High dose rate brachytherapy as monotherapy for localised prostate cancer

Efficacy and safety of 3-dimensional printing noncoplanar template (3D-PNCT)-assisted high-dose-rate interstitial brachytherapy (HDR-ISBT) for reirradiation of recurrent cervical cancer: a prospective cohort

OBJECTIVE

This study aimed to investigate the efficacy and safety of 3-dimensional printing noncoplanar template (3D-PNCT)-assisted computed tomography (CT)-guided high-dose-rate interstitial brachytherapy (HDR-ISBT) for reirradiation of pelvic recurrent cervical carcinoma after external beam radiotherapy.

METHODS

From January 2019 to August 2023, 45 eligible patients were enrolled in this prospective cohort. All patients underwent 3D-PNCT-assisted CT-guided HDR-ISBT with a prescribed dose of 4-7 Gy/fraction to the high-risk clinical target volume (HR-CTV) over 3-8 fractions, either for curative or palliative purposes. The primary endpoints were local progression-free survival (LPFS) and tumor response rate (TRR). The secondary outcome measures included overall survival (OS), toxicities, and symptom resolution.

RESULTS

Forty-five patients received 261 fractions of 3D-PNCT-assisted HDR-ISBT. Twenty-nine patients had isolated pelvic recurrence, and 16 patients had simultaneous extra-pelvic or distant recurrences. The TRR was 66.7%. The 2- and 5-year LPFS rates were 30.0% and 25.7%, respectively. The median OS was 23.2 months, and 2- and 5-year OS rates were 49.5% and 34.0%, respectively. The multivariate analysis indicated that squamous cell carcinoma, radical surgery, recurrence-free interval≥12 months, tumor diameter, pelvic recurrence type, and HR-CTV D90≥45 Gy were independent factors influencing LPFS (all p<0.05). D100≥21 Gy, V100≥83%, and V150≥45% were associated with better LPFS (all p<0.05). Tumor diameter and metastasis were independent predictive factors for OS (all p<0.05). The pain relief rate was 66.7% (10/15). Grade 3-4 toxicities occurred in 20.0% of patients.

CONCLUSION

3D-PNCT-assisted HDR-ISBT for reirradiation of recurrent cervical cancer proved to be an effective and safe alternative to radical surgery.

High-dose-rate Brachytherapy Monotherapy in Patients With Localised Prostate Cancer: Dose Modelling and Optimisation Using Computer Algorithms

AIMS

Interstitial high-dose-rate brachytherapy (HDR-BT) is an effective therapy modality for patients with localized prostate carcinoma. The objectives of the study were to optimise the therapy regime variables using two models: response surface methodology (RSM) and artificial neural network (ANN).

MATERIALS AND METHODS

Thirty-one studies with 5651 patients were included (2078 patients presented as low-risk, 3077 patients with intermediate-risk, and 496 patients with high-risk). A comparison of these therapy schedules was carried out using an effective biologically effective dose (BEDef) that was calculated assuming the number of treatment days and dose (D) per day. The modelling and optimization of therapy parameters (BEDef and risk level) in order to obtain the maximum biochemical free survival (BFS) were carried out by the RSM and ANN models.

RESULTS

An optimal treatment schedule (BFS = 97%) for patients presented with low-risk biochemical recurrence would be D = 26 Gy applied in one application, 2 fractions at least 6 h apart, within an overall treatment time of 1 day (BEDef = 251 Gy) by the RSM and ANN model. For patients presented with intermediate- or high-risk an optimal treatment regime (BFS = 94% and 90%, respectively) would be D = 38 Gy applied in one application, 4 fractions at least 6 h apart, with an overall treatment time of 2 days (BEDef = 279 Gy) by the RSM and ANN models.

CONCLUSIONS

The RSM and ANN models determine almost the same optimal values for the set of predicted therapy parameters that make a feasible selection of an optimal treatment regime.

21 Gy single fraction prostate HDR brachytherapy: 5-year results of a single institution prospective pilot study

PURPOSE

To present the outcome and toxicity results of a prospective trial of 21 Gy single fraction high-dose-rate (HDR) brachytherapy for men with low- or intermediate-risk prostate cancer.

METHODS AND MATERIALS

Patients were treated according to an IRB-approved prospective study of single fraction HDR brachytherapy. Eligible patients had low- or intermediate-risk prostate cancer with tumor stage ≤ T2b, PSA ≤ 15, and Gleason score ≤ 7. Patients underwent trans-rectal ultrasound-guided trans-perineal implant of the prostate followed by single fraction HDR brachytherapy to a dose of 21 Gy. The primary endpoint was grade ≥ 2 urinary/GI toxicity rates.

RESULTS

Twenty-six patients were enrolled with a median follow up of 5.1 years and median age of 64 years. 88.5% of patients had T1 disease, 15.4% had Gleason score 6 (84.6% Gleason 7), and median pre-treatment PSA was 5.0 ng/mL. Acute and chronic grade ≥ 2 urinary toxicity rates were 38.5% and 38.5%, respectively. There were no grade ≥ 2 acute or chronic GI toxicities. Six (23.1%) patients experienced biochemical failure, six (23.1%) patients experienced radiographic local failure, and five (19.2%) patients had biopsy-proven local failure. No patients developed regional lymph node recurrence or distant metastasis. 5-year overall survival and cause-specific survival were 96.2% and 100%, respectively.

CONCLUSIONS

21 Gy single fraction HDR brachytherapy was associated with modestly higher-than-anticipated chronic urinary toxicity, as well as high biochemical and local failure rates. The results from this prospective pilot study do not support the use of this regimen in standard clinical practice.

Safety and efficacy associated with single-fraction high-dose-rate brachytherapy in localized prostate cancer: a systematic review and meta-analysis

OBJECTIVE

Although single-fraction high-dose-rate brachytherapy (SFHDR) for localized prostate cancer has been tried in clinical trials, relevant medical evidence is currently lacking. It is necessary to systematically analyze the safety and efficacy of SFHDR.

METHODS

Comprehensive and systematic searches for eligible studies were performed in PubMed, Embase, and the Cochrane Library databases. The primary endpoints included safety and efficacy, represented by toxic effects and biochemical recurrence-free survival (bRFS), respectively. The proportion rates were used as the effect measure for each study and were presented with corresponding 95% confidence intervals (CI) and related 95% prediction interval (PI). Restricted maximum-likelihood estimator (REML) and the Hartung-Knapp method were used in the meta-analysis.

RESULTS

Twenty-five studies met the inclusion criteria for quantitative analysis, including 1440 patients. The median age of patients was 66.9 years old (62-73 years old) and the median follow-up was 47.5 months (12-75 months). The estimates of cumulative occurrence for severe gastrointestinal (GI) and genitourinary (GU) toxic effects were 0.1% (95% CI 0-0.2%) and 0.4% (95% CI 0-1.2%), and for grade 2 toxic effects were 1.6% (95% CI 0.1-4.7%) and 17.1% (95% CI 5.4-33.5%), respectively. The estimate of 3‑year bRFS was 87.5% (95% CI 84.4-90.3%) and 71.0% (95% CI 63.0-78.3%) for 5‑year bRFS. The pooled bRFS rates for low-risk patients were 99.0% (95% CI 85.2-100.0%) at 3 years and 80.9% (95% CI 75.4-85.9%) at 5 years, and the risk group was found to be statistically correlated with bRFS (3-year bRFS, P < 0.01; 5‑year bRFS, P = 0.04).

CONCLUSION

SFHDR is associated with favorable tolerability and suboptimal clinical benefit in patients with localized prostate cancer. Ongoing and planned high-quality prospective studies are necessary to verify its safety and efficacy.

Feasibility of MRI targeted single fraction HDR brachytherapy for localized prostate carcinoma: ProFocAL-study

Purpose

A potential method for focal therapy in locally advanced prostate cancer is focal brachytherapy (F-BT). The purpose of this research was to evaluate midterm F-BT oncologic, functional, and toxicological results in men who had therapy for prostate cancer.

Materials and methods

Between 2016 and 2020, F-BT was used to treat 37 patients with low- to intermediate-risk prostate cancer. The recommended dosage was 20 Gy. Failure was defined as the existence of any prostate cancer that has persisted in-field after treatment. The F-BT oncologic and functional outcomes served as the main and secondary objectives, respectively.

Results

A median 20-month follow-up (range 14–48 months). 37 patients received F-BT and enrolled in the study; no patient experienced a biochemical recurrence in the first 24 months, according to Phoenix criteria. In the control biopsies, only 6 patients showed in-field failure. The median initial IPSS was 6.5, at 6 months was 6.0, and at 24 months was 5.0. When the median ICIQ-SF score was 0 at the baseline, it remained 0 at 6-, 12-, and 24 months. Overall survival and biochemical disease-free survival after 3 years were all at 100% and 86.4%, respectively. There was no notable acute gastro-intestinal (GI) or genitourinary (GU) adverse effects. No intraoperative or perioperative complications occurred.

Conclusions

For selected patients with low- or intermediate-risk localized prostate cancer, F-BT is a safe and effective therapy.

HDR Brachytherapy Planning using Active Needles - Preliminary Investigation on Dose Planning

In this study we present a new approach to plan a high-dose-rate (HDR) prostate brachytherapy (BT) using active needles recently developed by our group. The active needles realize bi-directional bending inside the tissue, and thereby more compliant with the patient's anatomy compared with conventional straight needles. A computational method is presented to first generate a needle arrangement configuration based on the patient's prostate anatomy. The needle arrangement is generated to cover the prostate volume, providing accessible channels for the radiation source during a HDR BT. The needle arrangement configuration avoids healthy organs and prevents needle collision inside the body. Then a treatment plan is proposed to ensure sufficient prescribed dosage to the whole prostate gland. The method is applied to a prostate model reconstructed from an anonymized patient to show the feasibility of this method. Finally, the active needle's capability to generate the required bending is shown. We have shown that our method is able to automatically generate needle arrangement configuration using active needles, and plan for a treatment that meets the dose objectives while using fewer needles (about 20% of conventional straight needles) than the conventional HDR BT performed by straight needles.

Ultrahypofractionated Radiotherapy for Localised Prostate Cancer: How Far Can We Go?

Following adoption of moderately hypofractionated radiotherapy as a standard for localised prostate cancer, ultrahypofractioned radiotherapy delivered in five to seven fractions is rapidly being embraced by clinical practice and international guidelines. However, the question remains: how low can we go? Can radiotherapy for prostate cancer be delivered in fewer than five fractions? The current review summarises the evidence that radiotherapy for localised prostate cancer can be safely and effectively delivered in fewer than five fractions using high dose rate brachytherapy or stereotactic body radiotherapy. We also discuss important lessons learned from the single-fraction high dose rate brachytherapy experience.

High-Dose-Rate Brachytherapy as Monotherapy for Low- and Intermediate-Risk Prostate Cancer. Oncological Outcomes After a Median 15-Year Follow-Up

Introduction

To evaluate the oncological outcome of high dose rate (HDR) brachytherapy (BRT) as monotherapy for clinically localised prostate cancer (PCA).

Material and Methods

Between January 2002 and February 2004, 141 consecutive patients with clinically localised PCA were treated with HDR-BRT monotherapy. The cohort comprised 103 (73%) low-, 32 (22.7%) intermediate- and 6 (4.3%) high risk patients according to D’Amico classification or 104 (73.8%) low-, 24 (17.0%) intermediate favourable-, 12 (8.5%) intermediate unfavourable- and one (0.7%) very high risk patient according to National Comprehensive Cancer Network (NCCN) one. Patients received four fractions of 9.5 Gy delivered within a single implant up to a total physical dose of 38 Gy. Catheter-implantation was transrectal ultrasound-based whereas treatment planning CT-based. Thirty-three patients (23.4%) received ADT neoadjuvantly and continued concurrently with BRT. Biochemical relapse-free survival (BRFS) was defined according to the Phoenix Consensus Criteria and genitourinary (GU)/gastrointestinal (GI) toxicity evaluated using the Common Toxicity Criteria for Adverse Events version 5.0.

Results

Median age at treatment and median follow-up time was 67.2 and 15.2 years, respectively. Twenty-three (16.3%) patients experienced a biochemical relapse and 5 (3.5%) developed distant metastases, with only one patient dying of PCA. The BRFS was 85.1% at 15 years and 78.7% at 18 years. The corresponding overall survival, metastases-free survival, and prostate cancer specific mortality at 15- and 18-years was 73.9%/59.1%, 98.3%/90.6%, and 100%/98.5% respectively. Late grade 3 GI and GU toxicity was 4.2% and 5.6% respectively. Erectile dysfunction grade 3 was reported by 27 (19%) patients. From the prognostic factors evaluated, tumor stage (≤T2b compared to ≥T2c) along with the risk group (low-intermediate vs. high) when using the D’Amico classification but not when the NCCN one was taken into account, correlated significantly with BRFS.

Conclusion

Our long-term results confirm HDR-BRT to be a safe and effective monotherapeutic treatment modality for low- and intermediate risk PCA.

PSA outcomes and late toxicity of single-fraction HDR brachytherapy and LDR brachytherapy as monotherapy in localized prostate cancer: A phase 2 randomized pilot study

PURPOSE

To evaluate the PSA outcomes and the late patient's reported health related quality of life (HRQOL) and toxicity after single-fraction High-Dose-Rate brachytherapy (HDRB) and Low-Dose-Rate brachytherapy (LDRB) for prostate cancer.

METHODS

Men with low and favorable intermediate-risk prostate cancer across 3 centres were randomized between monotherapy brachytherapy with either Iodine-125 LDRB or 19 Gy single-fraction HDRB. Biochemical outcomes were evaluated using the Phoenix definition, PSA nadir and absolute PSA value <0.4 ng/mL. Toxicities and HRQOL were recorded at 24 and 36 months.

RESULTS

A total of 31 patients were randomized, 15 in the LDRB arm and 16 patients in the HDRB arm. After a median follow-up of 45(36-53) months, 3 patients in the HDRB arm experienced biochemical failure (p = 0.092). Nineteen Gy single-fraction HDRB was associated with significantly higher PSA nadir compared to LDRB (1.02 ± 0.66vs 0.25 ± 0.39, p < 0.0001). Moreover, a significantly larger proportion of patients in the LDRB group had a PSA <0.4 ng/mL (13/15 vs 2/16, p < 0.0001). For late Genito-Urinary, Gastro-Intestinal, and sexual toxicities at 24 and 36 months, no significant differences were found between the 2 arms. As for HRQOL, the IPSS and EPIC-26 urinary irritative score were significantly better for patients treated with HDRB over the first 36 months post-treatment (p = 0.001 and p = 0.01, respectively), reflecting superior HRQOL.

CONCLUSION

HDRB resulted in superior HRQOL in the irritative urinary domain compared to LDRB. PSA nadir was significantly lower in the LDRB group and a higher proportion of patients in the LDRB group reached PSA <0.4 ng/mL.

High-dose-rate brachytherapy for prostate cancer: Rationale, current applications, and clinical outcome

Background

High‐dose‐rate brachytherapy (HDR BRT) has been enjoying rapid acceptance as a treatment modality offered to selected prostate cancer patients devoid of risk group, employed either in monotherapy setting or combined with external beam radiation therapy (EBRT) and is currently one of the most active clinical research areas.

Recent findings

This review encompasses all the current evidence to support the use of HDR BRT in various clinical scenario and shines light to the HDR BRT rationale, as an ultimately conformal dose delivery method enabling safe dose escalation to the prostate.

Conclusion

Valid long‐term data, both in regard to the oncologic outcomes and toxicity profile, support the current clinical indication spectrum of HDR BRT. At the same time, this serves as solid, rigid ground for emerging therapeutic applications, allowing the technique to remain in the spotlight alongside stereotactic radiosurgery.

Accuracy of an in vivo dosimetry-based source tracking method for afterloading brachytherapy - A phantom study

PURPOSE

To report on the accuracy of an in vivo dosimetry (IVD)-based source tracking (ST) method for high dose rate (HDR) prostate brachytherapy (BT).

METHODS

The ST was performed on a needle-by-needle basis. A least square fit of the expected to the measured dose rate was performed using the active dwell positions in the given needle. Two fitting parameters were used to determine the position of each needle relative to the IVD detector: radial (away or toward the detector) and longitudinal (along the axis of the treatment needle). The accuracy of the ST was assessed in a phantom where the geometries of five HDR prostate BT treatments previously treated at our clinic were reproduced. For each of the five treatment geometries, one irradiation was performed with the detector placed in the middle of the implant. Furthermore, four additional irradiations were performed for one of the geometries where the detector was retracted caudally in four steps of 10-15 mm and up to 12 mm inferior of the most inferior active dwell position, which represented the prostate apex. The time resolved dose measurements were retrieved at a rate of 20 Hz using a detector based on an Al₂ O₃ :C radioluminescence crystal, which was placed inside a standard BT needle. Individual calibrations of the detector were performed prior to each of the nine irradiations.

RESULTS

Source tracking could be applied in all needles across all nine irradiations. For irradiations with the detector located in the middle region of the implant (a total of 89 needles), the mean ± standard deviation (SD, k = 1) accuracy was -0.01 mm ± 0.38 mm and 0.30 mm ± 0.38 mm in the radial and longitudinal directions, respectively. Caudal retraction of the detector did not lead to reduced accuracy as long as the detector was located superior to the most inferior active dwell positions in all needles. However, reduced accuracy was observed for detector positions inferior to the most inferior active dwell positions which corresponded to detector positions in and inferior to the prostate apex region. Detector positions in the prostate apex and 12 mm inferior to the prostate resulted in mean ± SD (k = 1) ST accuracy of 0.7 mm ± 1 mm and 2.8 mm ± 1.6 mm, respectively, in radial direction, and -1.7 mm ± 1 mm and -2.1 mm ± 1.1 mm, respectively, in longitudinal direction. The largest deviations for the configurations with those detector positions were 2.6 and 5.4 mm, respectively, in the radial direction and -3.5 and -3.8 mm, respectively, in the longitudinal direction.

CONCLUSION

This phantom study demonstrates that ST based on IVD during prostate BT is adequately accurate for clinical use. The ST yields submillimeter accuracy on needle positions as long as the IVD detector is positioned superior to at least one active dwell position in all needles. Locations of the detector inferior to the prostate apex result in decreased ST accuracy while detector locations in the apex region and above are advantageous for clinical applications.

Complications and side effects of high-dose-rate prostate brachytherapy

PURPOSE

To describe technical challenges and complications encountered during and after high-dose-rate prostate brachytherapy (HDR-BT) and review management of these complications.

METHODS AND MATERIALS

The authors performed a systematic review of the literature on toxicities encountered after prostate HDR-BT +/- external beam radiotherapy. A total of 397 studies were identified, of which 64 were included. A focused review of literature regarding the management of acute and late toxicities also performed.

RESULTS

Most acute toxicities include grade 0-2 genitourinary and gastrointestinal toxicity. Overall, Grade 3+ Common Terminology Criteria for Adverse Events toxicity after HDR-BT was low [genitourinary: 0-1%; gastrointestinal 0-3%]. Rates of fistula formation were <1%, and radiation cystitis/proctitis were <14% and more commonly reported in cohorts treated with HDR-BT boost and external beam radiotherapy.

CONCLUSIONS

HDR-BT both as monotherapy or combined with external beam radiotherapy for prostate cancer is well tolerated. Serious complications are rare.

HDR brachytherapy as monotherapy for prostate cancer: A systematic review with meta-analysis

PURPOSE

The effectiveness and safety of high dose brachytherapy as monotherapy (HDR-BRT-M) in prostate cancer is limited to retrospective studies. We performed a meta-analysis to summarize existing data and identify trends in biochemical recurrence-free survival (bRFS) and toxicity after HDR-BRT-M in patients with prostate cancer.

METHODS AND MATERIALS

Retrospective, prospective, or randomized clinical trials were identified on electronical databases through June 2020. We followed the PRISMA and MOOSE guidelines. A meta-regression analysis was performed to assess if there is a relationship between moderator variables and bRFS. A p-value < 0.05 was considered significant.

RESULTS

Fourteen studies with a total of 3534 patients treated were included. The cumulative size of the bRFS at 5 years was 0.92 (95% confidence interval (CI) 0.48-0.61). The five-year bRFS for low, intermediate, and high risk was 97.5% (95% CI 96-98%), 93.5% (95% CI 91-96%), and 91% (95% CI 88-93%), respectively. The total biological effective dose (BED) (p = 0.02), the BED per fraction (p = 0.001), androgen deprivation therapy usage (p = 0.04), and the number of fractions of HDR-BRT-M (p = 0.024) were significantly associated with bRFS rate. The rate of late Grade 2/3 or > genitourinary and gastrointestinal toxicity was 22.4% (95% CI 9-35,2%)/1.4% (95% CI 0.8-2.1%) and 2.7% (95% CI 0-6.8%) and 0.2% (95% CI 0.1%-0.4%), respectively.

CONCLUSIONS

HDR-BRT-M is safe with excellent rates of bRFS for all risk groups. The total BED, the BED per fraction, and number of fractions were the key factors associated with the biochemical control. These data can be useful to choose the size and number of BRT fractionation.

Feasibility of MR-guided ultrahypofractionated radiotherapy in 5, 2 or 1 fractions for prostate cancer

The drive towards hypofractionated prostate radiotherapy is motivated by a low alpha/beta ratio for prostate cancer (1 to 3 Gy) compared to surrounding organs at risk, implying an improved therapeutic ratio with increasing dose per fraction. Early evidence from studies of ultrahypofractionated (UHF) prostate HDR brachytherapy has shown good tolerability in terms of normal tissue toxicities and clinical outcomes similar to conventional fractionation schedules. MR-guided stereotactic body radiotherapy (SBRT) with online plan adaptation and real-time tumour imaging may enable UHF doses to be delivered to the prostate safely, without the invasiveness of brachytherapy. The feasibility of UHF prostate treatment planning for the Unity MR-Linac (MRL, Elekta AB, Stockholm) was investigated for target prescriptions and planning constraints derived from the HDR brachytherapy and SBRT literature. Monaco 5.40 (Elekta) was used to generate MRL step-and-shoot IMRT plans for three dose fractionation protocols (5, 2 and 1 fractions), for ten randomly selected previously treated prostate cancer patients. Of the ten plans per UHF scheme, all clinical goals were met in all cases for 5 fractions, and in six cases for both 2 and 1 fraction schemes. PTV D95% was compromised by up to 6.4% and 3.9% of the associated target dose for 2 and 1 fraction plans respectively. There were two cases of PTV D95% compromise greater than a 5% dose decrease for the 2 fraction plans. The study suggests feasibility of the UHF treatment planning approaches if combined with real-time motion mitigation strategies.

High-dose-rate brachytherapy as monotherapy for localized prostate cancer using three different doses - 14 years of single-centre experience

Purpose

To evaluate clinical outcomes in patients with localized prostate cancer (LPC) treated with 3D conformal high-dose-rate (HDR) brachytherapy (BT) as monotherapy.

Material and methods

From March 2004 to November 2017, 277 men with LPC underwent 3D conformal HDR-BT as monotherapy, with a temporary implant. The dose prescription was: 38 Gy in 4 fractions (149 patients), 27 Gy in 2 fractions (41 patients), and 19-20 Gy in a single fraction (87 patients). Biochemical progression-free survival (bPFS), progression-free survival (PFS), and cancer-specific survival (CSS) were calculated. Acute and late genitourinary (GU) and gastrointestinal (GI) toxicity assessment were performed using Common Terminology Criteria for Adverse Events v5.0.

Results

The mean age was 67 (range, 47-81) years. Overall, 145 patients were low-risk, 116 intermediate-risk, and 16 high-risk prostate cancer. After a median follow-up of six years (range, 6-160 months), bPFS, PFS, and CSS were 81%, 96%, and 97%, respectively. Dose prescription, initial prostate specific antigen (iPSA) ≥ 9,5 ng/ml, and high-risk disease resulted in prognostic factors regarding bPFS. Only G2-G3 acute or late GI and GU toxicities were observed.

Conclusions

HDR-BT as monotherapy is a valid and safe treatment modality for localized prostate cancer. After a long follow-up, patients receiving 19-20 Gy in a single fraction had a lower biochemical control rate compared to patients receiving 38 Gy in 4 fractions or 27 Gy in 2 fractions. Randomized prospective trials with a longer follow-up are necessary to confirm our results, and define total doses and dose per fraction for HDR-BT in patients with LPC.

Ablative Radiotherapy in Prostate Cancer: Stereotactic Body Radiotherapy and High Dose Rate Brachytherapy

Simple Summary

Radiation therapy is a standard of care treatment option for men with localized prostate cancer. Over the years, various radiation delivery modalities have contributed to the increased precision of radiation, employing radiobiological insights to shorten the overall treatment time with hypofractionation, while improving oncological control without increasing toxicities. Here, we discuss and compare two ablative radiation modalities, stereotactic body radiation therapy (SBRT) and high-dose-rate brachytherapy (HDRBT), in terms of oncological control, dose/fractionation and toxicities in men with localized prostate cancer. This review will highlight the levels of evidence available to support either modality as a monotherapy, will summarize safety and efficacy, help clinicians gain a deeper understanding of the safety and efficacy profiles of these two modalities, and highlight ongoing research efforts to address many unanswered questions regarding ablative prostate radiation.

Abstract

Prostate cancer (PCa) is the most common noncutaneous solid organ malignancy among men worldwide. Radiation therapy is a standard of care treatment option that has historically been delivered in the form of small daily doses of radiation over the span of multiple weeks. PCa appears to have a unique sensitivity to higher doses of radiation per fraction, rendering it susceptible to abbreviated forms of treatment. Stereotactic body radiation therapy (SBRT) and high-dose-rate brachytherapy (HDRBT) are both modern radiation modalities that allow the precise delivery of ablative doses of radiation to the prostate while maximally sparing sensitive surrounding normal structures. In this review, we highlight the evidence regarding the radiobiology, oncological outcomes, toxicity and dose/fractionation schemes of SBRT and HDRBT monotherapy in men with low-and intermediate-risk PCa.

Computed tomography versus magnetic resonance imaging in high-dose-rate prostate brachytherapy planning: The impact on patient-reported health-related quality of life

PURPOSE

High-dose-rate (HDR) prostate brachytherapy uses volumetric imaging for treatment planning. Our institution transitioned from computed tomography (CT)-based planning to MRI-based planning with the hypothesis that improved visualization could reduce treatment-related toxicity. This study aimed to compare the patient-reported health-related quality of life (hrQOL) and physician-graded toxicity outcomes of CT-based and MRI-based HDR prostate brachytherapy.

METHODS

From 2016 to 2019, 122 patients with low- or intermediate-risk prostate cancer were treated with HDR brachytherapy as monotherapy. Patients underwent CT only or CT and MRI imaging for treatment planning and were grouped per treatment planning imaging modality. Patient-reported hrQOL in the genitourinary (GU), gastrointestinal (GI), and sexual domains was assessed using International Prostate Symptom Score and Expanded Prostate Cancer Index Composite Short Form-26 questionnaires. Baseline characteristics, changes in hrQOL scores, and physician-graded toxicities were compared between groups.

RESULTS

The median follow-up was 18 months. Patient-reported GU, GI, and sexual scores worsened after treatment but returned toward baseline over time. The CT cohort had a lower baseline mean International Prostate Symptom Score (5.8 vs. 7.8, p = 0.03). The other patient-reported GU and GI scores did not differ between groups. Overall, sexual scores were similar between the CT and MRI cohorts (p = 0.08) but favored the MRI cohort at later follow-up with a smaller decrease in Expanded Prostate Cancer Index Composite Short Form-26 sexual score from baseline at 18 months (4.9 vs. 19.8, p = 0.05). Maximum physician-graded GU, GI, and sexual toxicity rates of grade ≥2 were 68%, 3%, and 53%, respectively, with no difference between the cohorts (p = 0.31).

CONCLUSION

Our study shows that CT- and MRI-based HDR brachytherapy results in similar rates of GU and GI toxicity. MRI-based planning may result in improved erectile function recovery compared with CT-based planning.

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.

Building a High-Dose-Rate Prostate Brachytherapy Program With Real-Time Ultrasound-Based Planning: Initial Safety, Quality, and Outcome Results

Purpose

Growing evidence supports the efficacy and safety of high-dose-rate (HDR) brachytherapy as a boost or monotherapy in prostate cancer treatment. We initiated a new HDR prostate brachytherapy practice in April 2014. Here, we report the learning experiences, short-term safety, quality, and outcome.

Methods and Materials

From April 2014 to December 2017, 164 men were treated with HDR brachytherapy with curative intent. Twenty-eight men (17.1%) underwent HDR brachytherapy as monotherapy, receiving 25 to 27 Gy in 2 fractions. Men treated with HDR brachytherapy as a boost received 19 to 21 Gy in 2 fractions. Fifty-two men (31.7%) had high-risk disease. HDR procedure times, dosimetry, and response were recorded and analyzed. Genitourinary (GU) and gastrointestinal (GI) toxicities were recorded according to the toxicity criteria of the Radiation Therapy Oncology Group.

Results

Mean HDR procedure times decreased yearly from 179 minutes in 2014 to 115 minutes in 2017. Median follow-up was 18.6 months (range, 3-55 months). At last review, 79% of patients reported returning to baseline GU status, and 100% of patients noted no change in GI status from their baseline. Four patients experienced acute urinary retention. Treatment planning target volume (PTV) was defined as prostate with margins. Dosimetrically, 97.5% of all HDR implants had PTV D90 ≥100%, 81.5% had PTV V100 ≥95%, 73.6% had maximal urethral doses ≤120%, and 77.5% had rectal 1 mL dose ≤70% (all but one ≤10.8 Gy). The estimated 3-year overall survival was 98.7% (95% confidence interval, 91.4%-99.8%), and disease-free survival was 96.2% (95% confidence interval, 89.5%-98.7%).

Conclusions

The low incidence of GU and GI complications in our cohort demonstrates that a HDR brachytherapy program can be successfully developed as a treatment option for patients with localized prostate cancer.

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.

Prostate high dose-rate brachytherapy as monotherapy for low and intermediate risk prostate cancer: Efficacy results from a randomized phase II clinical trial of one fraction of 19 Gy or two fractions of 13.5 Gy

BACKGROUND AND PURPOSE

High dose-rate (HDR) brachytherapy as monotherapy is a treatment option for localized prostate cancer, but optimal dose and fractionation is unknown. We report efficacy results of a randomized phase II trial of HDR monotherapy delivered as either one or two fractions.

MATERIALS AND METHODS

Eligible patients had low or intermediate risk prostate cancer, prostate volume <60 cc, and no androgen deprivation use. 170 patients were randomized to receive HDR as either a single fraction of 19 Gy or as two fractions of 13.5 Gy one week apart. Median age was 65 years, median PSA was 6.33 ng/ml, and Grade Group 1, 2 and 3 was present in 28%, 60%, and 12%, respectively. There was no difference in baseline factors between arms and 19%, 51% and 30% had low risk, favourable intermediate and unfavourable intermediate risk disease, respectively. The Phoenix definition was used to define biochemical failure, all local failures were confirmed by biopsy and toxicity was assessed using CTCAE v.4.

RESULTS

Median follow-up was 60 months. PSA decreased more quickly in the 2-fraction arm (p = 0.009). Median PSA at 5-years was 0.65 ng/ml in the single fraction and 0.16 ng/ml in the 2-fraction arm. The 5-year biochemical disease-free survival and cumulative incidence of local failure was 73.5% and 29% in the single fraction arm and 95% (p = 0.001) and 3% (p < 0.001) in the 2-fraction arm, respectively. Recurrence was not associated with initial stage, grade group, or risk group. Grade 2 late rectal toxicity occurred in 1% while the incidence of grade 2 and 3 urinary toxicity was 45% and 1%, respectively, with no difference between arms.

CONCLUSIONS

HDR monotherapy delivered as two fraction of 13.5 Gy is well tolerated with a high cancer control rate at 5 years. Single fraction monotherapy is inferior and should not be used.

Single dose high-dose rate (HDR) brachytherapy (BT) as monotherapy for localised prostate cancer: Early results of a UK national cohort study

BACKGROUND

HDR brachytherapy alone is effective for the treatment of localised prostate cancer when given in 2-4 or more fractions. Single dose treatment has been explored in small cohort studies to date. This paper reports a large patient population with localised prostate cancer treated with single dose HDR brachytherapy delivering 19 Gy providing early outcome data from this approach.

PATIENTS AND METHODS

Seven centres across the UK collaborated in this national protocol to deliver 19 Gy to the PTV defined by the prostate capsule and a 3 mm expansion with clearly defined planning constraints for the urethra and rectum. Entry criteria allowed all risk groups provided PSA ≤40 µg/L and staging investigations were negative for metastases. The primary end point was biochemical relapse free survival (bRFS) defined using the Phoenix definition. Toxicity was measured using CTCAE v4.0.

RESULTS

A total of 441 patients were entered with median follow up 26 months (range 2-56). Median age was 73 (range 54-84) and 10% were low risk, 65% intermediate risk and 25% high risk. ADT was received by 37.6% overall and 90% of high risk patients for a median period of 6 months. Three year bRFS was overall 88%: this was 100% in low risk, 86% in intermediate risk and 75% in high risk. Only Gleason score was an independent predictor of bRFS. Relapse in 25 patients was assessed radiologically and occurred in the prostate in 15 of these, 11 of whom had localised prostate relapse only. Acute toxicity was low with no grade 3 or 4 events; there were two cases of late urinary stricture and two grade 3 late rectal events.

CONCLUSION

This is the largest cohort of single dose HDR brachytherapy patients treated with a single dose published to date. It shows that with 19 Gy there is 100% bRFS at 3 years in low risk patients but results in intermediate and high risk groups are less encouraging falling to 86% and 75% at 3 years with relapse predominantly in the prostate. Limited by the short follow up period of this study, the long-term outcomes of this single dose HDR approach remains uncertain. It is important to have close ongoing surveillance of this cohort as the data matures.

High Dose Rate Brachytherapy in High-Risk Localised Disease - Why Do Anything Else?

The management of high-risk prostate cancer is challenging, as patients have a high risk of both local and distant relapse. Although adjuvant systemic treatment remains an important component of management, for those receiving radiotherapy, optimal local treatment should include a brachytherapy boost. This may be given by low dose rate (LDR) or high dose rate (HDR) techniques, but HDR has several advantages over LDR by virtue of more consistent dose optimisation, ability to treat outside the prostate and lower toxicity. A significant body of evidence now supports the use of HDR brachytherapy in addition to supplementary pelvic external beam radiotherapy for men with high-risk disease. Consistent evidence has emerged from randomised clinical trials, meta-analyses, and from institutional and multicentre cohort studies. It has been shown to improve local disease control and possibly reduce metastases and improve cancer-specific survival compared with external beam radiotherapy alone. It should be considered as standard treatment.

A pilot study on dosimetric and radiomics analysis of urethral strictures following HDR brachytherapy as monotherapy for localized prostate cancer

OBJECTIVE

A cohort of high dose-rate (HDR) monotherapy patients was analyzed to (i) establish the frequency of non-malignant urethral stricture; (ii) explore the relation between stricture formation with the dose distribution along the length of the urethra, and MRI radiomics features of the prostate gland.

METHODS

A retrospective review of treatment records of patients who received 19 Gy single fraction of HDR brachytherapy (BT) was carried out. A matched pair analysis used one control for each stricture case matched with pre-treatment International Prostate Symptom Score (IPSS) score, number of needles used and clinical target volume volume for each stricture case identified.For all data sets, pre-treatment T₂ weighted MRI images were used to define regions of interests along the urethra and within the whole prostate gland. MRI textural radiomics features-energy, contrast and homogeneity were selected. Wilcoxon signed-rank test was performed to investigate significant differences in dosimetric parameters and MRI radiomics feature values between cases and controls.

RESULTS

From Nov 2010 to July 2017, there were 178 patients treated with HDR BT delivering 19 Gy in a single dose. With a median follow-up of 28.2 months, a total of 5/178 (3%) strictures were identified.10 patients were included in the matched pair analysis. The urethral dosimetric parameters investigated were not statistically different between cases and controls (p > 0.05). With regards to MRI radiomics feature analysis, significant differences were found in contrast and homogeneity between cases and controls (p < 0.05). However, this did not apply to the energy feature (p = 0.28).

CONCLUSION

In this matched pair analysis, no association between post-treatment stricture and urethral dosimetry was identified. Our study generated a preliminary clinical hypothesis suggesting that the MRI radiomics features of homogeneity and contrast of the prostate gland can potentially identify patients who develop strictures after HDR BT. Although the sample size is small, this warrants further validation in a larger patient cohort.

ADVANCES IN KNOWLEDGE

Urethral stricture has been reported as a specific late effect with prostate HDR brachytherapy. Our study reported a relatively low stricture rate of 3% and no association between post-treatment stricture and urethral dosimetry was identified. MRI radiomics features can potentially identify patients who are more prone to develop strictures.

Investigating the role of constrained CVT and CVT in HIPO inverse planning for HDR brachytherapy of prostate cancer

PURPOSE

The purpose of this study is to investigate the role of the centroidal Voronoi tessellation (CVT) and constrained CVT (CCVT) in inverse planning in combination with the Hybrid Inverse Planning Optimization (HIPO) algorithm in HDR brachytherapy of prostate cancer. HIPO implemented in Oncentra© Prostate treatment planning system, is used for three-dimensional (3D)-ultrasound-based intraoperative treatment planning in high dose rate brachytherapy. HIPO utilizes a hybrid iterative process to determine the most appropriate placement of a given number of catheters to fulfil predefined dose-volume constraints. The main goals of the current investigation were to identify a way of improving the performance of HIPO inverse planning; accelerating the HIPO, and to evaluate the effect of the two CVT-based initialization methods on the dose distribution in the sub-region of prostate that is not accessible by catheters, when trying to avoid perforation of urethra.

METHODS

We implemented the CVT algorithm to generate initial catheter configurations before the initialization of the HIPO algorithm. We introduced the CCVT algorithm to improve the dose distribution to the sub-volume of prostate within the bounding box of the urethra contours including its upper vertical extension (U-P). For the evaluation, we considered a total of 15 3D ultrasound-based HDRBT prostate implants. Execution time and treatment plan quality were evaluated based on the dose-volume histograms of prostate (PTV), its sub-volume U-P, and organs at risk (OARs). Furthermore, the conformity index COIN, the homogeneity index HI and the complication-free tumor control probability (P₊ ) were used for our treatment plan comparisons. Finally, the plans with the recommended HIPO execution mode were compared to the clinically used intraoperative pre-plans.

RESULTS

The plan quality achieved with CCVT-based HIPO initialization was superior to the default HIPO initialization method. Focusing on the U-P sub-region of the prostate, the CCVT method resulted in a significant improvement of all dosimetric indices compared to the default HIPO, when both were executed in the adaptive mode. For that recommended HIPO execution mode, and for U-P, CCVT demonstrated in general higher dosimetric indices than CVT. Additionally, the execution time of CCVT initialized HIPO was lower compared to both alternative initialization methods. This is also valid for the values of the aggregate objective function with the differences to the default initialization method being highly significant. Paired non-parametric statistical tests (Wilcoxon signed-rank) showed a significant improvement of dose-volume indices, COIN and P₊ for the plans generated by the CCVT-based catheter configuration initialization in HIPO compared to the default HIPO initialization process. Furthermore, in ten out of 15 cases, the CCVT-based HIPO plans fulfilled all the clinical dose-volume constraints in a single trial without any need for further catheter position adaption.

CONCLUSION

HIPO with CCVT-based initialization demonstrates better performance regarding the aggregate objective function and convergence when compared to the CVT-based and default catheter configuration initialization methods. This improved performance of HIPO inverse planning is clearly not at the cost of the dosimetric and radiobiologically evaluated plan quality. We recommend the use of the CCVT method for HIPO initialization especially in the adaptive planning mode.

Five-Year Outcomes of a Single-Institution Prospective Trial of 19-Gy Single-Fraction High-Dose-Rate Brachytherapy for Low- and Intermediate-Risk Prostate Cancer

PURPOSE

To update outcome and toxicity results of a prospective trial of 19-Gy single-fraction high-dose-rate (HDR) brachytherapy for men with low- and intermediate-risk prostate cancer.

METHODS AND MATERIALS

Patients were treated on a prospective study of single-fraction HDR brachytherapy. All patients had low- or intermediate-risk prostate cancer. Patients with prostate volumes >50 cm³, taking alpha-blockers for urinary symptoms, or with baseline American Urologic Association symptom scores >12 were ineligible. Patients underwent transrectal ultrasound-guided interstitial implant of the prostate followed by single-fraction HDR brachytherapy to a prescription dose of 19 Gy.

RESULTS

Sixty-eight patients were enrolled with a median follow-up of 3.9 years. Median age was 62 years. Median gland volume at the time of treatment was 35 cm³, 92.6% of patients had T1 disease, 63.2% had a Gleason score of 6, and median pretreatment prostate-specific antigen was 5.0 ng/mL. Chronic grade 2 genitourinary toxicity was 14.7%. No grade 3 urinary toxicity occurred. A single patient experienced grade 2+ rectal toxicity (grade 3 diarrhea) that was transient and resolved with medical management. The 5-year estimated disease-free survival was 77.2% with no significant difference between low- and intermediate-risk patients. A single patient developed distant metastases during the follow-up period. Biopsy-proven local failure at 5 years was 18.8%, occurring at a median interval of 4.0 years posttreatment. No deaths occurred during follow-up.

CONCLUSIONS

With extended follow-up, toxicity rates after single-fraction 19-Gy HDR brachytherapy remain low. Higher-than-expected rates of biochemical and local failure, however, raise concerns regarding the adequacy of this dose. Additional investigation to define the optimal single-fraction HDR brachytherapy dose is warranted, and single-fraction treatment currently should not be offered outside the context of a clinical trial.

High dose-rate brachytherapy in the treatment of prostate cancer

High dose-rate (HDR) brachytherapy involves delivery of a high dose of radiation to the cancer with great sparing of surrounding organs at risk. Prostate cancer is thought to be particularly sensitive to radiation delivered at high dose-rate or at high dose per fraction. The rapid delivery and high conformality of dose results in lower toxicity than that seen with low dose-rate (LDR) implants. HDR combined with external beam radiotherapy results in higher cancer control rate than external beam only, and should be offered to eligible high and intermediate risk patients. While a variety of dose and fractionations have been used, a single 15 Gy HDR combined with 40-50 Gy external beam radiotherapy results in a disease-free survival of over 90% for intermediate risk and 80% for high risk. HDR monotherapy in two or more fractions (e.g., 27 Gy in 2 fractions or 34.5 Gy in 3) is emerging as a viable alternative to LDR brachytherapy for low and low-intermediate risk patients, and has less toxicity. The role of single fraction monotherapy to a dose of 19-20 Gy is evolving, with some conflicting data to date. HDR should also be considered as a salvage approach for recurrent disease following previous external beam radiotherapy. A particular advantage of HDR in this setting is the ease of delivering focal treatments, which combined with modern imaging allows focal dose escalation with minimal toxicity. Trans-rectal ultrasound (TRUS) based planning is replacing CT-based planning as the technique of choice as it minimizes or eliminates the need to move the patient between insertion, planning and treatment delivery, thus ensuring high accuracy and reproducibility of treatment.