Hypofractionated radiotherapy for localized prostate cancer

Cyberknife Radiosurgery for Prostate Cancer after Abdominoperineal Resection (CYRANO): The Combined Computer Tomography and Electromagnetic Navigation Guided Transperineal Fiducial Markers Implantation Technique

In this technical development report, we present the strategic placement of fiducial markers within the prostate under the guidance of computed tomography (CT) and electromagnetic navigation (EMN) for the delivery of ultra-hypofractionated cyberknife (CK) therapy in a patient with localized prostate cancer (PCa) who had previously undergone chemo-radiotherapy for rectal cancer and subsequent abdominoperineal resection due to local recurrence. The patient was positioned in a prone position with a pillow under the pelvis to facilitate access, and an electromagnetic fiducial marker was placed on the patient's skin to establish a stable position. CT scans were performed to plan the procedure, mark virtual points, and simulate the needle trajectory using the navigation system. Local anesthesia was administered, and a 21G needle was used to place the fiducial markers according to the navigation system information. A confirmatory CT scan was obtained to ensure proper positioning. The implantation procedure was safe, without any acute side effects such as pain, hematuria, dysuria, or hematospermia. Our report highlights the ability to use EMN systems to virtually navigate within a pre-acquired imaging dataset in the interventional room, allowing for non-conventional approaches and potentially revolutionizing fiducial marker positioning, offering new perspectives for PCa treatment in selected cases.

Robotic stereotactic body radiotherapy for localized prostate cancer: final analysis of the German HYPOSTAT trial

PURPOSE

We report results of the first German prospective multicenter single-arm phase II trial (ARO 2013-06; NCT02635256) of hypofractionated robotic stereotactic body radiotherapy (SBRT) for patients with localized prostate cancer (HYPOSTAT).

METHODS

Patients eligible for the HYPOSTAT study had localized prostate cancer (cT1‑3 cN0 cM0), Gleason score ≤ 7, prostate-specific antigen (PSA) ≤ 15 ng/ml, prostate volume ≤ 80 cm³, and an International Prostate Symptom Score (IPSS) ≤ 12. Initially, inclusion was limited to patients ≥ 75 years or patients 70-74 years with additional risk factors. The trial protocol was later amended to allow for enrolment of patients aged ≥ 60 years. The treatment consisted of 35 Gy delivered in 5 fractions to the prostate and for intermediate- or high-risk patients, also to the proximal seminal vesicles using the CyberKnife system (Accuray Inc., Sunnyvale, CA, USA). Primary endpoint was the rate of treatment-related gastrointestinal or genitourinary grade ≥ 2 toxicity based on the RTOG scale 12-15 months after treatment. Secondary endpoints were acute toxicity, late toxicity, urinary function, quality of life, and PSA response.

RESULTS

From July 2016 through December 2018, 85 eligible patients were enrolled and received treatment, of whom 83 could be evaluated regarding the primary endpoint. Patients mostly had intermediate-risk disease with a median PSA value of 7.97 ng/ml and Gleason score of 7a and 7b in 43.5% and 25.9% of patients, respectively. At the final follow-up 12-15 months after treatment, no patient suffered from treatment-related gastrointestinal or genitourinary grade ≥ 2 toxicity. Acute toxicity was mostly mild, with three grade 3 events, and the cumulative rate of grade ≥ 2 genitourinary toxicity was 8.4% (95% CI 4.1-16.4%). There were no major changes in urinary function or quality of life. The median PSA value dropped to 1.18 ng/ml 12-15 months after treatment. There was one patient who developed distant metastases.

CONCLUSION

Robotic SBRT with 35 Gy in 5 fractions was associated with a favorable short-term toxicity profile. Recruitment for the HYPOSTAT‑2 trial (ARO-2018‑4; NCT03795337), which further analyses the late toxicity of this regimen with a planned sample size of 500 patients, is ongoing.

Predictive modelling for late rectal and urinary toxicities after prostate radiotherapy using planned and delivered dose

Background and purpose

Normal tissue complication probability (NTCP) parameters derived from traditional 3D plans may not be ideal in defining toxicity outcomes for modern radiotherapy techniques. This study aimed to derive parameters of the Lyman-Kutcher-Burman (LKB) NTCP model using prospectively scored clinical data for late gastrointestinal (GI) and genitourinary (GU) toxicities for high-risk prostate cancer patients treated using volumetric-modulated-arc-therapy (VMAT). Dose-volume-histograms (DVH) extracted from planned (D_P) and accumulated dose (D_A) were used.

Material and methods

D_P and D_A obtained from the DVH of 150 prostate cancer patients with pelvic-lymph-nodes irradiation treated using VMAT were used to generate LKB-NTCP parameters using maximum likelihood estimations. Defined GI and GU toxicities were recorded up to 3-years post RT follow-up. Model performance was measured using Hosmer-Lemeshow goodness of fit test and the mean area under the receiver operating characteristics curve (AUC). Bootstrapping method was used for internal validation.

Results

For mild-severe (Grade ≥1) GI toxicity, the model generated similar parameters based on D_A and D_P DVH data (D_A-D₅₀:71.6 Gy vs D_P-D₅₀:73.4; D_A-m:0.17 vs D_P-m:0.19 and D_A/P-n 0.04). The 95% CI for D_A-D₅₀ was narrower and achieved an AUC of >0.6. For moderate-severe (Grade ≥2) GI toxicity, D_A-D₅₀ parameter was higher and had a narrower 95% CI (D_A-D₅₀:77.9 Gy, 95% CI:76.4-79.6 Gy vs D_P-D₅₀:74.6, 95% CI:69.1-85.4 Gy) with good model performance (AUC>0.7). For Grade ≥1 late GU toxicity, D₅₀ and n parameters for D_A and D_P were similar (D_A-D₅₀: 58.8 Gy vs D_P-D₅₀: 59.5 Gy; D_A-n: 0.21 vs D_P-n: 0.19) with a low AUC of<0.6. For Grade ≥2 late GU toxicity, similar NTCP parameters were attained from D_A and D_P DVH data (D_A-D₅₀:81.7 Gy vs D_P-D₅₀:81.9 Gy; D_A-n:0.12 vs D_P-n:0.14) with an acceptable AUCs of >0.6.

Conclusions

The achieved NTCP parameters using modern RT techniques and accounting for organ motion differs from QUANTEC reported parameters. D_A-D₅₀ of 77.9 Gy for GI and D_A/D_P-D₅₀ of 81.7-81.9 Gy for GU demonstrated good predictability in determining the risk of Grade ≥2 toxicities especially for GI derived D₅₀ and are recommended to incorporate as part of the DV planning constraints to guide dose escalation strategies while minimising the risk of toxicity.

Improvement in bladder volume reproducibility using A-mode portable ultrasound bladder scanner in moderate-hypofractionated volumetric modulated arc therapy for prostate cancer patients

Purpose

This study introduced an A‐mode portable ultrasound bladder scanner, the Lilium® α‐200 (here after Lilium; Lilium Otsuka, Kanagawa, Japan), for the treatment of prostate cancer patients with hypofractionated volumetric modulated arc therapy to improve the reproducibility of bladder volume (BV).

Materials and methods

Thirty patients were advised to maintain full BV prior to computed tomography (CT) simulation and daily treatment. Among these, the BV of 15 patients was measured using Lilium until a BV of 80% in the simulation was achieved (with the Lilium group). Daily cone‐beam CT (CBCT) was performed for treatment. The correlation between BV measured by CBCT and Lilium was assessed. The differences in the BV and dosimetric parameters of the bladder in the CBCT versus planning CT were compared between the groups with and without Lilium.

Results

There was a significantly strong relationship (r = 0.796, p < 0.05) between the BVs measured using CBCT and Lilium. The relative BV ratios to simulation CT < 0.5 and > 2 were observed in 10.3% and 12.7%, respectively, of treatment sessions without Lilium group, while these ratios were 1% and 2.8%, respectively, in the Lilium group. The mean absolute difference in the range of V_30Gy to V_40Gy without Lilium sessions was significantly larger (p < 0.05) than that in the Lilium group.

Conclusion

The use of the A‐mode portable ultrasound bladder scanner significantly improved the reproducibility of the BV, resulting in few variations in the dosimetric parameters for the bladder.

Trends in radiotherapy inpatient admissions in Germany: a population-based study over a 10-year period

Objective

With the increasing complexity of oncological therapy, the number of inpatient admissions to radiotherapy and non-radiotherapy departments might have changed. In this study, we aim to quantify the number of inpatient cases and the number of radiotherapy fractions delivered under inpatient conditions in radiotherapy and non-radiotherapy departments.

Methods

The analysis is founded on data of all hospitalized cases in Germany based on Diagnosis-Related Group Statistics (G-DRG Statistics, delivered by the Research Data Centers of the Federal Statistical Office). The dataset includes information on the main diagnosis of cases (rather than patients) and the performed procedures during hospitalization based on claims of reimbursement. We used linear regression models to analyze temporal trends. The considered data encompass the period from 2008 to 2017.

Results

Overall, the number of patients treated with radiotherapy as inpatients remained constant between 2008 (N = 90,952) and 2017 (N = 88,998). Starting in January 2008, 48.9% of 4000 monthly cases received their treatment solely in a radiation oncology department. This figure decreased to 43.7% of 2971 monthly cases in October 2017. We found a stepwise decrease between December 2011 and January 2012 amounting to 4.3%. Fractions received in radiotherapy departments decreased slightly by 29.3 (95% CI: 14.0–44.5) fractions per month. The number of days hospitalized in radiotherapy departments decreased by 83.4 (95% CI: 59.7, 107.0) days per month, starting from a total of 64,842 days in January 2008 to 41,254 days in 2017. Days per case decreased from 16.2 in January 2008 to 13.9 days in October 2017.

Conclusion

Our data give evidence to the notion that radiotherapy remains a discipline with an important inpatient component. Respecting reimbursement measures and despite older patients with more comorbidities, radiotherapy institutions could sustain a constant number of cases with limited temporal shifts.

Supplementary Information

The online version of this article (10.1007/s00066-021-01829-7) contains supplementary material, which is available to authorized users.

Moderately hypofractionated radiotherapy as definitive treatment for localized prostate cancer: Pattern of practice in German-speaking countries : A survey of the Prostate Cancer Expert Panel of the German Society of Radiation Oncology (DEGRO) and the Working Party on Radiation Oncology of the German Cancer Society (DKG-ARO)

Purpose

Various randomized phase III clinical trials have compared moderately hypofractionated to normofractionated radiotherapy (RT). These modalities showed similar effectiveness without major differences in toxicity. This project was conducted by the Prostate Cancer Expert Panel of the German Society of Radiation Oncology (DEGRO) and the Working Party on Radiation Oncology of the German Cancer Society. We aimed to investigate expert opinions on the use of moderately hypofractionated RT as a definitive treatment for localized prostate cancer in German-speaking countries.

Methods

A 25-item, web-based questionnaire on moderate-hypofractionation RT was prepared by an internal committee. The experts of the DEGRO were asked to complete the questionnaire.

Results

Fourteen active members of DEGRO completed the questionnaire. The questions described indications for selecting patients eligible to receive moderate hypofractionation based on clinical and pathological factors such as age, urinary symptoms, and risk-group. The questions also collected information on the technical aspects of selection criteria, including the definition of a clinical target volume, the use of imaging, protocols for bladder and rectal filling, the choice of a fractionation schedule, and the use of image guidance. Moreover, the questionnaire collected information on post-treatment surveillance after applying moderately hypofractionated RT.

Conclusion

Although opinions varied on the use of moderate-hypofractionation RT, the current survey reflected broad agreement on the notion that moderately hypofractionated RT could be considered a standard treatment for localized prostate cancer in German-speaking countries.

Dosimetric benefits of daily treatment plan adaptation for prostate cancer stereotactic body radiotherapy

BACKGROUND

Hypofractionation is increasingly being applied in radiotherapy for prostate cancer, requiring higher accuracy of daily treatment deliveries than in conventional image-guided radiotherapy (IGRT). Different adaptive radiotherapy (ART) strategies were evaluated with regard to dosimetric benefits.

METHODS

Treatments plans for 32 patients were retrospectively generated and analyzed according to the PACE-C trial treatment scheme (40 Gy in 5 fractions). Using a previously trained cycle-generative adversarial network algorithm, synthetic CT (sCT) were generated out of five daily cone-beam CT. Dose calculation on sCT was performed for four different adaptation approaches: IGRT without adaptation, adaptation via segment aperture morphing (SAM) and segment weight optimization (ART1) or additional shape optimization (ART2) as well as a full re-optimization (ART3). Dose distributions were evaluated regarding dose-volume parameters and a penalty score.

RESULTS

Compared to the IGRT approach, the ART1, ART2 and ART3 approaches substantially reduced the V37Gy(bladder) and V36Gy(rectum) from a mean of 7.4cm3 and 2.0cm3 to (5.9cm3, 6.1cm3, 5.2cm3) as well as to (1.4cm3, 1.4cm3, 1.0cm3), respectively. Plan adaptation required on average 2.6 min for the ART1 approach and yielded doses to the rectum being insignificantly different from the ART2 approach. Based on an accumulation over the total patient collective, a penalty score revealed dosimetric violations reduced by 79.2%, 75.7% and 93.2% through adaptation.

CONCLUSION

Treatment plan adaptation was demonstrated to adequately restore relevant dose criteria on a daily basis. While for SAM adaptation approaches dosimetric benefits were realized through ensuring sufficient target coverage, a full re-optimization mainly improved OAR sparing which helps to guide the decision of when to apply which adaptation strategy.

Ultrahypofractionation of localized prostate cancer : Statement from the DEGRO working group prostate cancer

Due to its low fractionation sensitivity, also known as “alpha/beta ratio,” in relation to its surrounding organs at risk, prostate cancer is predestined for hypofractionated radiation schedules assuming an increased therapeutic ratio compared to normofractionated regimens. While moderate hypofractionation (2.2–4 Gy) has been proven to be non-inferior to normal fractionation in several large randomized trials for localized prostate cancer, level I evidence for ultrahypofractionation (>4 Gy) was lacking until recently. An accumulating body of non-randomized evidence has recently been strengthened by the publication of two randomized studies comparing ultrahypofractionation with a normofractionated schedule, i.e., the Scandinavian HYPO-RT trial by Widmark et al. and the first toxicity results of the PACE‑B trial. In this review, we aim to give a brief overview of the current evidence of ultrahypofractionation, make an overall assessment of the level of evidence, and provide recommendations and requirements that should be followed before introducing ultrahypofractionation into routine clinical use.

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.

A radiobiological study of the schemes with a low number of fractions in high-dose-rate brachytherapy as monotherapy for prostate cancer

Purpose

Schemes with high doses per fraction and small number of fractions are commonly used in high-dose-rate brachytherapy (HDR-BT) for prostate cancer. Our aim was to analyze the differences between published clinical results and the predictions of radiobiological models for absorbed dose required in a single fraction monotherapy HDR-BT.

Material and methods

Published HDR-BT clinical results for low- and intermediate-risk patients with prostate cancer were revised. For 13 clinical studies with 16 fractionation schedules between 1 and 9 fractions, a dose-response relation in terms of the biochemical control probability (BC) was established using Monte Carlo-based statistical methods.

Results

We obtained a value of α/β = 22.8 Gy (15.1-60.2 Gy) (95% CI) much larger than the values in the range 1.5-3.0 Gy that are usually considered to compare the results of different fractionation schemes in prostate cancer radiotherapy using doses per fraction below 6 Gy. The doses in a single fraction producing BC = 90% and 95% were 22.3 Gy (21.5-24.2 Gy) and 24.3 Gy (23.0-27.9 Gy), respectively.

Conclusions

The α/β obtained in our analysis of 22.8 Gy for a range of dose per fraction between 6 and 20.5 Gy was much greater than the one currently estimated for prostate cancer using low doses per fraction. This high value of α/β explains reasonably well the data available in the region of high doses per fraction considered.

First statement on preparation for the COVID-19 pandemic in large German Speaking University-based radiation oncology departments

The COVID-19 pandemic is challenging modern radiation oncology. At University Hospitals, we have a mandate to offer high-end treatments to all cancer patients. However, in times of crisis we must learn to prioritize resources, especially personnel. Compromising oncological outcome will blur all statistics, therefore all measures must be taken with great caution. Communication with our neighboring countries, within societies and between departments can help meet the challenge. Here, we report on our learning system and preparation measures to effectively tackle the COVID-19 challenge in University-Based Radiation Oncology Departments.

Definitive, intensity modulated tomotherapy with a simultaneous integrated boost for prostate cancer patients - Long term data on toxicity and biochemical control

Aim

To report long-term data regarding biochemical control and late toxicity of simultaneous integrated boost intensity modulated radiotherapy (SIB-IMRT) with tomotherapy in patients with localized prostate cancer.

Background

Dose escalation improves cancer control after curative intended radiation therapy (RT) to patients with localized prostate cancer, without increasing toxicity, if IMRT is used.

Materials and methods

In this retrospective analysis, we evaluated long-term toxicity and biochemical control of the first 40 patients with intermediate risk prostate cancer receiving SIB-IMRT. Primary target volume (PTV) 1 including the prostate and proximal third of the seminal vesicles with safety margins was treated with 70 Gy in 35 fractions. PTV 2 containing the prostate with smaller safety margins was treated as SIB to a total dose of 76 Gy with 2.17 Gy per fraction. Toxicity was evaluated using an adapted CTCAE-Score (Version 3).

Results

Median follow-up of living patients was 66 (20-78) months. No late genitourinary toxicity higher than grade 2 has been reported. Grade 2 genitourinary toxicity rates decreased from 58% at the end of the treatment to 10% at 60 months. Late gastrointestinal (GI) toxicity was also moderate, though the prescribed PTV Dose of 76 Gy was accepted at the anterior rectal wall. 74% of patients reported any GI toxicity during follow up and no toxicity rates higher than grade 2 were observed. Grade 2 side effects were reported by 13% of the patients at 60 months. 5-year freedom from biochemical failure was 95% at our last follow up.

Conclusion

SIB-IMRT using daily MV-CT guidance showed excellent long-term biochemical control and low toxicity rates.

Moderate hypofractionated radiotherapy vs conventional fractionated radiotherapy in localized prostate cancer: a systemic review and meta-analysis from Phase III randomized trials

Purpose

To determine the efficacy and late toxicities of moderate (2.5–4 Gy) hypofractionated radiotherapy (H-RT) in localized prostate cancer, a meta-analysis of published randomized clinical trials comparing moderate H-RT with conventional fractionated RT (C-RT) was performed.

Materials and methods

Systematic search on published randomized clinical trials in English according to Cochrane review guidelines in databases of Pubmed, Embase, Cochrane, web of science, and Wiley Online Library was carried out. Outcomes of interests were biochemical and clinical disease failure (BCDF), biochemical failure (BF), overall survival (OS), and late toxicities.

Results

Seven of the 365 studies fulfilled inclusion criteria with 8,156 participants. Compared with C-RT, moderate H-RT showed a lower BF rate (risk ratio [RR] =0.80, 95% CI: 0.68–0.95, P=0.009), while did not improve OS (RR =0.68, 95% CI: 0.78–1.02, P=0.10). There was no significant difference in BCDF rates between H-RT and C-RT (RR =0.92, 95% CI: 0.82–1.02, P=0.12). The H-RT was deeply grouped into dose-escalated H-RT (with a higher biologically effective dose [BED_1.5] than C-RT) and no dose-escalated H-RT; dose-escalated H-RT significantly decreased BCDF rate compared with C-RT (RR =0.84, 95% CI: 0.73–0.96, P=0.01). Regarding late toxicities, there is no significant difference in late gastrointestinal (GI; RR =0.97, 95% CI: 0.71–1.33, P=0.85) and genitourinary (GU) toxicities (RR =1.04, 95% CI: 0.87–1.24, P=0.69). When subgrouped into dose-escalated H-RT (with a higher BED₅ compared with C-RT) and no dose-escalated H-RT, dose-escalated H-RT increased GI toxicity (RR =1.62, 95% CI: 1.26–2.09, P=0.0002) and GU toxicity (RR =1.28, 95% CI: 1.05–1.55, P=0.01), while no dose-escalated H-RT significantly lowered GI toxicity (RR =0.81, 95% CI: 0.70–0.94, P=0.005) and placed no influence on GU toxicity (RR =1.02, 95% CI: 0.88–1.20, P=0.77).

Conclusion

This meta-analysis provides reliable evidence that moderate H-RT decreases BF rate, while does not improve OS. Compared with C-RT, H-RT with an increase in BED_1.5 improved BCDF rates significantly, and accordingly, an increase in BED₅ will result in elevated late GI and GU toxicities.

Towards a universal MRI atlas of the prostate and prostate zones : Comparison of MRI vendor and image acquisition parameters

BACKGROUND AND PURPOSE

The aim of this study was to evaluate an automatic multi-atlas-based segmentation method for generating prostate, peripheral (PZ), and transition zone (TZ) contours on MRIs with and without fat saturation (±FS), and compare MRIs from different vendor MRI systems.

METHODS

T2-weighted (T2) and fat-saturated (T2FS) MRIs were acquired on 3T GE (GE, Waukesha, WI, USA) and Siemens (Erlangen, Germany) systems. Manual prostate and PZ contours were used to create atlas libraries. As a test MRI is entered, the procedure for atlas segmentation automatically identifies the atlas subjects that best match the test subject, followed by a normalized intensity-based free-form deformable registration. The contours are transformed to the test subject, and Dice similarity coefficients (DSC) and Hausdorff distances between atlas-generated and manual contours were used to assess performance.

RESULTS

Three atlases were generated based on GE_T2 (n = 30), GE_T2FS (n = 30), and Siem_T2FS (n = 31). When test images matched the contrast and vendor of the atlas, DSCs of 0.81 and 0.83 for T2 ± FS were obtained (baseline performance). Atlases performed with higher accuracy when segmenting (i) T2FS vs. T2 images, likely due to a superior contrast between prostate vs. surrounding tissue; (ii) prostate vs. zonal anatomy; (iii) in the mid-gland vs. base and apex. Atlases performance declined when tested with images with differing contrast and MRI vendor. Conversely, combined atlases showed similar performance to baseline.

CONCLUSION

The MRI atlas-based segmentation method achieved good results for prostate, PZ, and TZ compared to expert contoured volumes. Combined atlases performed similarly to matching atlas and scan type. The technique is fast, fully automatic, and implemented on commercially available clinical platform.

Practice-changing radiation therapy trials for the treatment of cancer: where are we 150 years after the birth of Marie Curie?

As we mark 150 years since the birth of Marie Curie, we reflect on the global advances made in radiation oncology and the current status of radiation therapy (RT) research. Large-scale international RT clinical trials have been fundamental in driving evidence-based change and have served to improve cancer management and to reduce side effects. Radiation therapy trials have also improved practice by increasing quality assurance and consistency in treatment protocols across multiple centres. This review summarises some of the key RT practice-changing clinical trials over the last two decades, in four common cancer sites for which RT is a crucial component of curative treatment: breast, lung, urological and lower gastro-intestinal cancer. We highlight the global inequality in access to RT, and the work of international organisations, such as the International Atomic Energy Agency (IAEA), the European SocieTy for Radiotherapy and Oncology (ESTRO), and the United Kingdom National Cancer Research Institute Clinical and Translational Radiotherapy Research Working Group (CTRad), that aim to improve access to RT and facilitate radiation research. We discuss some emerging RT technologies including proton beam therapy and magnetic resonance linear accelerators and predict likely future directions in clinical RT research.

Clinical estimation of α/β values for prostate cancer from isoeffective phase III randomized trials with moderately hypofractionated radiotherapy

BACKGROUND

The α/β values for prostate cancer (PCa) are usually assumed to be low (1.0-1.8 Gy). This study estimated the α/β values of PCa from phase III randomized trials of conventional (CRT) versus hypofractionated (HRT) external beam radiotherapy (RT), reported as isoeffective in terms of their 5-year biochemical (BF) or biochemical and/or clinical failure (BCF) rates.

MATERIAL AND METHODS

The α/β for each trial was estimated from the equivalent biological effective doses using the linear-quadratic model for each of their HRT and CRT schedules. The cumulative outcomes of these trials were evaluated by meta-analysis for odds ratio (OR), risk ratio (RR) and risk difference (RD).

RESULTS

Eight trials from seven studies, randomized 6993 patients between CRT (n = 2941) and HRT (n = 4052). RT treatment varied between the two treatment groups in terms of dose/fraction, total dose, overall treatment time and %patients on androgen deprivation therapy (ADT). Differences in OR, RR, and RD for both BF and BCF were nonsignificant. The computed α/β ranged from 1.3 to 11.1 Gy (4.9 ± 3.9 Gy; 95% CI: 1.6-8.2). On multivariate regression, %ADT was the sole determinant of computed α/β (model R²: 0.98, p < .001).

CONCLUSIONS

Clinically estimated α/β for PCa from isoeffective randomized trials using known variables in the linear-quadratic expression ranged between 1.3 and 11.1 Gy. The estimated α/β values were inversely related to %ADT usage, which should be considered when planning future RT dose-fractionation schedules.

Ex vivo γH2AX radiation sensitivity assay in prostate cancer: Inter-patient and intra-patient heterogeneity

INTRODUCTION

The aim of the study is to assess inter-patient and intra-patient heterogeneity in tumour cell radiosensitivity using the ex vivo γH2AX assay in prostate cancer specimens.

METHODS

Excised specimens from untreated prostate cancer patients were cultivated 24h in media, irradiated ex vivo and fixed after 24h. Residual γH2AX foci were counted and the slope of the dose response was calculated. Intra-patient heterogeneity was studied from three to seven different biopsies.

RESULTS

In pathology-confirmed tumour samples from 21 patients the slope of residual γH2AX foci and radiation dose showed a substantial heterogeneity ranging from 0.82 to 3.17 foci/Gy. No correlation was observed between the slope values and the Gleason score (p=0.37), prostate specific antigen (p=0.48) and tumour stage (p=0.89). ANOVA indicated that only in 1 out of 9 patients, biopsies from different tumour locations yielded statistically significant differences. Variance component analysis indicated higher inter-patient than intra-patient variability. Bootstrap simulation study demonstrated that one biopsy is sufficient to estimate the mean value of residual γH2AX per dose level and account for intra-patient heterogeneity.

CONCLUSIONS

In prostate cancer inter-patient heterogeneity in tumour cell radiation sensitivity is pronounced and higher than intra-patient heterogeneity supporting the further development of the γH2AX ex vivo assay as a biomarker for individualized treatment.

[Hypofractionated irradiation of prostate cancer: What is the radiobiological understanding in 2017?]

For prostate cancer, hypofractionation has been based since 1999 on radiobiological data, which calculated a very low alpha/beta ratio (1.2 to 1.5Gy). This suggested that a better local control could be obtained, without any toxicity increase. Consequently, two types of hypofractionated schemes were proposed: "moderate" hypofractionation, with fractions of 2.5 to 4Gy, and "extreme" hypofractionation, utilizing stereotactic techniques, with fractions of 7 to 10Gy. For moderate hypofractionation, the linear-quadratic (LQ) model has been used to calculate the equivalent doses of the new protocols. The available trials have often shown a "non-inferiority", but no advantage, while the equivalent doses calculated for the hypofractionated arms were sometimes very superior to the doses of the conventional arms. This finding could suggest either an alpha/beta ratio lower than previously calculated, or a negative impact of other radiobiological parameters, which had not been taken into account. For "extreme" hypofractionation, the use of the LQ model is discussed for high dose fractions. Moreover, a number of radiobiological questions are still pending. The reduced overall irradiation time could be either a positive point (better local control) or a negative one (reduced reoxygenation). The prolonged duration of the fractions could lead to a decrease of efficacy (because allowing for reparation of sublethal lesions). Finally, the impact of the large fractions on the microenvironment and/or immunity remains discussed. The reported series appear to show encouraging short to mid-term results, but the results of randomized trials are still awaited. Today, it seems reasonable to only propose those extreme hypofractionated schemes to well-selected patients, treating small volumes with high-level stereotactic techniques.

Optimization of radiotherapy fractionation schedules based on radiobiological functions

OBJECTIVE

To present a method for optimizing radiotherapy fractionation schedules using radiobiological tools and taking into account the patient´s dose-volume histograms (DVH).

METHODS

This method uses a figure of merit based on the uncomplicated tumour control probability (P⁺) and the generalized equivalent uniform dose (gEUD). A set of doses per fraction is selected in order to find the dose per fraction and the total dose, thus maximizing the figure of merit and leading to a biologically effective dose that is similar to the prescribed schedule.

RESULTS

As a clinical example, a fractionation schedule for a prostate treatment plan is optimized and presented herein. From a prescription schedule of 70 Gy/35 × 2  Gy, the resulting optimal schema, using a figure of merit which only takes into account P⁺, is 54.4 Gy/16 × 3.4  Gy. If the gEUD is included in that figure of merit, the result is 65 Gy/26 × 2.5  Gy. Alternative schedules, which include tumour control probability (TCP) and the normal tissue complication probability (NTCP) values are likewise shown. This allows us to compare different schedules instead of solely finding the optimal value, as other possible clinical factors must be taken into account to make the best decision for treatment.

CONCLUSION

The treatment schedule can be optimized for each patient through radiobiological analysis. The optimization process shown below offers physicians alternative schedules that meet the objectives of the prescribed radiotherapy. Advances in knowledge: This article provides a simple, radiobiological-function-based method to take advantage of a patient's dose-volume histograms in order to better select the most suitable treatment schedule.

Hypo-fractionated SBRT for localized prostate cancer: a German bi-center single treatment group feasibility trial

BACKGROUND

For prostate cancer treatment, treatment options with minimal side effects are desired. External beam radiation therapy (EBRT) is non-invasive, standard of care and delivered in either conventional fractionation over 8 weeks or with moderate hypo-fractionation over about 5 weeks. Recent advances in radiotherapy technology have made extreme hypo-fractionated stereotactic body radiation therapy (SBRT) of prostate cancer feasible, which has not yet been introduced as a standard treatment method in Germany. Initial results from other countries are promising, but long-term results are not yet available. The aim of this study is to investigate feasibility and effectiveness of SBRT for prostate cancer in Germany.

METHODS/DESIGN

This German bi-center single group trial (HYPOSTAT) is designed to evaluate feasibility and effectiveness, as measured by toxicity and PSA-response, respectively, of an extreme hypo-fractionated SBRT regimen with five fractions of 7 Gy in treatment of localized low and intermediate risk prostate cancer. The target volume includes the prostate with or without the base of seminal vesicles depending on risk stratification and uncertainty margins that are kept at 3-5 mm. SBRT treatment is delivered with the robotic CyberKnife system, which was recently introduced in Germany. Acute and late toxicity after one year will be evaluated according to Common Terminology Criteria for Adverse Events (CTCAE v. 4.0), Radiation Therapy Oncology Group (RTOG) and International Prostate Symptom Score (IPSS) Scores. The quality of life will be assessed before and after treatment with the EORTC QLQ C30 questionnaire. Hypothesizing that the proportion of patients with grade 2 side effects or higher is less or equal than 2.8%, thus markedly lower than the standard EBRT percentage (17.5%), the recruitment target is 85 patients.

DISCUSSION

The HYPOSTAT trial aims at demonstrating short term feasibility of extreme hypo-fractioned SBRT for the treatment of prostate cancer and might be used as the pilot study for a multi-center multi-platform or for randomized-controlled trials comparing conventional radiotherapy with SBRT for localized prostate cancer in the future. The study concept of patient enrollment, follow up and evaluation by multiple public university clinics and actual patient treatment in dedicated private radiosurgery practices with high-tech radiation equipment is unique for clinical trials.

STUDY STATUS

The study is ongoing and currently recruiting patients.

TRIAL REGISTRATION

Registration number: NCT02635256 ( clinicaltrials.gov ). Registered 8 December 2015.

An IGRT margin concept for pelvic lymph nodes in high-risk prostate cancer

Purpose

Gold-marker-based image-guided radiation therapy (IGRT) of the prostate allows to correct for inter- and intrafraction motion and therefore to safely reduce margins for the prostate planning target volume (PTV). However, pelvic PTVs, when coadministered in a single plan (registered to gold markers [GM]), require reassessment of the margin concept since prostate movement is independent from the pelvic bony anatomy to which the lymphatics are usually referenced to.

Methods

We have therefore revisited prostate translational movement relative to the bony anatomy to obtain adequate margins for the pelvic PTVs compensating mismatch resulting from referencing pelvic target volumes to GMs in the prostate. Prostate movement was analyzed in a set of 28 patients (25 fractions each, totaling in 684 fractions) and the required margins calculated for the pelvic PTVs according to Van Herk’s margin formula \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$M=2.5\Upsigma +1.64\left (\sigma^{\prime}-\sigma _{p}\right )$$\end{document}M=2.5Σ+1.64σ′-σp.

Results

The overall mean prostate movement relative to bony anatomy was 0.9 ± 3.1, 0.6 ± 3.4, and 0.0 ± 0.7 mm in anterior/posterior (A/P), inferior/superior (I/S) and left/right (L/R) direction, respectively. Calculated margins to compensate for the resulting mismatch to bony anatomy were 9/9/2 mm in A/P, I/S, and L/R direction and 10/11/6 mm if an additional residual error of 2 mm was assumed.

Conclusion

GM-based IGRT for pelvic PTVs is feasible if margins are adapted accordingly. Margins could be reduced further if systematic errors which are introduced during the planning CT were eliminated.

[When is a nonsurgical approach possible for metastatic primary tumors and lymph node metastases of the urinary bladder and prostate?]

For metastatic carcinomas of the urinary bladder and prostate, systemic therapy is of primary importance. Due to technological advances in radiation oncology such as stereotactic radiotherapy, intensity-modulated radiotherapy, interstitial radiotherapy, and the combination of radiotherapy and chemotherapy, pelvic irradiation can nowadays be carried out effectively and without the risk of major side effects. New data from other tumor entities and retrospective analyses suggest that the use of these technologies can lead to a clinical benefit in terms of improvement in quality of life, local control, and overall survival. For the time being, the decision to administer radiotherapy to the pelvic region should be made on an individual basis. Retrospective analyses of data from prostate carcinomas in particular are currently being planned. This review article introduces potential indications which are supported with real patient examples and discusses future developments giving an overview of the literature and referring to data from prospective randomized trials.