Focal salvage treatment for radiorecurrent prostate cancer: A magnetic resonance-guided stereotactic body radiotherapy versus high-dose-rate brachytherapy planning study

Background and Purpose: Magnetic resonance imaging (MRI)-guided focal salvage high-dose-rate brachytherapy (FS-HDR-BT) is one of the treatment options for radiorecurrent localized prostate cancer. However, due to the invasive nature of the treatment, not all patients are eligible. Magnetic resonance linear accelerator (MR-Linac) systems open up new treatment possibilities and could potentially replace FS-HDR-BT treatment. We conducted a planning study to investigate the feasibility of delivering a single 19 Gy dose to the recurrent lesion using a 1.5 Tesla MR-Linac system. Materials and Methods: Thirty patients who underwent FS-HDR-BT were included. The clinical target volume (CTV) encompassed the visible lesion plus a 5 mm margin. Treatment plans were created for a 1.5 Tesla MR-Linac system using a 1 mm planning target volume (PTV) margin. A dose of 19 Gy was prescribed to ≥ 95% of the PTV. In case this target could not be reached, i.e. when organs-at-risk (OAR) constraints were violated, a dose of ≥ 17 Gy to ≥ 90% of the PTV was accepted. MR-Linac plans were compared to clinical FS-HDR-BT plans. Results: Target dose coverage was achieved in 14/30 (47%) FS-HDR-BT plans and 17/30 (57%) MR-Linac plans, with comparable median D95% and D90%. In FS-HDR-BT plans, a larger volume reached ≥ 150% of the prescribed dose. Urethra D10%, rectum D1cm3, and rectum D2cm3 were lower in the FS-HDR-BT plans, while bladder dose was comparable for both modalities. Conclusion: Single fraction treatment of recurrent prostate cancer lesions may be feasible using stereotactic body radiotherapy (SBRT) on a MR-Linac system

Accumulated bladder wall dose is correlated with patient-reported acute urinary toxicity in prostate cancer patients treated with stereotactic, daily adaptive MR-guided radiotherapy

Background and purpose: Magnetic resonance (MR)-guided linear accelerators (MR-Linac) enable accurate estimation of delivered doses through dose accumulation using daily MR images and treatment plans. We aimed to assess the association between the accumulated bladder (wall) dose and patient-reported acute urinary toxicity in prostate cancer (PCa) patients treated with stereotactic body radiation therapy (SBRT). Materials and methods: One-hundred-and-thirty PCa patients treated on a 1.5 T MR-Linac were included. Patients filled out International Prostate Symptom Scores (IPSS) questionnaires at baseline, 1 month, and 3 months post-treatment. Deformable image registration-based dose accumulation was performed to reconstruct the delivered dose. Dose parameters for both bladder and bladder wall were correlated with a clinically relevant increase in IPSS (≥ 10 points) and/or start of alpha-blockers within 3 months using logistic regression. Results: Thirty-nine patients (30%) experienced a clinically relevant IPSS increase and/or started with alpha-blockers. Bladder D5cm3, V10–35Gy (in %), and Dmean and Bladder wall V10–35Gy (cm3 and %) and Dmean were correlated with the outcome (odds ratios 1.04–1.33, p-values 0.001–0.044). Corrected for baseline characteristics, bladder V10–35Gy (in %) and Dmean and bladder wall V10–35Gy (cm3 and %) and Dmean were still correlated with the outcome (odds ratios 1.04–1.30, p-values 0.001–0.028). Bladder wall parameters generally showed larger AUC values. Conclusion: This is the first study to assess the correlation between accumulated bladder wall dose and patient-reported urinary toxicity in PCa patients treated with MR-guided SBRT. The dose to the bladder wall is a promising parameter for prediction of patient-reported urinary toxicity and therefore warrants prospective validation and consideration in treatment planning

On-line daily plan optimization combined with a virtual couch shift procedure to address intrafraction motion in prostate magnetic resonance guided radiotherapy

Background and purpose: In daily adaptive magnetic resonance (MR)-guided radiotherapy, plans are adapted based on the patient's daily anatomy. During this adaptation phase, prostate intrafraction motion (IM) can occur. The aim of this study was to investigate the efficacy of always applying a subsequent virtual couch shift (VCS) to counter IM that occurred during the daily contour and plan adaption (CPa) procedure. Material and Methods: One hundred fifty patients with low and intermediate risk prostate cancer were treated with 5x7.25 Gy fractions on a 1.5 T MR-Linac. In each fraction, contour adaptation and dose re-optimization was performed using the session's first MR-scan. IM that occurred here was countered using two methods. One patient group had selective VCS (sVCS) applied if the CTV reached outside the PTV on a second MR acquired during plan optimization. The other group had always VCS (aVCS) applied for any prostate shift greater than 1 mm. Remaining IM during beam delivery was determined using 3D cine-MR. Results: Percentage of fractions where a VCS was applied was 28% (sVCS) vs 78% (aVCS). Always applying VCS significantly reduced influences of systematic prostate IM. Population random and systematic median values in all translations directions were lower for the aVCS than sVCS group, but not for the population random cranial-caudal direction. Conclusion: Applying VCS after daily CPa reduced impact of systematic prostate drift in especially the posterior and caudal translation direction. However, due to the continuous and stochastical nature of prostate IM, margin reduction below 4 mm requires fast intrafraction plan adaption methods

Recurrence characteristics after focal salvage HDR brachytherapy in prostate cancer

Background and purpose: Radiorecurrent prostate cancer is often confined to the prostate, predominantly near the index lesion. The purpose of this study was to look at recurrence characteristics in patients treated with focal salvage high dose-rate (HDR) brachytherapy. Materials and methods: Patients treated with MRI-guided HDR brachytherapy, with a single fraction of 19 Gy from July 2013 to October 2021 as focal salvage treatment, were prospectively included in the current study. Imaging data were collected regarding the occurrence of local, regional and distant recurrences, including location of local recurrences (LR) in relation to the HDR radiotherapy field. Results: One hundred seventy-five patients were included after focal salvage HDR brachytherapy (median follow-up 36 months (IQR 23–50)). Three-years biochemical recurrence-free survival, LR-free survival, in-field LR-free survival, out-of-field LR-free survival, any-recurrence-free survival and ADT-free survival were 43% (95%CI 34%–52%), 51% (41%–61%), 70% (61%–80%), 92% (88%–97%), 42% (32%–52%) and 86% (80%–92%), respectively. Larger GTV-size and shorter PSA doubling time were associated with in-field LR in multivariable analysis. Conclusion: After focal salvage HDR brachytherapy with a dose of 1x19 Gy for local prostate cancer recurrence, subsequent recurrences are mostly local and in-field

Long-Term Health-Related Quality of Life in Patients With Rectal Cancer After Preoperative Short-Course and Long-Course (Chemo) Radiotherapy

AbstractBackgroundBoth preoperative short-course radiotherapy (SC-PRT) and preoperative long-course chemo radiotherapy (CRT) have shown to reduce local recurrence rates after total mesorectal excision (TME), but neither resulted in improved survival. This study compared the long-term health-related quality of life (HRQL) and symptoms between CRT and SC-PRT.MethodsPatients who were preoperatively treated with a total dose of 50.0 to 50.4 Gy for locally advanced rectal cancers were identified from 2 hospital registries. Starting from 2011, all patients who were disease-free in the study population (n = 105) were sent a HRQL-questionnaire composed of the European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30 and questions on bowel and urinary function. Patients who underwent SC-PRT in the TME trial were used as a reference group.ResultsHRQL results from 85 patients receiving CRT (81.0%), with a median follow-up time of 58 months, were compared with the results of patients who underwent SC-PRT (n = 306). Apart from more nausea and vomiting reported by patients receiving CRT (mean score for CRT 5.9 vs. 1.3 for SC-PRT; P < .01; not clinically relevant) and less satisfaction with urinary function indicated by patients who received CRT (mean score for CRT 71.2 vs. 81.2 for SC-PRT; P < .01), no significant differences were found in HRQL and symptoms between patients who received CRT and SC-PRT.ConclusionsThis analysis of HRQL in patients who received CRT shows no clinically relevant differences in long-term HRQL and symptoms between patients who received CRT and SC-PRT, apart from less satisfaction with urinary function reported by patients who received CRT. These results indicate that both approaches have a comparable impact on long-term HRQL

Delivered dose quantification in prostate radiotherapy using online 3D cine imaging and treatment log files on a combined 1.5T magnetic resonance imaging and linear accelerator system

Background and purpose: Monitoring the intrafraction motion and its impact on the planned dose distribution is of crucial importance in radiotherapy. In this work we quantify the delivered dose for the first prostate patients treated on a combined 1.5T Magnetic Resonance Imaging (MRI) and linear accelerator system in our clinic based on online 3D cine-MR and treatment log files. Materials and methods: A prostate intrafraction motion trace was obtained with a soft-tissue based rigid registration method with six degrees of freedom from 3D cine-MR dynamics with a temporal resolution of 8.5–16.9 s. For each fraction, all dynamics were also registered to the daily MR image used during the online treatment planning, enabling the mapping to this reference point. Moreover, each fraction's treatment log file was used to extract the timestamped machine parameters during delivery and assign it to the appropriate dynamic volume. These partial plans to dynamic volume combinations were calculated and summed to yield the delivered fraction dose. The planned and delivered dose distributions were compared among all patients for a total of 100 fractions. Results: The clinical target volume underwent on average a decrease of 2.2% ± 2.9% in terms of D99% coverage while bladder V62Gy was increased by 1.6% ± 2.3% and rectum V62Gy decreased by 0.2% ± 2.2%. Conclusions: The first MR-linac dose reconstruction results based on prostate tracking from intrafraction 3D cine-MR and treatment log files are presented. Such a pipeline is essential for online adaptation especially as we progress to MRI-guided extremely hypofractionated treatments

Robotic MR-guided high dose rate brachytherapy needle implantation in the prostate (ROBiNSon)—a proof-of-concept study

Objective. A robotic needle implant device for MR-guided high-dose-rate (HDR) prostate brachytherapy was developed. This study aimed to assess the feasibility and spatial accuracy of HDR brachytherapy using the robotic device, for a single intraprostatic target point. Approach. Five patients were treated from November 2019-June 2022 with the robot. The robot fits a 1.5 T MR scanner and the needle can be shifted and angulated. An intraprocedural MR scan was fused with the diagnostic MR and one preplanned needle position was selected for robotic insertion. The needle entry point and angles were set for a needle tip target point within the intraprostatic target volume. The needle was tapped stepwise towards the target point pneumatically. Final needle position was verified with MR, followed by plan optimization and dose delivery. Any remaining planned needles were inserted manually. Needle tip to geometrical target error (NTG-error) was defined as the deviation of the actual tip position relative to the predefined geometric target point, using MR-coordinates. Needle tip to treatment target error (NTT-error) was defined as the deviation of the actual tip position relative to the treatment target point, using fused MR-images pre- and post-needle implantation taking into account prostate deformation. Difference between NTT-error and NTG-error and fiducial marker shifts indicated prostate movement. For determining prostate deformation, the Jaccard index and prostate volumes were assessed. Main results. The robotic device was able to tap the needle to the planned depth for all patients. Mean robotic procedure duration was 142 min. NTG-error was 3.2 (range 1.1-6.7) mm and NTT-error 4.5 (range 2.6-9.6) mm. Marker displacements were smaller than 3 mm. No treatment-related acute toxicity was reported. Feasibility of needle placement within the prostate was considered adequate. Significance. MR-guided robotic needle insertion is feasible with a mean geometric accuracy of 3.2 mm and <3 mm prostate movement