the majority of patients reporting low MR-related anxiety and completing their treatment as planned. Overall, patients were highly satisfied with their MR-linac radiation therapy and cancer care [ABSTRACT FROM AUTHOR]

Patients undergoing radiation therapy for prostate cancer are often required to have a full bladder for their CT-simulation (CTsim) and daily treatment. At our institution bladder fullness was considered acceptable when the bladder dome is 1-4cm above the femoral heads. However, this resulted in >50% of patients requiring a CTsim rescan to meet this criterion. A full dosimetric review of bladder filling during treatment suggested that 0.5-2.5cm above the femoral heads was a better representation of bladder filling on treatment. Herein we report our experiences after the clinical implementation of the modified bladder acceptance criterion (MBAC). The MBAC was implemented in September 2022 for all patients receiving treatment for prostate cancer. To assess its effect on the CT-simulation rescan rate, the total number of prostate patients CT-simulated between September and November 2022, the number of repeated CT-imaging in this cohort, along with the reason documented by the CTsim Therapists were collected from the Radiation Therapy Electronic Medical Record system (MosaiQ). These were compared against a similar cohort CT-simulated prior to the implementation of the MBAC, between September and November 2021. Descriptive statistics were used to analyze the data. There were 105 prostate patients CT-simulated using the MBAC. In the comparison cohort, 97 prostate patients were CT-simulated using the previous bladder filling acceptance criterion. The overall rescan rate was 45% (47 patients) for the MBAC cohort, and 48% (47 patients) for the comparison cohort. There were no statistical differences between the average number of scans per patient between the two cohorts (MBAC 1.66 scans, comparison 1.70 scans; p 0.74). In the MBAC cohort, 32% (34 patients) had one rescan, 8% (8 patients) had two rescans, 3% (3 patients) had three rescans and 2% (2 patients) had four or more rescans. In the comparison cohort 33% (32 patients) had one rescan, 11% (11 patients) had two rescans, 2% (2 patients) had three rescans, and 2% (2 patients) had four or more rescans. Using a chi-square test, no significant differences were found between the two cohorts (p=0.865). In 36% (17 patients) of the rescans, the documented reason was not meeting the MBAC. However, in the comparison cohort, failure to meet the previous bladder criterion accounted for 28% (13 patients) of the rescans. From the information documented by CTsim Therapists, two patients from the comparision cohort could not meet the previous acceptance criteria and required penile clamps, whereas post-MBAC implementation, no comments related to penile clamp use were documented. According to the data collected thus far, the implementation of a more lenient bladder filling criterion that could be considered more achievable by the patient did not decrease CTsimulation rescan rates. We continue to look for clinical factors that influence the dosimetric acceptance of CTsimulation scans for prostate radiation therapy. [ABSTRACT FROM AUTHOR]

Prostate cancer patients are commonly instructed to achieve a 'comfortably full' bladder at the time of CT simulation and throughout the course of radiotherapy. At our institution, bladder status is considered acceptable when the dome is between 10-40mm above the superior aspect of the femoral head. Despite explicit drinking instructions, repeated CT imaging is common due to failure to achieve an acceptable bladder status. There is operational value in re-assessing the validity of the assessment criteria for bladder by comparing the quality of two plans optimized based on either an 'Accepted' or 'Rejected' bladder status. Twenty prostate patients with repeated CTsimulation imaging due to suboptimal bladder filling were identified. These were treated with various dose/fractionation schemes. For each patient, a VMAT plan using the 'Rejected' bladder was created to evaluate if the 'rejected' bladder filling could have resulted in clinically acceptable dose-volume metrics. Delivered dose to bladder was estimated using ≥4 CBCTs to measure number of fractions with major bladder dose violation (>5% difference) for both plans. Bladder heights of fractions without major bladder dose violations were compared to those with a violation to determine a threshold height for bladder filling acceptability. The height of the 'Rejected' bladder was significantly shorter than the 'Accepted' bladder (mean 24mm vs 45mm, p < 0.05). Despite a shorter/smaller bladder, the plan was clinically acceptable in 17/20 patients. Using the 'Accepted' bladder plans for treatment resulted in 30/175 fractions with major dose violations. These 30 bladders were significantly shorter than those without major violation (mean 28mm vs 43mm, p < 0.05). The 'Rejected' bladder plans delivered a lower dose to the bladder by ≥5% than the 'Accepted' bladder plans in 59% of fractions, and the number of fractions with major dose violations was 17. Using a shorter bladder for plan optimization resulted in better bladder sparing during treatment and improved compliance to protocol specific bladder dose constraints. A bladder height range of 20-40mm measured between the bladder dome and the superior aspect of the symphysis pubis is recommended at time of CTsimulation for this clinical scenario. [ABSTRACT FROM AUTHOR]