Five-Year Outcomes of a Phase 1 Dose-Escalation Study Using Stereotactic Body Radiosurgery for Patients With Low-Risk and Intermediate-Risk Prostate Cancer

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.

The impact of neoadjuvant relugolix on multi-dimensional patient-reported fatigue

Introduction

Androgen deprivation therapy has been shown to improve cancer control when combined with radiotherapy. Relugolix is an oral GnRH receptor antagonist that achieves rapid profound testosterone suppression, which may increase the perception and/or impact of fatigue. This study sought to evaluate neoadjuvant relugolix-induced fatigue in prostate cancer patients prior to the start of stereotactic body radiation therapy (SBRT).

Methods

Relugolix was initiated at least two months before SBRT. The 13-item Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) questionnaire was collected at baseline and one hour prior to SBRT initiation. A five-point scale was used to score individual items. Overall scores range from 0-52 and individual item scores were converted to 0-100, with higher scores reflecting less fatigue. Five "experience" items explored self-perceptions of fatigue, and eight "impact" items sought to evaluate the effect of fatigue on daily activities. Items were evaluated for statistical significance (paired t-test, p < 0.05) and clinical significance (minimally important difference (MID); 0.5 standard deviation from baseline).

Results

Between March 2021 to December 2023, 89 men were treated at Georgetown with neoadjuvant relugolix and SBRT. Mean age was 71 years (range: 49-87). Median initiation of relugolix was 4.5 months prior to SBRT (range: 2-14.2 months). 93% patients achieved castration (testosterone levels ≤ 50 ng/dL) and 85% patients achieved profound castration (testosterone levels ≤ 20 ng/dL). 87 patients completed the FACIT-F questionnaire, with an average overall score of 45.6 at baseline and 41.0 at SBRT initiation. This difference was statistically and clinically significant (p < 0.01, MID = 3.55). Patients experienced an increase in fatigue for 12 of 13 items, with statistically significant changes for 11 items. Three of five experience items showed a clinically significant increase in fatigue. Only two of eight impact items were clinically significant.

Discussion

Our study shows that relugolix significantly increases fatigue, affecting multiple areas of life. While the fatigue does not appear to generally impact a patient's ability to carry out normal activities, patients demonstrate frustration with being too tired for these activities. It is essential for clinicians to counsel prostate cancer patients on the impact of neoadjuvant relugolix on quality-of-life issues like fatigue.

Evaluation of the safety and efficacy of high-dose rate brachytherapy for radiorecurrent prostate cancer: a systematic review and meta-analysis

BACKGROUND

High-dose-rate brachytherapy (HDR-BT) plays an important role in the treatment of locally recurrent prostate cancer after definitive treatment. The objective of this study is to summarize the efficacy and toxicity of HDR-BT in these patients.

METHODS

We performed a systematic review of PubMed and EMBASE from inception to July 2023. The primary endpoint was relapse-free survival (RFS) in different subgroups, and the secondary endpoint was gastrointestinal (GI) and genitourinary (GU) toxicity. A semi-automated tool (WebPlotDigitizer) and a new Shiny application combined with R software (R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria; https://www.R-project.org/ ) helped to reconstruct survival curves.

RESULTS

Twenty-six studies met the inclusion criteria for quantitative analysis, including 1447 patients. A total of 761 patients from 13 studies were included in survival reconstruction, and the median RFS time was 61.2 months (57.6-72.0 months). The estimated 2‑, 3‑, and 5‑year rates were 75.9% (95% confidence interval [CI] 72.8 ~ 79.2%), 66.7% (95% CI 63.0 ~ 70.5%), and 52.3% (95% CI 47.5 ~ 57.4%), respectively. Whole-gland irradiation with multiple fractions (≥ 2 F) resulted in better RFS compared with focal gland irradiation with fewer fractions (1 F mostly; hazard ratio [HR]: 0.60, 95% CI 0.47-0.77, p < 0.0001). According to the different median time from primary treatment to salvage therapy (TRS) and median age at recurrence, short median TRS (56-67.2 months vs. 70-120 months; HR 0.52, 95% CI 0.68-0.40; p < 0.0001) and younger median age (60-70 years vs. 71-75 years; HR 0.58, 95% CI 0.46-0.74; p < 0.0001) were positive factors for RFS. The cumulative incidences estimated for grade ≥ 3 acute and late GU toxicities were 1% (95% CI 0 ~ 1%) and 5% (95% CI 4 ~ 7%), respectively. Three patients (3/992) experienced grade ≥ 3 late GI toxicity, and no cases of grade ≥ 3 acute GI toxicity were reported.

CONCLUSION

HDR-BT has a high safety profile and good RFS benefit for salvage treatment of radiorecurrent prostate cancer. In terms of RFS, whole-gland irradiation with multiple fractions seems to be better than focal gland irradiation with fewer fractions, while short TRS and younger age are good prognostic factors. In view of the low level of evidence in the included studies and the large heterogeneity of each study, these conclusions still need to be confirmed by randomized controlled trials.

Long-term Outcomes from a Phase 1 Dose Escalation Study Using Stereotactic Body Radiotherapy for Patients with Low- or Intermediate-risk Prostate Cancer

BACKGROUND

Ultrahypofractionated stereotactic body radiation therapy (SBRT) has become a standard treatment intervention for localized prostate cancer.

OBJECTIVE

To report final long-term tumor control outcomes and late gastrointestinal (GI) and genitourinary (GU) toxicities from a single-center phase 1 dose escalation study using SBRT for patients with low- or intermediate-risk prostate cancer.

DESIGN, SETTING AND PARTICIPANTS

Between 2009 and 2012, 136 patients were enrolled and treated. The initial dose level was 32.5 Gy in five fractions. Doses were then sequentially escalated to 35 Gy, 37.5 Gy, and 40 Gy in five fractions delivered every other day.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was late treatment-related toxicity. Secondary endpoints included prostate-specific antigen (PSA) failure.

RESULTS AND LIMITATIONS

The median follow-up was 10.5 yr for the 32.5-Gy group, 9.9 yr for the 35-Gy group, 8.2 yr for the 37.5-Gy group, and 7.3 yr for the 40-Gy group. The 8-yr cumulative incidence of PSA failure was 26% for 32.5 Gy, 15% for 35 Gy, 3.4% for 37.5 Gy, and 6.6% for 40 Gy. Higher radiation dose (37.5-40 Gy) and favorable intermediate risk (vs unfavorable intermediate risk) were associated with better PSA recurrence rates (p = 0.011 and 0.002, respectively). The 8-yr actuarial probability rates for survival free from late grade ≥2 toxicity were 94% for GI toxicity and 86% for GU toxicity. No grade 4 events were recorded. Higher dose levels were not associated with higher rates of late grade ≥2 GI (p = 0.2) or GU (p > 0.9) toxicity.

CONCLUSIONS

SBRT doses ranging from 32.5 to 40 Gy were associated with low incidence of moderate or severe toxicities. Higher doses resulted in superior disease control outcomes 8 yr after treatment.

PATIENT SUMMARY

We investigated the association between the radiotherapy dose used and the rate of control of prostate cancer. We found that higher doses resulted in more favorable outcomes without excess toxicity. This trial is registered on ClinicalTrials.gov as NCT00911118.

Prostate radiotherapy may cause fertility issues: a retrospective analysis of testicular dose following modern radiotherapy techniques

BACKGROUND

Prostate cancer in younger men is rare but not exceptional. Radiotherapy is a cornerstone of prostate cancer treatment and yet, its impact on fertility is scarcely reported in literature. Given the radiosensitivity of testicular tissue, this study aimed to determine the testicular dose using modern radiotherapy techniques for definitive prostate irradiation.

METHODS

One hundred radiotherapy plans were reviewed. Testicles were contoured retrospectively without dosimetric optimization on testicles.

RESULTS

The median testicular dose was 0.58 Gy: 0.18 Gy in stereotactic plans, 0.62 Gy in Volumetric Modulated Arc Therapy plans and 1.50 Gy in Tomotherapy plans (p < 0.001). Pelvic nodal irradiation increased the median testicular dose to 1.18 Gy versus 0.26 Gy without nodal irradiation (p < 0.001). Weight and BMI were inversely associated with testicular dose (p < 0.005). 65% of patients reached the theoretical dose threshold for transient azoospermia, and 10% received more than 2 Gy, likely causing definitive azoospermia.

CONCLUSION

Despite being probably lower than doses from older techniques, the testicular dose delivered with modern prostate radiotherapy is not negligible and is often underestimated because the contribution of daily repositioning imaging is not taken into account and most Treatment Planning Systems underestimate the out of field dose. Radiation oncologists should consider the impact on fertility and gonadal endocrine function, counseling men on sperm preservation if they wish to maintain fertility.

TRIAL REGISTRATION

retrospectively registered.

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.

The impact of advancing the standard of care in radiotherapy on operational treatment resources

PURPOSE

To demonstrate the impact of implementing hypofractionated prescription regimens and advanced treatment techniques on institutional operational hours and radiotherapy personnel resources in a multi-institutional setting. The study may be used to describe the impact of advancing the standard of care with modern radiotherapy techniques on patient and staff resources.

METHODS

This study uses radiation therapy data extracted from the radiotherapy information system from two tertiary care, university-affiliated cancer centers from 2012 to 2021. Across all patients in the analysis, the average fraction number for curative and palliative patients was reported each year in the decade. Also, the institutional operational treatment hours are reported for both centers. A sub-analysis for curative intent breast and lung radiotherapy patients was performed to contextualize the impact of changes to imaging, motion management, and treatment technique.

RESULTS

From 2012 to 2021, Center 1 had 42 214 patient plans and Center 2 had 43 252 patient plans included in the analysis. Averaged over both centers across the decade, the average fraction number per patient decreased from 6.9 to 5.2 (25%) and 21.8 to 17.2 (21%) for palliative and curative patients, respectively. The operational treatment hours for both institutions increased from 8 h 15 min to 9 h 45 min (18%), despite a patient population increase of 45%.

CONCLUSION

The clinical implementation of hypofractionated treatment regimens has successfully reduced the radiotherapy workload and operational treatment hours required to treat patients. This analysis describes the impact of changes to the standard of care on institutional resources.

Late Toxicity of Prostate Ultrahypofractionated Radiation Therapy Compared With Moderate Hypofractionation in a Randomized Trial

PURPOSE

We report late toxicity, quality of life (QOL), and urinary symptom score with prostate cancer radiation therapy in a randomized trial comparing moderate hypofractionation and ultrahypofrationation.

METHODS AND MATERIALS

Patients with intermediate and high-risk prostate cancer were randomized to either Arm 1 (70 Gy/28 fractions) or Arm 2 (36.25 Gy/5 weekly fractions). Late toxicity was evaluated using the Common Terminology Criteria for Adverse Events and Radiation Therapy Oncology Group/Subjective, Objective, Management, Analytical scales. QOL was assessed with the Expanded Prostate Inventory Composite-26 Short Form and urinary function with the International Prostate Symptom Score.

RESULTS

Eighty participants were randomized. Two from Arm 1 withdrew, leaving 36 patients in Arm 1 and 42 in Arm 2. There were no significant differences in baseline characteristics, except for worse International Prostate Symptom Score in Arm 2. No difference was observed in freedom from grade 3 or worse toxicity between treatments (P = .921), with only a single grade 3 event in each arm. There was no significant difference in freedom from grade 2 or worse toxicity (P = .280). No difference was observed in freedom from grade 2 or worse genitorurinary toxicity, with cumulative probabilities of 69.0% and 87.0% at 5 years for Arms 1 and 2, respectively (0.132). No difference was observed in freedom from grade 2 or worse gastrointestinal toxicity, with cumulative probabilities of 74.0% in Arm 1 and 80.0% in Arm 2 (P = .430). There were no significant differences in Expanded Prostate Inventory Composite-26 Short Form QOL between arms.

CONCLUSIONS

Ultrahypofrationation, delivered weekly, is well tolerated with no significant differences in freedom from late toxicity compared with moderate hypofractionation.

In Curative Stereotactic Body Radiation Therapy for Prostate Cancer, There Is a High Possibility That 45 Gy in Five Fractions Will Not Be Tolerated without a Hydrogel Spacer

The purpose of this study was to determine the maximum tolerated dose (MTD) for stereotactic body radiation therapy (SBRT) in the treatment of non-metastatic prostate cancer. This study was a phase 1 dose escalation trial conducted in Japan. Patients with histologically proven prostate cancer without lymph nodes or distant metastases were enrolled. The prescribed doses were 42.5, 45, or 47.5 Gy in five fractions. Dose-limiting toxicity (DLT) was defined as grade (G) 3+ gastrointestinal or genitourinary toxicity within 180 days after SBRT completion, and a 6 plus 6 design was used as the method of dose escalation. A total of 16 patients were enrolled, with 6 in the 42.5 Gy group and 10 in the 45 Gy group. No DLT was observed in the 42.5 Gy group. In the 45 Gy group, one patient experienced G3 rectal hemorrhage, and another had G4 rectal perforation, leading to the determination of 42.5 Gy as the MTD. None of the patients experienced biochemical recurrence or death during the follow-up period. We concluded that SBRT for non-metastatic prostate cancer at 42.5 Gy in five fractions could be safely performed, but a total dose of 45 Gy increased severe toxicity.

Stereotactic Body Radiation Therapy: A Radiosurgery Society Guide to the Treatment of Localized Prostate Cancer Illustrated by Challenging Cases

Traditionally, external beam radiotherapy (EBRT) for localized prostate cancer (PCa) involved lengthy courses with low daily doses. However, advancements in radiation delivery and a better understanding of prostate radiobiology have enabled the development of shorter courses of EBRT. Ultrahypofractionated radiotherapy, administering doses greater than 5 Gy per fraction, is now considered a standard of care regimen for localized PCa, particularly for intermediate-risk disease. Stereotactic body radiotherapy (SBRT), a specific type of ultrahypofractionated radiotherapy employing advanced planning, imaging, and treatment technology to deliver in five or fewer fractions, is gaining prominence as a cost-effective, convenient, and safe alternative to longer radiotherapy courses. It is crucial to address practical considerations related to patient selection, fractionation scheme, target delineation, and planning objectives. This is especially important in challenging clinical situations where clear evidence for guidance may be lacking. The Radiosurgery Society endorses this case-based guide with the aim of providing a practical framework for delivering SBRT to the intact prostate, exemplified by two case studies. The article will explore common SBRT dose/fractionation schemes and dose constraints for organs-at-risk. Additionally, it will review existing evidence and expert opinions on topics such as SBRT dose escalation, the use of rectal spacers, the role of androgen deprivation therapy in the context of SBRT, SBRT in special patient populations (e.g., high-risk disease, large prostate, high baseline urinary symptom burdens, and inflammatory bowel disease), as well as new imaging-guidance techniques like Magnetic Resonance Imaging for SBRT delivery.

Validation of a Quality Metric Score to Assess the Placement of Hydrogel Rectal Spacer in Patients Treated With Prostate Stereotactic Radiation Therapy

Purpose

To evaluate the quality of the interspace between the prostate and rectum and assess the effect on the dose to the rectum by measuring the spacer quality score (SQS) before and after implanting a hydrogel rectal spacer.

Methods and Materials

Thirty patients with prostate cancer were treated with stereotactic ablative body radiation therapy as part of the SPORT clinical trial. Each patient had a 10 mL polyethylene glycol hydrogel spacer inserted transperineally. Computed tomography scans were acquired before and after spacer insertion, 10MV flattening filter free (FFF) stereotactic ablative body radiation therapy (SABR) treatment plans were generated using each image set. To calculate the SQS, the prostate-rectal interspace (PRI) was measured in the anterior-posterior orientation, parallel to the anatomic midline at the prostate base, apex, and midgland on the prespacer and postspacer computed tomography. Measurements were taken in 3 transverse positions between the prostate and the rectum, and PRI scores of 0, 1, and 2 were assigned if the interspace between prostate and rectum was <0.3, 0.3 to 0.9, or ≥1 cm, respectively. The overall SQS was the lowest of the PRI scores. Differences between prespacer and postspacer PRIs and SQS were investigated by performing Fisher's exact test and differences between doses to the rectum were investigated by performing the paired samples Wilcoxon rank-sum test and Student t test.

Results

Statistically significant differences between prespacer versus postspacer patients were found when grouping patients according to their overall SQS. The PRI summary score did not reach statistical significance between prespacer and postspacer at the base but was significantly higher for the prostate midline and apex. Statistically significant differences in some rectum dose-volume metrics were found when grouping patients according to their PRIs and SQS.

Conclusions

SQS before and after the spacer insertion was evaluated and was found to be correlated with pre- and postspacer rectal dosimetry. Sources of improvement of the SQS scoring metric and limitations are discussed.

Multiscale spatial relationship-based model for predicting bladder wall dose in pelvic radiotherapy

PURPOSE

This research aimed to develop a prediction model to assess bladder wall dosimetry during radiotherapy for patients with pelvic tumors, thereby facilitating the refinement and evaluation of radiotherapy treatment plans to mitigate bladder toxicity.

METHODS

Radiotherapy treatment plans of 49 rectal cancer patients and 45 gynecologic cancer patients were collected, and multiple linear regression analyses were used to generate prediction models for bladder wall dose parameters (V 10 - 45 G y ( c m 3 ) ${V_{10 - 45Gy\ }}( {{\mathrm{c}}{{\mathrm{m}}^3}} )$ ,D m e a n ( Gy ) ${D_{mean}}( {{\mathrm{Gy}}} )$ ). These models were based on the multiscale spatial relationship between the planning target volume (PTV) and the bladder or bladder wall. The proportion of bladder or bladder wall volume overlapped by the different distance expansions of the PTV was used as an indicator of the multiscale spatial relationship. The accuracy of these models was verified in a cohort of 12 new patients, with further refinement of radiotherapy treatment plans using the predicted values as optimization parameters. Model accuracy was assessed using root mean square error (RMSE) and mean percentage error (MPE).

RESULTS

Models derived from individual disease data outperformed those derived from combined datasets. Predicted bladder wall dose parameters were accurate, with the majority of initial calculated values for new patients falling within the 95% confidence interval of the model predictions. There was a robust correlation between the predicted and actual dose metrics, with a correlation coefficient of 0.943. Using the predicted values to optimize treatment plans significantly reduced bladder wall dose (p< $\ < \ $ 0.001), with bladder wallD mean ( G y ) ${D_{{\mathrm{mean}}}}( {Gy} )$ andV 10 - 45 G y ( c m 3 ) ${V_{10 - 45Gy\ }}( {{\mathrm{c}}{{\mathrm{m}}^3}} )$ decreasing by 2.27±0.80 Gy (5.8%±1.8%) and 2.96±2.05 cm3 (7.9%±5.4%), respectively.

CONCLUSION

The formulated prediction model provides a valuable tool for predicting and minimizing bladder wall dose and for optimizing and evaluating radiotherapy treatment plans for pelvic tumor patients. This approach holds promise for reducing bladder toxicity and potentially improving patient outcomes.

Treatment Optimization in Linac-Based SBRT for Localized Prostate Cancer: A Single-Arc versus Dual-Arc Plan Comparison

This study aimed to comprehensively present data on treatment optimization in linac-based SBRT for localized prostate cancer at a single institution. Moreover, the dosimetric quality and treatment efficiency of single-arc (SA) versus dual-arc (DA) VMAT planning and delivery approaches were compared. Re-optimization was performed on twenty low-to-intermediate-risk- (36.25 Gy in 5 fractions) and twenty high-risk (42.7 Gy in 7 fractions) prostate plans initially administered with the DA FFF-VMAT technique in 2021. An SA approach was adopted, incorporating new optimization parameters based on increased planning and clinical experience. Analysis included target coverage, organ-at-risk (OAR) sparing, treatment delivery time, and the pre-treatment verification's gamma analysis-passing ratio. The SA optimization technique has consistently produced superior plans. Rectum and bladder mean doses were significantly reduced, and comparable target coverage and homogeneity were achieved in order to maintain a urethra protection strategy. The mean SA treatment delivery time was reduced by 22%; the mean monitor units increased due to higher plan complexity; and dose measurements demonstrated optimal agreement with calculations. The substantial reduction in treatment delivery time decreased the probability of prostate motion beyond the applied margins, suggesting potential decrease in treatment-related toxicity and improved target coverage in prostate SBRT. Further investigations are warranted to assess the long-term clinical outcomes.

Every-Other-Day Versus Once-a-Week Urethra-Sparing Prostate Stereotactic Body Radiation Therapy: 5-Year Results of a Randomized Phase 2 Trial

PURPOSE

The objective of this study was to present the 5-year results from a prospective, multicenter, phase 2 randomized trial of every-other-day (EOD) versus once-a-week (QW) urethra-sparing stereotactic body radiation therapy for localized prostate cancer.

METHODS AND MATERIALS

Between 2012 and 2015, 170 patients with cT1c-3aN0M0 prostate cancer from 9 European institutions were randomized to 36.25 Gy in 5 fractions (6.5 Gy/fraction to the urethra) delivered either EOD (arm A, n = 84) or QW (arm B, n = 86). The median follow-up was 78 months (interquartile range, 66-89 months) and 77 months (interquartile range, 66-82 months) for arms A and B, respectively.

RESULTS

Among the 165 patients treated and retained for the final analysis (arm A, n = 82; arm B, n = 83), acute toxicity (National Cancer Institute Common Terminology Criteria for Adverse Events version 4.03 scale) was mild or absent, with no differences between arms. The 5-year grade 2 or greater genitourinary toxicity-free survival was 75.9% and 76.1% for arms A and B, respectively (P = .945), whereas the 5-year grade 2 or greater gastrointestinal toxicity-free survival was 89% and 92% for arms A and B, respectively (P = .596). No changes in European Organisation for Research and Treatment of Cancer QLQ-PR25 scores were observed in both arms for genitourinary, gastrointestinal, and sexual domains at 5-year follow-up compared with baseline. At the last follow-up, biochemical failure was observed in 14 patients in the EOD arm and in 7 patients in the QW arm, with a 5-year biochemical relapse-free survival rate of 92.2% and 93% for arms A and B, respectively (P = .13).

CONCLUSIONS

Stereotactic body radiation therapy for prostate cancer with a 10% dose reduction to urethra was associated with a minimal effect on urinary function and quality of life regardless of an EOD or QW fractionation schedule. Biochemical control so far has been encouraging and much alike in both study arms, although longer follow-up is probably needed to assess the true value of overall treatment time on disease outcome.

A new workflow of the on-line 1.5-T MR-guided adaptive radiation therapy

PURPOSE

The aim of this study was to develop a new workflow for 1.5-T magnetic resonance (MR)-guided on-line adaptive radiation therapy (MRgART) and assess its feasibility in achieving dose constraints.

MATERIALS AND METHODS

We retrospectively evaluated the clinical data of patients who underwent on-line adaptive radiation therapy using a 1.5-T MR linear accelerator (MR-Linac). The workflow in MRgART was established by reviewing the disease site, number of fractions, and re-planning procedures. Five cases of prostate cancer were selected to evaluate the feasibility of the new workflow with respect to achieving dose constraints.

RESULTS

Between December 2021 and September 2022, 50 consecutive patients underwent MRgART using a 1.5-T MR-Linac. Of these, 20 had prostate cancer, 10 had hepatocellular carcinoma, 6 had pancreatic cancer, 5 had lymph node oligo-metastasis, 3 had renal cancer, 3 had bone metastasis, 2 had liver metastasis from colon cancer, and 1 had a mediastinal tumor. Among a total of 247 fractions, 235 (95%) were adapt-to-shape (ATS)-based re-planning. The median ATS re-planning time in all 50 cases was 17 min. In the feasibility study, all dose constraint sets were met in all 5 patients by ATS re-planning. Conversely, a total of 14 dose constraints in 5 patients could not be achieved by virtual plan without using adaptive re-planning. These dose constraints included the minimum dose received by the highest irradiated volume of 1 cc in the planning target volume and the maximum dose of the rectal/bladder wall.

CONCLUSION

A new workflow of 1.5-T MRgART was established and found to be feasible. Our evaluation of the dose constraint achievement demonstrated the effectiveness of the workflow.

A pilot study of stereotactic body radiotherapy combined with pelvic radiotherapy and GTVp boost based on multiparameter magnetic resonance image in patients with high-risk prostate cancer

This pilot study aimed to explore the preliminary effects and safety of stereotactic body radiotherapy (SBRT) combined with preventive pelvic radiotherapy and primary gross tumor volumes (GTVp) boost in patients with high-risk prostate cancer based on multiparameter magnetic resonance image (mpMRI). Tumors were contoured as GTVp based on mpMRI. The prostate and proximal seminal vesicles were considered as the clinical target volume1. The pelvic lymphatic drainage area constituted clinical target volume 2. Radiation doses were 40Gy or 45Gy/5fractions to planning target volume of primary tumor, 37.5Gy/5f to prostate, seminal vesicle, and positive pelvic lymph nodes, and 25Gy/5f to pelvic synchronously. The treatment was delivered 3 times per week. Volumetric modulated arc radiotherapy and intensity-modulated radiotherapy were used to complete SBRT. The genitourinary (GU) and gastrointestinal (GI) toxicities were evaluated. Quality of life data was also captured. A total of 15 patients were enrolled in this study with a median age of 78 (56-87) from 2017 to 2020. All patients received SBRT. At 3 months after radiotherapy, the proportion of PSA < 0.006 ng/mL was 66.7% (10/15). The 2-year biochemical relapse-free survival was 93.3%. The incidence of grade 1 acute GU side effects was 80% (12/15); the incidence of acute grade 1 GI toxicity was 66.7% (10/15); and no grade 2 or higher acute GU and GI side effects was observed. Two patients presented with temporary late grade 2 GI toxicity. International Prostatic System Score increased rapidly after a transient increase at 1 week (P = .001). There were no significant differences in EORTC quality of life scores in all domains except global health status. In this pilot study, it was revealed that SBRT combined with preventive pelvic radiotherapy and GTVp boost based on mpMRI image was effective and well tolerated for patients with high-risk prostate cancer.

Prostate Stereotactic Body Radiation Therapy With a Focal Simultaneous Integrated Boost: 5-Year Toxicity and Biochemical Recurrence Results From a Prospective Trial

PURPOSE

Stereotactic body radiation therapy (SBRT) is increasingly used as a definitive treatment option for patients with prostate adenocarcinoma. The aim of this study was to assess the late toxicity, patient-reported quality of life outcomes, and biochemical recurrence rates after prostate SBRT with simultaneous integrated boost (SIB) targeting lesions defined by magnetic resonance imaging (MRI).

METHODS AND MATERIALS

Patients were eligible if they had biopsy-proven low- or intermediate-risk prostate adenocarcinoma, one or more focal lesions on MRI, and an MRI-defined total prostate volume of <120 mL. All patients received SBRT delivered to the entire prostate to a dose of 36.25 Gy in 5 fractions with an SIB to the lesions seen on MRI to 40 Gy in 5 fractions. Late toxicity was defined as any possible treatment-related adverse event occurring after 3 months from the completion of SBRT. Patient-reported quality of life was ascertained using standardized patient surveys.

RESULTS

A total of 26 patients were enrolled. Six patients (23.1%) had low-risk disease and 20 patients had intermediate-risk disease (76.9%). Seven patients (26.9%) received androgen deprivation therapy. Median follow-up was 59.5 months. No biochemical failures were observed. Three patients (11.5%) experienced late grade 2 genitourinary (GU) toxicity requiring cystoscopy, and 7 patients (26.9%) had late grade 2 GU toxicity requiring oral medications. Three patients (11.5%) had late grade 2 gastrointestinal toxicity characterized by hematochezia requiring colonoscopy and steroids per rectum. There were no grade 3 or higher toxicity events observed. The patient-reported quality-of-life metrics at the time of last follow-up were not significantly different than the pre-treatment baseline.

CONCLUSIONS

The results of this study support that SBRT to the entire prostate to a dose of 36.25 Gy in 5 fractions with focal SIB to 40 Gy in 5 fractions has excellent biochemical control and is not associated with undue late gastrointestinal or GU toxicity or long-term quality of life decrement. Focal dose escalation with an SIB planning approach may be an opportunity to improve biochemical control while limiting dose to nearby organs at risk.

Local Failure after Prostate SBRT Predominantly Occurs in the PI-RADS 4 or 5 Dominant Intraprostatic Lesion

BACKGROUND

A positive post-treatment prostate biopsy following definitive radiotherapy carries significant prognostic implications.

OBJECTIVE

To determine whether local recurrences after prostate stereotactic body radiation therapy (SBRT) are associated with the presence of and occur more commonly within the region of a PI-RADS 4 or 5 dominant intra-prostatic lesion (DIL) identified on pre-treatment multi-parametric magnetic resonance imaging (MRI).

DESIGN, SETTING, AND PARTICIPANTS

247 patients with localized prostate cancer treated with SBRT at our institution from 2009-2018 underwent post-treatment biopsies (median time to biopsy: 2.2 years) to evaluate local control.

INTERVENTIONS

Prostate SBRT (median 40 Gy in 5 fractions).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

MRIs were read by a single diagnostic radiologist blinded to other patient characteristics and treatment outcomes. The DIL presence, size, location, and extent were then analyzed to determine associations with the post-treatment biopsy outcomes.

RESULTS AND LIMITATIONS

Among patients who underwent post-treatment biopsies, 39/247 (15.8%) were positive for Gleason-gradable prostate adenocarcinoma, of which 35/39 (90%) had a DIL initially present and 29/39 (74.4%) had a positive biopsy within the DIL. Factors independently associated with post-treatment biopsy outcomes included the presence of a DIL (OR 6.95; p = 0.001), radiographic T3 disease (OR 5.23, p < 0.001), SBRT dose ≥40 Gy (OR 0.26, p = 0.003), and use of androgen deprivation therapy (ADT; OR 0.28, p = 0.027). Among patients with a DIL (N = 149), the only factors associated with post-treatment biopsy outcomes included ≥50% percent cores positive (OR 2.4, p = 0.037), radiographic T3 disease (OR 4.04, p = 0.001), SBRT dose ≥40 Gy (OR 0.22, p < 0.001), and use of ADT (OR 0.21, p = 0.014).

CONCLUSIONS

Our results suggest that men with PI-RADS 4 or 5 DILs have a higher risk of local recurrence after prostate SBRT and that most recurrences are located within the DIL.

PATIENT SUMMARY

We found the presence of a dominant tumor on pre-treatment MRI was strongly associated with residual cancer within the prostate after SBRT and that most recurrences were within the dominant tumor.

Salvage Prostate Brachytherapy in Radiorecurrent Prostate Cancer: An International Delphi Consensus Study

BACKGROUND AND PURPOSE

Local recurrences after previous radiotherapy (RT) are increasingly being identified in biochemically recurrent prostate cancer. Salvage prostate brachytherapy (BT) is an effective and well tolerated treatment option. We sought to generate international consensus statements on the use and preferred technical considerations for salvage prostate BT.

MATERIALS AND METHODS

International experts in salvage prostate BT were invited (n=34) to participate. A three-round modified Delphi technique was utilized, with questions focused on patient- and cancer-specific criteria, type and technique of BT, and follow-up. An a priori threshold for consensus of ≥ 75% was set, with a majority opinion being ≥ 50%.

RESULTS

Thirty international experts agreed to participate. Consensus was achieved for 56% (18/32) of statements. Consensus was achieved in several areas of patient selection: 1) A minimum of 2-3 years from initial RT to salvage BT; 2) MRI and PSMA PET should be obtained; and 3) Both targeted and systematic biopsies should be performed. Several areas did not reach consensus: 1) Maximum T stage/PSA at time of salvage; 2) Utilization/duration of ADT; 3) Appropriateness of combining local salvage with SABR for oligometastatic disease and 4) Repeating a second course of salvage BT. A majority opinion preferred High Dose-Rate salvage BT, and indicated that both focal and whole gland techniques could be appropriate. There was no single preferred dose/fractionation.

CONCLUSION

Areas of consensus within our Delphi study may serve as practical advice for salvage prostate BT. Future research in salvage BT should address areas of controversy identified in our study.

Magnetic Resonance Imaging-Guided vs Computed Tomography-Guided Stereotactic Body Radiotherapy for Prostate Cancer: The MIRAGE Randomized Clinical Trial

Importance

Magnetic resonance imaging (MRI) guidance offers multiple theoretical advantages in the context of stereotactic body radiotherapy (SBRT) for prostate cancer. However, to our knowledge, these advantages have yet to be demonstrated in a randomized clinical trial.

Objective

To determine whether aggressive margin reduction with MRI guidance significantly reduces acute grade 2 or greater genitourinary (GU) toxic effects after prostate SBRT compared with computed tomography (CT) guidance.

Design, Setting, and Participants

This phase 3 randomized clinical trial (MRI-Guided Stereotactic Body Radiotherapy for Prostate Cancer [MIRAGE]) enrolled men aged 18 years or older who were receiving SBRT for clinically localized prostate adenocarcinoma at a single center between May 5, 2020, and October 1, 2021. Data were analyzed from January 15, 2021, through May 15, 2022. All patients had 3 months or more of follow-up.

Interventions

Patients were randomized 1:1 to SBRT with CT guidance (control arm) or MRI guidance. Planning margins of 4 mm (CT arm) and 2 mm (MRI arm) were used to deliver 40 Gy in 5 fractions.

Main Outcomes and Measures

The primary end point was the incidence of acute (≤90 days after SBRT) grade 2 or greater GU toxic effects (using Common Terminology Criteria for Adverse Events, version 4.03 [CTCAE v4.03]). Secondary outcomes included CTCAE v4.03-based gastrointestinal toxic effects and International Prostate Symptom Score (IPSS)-based and Expanded Prostate Cancer Index Composite-26 (EPIC-26)-based outcomes.

Results

Between May 2020 and October 2021, 156 patients were randomized: 77 to CT (median age, 71 years [IQR, 67-77 years]) and 79 to MRI (median age, 71 years [IQR, 68-75 years]). A prespecified interim futility analysis conducted after 100 patients reached 90 or more days after SBRT was performed October 1, 2021, with the sample size reestimated to 154 patients. Thus, the trial was closed to accrual early. The incidence of acute grade 2 or greater GU toxic effects was significantly lower with MRI vs CT guidance (24.4% [95% CI, 15.4%-35.4%] vs 43.4% [95% CI, 32.1%-55.3%]; P = .01), as was the incidence of acute grade 2 or greater gastrointestinal toxic effects (0.0% [95% CI, 0.0%-4.6%] vs 10.5% [95% CI, 4.7%-19.7%]; P = .003). Magnetic resonance imaging guidance was associated with a significantly smaller percentage of patients with a 15-point or greater increase in IPSS at 1 month (6.8% [5 of 72] vs 19.4% [14 of 74]; P = .01) and a significantly reduced percentage of patients with a clinically significant (≥12-point) decrease in EPIC-26 bowel scores (25.0% [17 of 68] vs 50.0% [34 of 68]; P = .001) at 1 month.

Conclusions and Relevance

In this randomized clinical trial, compared with CT-guidance, MRI-guided SBRT significantly reduced both moderate acute physician-scored toxic effects and decrements in patient-reported quality of life. Longer-term follow-up will confirm whether these notable benefits persist.

Trial Registration

ClinicalTrials.gov Identifier: NCT04384770.

Error detection using EPID-based 3D in vivo dose verification for lung stereotactic body radiotherapy

PURPOSE

To investigate the error detectability limitations of an EPID-based 3D in vivo dosimetry verification system for lung stereotactic body radiation therapy (SBRT).

METHODS

Thirty errors were intentionally introduced, consisting of dynamic and constant machine errors, to simulate the possible errors that may occur during delivery. The dynamic errors included errors in the output, gantry angle and MLC positions related to gantry inertial and gravitational effects, while the constant errors included errors in the collimator angle, jaw positions, central leaf positions, setup shift and thickness to simulate patient weight loss. These error plans were delivered to a CIRS phantom using the SBRT technique for lung cancer. Following irradiation of these error plans, the dose distribution was reconstructed using iViewDose™ and compared with the no error plan.

RESULTS

All errors caused by the central leaf positions, dynamic MLC errors, Jaw inwards movements, setup shifts and patient anatomical changes were successfully detected. However, dynamic gantry angle and collimator angle errors were not detected in the lung case due to the rotation-symmetric target shape. The results showed that the γ_mean and γ_passrate indicators can detect 13 (81.3%) and 14 (87.5%) of the 16 errors respectively without including the gantry angle error, collimator angle error and output error.

CONCLUSIONS

In summary, iViewDose™ is an appropriate approach for detecting most types of clinical errors for lung SBRT. However, the phantom results also showed some detectability limitations of the system in terms of dynamic gantry angle and constant collimator angle errors.

SBRT focal dose intensification using an MR-Linac adaptive planning for intermediate-risk prostate cancer: An analysis of the dosimetric impact of intra-fractional organ changes

INTRODUCTION

Using an magnetic resonance linear accelerator (MR-Linac) may improve the precision of visible tumor boosting with ultra-hypofractionation by accounting for daily positional changes in the target and organs at risk (OAR).

PATIENTS AND METHODS

Fifteen patients with prostate cancer and an MR-detected dominant lesion were treated on the MR-Linac with stereotactic body radiation (SBRT) to 40 Gy in 5 fractions, boosting the gross tumor volume (GTV) to 45 Gy with daily adaptive planning. Imaging was acquired again after initial planning (verification scan), and immediately after treatment (post-treatment scan). Prior to beam-on, additional adjustments were made on the verification scan. Contours were retrospectively adjusted on verification and post-treatment scans, and the daily plan recalculated on these scans to estimate the true dose delivered.

RESULTS

The median prostate D95% for plan 1, 2 and 3 was 40.3 Gy, 40.5 Gy and 40.3 Gy and DIL D95% was 45.7 Gy, 45.2 Gy and 44.6 Gy, respectively. Bladder filling was associated with reduced GTV coverage (p = 0.03, plan 1 vs 2) and prostate coverage (p = 0.03, plan 2 vs 3). The D0.035 cc constraint was exceeded on verification and post-treatment plans in 24 % and 33 % of fractions for the urethra, 31 % and 45 % for the bladder, and 35 % and 25 % for the rectum, respectively.

CONCLUSION

MR-Linac guided, daily adaptive SBRT with focal boosting of the GTV yields acceptable planned and delivered dosimetry. Adaptive planning with a MR-Linac may reliably deliver the prescribed dose to the intended tumor target.

The Association of Radiation Dose With Overall Survival for Patients Treated With Prostate Stereotactic Body Radiation Therapy

Introduction Stereotactic body radiation therapy (SBRT) for prostate adenocarcinoma (PCa) has demonstrated excellent biochemical recurrence-free survival, with studies showing improved BRFS with higher-dose SBRT. However, current studies have been underpowered to evaluate the relationship of SBRT dose to overall survival (OS). In this retrospective study using the National Cancer Database (NCDB), we hypothesize that, given the low alpha/beta ratio of PCa, a relatively small increase in the dose-per-fraction would be associated with improved survival outcomes for intermediate-risk PCa (IR-PCa) comparing 36.25 Gy/5 fx [biologically equivalent dose (BEDα/β = 1.5 = 211.46 Gy vs. 35 Gy (BED1.5 = 198.33 Gy)]. Materials and methods We queried records from the NCDB from 2005 to 2015 for men receiving prostate SBRT for IR-PCa (n=2673). 82% were treated using either 35 Gy/5 fx or 36.25 Gy/5 fx. We compared OS in men receiving 35 Gy versus 36.25 Gy. Inverse probability of treatment weighting (IPTW) was used to adjust for covariable imbalances. Unweighted- and weighted-multivariable analysis (MVA) using Cox regression was used to compare OS hazard ratios, accounting for age, race, Charlson-Deyo comorbidity score, treatment facility type, prostate-specific antigen (PSA), clinical T-stage, Gleason Score, and use of androgen deprivation therapy (ADT). Kaplan-Meier analysis was performed. Results Seven hundred and eighty men (35%) were treated with 35 Gy/5 fx and 1434 men (65%) were treated with 36.25 Gy/5 fx (n=2214). Compared to 35 Gy, treatment with 36.25 Gy was associated with significantly improved OS (hazard ratio [HR]: 0.61 [95% CI: 0.43-0.89], P=0.009) on MVA. On Kaplan-Meier analysis, 36.25 Gy was associated with improved survival (p=0.034), with a five-year OS of 92% and 88%, respectively. Conclusions In a multi-institutional retrospective database of 2,214 IR patients treated with prostate SBRT, a prescription dose of 36.25 Gy/5 fx was associated with improved OS vs. 35 Gy/5 fx. Results are hypothesis-generating but do lend support to the current National Comprehensive Cancer Network (NCCN) guidelines that the minimum recommended dose for prostate SBRT is 36.25 Gy/5 fx.

Efficacy, toxicity, and quality-of-life outcomes of ultrahypofractionated radiotherapy in patients with localized prostate cancer: A single-arm phase 2 trial from Asia

AIMS

Ultra-hypofractionated radiotherapy (UHF-RT) is widely utilized in men with localized prostate cancer (PCa). There are limited data in Asian cohorts. We report the outcomes of a single-arm, phase II trial of UHF-RT from an Asian center.

METHODS

We recruited men with histologically confirmed, nonmetastatic localized PCa. UHF-RT regimens were 36.25 Gy (Cohort A) and 37.5 Gy (Cohort B) delivered in five fractions every other day over 1.5-2.5 weeks. Primary endpoint was physician-scored late genitourinary (GU) and gastrointestinal (GI) adverse events (AEs). Quality-of-life (QoL) was assessed by Expanded Prostate Cancer Index Composite (EPIC) at baseline, 1- and 2-year post-UHF-RT.

RESULTS

Between March 2014 and August 2019, 105 men were recruited; four were subsequently excluded from analysis. Median age was 68.0 (Interquartile range (IQR): 63.8-73.0) years. 26 (24.8%) and 68 (64.8%) men had NCCN-defined low-and intermediate-risk PCa, respectively. No late ≥G3 GU or GI toxicities were reported in both cohorts. Peak incidence of acute ≥G2 GU AEs at 14 days post-UHF-RT was 23.6% (17/72) and 24.0% (6/25) in Cohorts A and B, respectively; ≥G2 GI AEs were observed in 9.7% (7/72) and 36.0% (9/25), respectively. Late ≥G2 GU and GI AEs occurred in 4.7% and 3.1% of Cohort A patients, and 5.0% in Cohort B at 12 months, with no AEs at 24 months. EPIC scores changed minimally across all domains. At a median follow-up of 44.9 months, we recorded one (1.3%) biochemical relapse by the Phoenix criteria (Cohort A).

CONCLUSION

UHF-RT is well tolerated in Asian men and can be a recommended fractionation schema for localized PCa.

A comparison between high dose rate brachytherapy and stereotactic body radiotherapy boost after elective pelvic irradiation for high and very high-risk prostate cancer

Purpose: To compare biochemical recurrence-free survival (BRFS) and toxicity outcomes of high dose rate brachytherapy (HDRB) and stereotactic body radiotherapy (SBRT) boost after elective nodal irradiation for high/very high-risk prostate cancer.Materials and Methods: a retrospective analysis was performed in 149 male. In 98 patients, the boost to the prostate was delivered by HDRB as 2 fractions of 10 Gy (EQD2 for α/β = 1.5; 66 Gy) or 1 fraction of 15 Gy (EQD2 for α/β = 1.5; 71 Gy). In 51 male, SBRT was used for the boost delivery (3 fractions of 7 Gy; EQD2Gy for α/β = 1.5; 51 Gy) because brachytherapy equipment was out of order.Results: In 98 patients that received HDRB boost, 3- and 5-year BRFS were 74.6% and 66.8%. Late grade-II genitourinary toxicity was detected in 27, grade-III in 1 case. Grade-II (maximum) rectal toxicity was diagnosed in nine patients. For 51 male patients that received SBRT boost, 3- and 5-year BRFS was 76.5% and 67.7%. Late grade-II (maximum) genitourinary toxicity was detected in five cases, late grade-II rectal toxicity in four cases. Other three patients developed late grade-III–IV rectal toxicity that required diverting colostomy. SBRT boost was associated with higher maximum dose to 2 cm3 of anterior rectal wall (D2cm³rectum) compared to HDRB: 92% versus 55% of dose to prostate. Severe rectal toxicity was negligible at EQD2 D2cm³rectum <85 Gy and EQD2 D5cm³ rectum <75 Gy.Conclusion: Our results indicate similar 3- and 5-year BRFS in patients with high/very high-risk prostate cancer who received HDRB or SBRT boost, but SBRT boost is associated with higher rate of severe late rectal toxicity.

Magnetic Resonance-Guided Prostate Stereotactic Body Radiation Therapy With Daily Online Plan Adaptation: Results of a Prospective Phase 1 Trial and Supplemental Cohort

Purpose

Stereotactic magnetic resonance (MR)-guided adaptive radiation therapy (SMART) for prostate cancer allows for MR-based contouring, real-time MR motion management, and daily plan adaptation. The clinical and dosimetric benefits associated with prostate SMART remain largely unknown.

Methods and Materials

A phase 1 trial of prostate SMART was conducted with primary endpoints of safety and feasibility. An additional cohort of patients similarly treated with prostate SMART were included in the analysis. SMART was delivered to 36.25 Gy in 5 fractions to the prostate ± seminal vesicles using the MRIdian linear accelerator system (ViewRay, Inc). Rates of urinary and gastrointestinal toxic effects and patient-reported outcome measures were assessed. Dosimetric analyses were conducted to evaluate the specific benefits of daily plan adaptation.

Results

The cohort included 22 patients (n = 10 phase 1, n = 12 supplemental) treated in 110 fractions. Median follow-up was 7.9 months. Acute grade 2 urinary and gastrointestinal toxic effects were observed in 22.7% and 4.5%, respectively, and 4.5% and 0%, respectively, at last follow-up. No grade 3+ events were observed. Expanded Prostate Cancer Index-26 urinary obstructive scores decreased during SMART (mean, 9.3 points; P = .03) and returned to baseline by 3 months. No other significant changes in patient-reported outcome measures were observed. One-hundred percent of fractions required plan adaptation owing to exceeding organ-at-risk metrics (68%) or suboptimal target coverage (33%) resulting from anatomic changes. Minimum acceptable planning target volume, rectal, bladder, and urethra/bladder neck metrics were violated in 24%, 20%, 24%, and 33% of predicted plans, respectively; 0% of reoptimized plans violated metrics. Underlying causes for deficient dosimetry before reoptimization included changes in bladder filling, seminal vesicle position, prostate volume (median 4.7% increase by fraction 3; range, 0%-56%), and hotspots shifting into urethra/bladder neck.

Conclusions

Prostate SMART results in low risk of acute toxic effects with improvements in target and organ-at-risk dosimetry. The clinical benefits resulting from daily plan adaptation, including urethra/bladder neck protection, warrant further investigation.

Quality of life after definitive linear accelerator-based stereotactic radiotherapy for prostate cancer: a longitudinal study

BACKGROUND

Prostate cancer is the second most common malignancy worldwide, and the majority of patients are diagnosed with localized disease. We examined patients' quality of life after stereotactic body radiation therapy (SBRT) for prostate cancer.

METHODS

We included patients who were treated between 2016 and 2020. Inclusion criteria were adenocarcinoma of the prostate; class risk of low, intermediate, and high; and a World Health Organization performance status of 0-2. Quality of life was measured using the Functional Assessment of Cancer Therapy-Prostate (FACT-P).

RESULTS

A total of 439 patients were treated with SBRT, with a median age of 73 years old. The median follow-up period was 34 months. FACT-P Trial Outcome Index (p < 0.0001), FACT-General (p = 0.0003), and FACT-P-Total (p < 0.0001) scores declined at 1 month post-SBRT, then recovered and returned to the same level as before treatment at 3-4 months post-SBRT. The decrease in quality of life in the first month was particularly remarkable in patients who received long-term hormone injections (36%). One month after the end of SBRT, about 22% of patients experienced "quite a bit" or more troubling side effects.

CONCLUSIONS

This study showed longitudinal changes in quality of life by FACT-P after SBRT for prostate cancer. Overall, prostate SBRT was well tolerated.

Imaging Biomarkers in Prostate Stereotactic Body Radiotherapy: A Review and Clinical Trial Protocol

Advances in imaging have changed prostate radiotherapy through improved biochemical control from focal boost and improved detection of recurrence. These advances are reviewed in the context of prostate stereotactic body radiation therapy (SBRT) and the ARGOS/CLIMBER trial protocol. ARGOS/CLIMBER will evaluate 1) the safety and feasibility of SBRT with focal boost guided by multiparametric MRI (mpMRI) and ¹⁸F-PSMA-1007 PET and 2) imaging and laboratory biomarkers for response to SBRT. To date, response to prostate SBRT is most commonly evaluated using the Phoenix Criteria for biochemical failure. The drawbacks of this approach include lack of lesion identification, a high false-positive rate, and delay in identifying treatment failure. Patients in ARGOS/CLIMBER will receive dynamic ¹⁸F-PSMA-1007 PET and mpMRI prior to SBRT for treatment planning and at 6 and 24 months after SBRT to assess response. Imaging findings will be correlated with prostate-specific antigen (PSA) and biopsy results, with the goal of early, non-invasive, and accurate identification of treatment failure.

Rationale for Utilization of Hydrogel Rectal Spacers in Dose Escalated SBRT for the Treatment of Unfavorable Risk Prostate Cancer

In this review we outline the current evidence for the use of hydrogel rectal spacers in the treatment paradigm for prostate cancer with external beam radiation therapy. We review their development, summarize clinical evidence, risk of adverse events, best practices for placement, treatment planning considerations and finally we outline a framework and rationale for the utilization of rectal spacers when treating unfavorable risk prostate cancer with dose escalated Stereotactic Body Radiation Therapy (SBRT).

A phase II trial of stereotactic body radiotherapy in 4 fractions for patients with localized prostate cancer

Purpose/objective(s)

To report results from our phase II study of stereotactic body radiotherapy (SBRT) delivering 36 Gy in 4 fractions for patients with localized prostate cancer.

Materials/methods

We enrolled 55 patients treated with SBRT delivering 36 Gy in 4 fractions between 2015 to 2018. All patients were categorized as low-risk (n = 4), intermediate-risk (n = 31) or high-risk (n = 20) according to National Comprehensive Cancer Network criteria. Median age was 73 years (range 54–86 years). Two-thirds of patients (n = 37) had received androgen-deprivation therapy for 3–46 months (median, 31 months). Median duration of follow-up was 36 months (range 1–54 months). We used Radiation Therapy Oncology Group and National Cancer Institute—Common Toxicity Criteria version 4 for toxicity assessments. Quality of life (QOL) outcomes were also evaluated using the Expanded Prostate Cancer Index Composite (EPIC).

Results

Protocol treatments were completed for all patients. Six patients experienced biochemical failures. Among these six patients, three patients experienced clinical failure. One patient showed bone metastasis before biochemical failure. One patient died of gastric cancer. The 3-year biochemical control rate was 89.8%. Acute grade 2 genitourinary (GU) and gastrointestinal (GI) toxicities were observed in 5 patients (9%) and 6 patients (11%), respectively. No grade 3 or higher acute toxicities were observed. Late grade 2 GU and GI toxicities were observed in 7 patients (13%) and 4 patients (7%), respectively. Late grade 3 GU and GI toxicities were observed in 1 patient (1.8%) each. EPIC scores decreased slightly during the acute phase and recovered within 3 months after treatment.

Conclusion

Our phase II study showed that SBRT delivering 36 Gy in 4 fractions was safe and effective with favorable QOL outcomes, although this regimen showed slightly more severe toxicities compared to current standards.

Feasibility, pitfalls and results of a structured concept-development phase for a randomized controlled phase III trial on radiotherapy in primary prostate cancer patients

Objective

Failure rate in randomized controlled trials (RCTs) is > 50%, includes safety-problems, underpowered statistics, lack of efficacy, lack of funding or insufficient patient recruitment and is even more pronounced in oncology trials. We present results of a structured concept-development phase (CDP) for a phase III RCT on personalized radiotherapy (RT) in primary prostate cancer (PCa) patients implementing prostate specific membrane antigen targeting positron emission tomography (PSMA-PET).

Materials and methods

The 1 yr process of the CDP contained five main working packages: (i) literature search and scoping review, (ii) involvement of individual patients, patients’ representatives and patients’ self-help groups addressing the patients’ willingness to participate in the preparation process and the conduct of RCTs as well as the patient informed consent (PIC), (iii) involvement of national and international experts and expert panels (iv) a phase II pilot study investigating the safety of implementation of PSMA-PET for focal dose escalation RT and (v) in-silico RT planning studies assessing feasibility of envisaged dose regimens and effects of urethral sparing in focal dose escalation.

Results

(i) Systematic literature searches confirmed the high clinical relevance for more evidence on advanced RT approaches, in particular stereotactic body RT, in high-risk PCa patients. (ii) Involvement of patients, patient representatives and randomly selected males relevantly changed the PIC and initiated a patient empowerment project for training of bladder preparation. (iii) Discussion with national and international experts led to adaptions of inclusion and exclusion criteria. (iv) Fifty patients were treated in the pilot trial and in- and exclusion criteria as well as enrollment calculations were adapted accordingly. Parallel conduction of the pilot trial revealed pitfalls on practicability and broadened the horizon for translational projects. (v) In-silico planning studies confirmed feasibility of envisaged dose prescription. Despite large prostate- and boost-volumes of up to 66% of the prostate, adherence to stringent anorectal dose constraints was feasible. Urethral sparing increased the therapeutic ratio.

Conclusion

The dynamic framework of interdisciplinary working programs in CDPs enhances robustness of RCT protocols and may be associated with decreased failure rates. Structured recommendations are warranted to further define the process of such CDPs in radiation oncology trials.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09434-2.

Highly hypofractionated schedules for localized prostate cancer: Recommendations of the GETUG radiation oncology group

Stereotactic body radiotherapy (SBRT) has become treatment option for localized prostate cancer but the evidence base remains incomplete. Several clinical studies, both prospective and retrospective, have been published. However, treatment techniques, target volumes and dose constraints lack consistency between studies. Based on the current available literature, the French Genito-Urinary Group (GETUG) suggests that.

Evaluation of the impact of pre-operative stereotactic radiotherapy on the acute changes in histopathologic and immune marker profiles of brain metastases

The unique acute effects of the large fractional doses that characterize stereotactic radiosurgery (SRS) or radiotherapy (SRT), specifically in terms of antitumor immune cellular processes, vascular damage, tumor necrosis, and apoptosis on brain metastasis have yet to be empirically demonstrated. The objective of this study is to provide the first in-human evaluation of the acute biological effects of SRS/SRT in resected brain metastasis. Tumor samples from patients who underwent dose-escalated preoperative SRT followed by resection with available non-irradiated primary tumor tissues were retrieved from our institutional biorepository. All primary tumors and irradiated metastases were evaluated for the following parameters: tumor necrosis, T-cells, natural killer cells, vessel density, vascular endothelial growth factor, and apoptotic factors. Twenty-two patients with irradiated and resected brain metastases and paired non-irradiated primary tumor samples met inclusion criteria. Patients underwent a median preoperative SRT dose of 18 Gy (Range: 15–20 Gy) in 1 fraction, with 3 patients receiving 27–30 Gy in 3–5 fractions, followed by resection within median interval of 67.8 h (R: 18.25–160.61 h). The rate of necrosis was significantly higher in irradiated brain metastases than non-irradiated primary tumors (p < 0.001). Decreases in all immunomodulatory cell populations were found in irradiated metastases compared to primary tumors: CD3 + (p = 0.003), CD4 + (p = 0.01), and CD8 + (p = 0.01). Pre-operative SRT is associated with acute effects such as increased tumor necrosis and differences in expression of immunomodulatory factors, an effect that does not appear to be time dependent, within the limited intervals explored within the context of this analysis.

Dose-Intensified Stereotactic Ablative Radiation for Localized Prostate Cancer

Purpose

Stereotactic ablative radiation (SAbR) has been increasingly used in prostate cancer (PCa) given its convenience and cost efficacy. Optimal doses remain poorly defined with limited prospective comparative trials and long-term safety/efficacy data at higher dose levels. We analyzed toxicity and outcomes for SAbR in men with localized PCa at escalated 45 Gy in 5 fractions.

Methods and Materials

This study retrospectively analyzed men from 2015 to 2019 with PCa who received linear-accelerator-based SAbR to 45 Gy in 5 fractions, along with perirectal hydrogel spacer, fiducial placement, and MRI-based planning. Disease control outcomes were calculated from end of treatment. Minimally important difference (MID) assessing patient-reported quality of life was defined as greater than a one-half standard deviation increase in American Urological Association (AUA) symptom score after SAbR.

Results

Two-hundred and forty-nine (249) low-, intermediate-, and high-risk PCa patients with median follow-up of 14.9 months for clinical toxicity were included. Acute urinary grade II toxicity occurred in 20.4% of patients. Acute grade II GI toxicity occurred in 7.3% of patients. For follow-up > 2 years (n = 69), late GU and GI grade ≥III toxicity occurred in 5.8% and 1.5% of patients, respectively. MID was evident in 31.8%, 23.4%, 35.8%, 37.0%, 33.3%, and 26.7% of patients at 3, 6, 12, 24, 36, and 48 months, respectively. The median follow-up for biochemical recurrence was 22.6 months with biochemical failure-free survival of 100% at 1 year (n = 226) and 98.7% for years 2 (n = 113) and 3 (n = 54).

Conclusions

SAbR for PCa at 45 Gy in 5 fractions shows an encouraging safety profile. Prospective studies with longer follow-up are warranted to establish this dose regimen as standard of care for PCa.

Overview of the current role of stereotactic body radiotherapy in the treatment of unfavorable intermediate- and high-risk prostate cancer

Stereotactic body radiotherapy (SBRT) is well accepted for low- and intermediate-favorable risk prostate cancer. Available evidence about the application of SBRT in unfavorable- and high-risk prostate cancer is less solid. During last year's multiple variations in treatment, techniques have been reported making comparisons more complicated. This review's objective is to review current evidence in application of SBRT in intermediate unfavourable and high-risk prostate cancer and to outline variations in SBRT treatment techniques and relevant results.

Radiation Dose to the Intraprostatic Urethra Correlates Strongly With Urinary Toxicity After Prostate Stereotactic Body Radiation Therapy: A Combined Analysis of 23 Prospective Clinical Trials

PURPOSE

Clinical trials assessing evaluation prostate stereotactic body radiation therapy (SBRT) have used a wide range of allowed doses to the intraprostatic urethra, but the relationship between urethral dose and urinary toxicity has not been thoroughly evaluated. The goal of this study was to characterize urinary toxicity outcomes according to urethral dose administered during prostate SBRT.

METHODS AND MATERIALS

The MEDLINE (PubMed) database was searched for published prospective studies of prostate SBRT through August 2020 that documented a maximum urethral dose metric (MUDM). Reported acute and late urinary toxicity rates were collected. Logistic regression and weighted Pearson correlation models were used to assess associations between urinary toxicity rates and MUDM.

RESULTS

Twenty-three unique studies (n = 2232 patients) met the inclusion criteria and included a wide range of MUDMs (equivalent dose in 2 Gy fractions [EQD₂]: 69-141.75 Gy; α/β = 3 Gy). The median follow-up ranged from 3 to 67 months (median, 32 months). On logistic regression analysis, the MUDM EQD₂ was significantly associated with multiple urinary toxicity endpoints, including acute grade (G) 2+ (odds ratio [OR], 1.02; P < .001), late G2+ (OR, 1.03; P < .0001), and late G3+ (OR, 1.04; P = .003) urinary toxicity. On weighted Pearson correlation analysis, the MUDM was more closely associated with all evaluated urinary toxicity endpoints than prescription dose, including acute G2+ (r = 0.51; P = .02), late G2+ (r = 0.9; P < .0001), and late G3+ toxicity (r = 0.7; P = .003). Multivariate analysis accounting for age, prostate size, bladder dosimetry, and baseline urinary function confirmed associations between urinary outcomes and MUDM. Within the studied dose range, each increase of 1 Gy to the MUDM corresponded to a 0.8% and 1.0% increase in acute G2+ and late G2+ toxicity, respectively.

CONCLUSIONS

Radiation dose to the urethra correlates closely with urinary toxicity in patients with prostate cancer treated with SBRT. Attention should be paid to the urethral dose when delivering prostate SBRT to high doses, and approaches for urethral dose reduction warrant further investigation.

Ultrahypofractionated Radiotherapy versus Conventional to Moderate Hypofractionated Radiotherapy for Clinically Localized Prostate Cancer

The purpose of this study was to compare the toxicity (first endpoint) and efficacy (second endpoint) of ultrahypofractionated radiotherapy (UHF) and dose-escalated conventional to moderate hypofractionated radiotherapy (DeRT) for clinically localized prostate cancer. We compared 253 patients treated with UHF and 499 patients treated with DeRT using multi-institutional retrospective data. To analyze toxicity, we divided UHF into High-dose UHF (H-UHF; equivalent doses of 2 Gy per fraction: EQD2 > 100 Gy1.5) and low-dose UHF (L-UHF; EQD2 ≤ 100 Gy1.5). In toxicity, H-UHF elevated for 3 years accumulated late gastrointestinal and genitourinary toxicity grade ≥ 2 (11.1% and 9.3%) more than L-UHF (3% and 1.2%) and DeRT (3.1% and 4.8%, p = 0.00126 and p = 0.00549). With median follow-up periods of 32.0 and 61.7 months, the actuarial 3-year biochemical failure-free survival rates were 100% (100% and 100% in the L-UHF and H-UHF) and 96.3% in the low-risk group, 96.5% (97.1% and 95.6%) and 94.9% in the intermediate-risk group, and 93.7% (100% and 94.6%) and 91.7% in the high-risk group in the UHF and DeRT groups, respectively. UHF showed equivocal efficacy, although not conclusive but suggestive due to a short follow-up period of UHF. L-UHF using EQD2 ≤ 100 Gy1.5 is a feasible UHF schedule with a good balance between toxicity and efficacy.

SAbR for High-Risk Prostate Cancer-A Prospective Multilevel MRI-Based Dose Escalation Trial

PURPOSE

Radiation dose intensification improves outcome in men with high-risk prostate cancer (HR-PCa). A prospective trial was conducted to determine safety, feasibility, and maximal tolerated dose of multilevel magnetic resonance imaging (MRI)-based 5-fraction SAbR in patients with HR-PCa.

METHODS AND MATERIALS

This phase I clinical trial enrolled patients with HR-PCa with grade group ≥4, prostate-specific antigen (PSA) ≥20 ng/mL, or radiographic ≥T3, and well-defined prostatic lesions on multiparametric MRI (mpMRI) into 4 dose-escalation cohorts. The initial cohort received 47.5 Gy to the prostate, 50 Gy to mpMRI-defined intraprostatic lesion(s), and 22.5 Gy to pelvic lymph nodes in 5 fractions. Radiation doses were escalated for pelvic nodes to 25 Gy and mpMRI lesion(s) to 52.5 Gy and then 55 Gy. Escalation was performed sequentially according to rule-based trial design with 7 to 15 patients per cohort and a 90-day observation period. All men received peri-rectal hydrogel spacer, intraprostatic fiducial placement, and 2 years of androgen deprivation. The primary endpoint was maximal tolerated dose according to a 90-day acute dose-limiting toxicity (DLT) rate <33%. DLT was defined as National Cancer Institute Common Toxicity Criteria for Adverse Events ≥grade 3 treatment-related toxicity. Secondary outcomes included acute and delayed gastrointestinal (GI)/genitourinary (GU) toxicity graded with Common Toxicity Criteria for Adverse Events.

RESULTS

Fifty-five of the 62 enrolled patients were included in the analysis. Dose was escalated through all 4 cohorts without observing any DLTs. Median overall follow-up was 18 months, with a median follow-up of 42, 24, 12, and 7.5 months for cohorts 1 to 4 respectively. Acute and late grade 2 GU toxicities were 25% and 20%, while GI were 13% and 7%, respectively. Late grade 3 GU and GI toxicities were 2% and 0%, respectively.

CONCLUSIONS

SAbR dose for HR-PCa was safely escalated with multilevel dose painting of 47.5 Gy to prostate, 55 Gy to mpMRI-defined intraprostatic lesions, and 25 Gy to pelvic nodal region in 5 fractions. Longer and ongoing follow-up will be required to assess late toxicity.

Dosimetric feasibility of stereotactic irradiation of primary prostate cancer at 5x9 Gy with a method of urethral sparing

OBJECTIVE

The most commonly used dose for prostate cancer stereotactic body radiotherapy (SBRT) is 5 × 7.25 Gy. The aim of this study was to evaluate the dosimetric feasibility of a 5 × 9 Gy SBRT regimen while still limiting the dose to the urethra to 5 × 7.25 Gy. This dosimetric study is part of the groundwork for a future Phase III randomized trial.

METHODS

The prostate, the urethra and the tumors were delineated on 20 dosimetric CT-scans with MRI-registration. The planning target volume (PTVp) was defined as a 5 mm expansion (3 mm posteriorly) of the prostate. The planning at risk volume (PRVu) was defined as a 2 mm expansion of the urethra. The tumors were delineated on the MRI (GTVt) and a 3 mm-margin was added to create a tumoral planning target volume (PTVt). IMRT plans were optimized to deliver 5 × 9 Gy to the PTVp, limiting the dose to the PRVu to 5 × 7.25 Gy. Results are presented using average (range) values.

RESULTS

PTVp doses were D98% = 36.2 Gy (35.6-36.8), D2% = 46.9 Gy (46.5-47.5) and mean dose = 44.1 Gy (43.8-44.5). The dose to the PRVu was within tolerance limits for all 20 patients: V34.4Gy = 99.8% (99.2-100) and D5% = 38.7 Gy (38.6-38.8). Dose coverage of PTV-PRVu was D95% = 40.6 Gy (40.5-40.9), D5% = 46.6 Gy (46.2-47.2) and mean dose = 44.6 Gy (44.3-44.9). Dose to the PTVt reached 44.6 Gy (41.2-45.9). Doses to the OAR were respected, except V36Gy ≤1 cc for the rectum.

CONCLUSION

A SBRT dose-escalation to 5 × 9 Gy on the prostate while sparing the urethra + 2 mm at 36.25 Gy is feasible without compromising dose coverage to the tumor. This radiation regimen will be used for a Phase-III trial.

ADVANCES IN KNOWLEDGE

In prostate SBRT, dose optimization on the urethra is feasible and could decrease urinary toxicities.

Oncologic outcome of salvage high-intensity focused ultrasound (HIFU) in radiorecurrent prostate cancer. A systematic review

INTRODUCTION

External Beam Radiation Therapy (EBRT) is one of the option available for the treatment of clinically localized prostate cancer. In patients with radiorecurrent localized prostate cancer, Androgen Deprivation Therapy (ADT) is one of the most common therapeutic strategies. However, in the last decades, other salvage treatment options have been investigated, such as brachytherapy, cryoablation and High Intensity Focused Ultrasound (Hifu).

MATERIAL AND METHODS

The oncologic outcome of Hifu in a salvage setting after EBRT failure was investigated. We reviewed the literature from 2005 to 2020 in order to report the oncologic outcome of the technique.

RESULTS

A total of 1241 patients were analyzed, with a mean age of 68.6 years and a PSA value of 5.87 ng/mL before treatment. Mean follow-up was 24.3 months after treatment, ranging from 3 to 168 months.

CONCLUSION

Our review of the literature revealed that salvage Hifu is effective in the treatment of radiorecurrent clinically localized prostate cancer, with an overall survival of 85.2% at 5 years.

Visualising the urethra for prostate radiotherapy planning

INTRODUCTION

The prostatic urethra is an organ at risk for prostate radiotherapy with genitourinary toxicities a common side effect. Many external beam radiation therapy protocols call for urethral sparing, and with modulated radiotherapy techniques, the radiation dose distribution can be controlled so that maximum doses do not fall within the prostatic urethral volume. Whilst traditional diagnostic MRI sequences provide excellent delineation of the prostate, uncertainty often remains as to the true path of the urethra within the gland. This study aims to assess if a high-resolution isotropic 3D T2 MRI series can reduce inter-observer variability in urethral delineation for radiotherapy planning.

METHODS

Five independent observers contoured the prostatic urethra for ten patients on three data sets; a 2 mm axial CT, a diagnostic 3 mm axial T2 TSE MRI and a 0.9 mm isotropic 3D T2 SPACE MRI. The observers were blinded from each other's contours. A Dice Similarity Coefficient (DSC) score was calculated using the intersection and union of the five observer contours vs an expert reference contour for each data set.

RESULTS

The mean DSC of the observer vs reference contours was 0.47 for CT, 0.62 for T2 TSE and 0.78 for T2 SPACE (P < 0.001).

CONCLUSIONS

The introduction of a 0.9 mm isotropic 3D T2 SPACE MRI for treatment planning provides improved urethral visualisation and can lead to a significant reduction in inter-observer variation in prostatic urethral contouring.

A Multi-Institutional Phase 2 Trial of High-Dose SAbR for Prostate Cancer Using Rectal Spacer

PURPOSE

High-dose SABR for prostate cancer offers the radiobiologic potency of the most intensified radiation therapy regimens but was associated with >90% rates of ulceration of the anterior rectal wall on endoscopic assessment; this infrequently progressed to severe rectal toxicity in prior prospective series. A multi-institutional phase 2 prospective trial was conducted to assess whether placement of a perirectal hydrogel spacer would reduce acute periprostatic rectal ulcer events after high-dose (>40 Gy) SABR.

METHODS AND MATERIALS

Eligible patients included men with stage ≤T2c localized grade group 1 to 3 prostate cancer, a prostate-specific antigen (PSA) level ≤15 ng/mL, American Urological Association Symptom Index = AUA-SI scores ≤18, and a gland volume ≤80 cm³. Patients underwent perirectal hydrogel spacer placement, followed by SABR of 45 Gy in 5 fractions every other day to the prostate only. Androgen deprivation was not allowed except for cytoreduction. The rectal wall was directly assessed by serial anoscopy during follow-up to determine whether the spacer would reduce acute periprostatic rectal ulcer events from >90% to <70% within 9 months of treatment.

RESULTS

Forty-four men were enrolled and 43 were eligible for protocol analysis. The median follow-up for surviving patients was 48 months. Acute periprostatic ulcers were observed in 6 of 42 patients (14.3%; 95% confidence interval, 6.0%-27%; P < .001) at a median of 2.9 months posttreatment (range, 1.7-5.6 months). All ulcers (grade 1, 5 ulcers; grade 2, 1 ulcer) resolved on repeat anoscopy within 8 months of incidence. There were no grade ≥3 late gastrointestinal toxicities; the incidence of late grade-2 gastrointestinal toxicities was 14.3%, with a prevalence at 3 years of 0%. No toxicities greater than grade 3 occurred in any domain. Four-year freedom from biochemical failure was 93.8% (95% CI, 85.2%-100.0%).

CONCLUSIONS

Temporary hydrogel spacer placement before high-dose SABR treatment for localized prostate cancer and use of strict dose constraints are associated with a significant reduction in the incidence of rectal ulcer events compared with prior phase 1/2 trial results.

Toxicity at 1 Year After Stereotactic Body Radiation Therapy in 3 Fractions for Localized Prostate Cancer

PURPOSE

To assess the toxicity profile of prostate cancer stereotactic body radiation therapy (SBRT) in 3 fractions.

METHODS AND MATERIALS

This was a prospective, multicenter phase 2 toxicity study enrolling patients with low to favorable intermediate-risk prostate cancer. Before simulation, 3 to 4 fiducial markers along with a rectal spacer were placed. The target (prostate only) was prescribed 40 Gy, whereas the maximum dose to the urethra was limited to 33 Gy with the highest priority at planning; less stringent objectives were placed on the bladder, the filling of which was controlled via a Foley catheter. Treatment was delivered every other day. Toxicity was prospectively scored with Common Terminology Criteria for Adverse Events, and several patient-reported outcomes were collected. The maximum allowed prevalence rate of grade 2+ genitourinary (GU) toxicity at 1 year was set at 15%, and the study was sized accordingly.

RESULTS

Between November 2015 and May 2019, 59 patients were enrolled by 3 participating institutions. Acute gastrointestinal toxicity was occasional and mild, whereas 11.9% of patients developed acute grade 2 GU toxicity and 1.7% developed acute grade 3 GU toxicity. No patient had persistent treatment-related grade 2+ GU toxicity at 12 months after SBRT; thus, the null hypothesis was rejected. We observed a clinically relevant worsening of both International Prostate Symptom Score (IPSS) and International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF) scores at 12 months compared with baseline. Moreover, we found a strong association between all selected bladder dose/volume metrics at planning and ICIQ-SF worsening at 12 months, whereas for the IPSS, the correlation with bladder dose metrics was marginal.

CONCLUSIONS

The results suggest that at 12 months after treatment, the toxicity profile of SBRT in 3 fractions is acceptable.

Extreme Hypofractionation with SBRT in Localized Prostate Cancer

Prostate cancer is the most commonly diagnosed cancer among men around the world. Radiotherapy is a standard of care treatment option for men with localized prostate cancer. Over the years, radiation delivery modalities have contributed to increased precision of treatment, employing radiobiological insights to shorten the overall treatment time, improving the control of the disease without increasing toxicities. Stereotactic body radiation therapy (SBRT) represents an extreme form of hypofractionated radiotherapy in which treatment is usually delivered in 1–5 fractions. This review assesses the main efficacy and toxicity data of SBRT in non-metastatic prostate cancer and discusses the potential to implement this scheme in routine clinical practice.

Automatic localization of the prostatic urethra for image guided radiation therapy

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Prostatic urethra can be used for image guided radiation for prostate cancer.

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Computer “finds” the urethra by digital subtraction of scans with / without contrast.

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Urethra segmentation used to setup the patient and position prostate as in simulation.

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A catheter with continuous aerated gel flow is used to detect the urethra under US.

Treatment of prostate cancer with radiation therapy (RT) requires image guided RT (IGRT) to focus the radiation on the target volumes while minimizing doses to organs at risk. Here we describe a urinary catheter that allows imaging of the prostatic urethra and uses it for automatic localization of the prostate for IGRT. The catheter has a contrast lumen that can be empty or full with contrast. Computerized tomography is performed twice, with contrast lumen empty and full, allowing urethral autosegmentation using digital subtraction. Under ultrasound, continuous urethral visualization is possible by pumping aerated gel in- and out of the contrast lumen.

Multi-institutional retrospective analysis of ultrahypofractionated radiotherapy for Japanese prostate cancer patients

To report outcomes and risk factors of ultrahypofractionated (UHF) radiotherapy for Japanese prostate cancer patients. This multi-institutional retrospective analysis comprised 259 patients with localized prostate cancer from 6 hospitals. A total dose of 35–36 Gy in 4–5 fractions was prescribed for sequential or alternate-day administration. Biochemical failure was defined according to the Phoenix ASTRO consensus. Toxicities were assessed using National Cancer Institute Common Toxicity Criteria version 4. Tumor control and toxicity rates were analyzed by competing risk frames. Median follow-up duration was 32 months (range 22–97 months). 2- and 3-year biochemical control rates were 97.7% and 96.4%, respectively. Initial prostate-specific antigen (p < 0.01) and neoadjuvant androgen deprivation therapy (p < 0.05) were identified as risk factors for biochemical recurrence. 2- and 3-year cumulative ≥ Grade 2 late genitourinary (GU) toxicities were 5.8% and 7.4%, respectively. Corresponding rates of gastrointestinal (GI) toxicities were 3.9% and 4.5%, respectively. Grade 3 rates were lower than 1% for both GU and GI toxicities. No grade 4 or higher toxicities were encountered. Biologically effective dose was identified as a risk factor for ≥ Grade 2 late GU and GI toxicities (p < 0.05). UHF radiotherapy offered effective, safe treatment for Japanese prostate cancer with short-term follow-up. Our result suggest higher prescribed doses are related to higher toxicity rates.

Acute Toxicity in Hypofractionated/Stereotactic Prostate Radiotherapy of Elderly Patients: Use of the Image-guided Radio Therapy (IGRT) Clarity System

BACKGROUND

The use of intra-fractional monitoring and correction of prostate position with the Image Guided Radio Therapy (IGRT) system can increase the spatial accuracy of dose delivery. Clarity is a system used for intrafraction prostate-motion management, it provides a real-time visualization of prostate with a transperineal ultrasound. The aim of this study was to evaluate the use of Clarity-IGRT on proper intrafraction alignment and monitoring, its impact on Planning Tumor Volume margin and on urinary and rectal toxicity in elderly patients not eligible for surgery.

PATIENTS AND METHODS

Twenty-five elderly prostate cancer patients, median age=75 years (range=75-90 years) were treated with Volumetric Radiotherapy and Clarity-IGRT using 3 different schemes: A) 64.5/72 Gray (Gy) in 30 fractions on prostate and seminal vesicles (6 patients); B) 35 Gy in 5 fractions on prostate and seminal vesicles (12 patients); C): 35 Gy in 5 fractions on prostate (7 patients). Ultrasound identification of the overlapped structures to the detected ones during simulation has been used in each session. A specific software calculates direction and entity of necessary shift to obtain the perfect match. The average misalignment in the three-dimensional space has been determined and shown in a box-plot.

RESULTS

All patients completed treatment with mild-moderate toxicity. During treatment, genitourinary toxicity was 32% Grade 1; 4% Grade 2, rectal was 4% Grade 1. At follow-up of 3 months, genitourinary toxicity was 20% Grade 1; 4% Grade 2, rectal toxicity was 4% Grade 2. At follow-up of 6 months, genitourinary toxicity was 4% Grade 1; 4% Grade 2. Rectal toxicity was 4% Grade 2.

CONCLUSION

Radiotherapy with the Clarity System allows a reduction of PTV margins, the amount of fractions can be reduced increasing the total dose, not exacerbating urinary and rectal toxicity with greater patient's compliance.