Ultra-hypofractionated versus conventionally fractionated radiotherapy for prostate cancer: 5-year outcomes of the HYPO-RT-PC randomised, non-inferiority, phase 3 trial

Harnessing genome-wide association studies to minimize adverse radiation-induced side effects

Radiotherapy is used as definitive treatment in approximately two-thirds of all cancers. However, like any treatment, radiation has significant acute and long-term side effects including secondary malignancies. Even when similar radiation parameters are used, 5%–10% of patients will experience adverse radiation side effects. Genomic susceptibility is thought to be responsible for approximately 40% of the clinical variability observed. In the era of precision medicine, the link between genetic susceptibility and radiation-induced side effects is further strengthening. Genome-wide association studies (GWAS) have begun to identify single-nucleotide polymorphisms (SNPs) attributed to overall and tissue-specific toxicity following radiation for treatment of breast cancer, prostate cancer, and other cancers. Here, we review the use of GWAS in identifying polymorphisms that are predictive of acute and long-term radiation-induced side effects with a focus on chest, pelvic, and head-and-neck irradiation. Integration of GWAS with “omic” data, patient characteristics, and clinical correlates into predictive models could decrease radiation-induced side effects while increasing therapeutic efficacy.

Image quality evaluation of intra-irradiation cone-beam computed tomography acquired during one- and two-arc prostate volumetric-modulated arc therapy delivery: A phantom study

Purpose

To evaluate (a) the effects of megavoltage (MV)‐scatter on concurrent kilovoltage (kV) projections (P_MVkV) acquired during rotational delivery, and (b) the image quality of intra‐irradiation cone‐beam computed tomography (ii‐CBCT) images acquired during prostate volumetric‐modulated arc therapy (VMAT) delivery.

Methods

Experiment (1): P_MVkVs were acquired with various MV beam parameters using a cylindrical phantom: field size (FS), MV energy (6 or 15 MV), dose rate (DR), and gantry speed. The average pixel values were calculated in a region on each P_MVkV which were extracted at eight equally spaced gantry angles. Experiment (2): 11 one‐arc and seven two‐arc 15 MV prostate VMAT plans were used along with a pelvis phantom. One plan was selected from each of arc plans and its MV energy was changed to 6 MV. After P_MVkVs were acquired, projections consisting of MV‐scatter only (P_MVS) were acquired with closing kV blades and subtracted from P_MVkV (P_MVScorr). Projections by kV beams only were acquired (P_kV). The corresponding CBCT images were reconstructed (CBCT_MVkV, CBCT_MVScorr, and CBCT_kV). The root‐mean‐square errors (RMSEs) were calculated in prostate region and 3D gamma analysis was conducted, in which the CBCT‐number was used instead of doses between ii‐CBCT images and CBCT_kV (30 HU/1 mm).

Results

Experiment (1): The MV‐scatters were dependent on the FSs, MV energies, and DRs. Experiment (2): The median RMSEs for CBCT_MVScorr were decreased by 107.5 HU (1‐arc) and 42.9 HU (2‐arc) compared to those for CBCT_MVkV. The median GPRs for CBCT_MVScorr were 94.7% (1‐arc) and 93.4% (2‐arc), while those for CBCT_MVkV were 61.1% and 79.9%, respectively. GPRs for 6 MV plans were smaller than those for 15 MV plans.

Conclusions

The number of MV‐scatters increased with larger FSs and DRs, and smaller MV energy. The MV‐scatters were corrected on the CBCT_MVScorr regardless of the number of arcs.

Prostate Cancer Radiotherapy: Increased Biochemical Control and Late Toxicity in Men With Medication Allergies

Background

Given similarities in the mediators of medication allergy (MA) and tissue response to radiotherapy, we assessed whether outcomes following prostate radiotherapy differ in patients with MAs.

Methods

A total 587 men with known MA history and nonmetastatic prostate cancer underwent radiotherapy from 1989 to 2006. Clinicopathologic and treatment variables were analyzed for association with freedom from biochemical failure (FFBF) and late treatment–related, physician-defined Radiation Therapy Oncology Group gastrointestinal (GI) and genitourinary (GU) toxicity. Covariates identified on univariate analysis for toxicity and disease control were examined on multivariable analysis. All statistical tests were 2-sided, and a P less than .05 was considered statistically significant.

Results

A total of 155 of 587 men (26.4%) had 1 or more MAs, most commonly to penicillin (n = 71), sulfa (n = 35), and aspirin or nonsteroidal antiinflammatory drugs (n = 28). On univariate analysis, men with MAs had superior 10-y FFBF (71.5% vs 63.5%, P = .02) and higher incidence of late GI grade 2 or higher (G2+; 20.6% vs 13.2%, P = .04) and grade 3 or higher (G3+; 7.5% vs 3.9%, P = .08) as well as late GU G2+ (42.5% vs 33.2%, P = .04) and G3+ (7.5% vs 3.0%, P = .02) toxicity than men without MAs. On multivariable analysis, MA history remained a statistically significant predictor of FFBF (hazard ratio [HR] = 0.64, 95% confidence interval [CI] = 0.43 to 0.93, P = .02), late G2+ GI (HR = 1.76, 95% CI = 1.06 to 2.90, P=.03), and G3+ GU (HR = 2.69, 95% CI = 1.16 to 6.27, P = .02) toxicity after controlling for corresponding covariates in each model.

Conclusions

Men with MAs had improved FFBF and increased treatment-related toxicity following radiotherapy for prostate cancer. MA history could be a relevant consideration in the management of men with localized prostate cancer.

Imputing radiobiological parameters of the linear-quadratic dose-response model from a radiotherapy fractionation plan

The objective in cancer radiotherapy is to maximize tumor-kill while limiting toxic effects of radiation dose on nearby organs-at-risk (OAR). Given a fixed number of treatment sessions, planners thus face the problem of finding a dosing sequence that achieves this goal. This is called the fractionation problem, and has received steady attention over a long history in the clinical literature. Mathematical formulations of the resulting optimization problem utilize the linear-quadratic (LQ) framework to characterize radiation dose-response of tumors and OAR. This yields a nonconvex quadratically constrained quadratic program. The optimal dosing plan in this forward problem crucially depends on the parameters of the LQ model. Unfortunately, these parameters are difficult to estimate via in vitro or in vivo studies, and as such, their values are unknown to treatment planners. The clinical literature is thus replete with debates about what parameter values will make specific dosing plans effective. This paper formulates this as an inverse optimization problem. The LQ dose-response parameters appear in the objective function, the left hand side, and the right hand side of the forward problem, and none of the existing generic methods can provide an exact solution of the inverse problem. This paper exploits the structure of the problem and identifies all possible parameter values that render the given dosing plan optimal, in closed-form. This closed-form formula is applied to dosing-plans from three clinical studies published within the last two years.

Biochemical Control and Toxicity Outcomes of Stereotactic Body Radiation Therapy Versus Low-Dose-Rate Brachytherapy in the Treatment of Low- and Intermediate-Risk Prostate Cancer

PURPOSE

Low-dose-rate (LDR) brachytherapy and stereotactic body radiation therapy (SBRT) have both shown acceptable outcomes in the treatment of low- and intermediate-risk prostate cancer. Minimal data have been published directly comparing rates of biochemical control and toxicity with these 2 modalities. We hypothesize that LDR and SBRT will provide similar rates of biochemical control.

METHODS AND MATERIALS

All low- and intermediate-risk patients with prostate cancer treated definitively with SBRT or LDR between 2010 and 2018 were captured. Phoenix definition was used for biochemical failure. Independent t tests were used to compare baseline characteristics, and repeated measure analysis of variance test was used to compare American Urologic Association (AUA) and the Expanded Prostate Cancer Index Composite (EPIC) scores between treatment arms over time. Biochemical control was estimated using the Kaplan-Meier method. Differences in acute and late toxicity were assessed via Pearson χ².

RESULTS

In the study, 219 and 118 patients were treated with LDR and SBRT. Median follow-up was 4.3 years (interquartile range, 3.1-6.1). All patients treated with LDR received 125.0 Gy in a single fraction. SBRT consisted of 42.5 Gy in 5 fractions. Five-year biochemical control for LDR versus SBRT was 91.6% versus 97.6% (P = .108). LDR patients had a larger increase in mean AUA scores at 1 month (17.2 vs 10.3, P < .001) and 3 months posttreatment (14.0 vs 9.7, P < .001), and in mean EPIC scores at 1 month (15.7 vs 13.8, P < .001). There was no significant difference between LDR and SBRT in late grade 3 genitourinary toxicity (0.9% vs 2.5%, P = .238); however, LDR had lower rates of late grade 3 gastrointestinal toxicity (0.0% vs 2.5%, P = .018).

CONCLUSIONS

Our data show similar biochemical control and genitourinary toxicity rates at 5 years for both SBRT and LDR, with slightly higher gastrointestinal toxicity with SBRT and higher AUA and EPIC scores with LDR.

EAU-EANM-ESTRO-ESUR-SIOG Guidelines on Prostate Cancer-2020 Update. Part 1: Screening, Diagnosis, and Local Treatment with Curative Intent

OBJECTIVE

To present a summary of the 2020 version of the European Association of Urology (EAU)-European Association of Nuclear Medicine (EANM)-European Society for Radiotherapy and Oncology (ESTRO)-European Society of Urogenital Radiology (ESUR)-International Society of Geriatric Oncology (SIOG) guidelines on screening, diagnosis, and local treatment of clinically localised prostate cancer (PCa).

EVIDENCE ACQUISITION

The panel performed a literature review of new data, covering the time frame between 2016 and 2020. The guidelines were updated and a strength rating for each recommendation was added based on a systematic review of the evidence.

EVIDENCE SYNTHESIS

A risk-adapted strategy for identifying men who may develop PCa is advised, generally commencing at 50 yr of age and based on individualised life expectancy. Risk-adapted screening should be offered to men at increased risk from the age of 45 yr and to breast cancer susceptibility gene (BRCA) mutation carriers, who have been confirmed to be at risk of early and aggressive disease (mainly BRAC2), from around 40 yr of age. The use of multiparametric magnetic resonance imaging in order to avoid unnecessary biopsies is recommended. When a biopsy is performed, a combination of targeted and systematic biopsies must be offered. There is currently no place for the routine use of tissue-based biomarkers. Whilst prostate-specific membrane antigen positron emission tomography computed tomography is the most sensitive staging procedure, the lack of outcome benefit remains a major limitation. Active surveillance (AS) should always be discussed with low-risk patients, as well as with selected intermediate-risk patients with favourable International Society of Urological Pathology (ISUP) 2 lesions. Local therapies are addressed, as well as the AS journey and the management of persistent prostate-specific antigen after surgery. A strong recommendation to consider moderate hypofractionation in intermediate-risk patients is provided. Patients with cN1 PCa should be offered a local treatment combined with long-term hormonal treatment.

CONCLUSIONS

The evidence in the field of diagnosis, staging, and treatment of localised PCa is evolving rapidly. The 2020 EAU-EANM-ESTRO-ESUR-SIOG guidelines on PCa summarise the most recent findings and advice for their use in clinical practice. These PCa guidelines reflect the multidisciplinary nature of PCa management.

PATIENT SUMMARY

Updated prostate cancer guidelines are presented, addressing screening, diagnosis, and local treatment with curative intent. These guidelines rely on the available scientific evidence, and new insights will need to be considered and included on a regular basis. In some cases, the supporting evidence for new treatment options is not yet strong enough to provide a recommendation, which is why continuous updating is important. Patients must be fully informed of all relevant options and, together with their treating physicians, decide on the most optimal management for them.

The Impact of Prostate Cancer Treatment on Quality of Life: A Narrative Review with a Focus on Randomized Data

Despite excellent oncologic outcomes, the management of localized prostate cancer remains complex and is dependent on multiple factors, including patient life expectancy, medical comorbidities, tumor characteristics, and genetic risk factors. Decades of iterative clinical trials have improved the optimization and utilization of surgical and radiation-based modalities, as well as their combinatorial use with anti-androgen and systemic therapies. While cure rates are high and converging on equivalent disease control should an upfront surgical or radiotherapeutic approach be optimized, the long-term side effects of surgical and radiation-based treatments can differ significantly in nature. Decisions regarding the selection of therapy are therefore best made in an informed and shared medical decision-making process between clinician and patient with respect to cancer control as well as adverse effects. We outline in this narrative review an understanding regarding implications of surgical and radiation treatment on quality of life after treatment, and how these data may be considered in the context of advising patients regarding the selection of therapy. This narrative review largely focuses on the quality of life data obtained from prospective randomized trials of men treated for prostate cancer. We believe this provides the best assessment of the quality of life and can be used to inform patients when making treatment decisions.

Stereotactic body radiotherapy as a boost after external beam radiotherapy for high-risk prostate cancer patients

Background

The effect of high-dose-rate (HDR) brachytherapy after external radiation in high-risk prostate cancer patients has been proven. Stereotactic body radiotherapy as a less invasive method has similar dosimetric results with HDR brachytherapy. This study aims to evaluate the prostate-specific antigen (PSA) response, acute side effects, and quality of life of patients who underwent stereotactic body radiotherapy (SBRT) as a boost after pelvic radiotherapy (RT).

Methods

A total of 34 patients diagnosed with high-risk prostate cancer treated with SBRT boost (21 Gy in three fractions) combined with whole pelvic RT (50 Gy in 25 fractions) were evaluated. Biochemical control has been evaluated with PSA before, and after treatment, acute adverse events were evaluated with radiation therapy oncology group (RTOG) grading scale and quality of life with the Expanded Prostate Cancer Index Composite (EPIC) scoring system.

Results

The mean follow-up of 34 patients was 41.2 months (range 7-52). The mean initial PSA level was 22.4 ng/mL. None of the patients had experienced a biochemical or clinical relapse of the disease. Grade 2 and higher acute gastrointestinal (GI) was observed in 14%, and genitourinary (GU) toxicity was observed in 29%. None of the patients had grade 3-4 late toxicity.

Conclusions

SBRT boost treatment after pelvic irradiation has been used with a good biochemical control and acceptable toxicity in high-risk prostate cancer patients. More extensive randomized trial results are needed on the subject.

Prostate Cancer Radiation Therapy Recommendations in Response to COVID-19

PURPOSE

During a global pandemic, the benefit of routine visits and treatment of patients with cancer must be weighed against the risks to patients, staff, and society. Prostate cancer is one of the most common cancers radiation oncology departments treat, and efficient resource utilization is essential in the setting of a pandemic. Herein, we aim to establish recommendations and a framework by which to evaluate prostate radiation therapy management decisions.

METHODS AND MATERIALS

Radiation oncologists from the United States and the United Kingdom rapidly conducted a systematic review and agreed upon recommendations to safely manage patients with prostate cancer during the COVID-19 pandemic. A RADS framework was created: remote visits, and avoidance, deferment, and shortening of radiation therapy was applied to determine appropriate approaches.

RESULTS

Recommendations were provided by the National Comprehensive Cancer Network risk group regarding clinical node-positive, postprostatectomy, oligometastatic, and low-volume M1 disease. Across all prostate cancer stages, telemedicine consultations and return visits were recommended when resources/staff available. Delays in consultations and return visits of between 1 and 6 months were deemed safe based on stage of disease. Treatment can be avoided or delayed until safe for very low, low, and favorable intermediate-risk disease. Unfavorable intermediate-risk, high-risk, clinical node-positive, recurrence postsurgery, oligometastatic, and low-volume M1 disease can receive neoadjuvant hormone therapy for 4 to 6 months as necessary. Ultrahypofractionation is preferred for localized, oligometastatic, and low-volume M1, and moderate hypofractionation is preferred for postprostatectomy and clinical node positive disease. Salvage is preferred to adjuvant radiation.

CONCLUSIONS

Resources can be reduced for all identified stages of prostate cancer. The RADS (remote visits, and avoidance, deferment, and shortening of radiation therapy) framework can be applied to other disease sites to help with decision making in a global pandemic.

Hypofractionated Postoperative Radiotherapy for Prostate Cancer: Is the Field Ready Yet?

Context

Radiotherapy (RT) is a valid adjuvant treatment for men with high-risk pathological features after radical prostatectomy and a salvage treatment for biochemical recurrence. A major inconvenience is that RT takes course over 7–8 wk in these settings, which has been shown to limit its use. Retrospective and pilot prospective investigations suggest that hypofractionation may provide noninferior outcomes but report variable results regarding toxicities. Additionally, our evolving understanding of prostate cancer radiobiology suggests that hypofractionated regimens may not increase toxicity.

Objective

We examine and review the rationale and clinical evidence of hypofractionated RT in the adjuvant and salvage settings for prostate cancer.

Evidence acquisition

We reviewed relevant literature, with a particular focus on recent studies employing hypofractionated RT.

Evidence synthesis

Hypofractionated RT in the adjuvant or salvage setting is not a standard option for prostate cancer RT outside of an investigational trial. While smaller studies show conflicting data regarding toxicity, initial evidence from larger clinical trials appears to demonstrate that hypofractionated postoperative RT is as effective and safe as conventionally fractionated courses.

Conclusions

With the growing acceptance of hypofractionation across other cancer sites and the rise of extreme hypofractionation for definitive prostate cancer treatment, hypofractionated postoperative therapy for prostate cancer is poised to become an option, as it may reduce the burden on men and treatment centers while maintaining clinical efficacy and safety. Prospective trials are currently ongoing to address efficacy and safety concerns.

Patient summary

Postoperative radiotherapy is a potentially curative treatment for patients with high-risk disease or recurrence after surgery. Shortening of the treatment regimen with the availability of modern treatment delivery techniques in conjunction with the integration of molecular imaging information to refine treatment volumes may improve therapeutic benefit without increasing toxicity.

Strict bladder filling and rectal emptying during prostate SBRT: Does it make a dosimetric or clinical difference?

Background

To evaluate inter-fractional variations in bladder and rectum during prostate stereotactic body radiation therapy (SBRT) and determine dosimetric and clinical consequences.

Methods

Eighty-five patients with 510 computed tomography (CT) images were analyzed. Median prescription dose was 40 Gy in 5 fractions. Patients were instructed to maintain a full bladder and empty rectum prior to simulation and each treatment. A single reviewer delineated organs at risk (OARs) on the simulation (Sim-CT) and Cone Beam CTs (CBCT) for analyses.

Results

Bladder and rectum volume reductions were observed throughout the course of SBRT, with largest mean reductions of 86.9 mL (19.0%) for bladder and 6.4 mL (8.7%) for rectum noted at fraction #5 compared to Sim-CT (P < 0.01). Higher initial Sim-CT bladder volumes were predictive for greater reduction in absolute bladder volume during treatment (ρ = − 0.69; P < 0.01). Over the course of SBRT, there was a small but significant increase in bladder mean dose (+ 4.5 ± 12.8%; P < 0.01) but no significant change in the D2cc (+ 0.8 ± 4.0%; P = 0.28). The mean bladder trigone displacement was in the anterior direction (+ 4.02 ± 6.59 mm) with a corresponding decrease in mean trigone dose (− 3.6 ± 9.6%; P < 0.01) and D2cc (− 6.2 ± 15.6%; P < 0.01). There was a small but significant increase in mean rectal dose (+ 7.0 ± 12.9%, P < 0.01) but a decrease in rectal D2cc (− 2.2 ± 10.1%; P = 0.04). No significant correlations were found between relative bladder volume changes, bladder trigone displacements, or rectum volume changes with rates of genitourinary or rectal toxicities.

Conclusions

Despite smaller than expected bladder and rectal volumes at the time of treatment compared to the planning scans, dosimetric impact was minimal and not predictive of detrimental clinical outcomes. These results cast doubt on the need for excessively strict bladder filling and rectal emptying protocols in the context of image guided prostate SBRT and prospective studies are needed to determine its necessity.

Is hypofractionated whole pelvis radiotherapy (WPRT) as well tolerated as conventionally fractionated WPRT in prostate cancer patients? The HOPE trial

BACKGROUND

Patients with high-risk prostate cancer are at increased risk of lymph node metastasis and are thought to benefit from whole pelvis radiotherapy (WPRT). There has been recent interest in the use of hypofractionated radiotherapy in treating prostate cancer. However, toxicity and cancer outcomes associated with hypofractionated WPRT are unclear at this time. This phase II study aims to investigate the impact in quality of life associated with hypofractionated WPRT compared to conventionally fractionated WPRT.

METHODS

Fifty-eight patients with unfavourable intermediate-, high- or very high-risk prostate cancer will be randomized in a 1:1 ratio between high-dose-rate brachytherapy (HDR-BT) + conventionally fractionated (45 Gy in 25 fractions) WPRT vs. HDR-BT + hypofractionated (25 Gy in 5 fractions) WPRT. Randomization will be performed with a permuted block design without stratification. The primary endpoint is late bowel toxicity and the secondary endpoints include acute and late urinary and sexual toxicity, acute bowel toxicity, biochemical failure-, androgen deprivation therapy-, metastasis- and prostate cancer-free survival of the hypofractionated arm compared to the conventionally fractionated arm.

DISCUSSION

To our knowledge, this is the first study to compare hypofractionated WPRT to conventionally fractionated WPRT with HDR-BT boost. Hypofractionated WPRT is a more attractive and convenient treatment approach, and may become the new standard of care if demonstrated to be well-tolerated and effective.

TRIAL REGISTRATION

This trial was prospectively registered in ClinicalTrials.gov as NCT04197141 on December 12, 2019.

Long-term outcomes of moderately hypofractionated radiotherapy (67.5 Gy in 25 fractions) for prostate cancer confined to the pelvis: a single center retrospective analysis

Background

There is an increasing application of moderately hypofractionated radiotherapy for prostate cancer. We presented our outcomes and treatment-related toxicities with moderately hypofractionated (67.5 Gy in 25 fractions) radiotherapy for a group of advanced prostate cancer patients from China.

Methods

From November 2006 to December 2018, 246 consecutive patients with prostate cancer confined to the pelvis were treated with moderately hypofractionated radiotherapy (67.5 Gy in 25 fractions). 97.6% of the patients received a different duration of androgen deprivation therapy. Failure-free survival (FFS), prostate cancer-specific survival (PCSS), overall survival (OS), and cumulative grade ≥ 2 late toxicity were evaluated using the Kaplan–Meier actuarial method. Prognostic factors for FFS, PCSS, and OS were analyzed.

Results

The median follow-up time was 74 months (range: 6–150 months). For all patients, the 5- and 10-year FFS rates were 80.0% (95% CI: 74.7–85.7%) and 63.5% (95% CI 55.4–72.8%). The failure rates for the intermediate, high-risk, locally advanced, and N1 groups were 6.1%, 13.0%, 18.4%, and 35.7%, respectively (P = 0.003). Overall, 5- and 10-year PCSS rates were 95.7% (95% CI 93.0–98.5%) and 88.2% (95% CI 82.8–93.8%). Prostate cancer-specific mortality rates for the high-risk, locally advanced, and N1 groups were 4.0%, 8.2%, and 23.8%, respectively (P < 0.001). Overall, 5- and 10-year actuarial OS rates were 92.4% (95% CI 88.8–96.1%) and 72.7% (95% CI 64.8–81.5%). High level prostate-specific antigen and positive N stage were significantly associated with worse FFS (P < 0.05). Advanced T stage and positive N stage emerged as worse predictors of PCSS (P < 0.05). Advanced age, T stage, and positive N stage were the only factors that were significantly associated with worse OS (P < 0.05). The 5-year cumulative incidence rate of grade ≥ 2 late GU and GI toxicity was 17.8% (95% CI 12.5–22.7%) and 23.4% (95% CI 17.7–28.7%), respectively.

Conclusions

Moderately hypofractionated radiotherapy (67.5 Gy in 25 fractions) for this predominantly high-risk, locally advanced, or N1 in Chinese patients demonstrates encouraging long-term outcomes and acceptable toxicity. This fractionation schedule deserves further evaluation in similar populations.

Radiation oncology in times of COVID-2019: A review article for those in the eye of the storm - An Indian perspective

The global COVID-2019 pandemic has presented to the field of radiation oncology a management dilemma in providing evidence-based treatments to all cancer patients. There is a need for appropriate measures to be taken to reduce infectious spread between the medical healthcare providers and the patient population. Such times warrant resource prioritization and to continue treatment with best available evidence, thereby reducing the risk of COVID-2019 transmission in times where the workforce is reduced. There has been literature presented in different aspects related to providing safety measures, running of a radiation department and for the management of various cancer subsites. In this article, we present a comprehensive review for sustaining a radiation oncology department in times of the COVID-2019 pandemic.

Radiation Fractionation Schedules Published During the COVID-19 Pandemic: A Systematic Review of the Quality of Evidence and Recommendations for Future Development

PURPOSE

Numerous publications during the COVID-19 pandemic recommended the use of hypofractionated radiation therapy. This project assessed aggregate changes in the quality of the evidence supporting these schedules to establish a comprehensive evidence base for future reference and highlight aspects for future study.

METHODS AND MATERIALS

Based on a systematic review of published recommendations related to dose fractionation during the COVID-19 pandemic, 20 expert panelists assigned to 14 disease groups named and graded the highest quality of evidence schedule(s) used routinely for each condition and also graded all COVID-era recommended schedules. The American Society for Radiation Oncology quality of evidence criteria were used to rank the schedules. Process-related statistics and changes in distributions of quality ratings of the highest-rated versus recommended COVID-19 era schedules were described by disease groups and for specific clinical scenarios.

RESULTS

From January to May 2020 there were 54 relevant publications, including 233 recommended COVID-19-adapted dose fractionations. For site-specific curative and site-specific palliative schedules, there was a significant shift from established higher-quality evidence to lower-quality evidence and expert opinions for the recommended schedules (P = .022 and P < .001, respectively). For curative-intent schedules, the distribution of quality scores was essentially reversed (highest levels of evidence "pre-COVID" vs "in-COVID": high quality, 51.4% vs 4.8%; expert opinion, 5.6% vs 49.3%), although there was variation in the magnitude of shifts between disease sites and among specific indications.

CONCLUSIONS

A large number of publications recommended hypofractionated radiation therapy schedules across numerous major disease sites during the COVID-19 pandemic, which were supported by a lower quality of evidence than the highest-quality routinely used dose fractionation schedules. This work provides an evidence-based assessment of these potentially practice-changing recommendations and informs individualized decision-making and counseling of patients. These data could also be used to support radiation therapy practices in the event of second waves or surges of the pandemic in new regions of the world.

Favorable Biochemical Freedom From Recurrence With Stereotactic Body Radiation Therapy for Intermediate and High-Risk Prostate Cancer: A Single Institutional Experience With Long-Term Follow-Up

Purpose/Objective(s): The current study reports long-term overall survival (OS) and biochemical freedom from recurrence (BFFR) after stereotactic body radiation therapy (SBRT) for men with intermediate and high-risk prostate cancer in a single community hospital setting with early adoption. Materials/Methods: Ninety-seven consecutive men with intermediate and high-risk prostate cancer treated with SBRT between 2007 and 2015 were retrospectively studied. Categorical variables for analysis included National Comprehensive Cancer Network risk group, race, Gleason grade group, T stage, use of androgen deprivation therapy, and planning target volume dose. Continuous variables for analysis included pretreatment prostate-specific antigen (PSA), percent cores positive, age at diagnosis, PSA nadir, prostate volume, percent prostate that received 40 Gy, and minimum dose to 0.03 cc of prostate (Dmin). BFFR was assessed using the Phoenix nadir +2 definition. OS and BFFR were estimated using Kaplan-Meier (KM) methodology with comparisons accomplished using log-rank statistics. Multivariable analysis (MVA) was accomplished with a backwards selection Cox proportional-hazards model with statistical significance taken at the p < 0.05 level. Results: Median FU is 78.4 months. Five- and ten-year OS KM estimates are 90.9 and 73.2%, respectively, with 19 deaths recorded. MVA reveals pretreatment PSA (p = 0.032), percent prostate 40 Gy (p = 0.003), and race (p = 0.031) were predictive of OS. Five- and nine-year BFFR KM estimates are 92.1 and 87.5%, respectively, with 10 biochemical failures recorded. MVA revealed PSA nadir (p < 0.001) was the only factor predictive of BFFR. Specifically, for every one-unit increase in PSA nadir, there was a 4.2-fold increased odds of biochemical failure (HR = 4.248). No significant differences in BFFR were found between favorable intermediate, unfavorable intermediate, and high-risk prostate cancer (p = 0.054) with 7-year KM estimates of 96.6, 81.0, and 85.7%, respectively. Conclusions: Favorable OS and BFFR can be expected after SBRT for intermediate and high-risk prostate cancer with non-significant differences seen for BFFR between favorable intermediate, unfavorable intermediate, and high-risk groups. Our 5-year BFFR compares favorably with the HYPO-RT-PC trial of 84%. PSA nadir was predictive of biochemical failure. This study is ultimately limited by the small absolute number of high-risk patients included.

Stereotactic body radiotherapy versus conventional/moderate fractionated radiation therapy with androgen deprivation therapy for unfavorable risk prostate cancer

Background

Ultrahypofractionation using stereotactic body radiotherapy (SBRT) is an increasingly utilized technique for men with prostate cancer (PC). The comparative efficacy of SBRT plus androgen deprivation therapy (ADT) compared to fractionated radiotherapy (EBRT) plus ADT in higher-risk prostate cancer is unknown.

Methods

Men > 40 years old with localized PC treated with external beam radiation and concomitant ADT for curative intent between 2004 and 2016 were analyzed from the National Cancer Database. Patients who lacked ADT or risk stratification data were excluded. 558 men treated with SBRT versus 40,797 men treated with conventional or moderately hypofractionated EBRT were included. Patients were stratified by unfavorable intermediate (UIR) and high (HR) risk using NCCN criteria. Kaplan Meier and Cox proportional hazards were used to compare overall survival (OS) between RT modality, adjusting for age, race, and comorbidity index.

Results

With a median follow up of 74 months, there was no difference in estimated 6-year OS between men treated with SBRT versus EBRT regardless of risk group. On multivariable analysis, there was no difference in risk of death for men treated with SBRT compared to EBRT (UIR: adjusted HR 1.09, 95% CI 0.68–1.74, p = .72; HR: adjusted HR 0.93, 95% CI 0.76–1.14, p = .51). On sensitivity analyses, when confining the cohort to men treated with NCCN-preferred dose fractionations, with no comorbidities, or < 65 years old, there remained no survival difference between treatment groups for both UIR and HR.

Conclusion

Within study limitations, we found no difference in survival between SBRT+ADT and standard of care EBRT+ADT for UIR or HR PC. These results support recent NCCN guideline updates, which include SBRT as a non-preferred option for higher risk men. Prospective validation would further strengthen the evidence basis behind these recommendations.

Trends in Use and Comparison of Stereotactic Body Radiation Therapy, Brachytherapy, and Dose-Escalated External Beam Radiation Therapy for the Management of Localized, Intermediate-Risk Prostate Cancer

This cohort study examines trends in the use of brachytherapy, external beam radiotherapy, and stereotactic body radiation therapy for disease management in patients with localized prostate cancer and compares outcomes between these therapies.

Stereotactic Body Radiation Therapy for Intermediate-risk Prostate Cancer With VMAT and Real-time Electromagnetic Tracking: A Phase II Study

OBJECTIVES

Stereotactic body radiation treatment represents an intriguing therapeutic option for patients with early-stage prostate cancer. In this phase II study, stereotactic body radiation treatment was delivered by volumetric modulated arc therapy with flattening filter free beams and was gated using real-time electromagnetic transponder system to maximize precision of radiotherapy and, potentially, to reduce toxicities.

MATERIALS AND METHODS

Patients affected by histologically proven prostate adenocarcinoma and National Comprehensive Cancer Network (NCCN) intermediate class of risk were enrolled in this phase II study. Beacon transponders were positioned transrectally within the prostate parenchyma 7 to 10 days before simulation computed tomography scan. The radiotherapy schedule was 38 Gy in 4 fractions delivered every other day. Toxicity assessment was performed according to Common Terminology Criteria for Adverse Events (CTCAE), v4.0.

RESULTS

Thirty-six patients were enrolled in this study. Median initial prostate-specific antigen was 7.0 ng/mL (range: 2.3 to 14.0 ng/mL). Median nadir-prostate-specific antigen after treatment was 0.2 ng/mL (range: 0.006 to 4.8 ng/mL). A genitourinary acute toxicity was observed in 21 patients (dysuria grade [G] 1: 41.7%, G2: 16.7%). Gastrointestinal acute toxicity was found in 9 patients (proctitis G1: 19.4%, G2: 5.6%). Late toxicity was mild (genitourinary toxicity G1: 30.6%; G2: 8.3%; gastrointestinal toxicity G1: 13.9%; G2: 19.4%). At a median follow-up time of 41 months, 3 biochemical recurrences were observed (2 local recurrences, 1 distant metastasis). Three-year biochemical recurrence-free survival was 89.8% (International Society of Urologic Pathology Grade Group 2: 100%, Grade Group 3: 77.1%, P=0.042).

CONCLUSION

Ultrahypofractionated radiotherapy, delivered with flattening filter free-volumetric modulated arc therapy and gated by electromagnetic transponders, is a valid option for intermediate-risk prostate cancer.

[Retrospective study on the intensification of hypofractionated radiotherapy: The organizational change]

Objectif de l’étude

Le processus de réalisation de la radiothérapie externe est une chaine d’étapes dans laquelle chacune d’entre elles est réalisée seulement si la précédente a été complétée. Le développement des pratiques d’hypofractionnement ces dernières années a tendance à augmenter la charge de travail des étapes de préparation à une irradiation et à diminuer le nombre de séances par patient. Cette étude rétrospective vise à analyser l’évolution de ces pratiques dans un centre de lutte contre le cancer et d’en apprécier les enjeux organisationnels.

Matériel et méthodes

L’ensemble des données de gestion des dossiers de radiothérapie ont été extraites du système d’information de radiothérapie. Les séances de radiothérapie ont été identifiées par patient et par code CIM (Classification internationale des maladies). Le taux de remplissage des appareils de traitement a été calculé avec les données réelles du département de radiothérapie.

Résultats

De 2015 à 2019, une augmentation du nombre de scanographies (+16 %), du nombre de patients pris en charge (+11,6 %) et du volume d’heures disponibles pour les traitements (+12 %) ont été observées. Aussi, une diminution du nombre total de séances de radiothérapie (−5 %), de la moyenne de séances réalisées par séquence de traitement (−19 %), du taux de remplissage des appareils (−7 %) et de la moyenne de séances réalisées par patients traités des tumeurs malignes des bronches et du poumon (−38 %), des organes digestifs (−37 %), secondaires (−19 %) du sein (−15 %) et de la prostate (−15 %) ont été observées. Le nombre de séances administrées par séquence de traitement entre 2015 et 2019 a diminué significativement pour les patients des classes d’âge [20–69 ans] (p < 0,001) et [> 70 ans] (p < 0,001).

Conclusion

Un paradoxe apparait entre l’augmentation du nombre total de patients pris en charge et la diminution du taux de remplissage des appareils de traitement. Ce transfert de charge de travail a un impact sur la qualité et la sécurité des soins et sur les stratégies d’organisation et d’investissement. Il a également un impact économique lié au modèle de remboursement basé sur la tarification à la séance. Une réorganisation des services de radiothérapie s’avère inéluctable.

[Stereotaxic radiotherapy of primary extracranial tumors]

Stereotactic radiotherapy is a fundamental change from the conventional fractionated radiotherapy and represents a new therapeutic indication. Stereotactic radiotherapy is now a standard of care for inoperable patients or patients who refuse surgery. The results are encouraging with local control and survival rates very high in selected populations. The rate of late toxicity remains acceptable. Good tolerability makes it appropriate even for elderly and frail patients. In these fragile patients or in certain specific clinical situations, different surgical, radiotherapy or interventional radiology attitudes can be discussed on a case-by-case basis. These situations are considered in this article for the pulmonary, hepatic and prostatic localizations.

Moderately hypofractionated radiotherapy for localized prostate cancer: updated long-term outcome and toxicity analysis

PURPOSE

Evaluation of long-term outcome and toxicity of moderately hypofractionated radiotherapy using intensity-modulated radiotherapy (IMRT) with simultaneous integrated boost treatment planning and cone beam CT-based image guidance for localized prostate cancer.

METHODS

Between 2005 and 2015, 346 consecutive patients with localized prostate cancer received primary radiotherapy using cone beam CT-based image-guided intensity-modulated radiotherapy (IG-IMRT) and volumetric modulated arc therapy (IG-VMAT) with a simultaneous integrated boost (SIB). Total doses of 73.9 Gy (n = 44) and 76.2 Gy (n = 302) to the high-dose PTV were delivered in 32 and 33 fractions, respectively. The low-dose PTV received a dose (D95) of 60.06 Gy in single doses of 1.82 Gy. The pelvic lymph nodes were treated in 91 high-risk patients to 45.5 Gy (D95).

RESULTS

Median follow-up was 61.8 months. The 5‑year biochemical relapse-free survival (bRFS) was 85.4% for all patients and 93.3, 87.4, and 79.4% for low-, intermediate-, and high-risk disease, respectively. The 5‑year prostate cancer-specific survival (PSS) was 94.8% for all patients and 98.7, 98.9, 89.3% for low-, intermediate-, and high-risk disease, respectively. The 5‑year and 10-year overall survival rates were 83.8 and 66.3% and the 5‑year and 10-year freedom from distant metastasis rates were 92.2 and 88.0%, respectively. Cumulative 5‑year late GU toxicity and late GI toxicity grade ≥2 was observed in 26.3 and 12.1% of the patients, respectively. Cumulative 5‑year late grade 3 GU/GI toxicity occurred in 4.0/1.2%.

CONCLUSION

Moderately hypofractionated radiotherapy using SIB treatment planning and cone beam CT image guidance resulted in high biochemical control and survival with low rates of late toxicity.

Real-world dosimetric comparison between CyberKnife SBRT and HDR brachytherapy for the treatment of prostate cancer

PURPOSE

High-dose-rate (HDR) brachytherapy (BRT) and stereotactic body radiotherapy (SBRT) are currently the two treatment options for definitive radiotherapy of prostate cancer, employing extreme hypofractionation. There are only very few studies comparing their dosimetry, all using computed tomography for treatment planning. We present here a real-word dosimetric comparison between SBRT and ultrasound-based virtual HDR-BRT, with both imaging modalities coming from the same patient.

METHODS AND MATERIALS

Patients with prostate cancer on a prospective trial evaluating the toxicity of robotic-based SBRT were treated to a total dose of 35 Gy in 5 fractions. Fifteen patients were included in this analysis. During ultrasound-based fiducial implantation, a three-dimensional data set as in real HDR-BRT procedure was acquired. Virtual HDR-BRT plans were generated and various organs at risk and prostate dosimetric parameters were evaluated.

RESULTS

Concerning prostate, SBRT achieved significant higher D₉₈, V₃₅ Gy, and V_37.5 Gy coverage, whereas virtual HDR-BRT achieved significant higher intratumoral doses reflected in the V₄₂ Gy and V_52.5 Gy. Rectal D_max, V₃₆ Gy, and V₂₉ Gy were significantly lower for HDR-BRT with no difference as for V₁₈ Gy. SBRT was significantly inferior regarding bladder dosimetry (D_max, V₃₆ Gy, V₁₈ Gy), whereas urethra D_max and V₄₄ Gy where significantly higher at the expense of HDR-BRT.

CONCLUSIONS

HDR-BRT is superior regarding rectum and bladder dosimetry, with SBRT being superior relative to urethra dosimetry. A randomized study is warranted to define the best extreme hypofractionated modality.

Online-adaptive versus robust IMPT for prostate cancer: How much can we gain?

BACKGROUND/PURPOSE

Intensity-modulated proton therapy (IMPT) is highly sensitive to anatomical variations which can cause inadequate target coverage during treatment. Available mitigation techniques include robust treatment planning and online-adaptive IMPT. This study compares a robust planning strategy to two online-adaptive IMPT strategies to determine the benefit of online adaptation.

MATERIALS/METHODS

We derived the robustness settings and safety margins needed to yield adequate target coverage (V_95%≥98%) for >90% of 11 patients in a prostate cancer cohort (88 repeat CTs). For each patient, we also adapted a non-robust prior plan using a simple restoration and a full adaptation method. The restoration uses energy-adaptation followed by a fast spot-intensity re-optimization. The full adaptation uses energy-adaptation followed by the addition of new spots and a range-robust spot-intensity optimization. Dose was prescribed as 55 Gy(RBE) to the low-dose target (lymph nodes and seminal vesicles) with a boost to 74 Gy(RBE) to the high-dose target (prostate). Daily patient set-up was simulated using implanted intra-prostatic markers.

RESULTS

Margins of 4 and 8 mm around the high- and low-dose target regions, a 6 mm setup error and a 3% range error were found to obtain adequate target coverage for all repeat CTs of 10/11 patients (94.3% of all 88 repeat CTs). Both online-adaptive strategies yielded V_95%≥98% and better OAR sparing in 11/11 patients. Median OAR improvements up to 11%-point and 16%-point were observed when moving from robust planning to respectively restoration and full adaption.

CONCLUSION

Both full plan adaptation and simple dose restoration can increase OAR sparing besides better conforming to the target criteria compared to robust treatment planning.

Long-Term Results of Moderate Hypofractionation to Prostate and Pelvic Nodes Plus Androgen Suppression in High-Risk Prostate Cancer

PURPOSE

Moderate hypofractionated radiation therapy (HypoRT) is an attractive alternative to conventionally fractionated radiation therapy for prostate cancer. However, most studies using HypoRT only included the prostate as the target volume. We report long-term outcomes of patients with high-risk prostate cancer treated with androgen deprivation therapy (ADT) and HypoRT to the prostate and nodal areas with a simultaneous integrated boost technique.

METHODS AND MATERIALS

Patients with localized, high-risk prostate cancer entered a prospective phase I/II study with a HypoRT regimen of 60 Gy/20 fractions (4 weeks) to the prostate volume while the nodal areas received 44 Gy in the same 20 fractions delivered with intensity modulated radiation therapy with a simultaneous integrated boost technique. ADT started 2 to 3 months before HypoRT. Toxicity was prospectively assessed according to the Common Terminology Criteria for Adverse Events v3. Outcomes rates were calculated by the actuarial method of Kaplan-Meier from the date of last radiation treatment until date of event.

RESULTS

We report on the first 105 patients treated between October 2010 and February 2014. Median follow-up was 74 months, with 97% of patients followed for more than 36 months. Median ADT duration was 18 months. The worst grade 2 or higher late gastrointestinal or genitourinary toxicity was seen in 7% and 9%, respectively. There was no grade 4 or 5 toxicity. At the last follow-up, the rates of grade ≥2 gastrointestinal or genitourinary toxicity were 2% and 3%, respectively, with no residual grade ≥3 toxicity. The 5- and 7-year actuarial overall survival and relapse free survival were 91% and 85% and 87% and 81%, respectively.

CONCLUSIONS

The longest follow-up report of moderate HypoRT (plus ADT) to the prostate and pelvic nodes shows that this approach is feasible, well tolerated, and effective. It is convenient for patients and the health system. A larger randomized trial using this approach is warranted.

Hypofractionated Radiotherapy in Locally Advanced Myxoid Liposarcomas of Extremities or Trunk Wall: Results of a Single-Arm Prospective Clinical Trial

Introduction: Myxoid liposarcoma (MLPS) has been reported to be more radiosensitive compared with other soft tissue sarcomas. The main objective of the study was to assess the efficacy of hypofractionated radiotherapy (RT) in the preoperative setting in patients with locally advanced primary MLPS. Methods: Single-arm prospective exploratory clinical trial enrolled MLPS patients for preoperative 5 × 5 Gy RT with delayed surgery. The endpoints of the study were the rate of early wound healing complications and 5-year local control rate. Results: 29 patients (pts) were included, all had tumors located on the lower limb. The median maximum size of the tumor was 13 cm (IQR 10–15 cm). Early RT tolerance was good. Postoperative wound complications occurred in 11 pts (37.9%), late complications concerned 13.8% of patients. A total of 27 patients were included for the efficacy analyses. The pathological features of response to RT were detected in all analyzed surgical specimens. In 25 patients R0 margins were achieved, two patients had an R1 resection. None of the patients had local recurrence. Conclusion: Preoperative hypofractionated RT with a prolonged gap between RT and surgery is a feasible method of the management of MLPS, providing a good local control and low rates of treatment toxicity.

Phase II prospective trial "Give Me Five" short-term high precision radiotherapy for early prostate cancer with simultaneous boost to the dominant intraprostatic lesion: the impact of toxicity on quality of life (AIRC IG-13218)

As part of the AIRC IG-13218 (NCT01913717), we analyzed data from patients with low- and intermediate-risk prostate cancer treated with extreme hypofractionated radiotherapy (RT) and simultaneous boost to the intraprostatic lesion. The aim of the study is to identify clinically meaningful information through the analysis of validated questionnaires testing gastrointestinal (GI) and genitourinary (GU) RT-related toxicity and their impact on quality of life (QoL). At the end of RT treatment, clinical assessment and prostate-specific antigen (PSA) measurements were performed every 3 months for at least 2 years and GI and GU toxicities were evaluated contextually. QoL of enrolled patients was assessed by International Prostate Symptoms score (IPSS), European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30), EORTC QLQ prostate specific (QLQ-PR25), and sexual activity by International Index of Erectile Function (IIEF-5). Patients' score changes were calculated at the end of RT, at one month after RT and at 12 and 24 months. Sixty-five prospectively enrolled patients were analyzed. Extensive analysis of different QoL assessments showed that patients' tolerance was satisfactory across all the considered time points, with no statistically significant change of QoL from baseline compared to that before RT. Overall survival and biochemical progression-free survival at 2-years were of 98% and 97%, respectively. Despite the toxicity of extreme hypofractionation was low and tumor control was encouraging, a longer follow-up is necessary to confirm our findings. The increasing dose to the dominant intraprostatic lesion does not worsen the RT toxicity and consequently does not affect patients' QoL, thus questioning the possibility of an even more escalated treatment.

Impact of hydrogel peri-rectal spacer insertion on prostate gland intra-fraction motion during 1.5 T MR-guided stereotactic body radiotherapy

Background

The assessment of organ motion is a crucial feature for prostate stereotactic body radiotherapy (SBRT). Rectal spacer may represent a helpful device in order to outdistance rectal wall from clinical target, but its impact on organ motion is still a matter of debate. MRI-Linac is a new frontier in radiation oncology as it allows a superior visualization of the real-time anatomy of the patient and the current highest level of adaptive radiotherapy.

Methods

We present data regarding a total of 100 fractions in 20 patients who underwent MRI-guided prostate SBRT for low-to-intermediate risk prostate cancer with or without spacer. Translational and rotational shifts were computed on the pre- and post-treatment MRI acquisitions referring to the delivery position for antero-posterior, latero-lateral and cranio-caudal direction, and assessed using the Mann-Whitney U-Test.

Results

All patients were treated with a five sessions schedule (35 Gy/5fx) using MRI-Linac for a median fraction treatment time of 50 min (range, 46–65). In the entire study sample, median rotational displacement was 0.1° in cranio-caudal, − 0.002° in latero-lateral and 0.01° in antero-posterior direction; median translational shift was 0.11 mm in cranio-caudal, − 0.24 mm in latero-lateral and − 0.22 mm in antero-posterior. A significant difference between spacer and no-spacer patients in terms of rotational shifts in the antero-posterior direction (p = 0.033) was observed; also for translational shifts a positive trend was detected in antero-posterior direction (p = 0.07), although with no statistical significance. We observed statistically significant differences in the pre-treatment planning phase in favor of the spacer cohort for several rectum dose constraints: rectum V32Gy < 5% (p = 0.001), V28 Gy < 10% (p = 0.001) and V18Gy < 35% (p = 0.039). Also for bladder V35 Gy < 1 cc, the use of spacer provided a dosimetric advantage compared to the no-spacer subpopulation (p = 0.04). Furthermore, PTV V33.2Gy > 95% was higher in the spacer cohort compared to the no-spacer one (p = 0.036).

Conclusion

In our experience, the application of rectal hydrogel spacer for prostate SBRT resulted in a significant impact on rotational antero-posterior shifts contributing to limit prostate intra-fraction motion. Further studies with larger sample size and longer follow-up are required to confirm this ideally favorable effect and to assess any potential impact on clinical outcomes.

Stereotactic body radiotherapy for localized prostate cancer - 5-year efficacy results

BACKGROUND

The use of stereotactic body radiotherapy (SBRT) as the primary treatment modality in clinically localized prostate cancer (PCa) is emerging. The aim of the study was to analyze the long-term results of PCa patients treated with SBRT.

METHODS

This non-selected, real-life patient cohort included 213 patients with localized PCa treated with a robotic SBRT device during 2012-2015.

RESULTS

The median follow-up was 64 months (range, 10-85 months), and all risk-groups were represented as 47 (22.1%), 56 (26.3%) and 110 (51.6%) patients were classified into D'Amico risk stratification of low, intermediate and high-risk groups, respectively. Androgen deprivation therapy (ADT) was administered to 64.3% of the patients. At cut-off, the biochemical relapse-free survival (bRFS) was 100, 87.5 and 80.0% for patients at low, intermediate and high-risk (p = 0.004), and 92.5, 84.2 and 66.7% for patients with Gleason score ≤ 6, 7 and ≥ 8, respectively (p = 0.001). The actuarial 5-year overall survival (OS) rates were 97.9, 96.4 and 88.6% in the low, intermediate and high-risk groups, respectively, and at the cut-off, the disease-specific survival (DSS) rate of the whole cohort was high (99.1%), as only two high-risk patients died due to PCa.

CONCLUSION

Our present results of SBRT delivered with CyberKnife produced excellent long-term bRFS, OS and DSS outcomes among patients with localized PCa. We conclude that SBRT provides an efficient and convenient treatment option for patients with localized PCa, irrespective of the risk-group.

Dosimetric effects of adaptive prostate cancer radiotherapy in an MR-linac workflow

BACKGROUND

The purpose was to evaluate the dosimetric effects in prostate cancer treatment caused by anatomical changes occurring during the time frame of adaptive replanning in a magnetic resonance linear accelerator (MR-linac) workflow.

METHODS

Two MR images (MR1 and MR2) were acquired with 30 min apart for each of the 35 patients enrolled in this study. The clinical target volume (CTV) and organs at risk (OARs) were delineated based on MR1. Using a synthetic CT (sCT), ultra-hypofractionated VMAT treatment plans were created for MR1, with three different planning target volume (PTV) margins of 7 mm, 5 mm and 3 mm. The three treatment plans of MR1, were recalculated onto MR2 using its corresponding sCT. The dose distribution of MR2 represented delivered dose to the patient after 30 min of adaptive replanning, omitting motion correction before beam on. MR2 was registered to MR1, using deformable registration. Using the inverse deformation, the structures of MR1 was deformed to fit MR2 and anatomical changes were quantified. For dose distribution comparison the dose distribution of MR2 was warped to the geometry MR1.

RESULTS

The mean center of mass vector offset for the CTV was 1.92 mm [0.13 - 9.79 mm]. Bladder volume increase ranged from 12.4 to 133.0% and rectum volume difference varied between -10.9 and 38.8%. Using the conventional 7 mm planning target volume (PTV) margin the dose reduction to the CTV was 1.1%. Corresponding values for 5 mm and 3 mm PTV margin were 2.0% and 4.2% respectively. The dose to the PTV and OARs also decreased from D1 to D2, for all PTV margins evaluated. Statistically significant difference was found for CTV Dmin between D1 and D2 for the 3 mm PTV margin (p < 0.01).

CONCLUSIONS

A target underdosage caused by anatomical changes occurring during the reported time frame for adaptive replanning MR-linac workflows was found. Volume changes in both bladder and rectum caused large prostate displacements. This indicates the importance of thorough position verification before treatment delivery and that the workflow needs to speed up before introducing margin reduction.

Stereotactic Body Radiation Therapy (SBRT) for Prostate Cancer in Men With a High Baseline International Prostate Symptom Score (IPSS ≥ 15)

Background: Patients with a high pretreatment IPSS may have higher rates of late urinary morbidity after radiation therapy for prostate cancer (1). Stereotactic body radiation therapy (SBRT) delivers fewer high-dose fractions of radiation, which may be radiobiologically favorable to the conventional low-dose external beam fractions. The urinary toxicity associated with SBRT, however, remains unclear in patients with a high IPSS (1). We report our experience using SBRT for localized prostate cancer in patients with pretreatment IPSS ≥ 15.

Methods: Localized prostate cancer patients with a pre-treatment IPSS ≥ 15 treated with SBRT at Georgetown University Hospital from 2009 to 2016 were included in this retrospective review of prospectively collected data. These patients were treated to 35–36.25 Gy in five fractions delivered via CyberKnife (Accuray Inc., Sunnyvale, CA). Urinary toxicity was assessed using the Common Terminology Criteria for Adverse Events version 4.0 (CTCAE v4). Urinary quality of life was assessed using validated questionnaires (IPSS and EPIC-26).

Results: 53 patients at a median age of 71 years (range 57–89 years) received SBRT with a minimum follow up of 3 years. The median prostate size was 37 cm³ (range 12–100 cm³) and 30.2% patients received ADT. The 3-years incidence rate of Grade 3 urinary toxicity was 7.5% with median time to toxicity of 2.9 years. There were no Grade 4 or 5 toxicities. A mean baseline IPSS score of 19.8 significantly decreased to 12.9 at 3 months post-SBRT (p = 0.002) and remained stable at 36 months (13.7). A mean baseline EPIC-26 obstructive/irritative score of 64.1 significantly improved to 80.2 at 3 months (p = 0.002). This improvement was maintained to 36 months. There was no significant change from the mean baseline EPIC-26 urinary incontinence score at any point during follow up.

Conclusions: SBRT for clinically localized prostate cancer was well-tolerated in men with baseline IPSS ≥ 15 (1). Grade 3 toxicities occurred but resolved with time. Our data suggest that poor baseline urinary function does not worsen following SBRT and may even improve. High baseline IPSS score should not be considered a contraindication to SBRT.

Prostate Cancer Radiation Therapy Recommendations in Response to COVID-19

PURPOSE

During a global pandemic, the benefit of routine visits and treatment of patients with cancer must be weighed against the risks to patients, staff, and society. Prostate cancer is one of the most common cancers radiation oncology departments treat, and efficient resource utilization is essential in the setting of a pandemic. Herein, we aim to establish recommendations and a framework by which to evaluate prostate radiation therapy management decisions.

METHODS AND MATERIALS

Radiation oncologists from the United States and the United Kingdom rapidly conducted a systematic review and agreed upon recommendations to safely manage patients with prostate cancer during the COVID-19 pandemic. A RADS framework was created: remote visits, and avoidance, deferment, and shortening of radiation therapy was applied to determine appropriate approaches.

RESULTS

Recommendations were provided by the National Comprehensive Cancer Network risk group regarding clinical node-positive, postprostatectomy, oligometastatic, and low-volume M1 disease. Across all prostate cancer stages, telemedicine consultations and return visits were recommended when resources/staff available. Delays in consultations and return visits of between 1 and 6 months were deemed safe based on stage of disease. Treatment can be avoided or delayed until safe for very low, low, and favorable intermediate-risk disease. Unfavorable intermediate-risk, high-risk, clinical node-positive, recurrence postsurgery, oligometastatic, and low-volume M1 disease can receive neoadjuvant hormone therapy for 4 to 6 months as necessary. Ultrahypofractionation is preferred for localized, oligometastatic, and low-volume M1, and moderate hypofractionation is preferred for postprostatectomy and clinical node positive disease. Salvage is preferred to adjuvant radiation.

CONCLUSIONS

Resources can be reduced for all identified stages of prostate cancer. The RADS (remote visits, and avoidance, deferment, and shortening of radiation therapy) framework can be applied to other disease sites to help with decision making in a global pandemic.

Prostate bed and organ-at-risk deformation: Prospective volumetric and dosimetric data from a phase II trial of stereotactic body radiotherapy after radical prostatectomy

PURPOSE

Stereotactic body radiotherapy (SBRT) in the post-prostatectomy setting is investigational. A major concern is the deformable prostate bed clinical target volume (CTV) and the closely juxtaposed organs-at-risk (OARs). We report a volumetric and dosimetric analysis of kilovoltage cone-beam CT (CBCT) data from the first 18 patients enrolled on a phase II trial of post-prostatectomy SBRT. With instructions on bladder filling and rectal preparation, we hypothesized acceptable CTV coverage while minimal overdosing to OARs could be achieved.

METHODS

All patients received 5 fractions of 6-6.8 Gy to the prostate bed. CBCT were taken prior to and halfway through each fraction. CTV and OARs were contoured for each CBCT. Changes in inter- and intra-fraction volume and dose were calculated. Relative changes in CTV V95%, bladder V32.5 Gy, and rectal V32.5 Gy and V27.5 Gy were evaluated.

RESULTS

Interfraction CTV volume remained stable, with median change +5.69% (IQR -1.73% to +9.84%). CTV V95% exhibited median change -0.74% (IQR -9.15% to -0.07%). Volumetric and dosimetric changes were minor from interfraction rotation and intrafraction motion. CTV V95% was ≥93% in 13 of 18 (72%) patients; in the remaining five, median change was -14.09% (IQR -16.64% to -13.56%). Interfraction CTV volume change was significantly larger among patients with CTV V95% <93% (+25.04% vs. +2.85%, p = 0.002).

CONCLUSIONS

With specific bladder and rectum filling protocols, CTV underdosing and overdosing to bladder and rectum are avoided in majority of patients. Changes in CTV shape may account for the underdosing that may be observed.

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.

Single-Fraction Stereotactic Body Radiation Therapy: A Paradigm During the Coronavirus Disease 2019 (COVID-19) Pandemic and Beyond?

PURPOSE

Owing to the coronavirus disease 2019 (COVID-19) pandemic, radiation oncology departments have adopted various strategies to deliver radiation therapy safely and efficiently while minimizing the risk of severe acute respiratory syndrome coronavirus-2 transmission among patients and health care providers. One practical strategy is to deliver stereotactic body radiation therapy (SBRT) in a single fraction, which has been well established for treating bone metastases, although it has been infrequently used for other extracranial sites.

METHODS AND MATERIALS

A PubMed search of published articles in English related to single-fraction SBRT was performed. A critical review was performed of the articles that described clinical outcomes of single-fraction SBRT for treatment of primary extracranial cancers and oligometastatic extraspinal disease.

RESULTS

Single-fraction SBRT for peripheral early-stage non-small cell lung cancer is supported by randomized data and is strongly endorsed during the COVID-19 pandemic by the European Society for Radiotherapy and Oncology-American Society for Radiation Oncology practice guidelines. Prospective and retrospective studies supporting a single-fraction regimen are limited, although outcomes are promising for renal cell carcinoma, liver metastases, and adrenal metastases. Data are immature for primary prostate cancer and demonstrate excess late toxicity in primary pancreatic cancer.

CONCLUSIONS

Single-fraction SBRT should be strongly considered for peripheral early-stage non-small cell lung cancer during the COVID-19 pandemic to mitigate the potentially severe consequences of severe acute respiratory syndrome coronavirus-2 transmission. Although single-fraction SBRT is promising for the definitive treatment of other primary or oligometastatic cancers, multi-fraction SBRT should be the preferred regimen owing to the need for additional prospective evaluation to determine long-term efficacy and safety.