Canadian prostate brachytherapy in 2012

Risk and Quality in Brachytherapy From a Technical Perspective

AIMS

To provide an overview of the history of incidents in brachytherapy and to describe the pillars in place to ensure that medical physicists deliver high-quality brachytherapy.

MATERIALS AND METHODS

A review of the literature was carried out to identify reported incidents in brachytherapy, together with an evaluation of the structures and processes in place to ensure that medical physicists deliver high-quality brachytherapy. In particular, the role of education and training, the use of process and technical quality assurance and the role of international guidelines are discussed.

RESULTS

There are many human factors in brachytherapy procedures that introduce additional risks into the process. Most of the reported incidents in the literature are related to human factors. Brachytherapy-related education and training initiatives are in place at the societal and departmental level for medical physicists. Additionally, medical physicists have developed process and technical quality assurance procedures, together with international guidelines and protocols. Education and training initiatives, together with quality assurance procedures and international guidelines may reduce the risk of human factors in brachytherapy.

CONCLUSION

Through application of the three pillars (education and training; process control and technical quality assurance; international guidelines), medical physicists will continue to minimise risk and deliver high-quality brachytherapy treatments.

Diagnostic assessment program for prostate cancer: Lessons learned after 2 years and degree of compliance to Canadian guidelines

BACKGROUND

In 2018, our Institute launched the Diagnostic Assessment Program (DAP) for prostate cancer. It enabled quick access to a urologist for patients presented to family physician with elevated PSA and allowed fast multidisciplinary patient care. We aim to document our data over 2 years in comparison to data before implementation of DAP and its impact on the degree of adherence to Canadian guidelines.

METHODS

From April 2016 to April 2020, 880 patients who were evaluated for prostate cancer at Thunder Bay Regional Health Sciences Centre (TBRHSC) were included in this study. Patients' characteristics, clinical data, waiting times and line of treatment before and after implementation of DAP were calculated and statistically analysed.

RESULTS

The median waiting time to urology consultation was significantly reduced from 68 (IQR 27-168) days to 34 (23-44) days (p < 0.001). The time from patient's referral to prostate biopsy decreased substantially from 34 (20-66) days to 18(11- 25) days after DAP (p < 0.001). After DAP, the percentage of Gleason 6 detected prostate cancers were significantly increased (19.7% to 30%) (p = 0.02). After DAP, rate for intermediate-risk patients elected for external beam radiotherapy (from 53.5% to 57.9%, p = 0.53) and radical prostatectomy (from 34.5% to 39.4%, p = 0.47) increased. More compliance to Canadian guidelines was observed in intermediate risk patients (88% vs 97.3%, p =.008).

CONCLUSIONS

Implementation of DAP has led to a notable reduction of waiting time to urology consult and prostate biopsy. There is significant increase in Gleason 6 detected prostate cancer. Increased compliance to Canadian guidelines was detected in intermediate risk patients.

Utilization of brachytherapy in Quebec, Canada

BACKGROUND AND PURPOSE

Despite the excellent clinical outcomes from brachytherapy treatments compared with other modalities and the low associated costs, there have been reports of a decline in utilization of brachytherapy. The aim of this study was to investigate in detail the trend in utilization of brachytherapy in the province of Québec, Canada, from 2011 to 2019.

MATERIALS AND METHODS

All radiotherapy clinics in the province of Quebec, and among these the clinics that provide brachytherapy treatments, were identified. This observational retrospective cohort study involved analysis of data compiled by the Ministère de la Santé et des Services Sociaux du Québec for the period of 2011 to end of 2019 on all brachytherapy procedures performed in the province of Quebec. Time series graphs were used to describe the number of high dose rate (HDR) and low dose rate (LDR) brachytherapy treatments during the studied time period. Statistical analysis was conducted using R statistical software.

RESULTS

Between 2011 and 2019, 12 hospitals in the province of Québec provided radiotherapy treatments, and all of them offered brachytherapy services. The median annual number of brachytherapy sessions was 4413 (range 3930-4829). HDR brachytherapy represented over 90% of all brachytherapy treatments throughout the study period. Significant changes over time were observed in the number of treatments: at least 5% change was seen only for the two most common subtypes of brachytherapy, HDR interstitial and HDR intracavitary, with an increase of 9.6% and a decrease of 9.2%, respectively. The use of other subtypes of brachytherapy (HDR-plesiotherapy, LDR-interstitial, LDR-intracavitary, LDR-eye plaque) was stable between 2011 and 2019, with ≤ 2.5% variation.

CONCLUSION

This study demonstrates an overall steady use of brachytherapy between 2011 and 2019 in Quebec. Brachytherapy offers numerous advantages for the treatment of diverse cancer sites. Although more sophisticated external beam radiotherapy treatments have emerged in the last decades, the precision and cost-effectiveness of brachytherapy remain unbeaten. To ensure the continued use and availability of brachytherapy, governments must put in place policies and regulations to that effect. Training and exposure of future health care professionals to brachytherapy within Quebec and Canada is essential to provide all patients the same access to this life saving modality.

Centre-specific autonomous treatment plans for prostate brachytherapy using cGANs

PURPOSE

In low-dose-rate prostate brachytherapy (LDR-PB), treatment planning is the process of determining the arrangement of implantable radioactive sources that radiates the prostate while sparing healthy surrounding tissues. Currently, these plans are prepared manually by experts incorporating the centre's planning style and guidelines. In this article, we develop a novel framework that can learn a centre's planning strategy and automatically reproduce rapid clinically acceptable plans.

METHODS

The proposed framework is based on conditional generative adversarial networks that learn our centre's planning style using a pool of 931 historical LDR-PB planning data. Two additional losses that help constrain prohibited needle patterns and produce similar-looking plans are also proposed. Once trained, this model generates an initial distribution of needles which is passed to a planner. The planner then initializes the sources based on the predicted needles and uses a simulated annealing algorithm to optimize their locations further.

RESULTS

Quantitative analysis was carried out on 170 cases which showed the generated plans having similar dosimetry to that of the manual plans but with significantly lower planning durations. Indeed, on the test cases, the clinical target volumes achieving [Formula: see text] of the prescribed dose for the generated plans was on average [Formula: see text] ([Formula: see text] for manual plans) with an average planning time of [Formula: see text] min ([Formula: see text] min for manual plans). Further qualitative analysis was conducted by an expert planner who accepted [Formula: see text] of the plans with some changes ([Formula: see text] requiring minor changes & [Formula: see text] requiring major changes).

CONCLUSION

The proposed framework demonstrated the ability to rapidly generate quality treatment plans that not only fulfil the dosimetric requirements but also takes into account the centre's planning style. Adoption of such a framework would save significant amount of time and resources spent on every patient; boosting the overall operational efficiency of this treatment.

A surrogate urethra for real-time planning of high-dose-rate prostate brachytherapy

PURPOSE

This study characterizes prostatic urethra cross-section to develop a surrogate urethra for accurate prediction of urethral dose during real-time high-dose-rate prostate brachytherapy.

MATERIALS AND METHODS

Archived preoperative transrectal ultrasound images from 100 patients receiving low-dose-rate prostate brachytherapy were used to characterize the prostatic urethra, contoured on ultrasound using aerated gel. Consensus contours, defined using majority vote, described commonalities in cross-sectional shape across patients. Potential simplified surrogates were defined and evaluated against the true urethra. The best performing surrogate, a circle of varying size (CS) was retrospectively contoured on 85 high-dose-rate prostate brachytherapy treatment plans. Dose to this recommended surrogate was compared with urethral doses estimated by the standard 6 mm circle surrogate.

RESULTS

Clear variation in urethral cross-sectional shape was observed along its length and between patients. The standard circle surrogate had low predictive sensitivity (61.1%) compared with true urethra because of underrepresentation of the verumontanum midgland. The CS best represented the true urethra across all validation metrics (dice: 0.73, precision: 67.0%, sensitivity: 83.2%, conformity: 0.78). Retrospective evaluation of planned doses using the CS surrogate resulted in significant differences in all reported urethral dose parameters compared with the standard circle, with the exception of D_100%. The urethral dose limit (115%) was exceeded in 40% of patients for the CS surrogate.

CONCLUSIONS

The proposed CS surrogate, consisting of circles of varying diameter, is simple yet better represents the true urethra compared with the standard 6 mm circle. Higher urethral doses were predicted using CS, and the improved accuracy of CS may offer increased predictive power for urethral toxicity, a subject of future work.

A Phase 2 Randomized Pilot Study Comparing High-Dose-Rate Brachytherapy and Low-Dose-Rate Brachytherapy as Monotherapy in Localized Prostate Cancer

Purpose

To compare health-related quality of life (HRQOL) of high-dose-rate brachytherapy (HDRB) versus low dose-rate brachytherapy (LDRB) for localized prostate cancer in a multi-institutional phase 2 randomized trial.

Methods and Materials

Men with favorable-risk prostate cancer were randomized between monotherapy brachytherapy with either Iodine-125 LDRB to 144 Gy or single-fraction Iridium-192 HDRB to 19 Gy. HRQOL and urinary toxicity were recorded at baseline and at 1, 3, 6, and 12 months using the Expanded Prostate Cancer Index Composite (EPIC)-26 scoring and the International Prostate Symptom Score (IPSS). Independent samples t test and mixed effects modeling were performed for continuous variables. Time to IPSS resolution, defined as return to its baseline score ±5 points, was calculated using Kaplan-Meier estimator curves with the log-rank test. A multiple-comparison adjusted P value of ≤.05 was considered significant.

Results

LDRB and HDRB were performed in 15 and 16 patients, respectively, for a total of 31 patients. At 3 months, patients treated with LDRB had a higher IPSS score (mean, 15.5 vs 6.0, respectively; P = .003) and lower EPIC urinary irritative score (mean, 69.2 vs 85.3, respectively; P = .037) compared with those who received HDRB. On repeated measures at 1, 3, 6, and 12 months, the IPSS (P = .003) and EPIC urinary irritative scores (P = .019) were significantly better in the HDR arm, translating into a lower urinary toxicity profile. There were no significant differences in the EPIC urinary incontinence, sexual, or bowel habit scores between the 2 groups at any measured time point. Time to IPSS resolution was significantly shorter in the HDRB group (mean, 2.0 months) compared with the LDRB group (mean, 6.0 months; P = .028).

Conclusions

HDRB monotherapy is a promising modality associated with a lower urinary toxicity profile and higher HRQOL in the first 12 months compared with LDRB.

Does Seed Migration Increase the Risk of Second Malignancies in Prostate Cancer Patients Treated With Iodine-125 Loose Seeds Brachytherapy?

PURPOSE

To evaluate the risk of second malignancies after migration of seeds (MS) in prostate cancer patients treated with ¹²⁵I loose seeds brachytherapy.

METHODS AND MATERIALS

Data from 2802 prostate cancer patients treated with ¹²⁵I loose seeds brachytherapy in 3 Canadian centers were reviewed. After seeds implant, all patients underwent postimplant pelvic radiography and computed tomography scan for postimplant dosimetry. These images were used to assess whether seed migration occurred. The incidence of second malignancies was determined through the review of patient charts. The 7- and 10-year cumulative incidences of second malignancies and their 95% confidence intervals (CIs) were calculated. Fine and Gray competing risk regression analysis was used to assess the factors associated with the development of second malignancies.

RESULTS

Mean age and median follow-up were 63.5 years and 74 (range, 12-246) months, respectively. Migration of seeds occurred in 263 of 2802 patients (9.4%). Second malignancy occurred in 87 patients (3.1%) for the entire cohort and was not different between patients who experienced MS (9, 3.4%) and those who did not (78, 3.1%) (P = .755). The 7-year cumulative incidence rates of second malignancies were 2.95% (95% CI 1.20%-6.00%) (with MS) versus 2.82% (2.10%-3.70%) (without MS) (P = .756). The corresponding values at 10 years were 6.16% (2.20%-12.3%) versus 4.51% (3.20%-5.50%) (P = .570). Migration of seeds did not seem to be a significant predictive factor for second malignancies development (adjusted hazard ratio 1.27 [95% CI 0.63-2.55]; P = .510). In both models, only advanced age was significantly associated with second malignancies development.

CONCLUSIONS

These results did not show an increased risk of second malignancies associated with MS after ¹²⁵I loose seeds brachytherapy for prostate cancer patients. Longer follow-up and more events are required to better correlate MS and second malignancies.

Evaluation of a Machine-Learning Algorithm for Treatment Planning in Prostate Low-Dose-Rate Brachytherapy

PURPOSE

This work presents the application of a machine learning (ML) algorithm to automatically generate high-quality, prostate low-dose-rate (LDR) brachytherapy treatment plans. The ML algorithm can mimic characteristics of preoperative treatment plans deemed clinically acceptable by brachytherapists. The planning efficiency, dosimetry, and quality (as assessed by experts) of preoperative plans generated with an ML planning approach was retrospectively evaluated in this study.

METHODS AND MATERIALS

Preimplantation and postimplantation treatment plans were extracted from 100 high-quality LDR treatments and stored within a training database. The ML training algorithm matches similar features from a new LDR case to those within the training database to rapidly obtain an initial seed distribution; plans were then further fine-tuned using stochastic optimization. Preimplantation treatment plans generated by the ML algorithm were compared with brachytherapist (BT) treatment plans in terms of planning time (Wilcoxon rank sum, α = 0.05) and dosimetry (1-way analysis of variance, α = 0.05). Qualitative preimplantation plan quality was evaluated by expert LDR radiation oncologists using a Likert scale questionnaire.

RESULTS

The average planning time for the ML approach was 0.84 ± 0.57 minutes, compared with 17.88 ± 8.76 minutes for the expert planner (P=.020). Preimplantation plans were dosimetrically equivalent to the BT plans; the average prostate V150% was 4% lower for ML plans (P=.002), although the difference was not clinically significant. Respondents ranked the ML-generated plans as equivalent to expert BT treatment plans in terms of target coverage, normal tissue avoidance, implant confidence, and the need for plan modifications. Respondents had difficulty differentiating between plans generated by a human or those generated by the ML algorithm.

CONCLUSIONS

Prostate LDR preimplantation treatment plans that have equivalent quality to plans created by brachytherapists can be rapidly generated using ML. The adoption of ML in the brachytherapy workflow is expected to improve LDR treatment plan uniformity while reducing planning time and resources.

Diagnosis, referral, and primary treatment decisions in newly diagnosed prostate cancer patients in a multidisciplinary diagnostic assessment program

INTRODUCTION

We aimed to report on data from the multidisciplinary diagnostic assessment program (DAP) at the Gale and Graham Wright Prostate Centre (GGWPC) at North York General Hospital (NYGH). We assessed referral, diagnosis, and treatment decisions for newly diagnosed prostate cancer (PCa) patients as seen over time, risk stratification, and clinic type to establish a deeper understanding of current decision-making trends.

METHODS

From June 2007 to April 2012, 1277 patients who were diagnosed with PCa at the GGWPC were included in this study. Data was collected and reviewed retrospectively using electronic patient records.

RESULTS

1031 of 1260 patients (81.8%) were seen in a multidisciplinary clinic (MDC). Over time, a decrease in low-risk (LR) diagnoses and an increase intermediate-risk (IR) diagnoses was observed (p<0.0001). With respect to overall treatment decisions 474 (37.1%) of patients received primary radiotherapy, 340 (26.6%) received surgical therapy, and 426 (33.4%) had conservative management; 57% of patients who were candidates for active surveillance were managed this way. No significant treatment trends were observed over time (p=0.8440). Significantly, different management decisions were made in those who attended the MDC compared to those who only saw a urologist (p<0.0001).

CONCLUSIONS

In our DAP, the vast majority of patients presented with screen-detected disease, but there was a gradual shift from low- to intermediate-risk disease over time. Timely multidisciplinary consultation was achievable in over 80% of patients and was associated with different management decisions. We recommend that all patients at risk for prostate cancer be worked up in a multi-disciplinary DAP.

Development of ProCaRS Clinical Nomograms for Biochemical Failure-free Survival Following Either Low-Dose Rate Brachytherapy or Conventionally Fractionated External Beam Radiation Therapy for Localized Prostate Cancer

Purpose: Although several clinical nomograms predictive of biochemical failure-free survival (BFFS) for localized prostate cancer exist in the medical literature, making valid comparisons can be challenging due to variable definitions of biochemical failure, the disparate distribution of prognostic factors, and received treatments in patient populations. The aim of this investigation was to develop and validate clinically-based nomograms for 5-year BFFS using the ASTRO II “Phoenix” definition for two patient cohorts receiving low-dose rate (LDR) brachytherapy or conventionally fractionated external beam radiation therapy (EBRT) from a large Canadian multi-institutional database.

Methods and Materials: Patients were selected from the GUROC (Genitourinary Radiation Oncologists of Canada) Prostate Cancer Risk Stratification (ProCaRS) database if they received (1) LDR brachytherapy ≥ 144 Gy (n=4208) or (2) EBRT ≥ 70 Gy  (n=822). Multivariable Cox regression analysis for BFFS was performed separately for each cohort and used to generate clinical nomograms predictive of 5-year BFFS. Nomograms were validated using calibration plots of nomogram predicted probability versus observed probability via Kaplan-Meier estimates.

Results: Patients receiving LDR brachytherapy had a mean age of 64 ± 7 years, a mean baseline PSA of 6.3 ± 3.0 ng/mL, 75% had a Gleason 6, and 15% had a Gleason 7, whereas patients receiving EBRT had a mean age of 70 ± 6 years, a mean baseline PSA of 11.6 ± 10.7 ng/mL, 30% had a Gleason 6, 55% had a Gleason 7, and 14% had a Gleason 8-10. Nomograms for 5-year BFFS included age, use and duration of androgen deprivation therapy (ADT), baseline PSA, T stage, and Gleason score for LDR brachytherapy and an ADT (months), baseline PSA, Gleason score, and biological effective dose (Gy) for EBRT.

Conclusions: Clinical nomograms examining 5-year BFFS were developed for patients receiving either LDR brachytherapy or conventionally fractionated EBRT and may assist clinicians in predicting an outcome. Future work should be directed at examining the role of additional prognostic factors, comorbidities, and toxicity in predicting survival outcomes.

Comparing CTVs for permanent prostate brachytherapy

BACKGROUND AND PURPOSE

To delineate the clinical target volume (CTV) in low dose rate (LDR) brachytherapy for prostate cancer, American Brachytherapy Society (ABS) recommends a CTV = prostate. ESTRO advocates a CTV = prostate + 3 mm excluding rectum and many authors use and recommend other different CTVs. This study aims to: (1) evaluate the appropriateness of these recommendations and (2) test the applicability of seed distributions on the different CTVs and contrast the dosimetric differences.

MATERIALS AND METHODS

Ninety-eight patients treated with (125)I seeds (dose 145 Gy; CTV = prostate) were studied. We established for every patient: (1) risk of extraprostatic extension (EPE), (2) adequacy of original plan to an extended CTV with 3 mm-margin (3) a new planning and seed distribution for this CTV and (4) comparison of dosimetry of both plans.

RESULTS

Mean risk of EPE was 28.46 %. Original plan, when applied to the extended CTV, resulted in unsatisfactory dosimetry. A plan was generated for the 98 extended CTVs meeting all dosimetric specifications.

CONCLUSIONS

The risk of EPE is high enough to consider a 3 mm-margin around prostate necessary for all cases. A CTV = prostate + 3 mm except rectum as ESTRO recommends is feasible and would adjust planning to the most probable extension of the tumor.

Survey of high-dose-rate prostate brachytherapy practice in Australia and New Zealand, 2010-2011

INTRODUCTION

A survey was designed to establish a baseline data set for the current routine practice of high-dose-rate prostate brachytherapy (HDR-PB) in Australia and New Zealand. Existing treatment protocols and clinical implementations are not generally known.

METHODS

The survey, for the 2010 and 2011 calendar years, collected data including number of patients treated; equipment used; imaging modalities; applicator verification and correction methods; dose prescriptions and normal tissue dose constraints. The number of HDR-PB patients treated was compared with the most recently published prostate cancer incidence data in Australia and in New Zealand. Total biologically equivalent doses in 2.0 Gy fractions (EQD2) were calculated for each prescription regime reported.

RESULTS

There were reductions, of 25-60%, in patients treated with HDR-PB from 2010 to 2011 in four departments. Prostate cancer patients are two to six times more likely to be prescribed HDR-PB in Western Australia than elsewhere in the region. There were 12 different treatment prescriptions, with EQD2 doses ranging from 73.5 to 97.6 Gy, among the 18 reported by survey respondents. Normal tissue definition methodology and dose constraints varied, and 13 of 15 departments reported that no particular published external guidelines were followed in full.

CONCLUSION

The high survey response rate, 15 of 17 departments, has provided a representative baseline data set of contemporary HDR-PB practice in Australia and New Zealand that may assist government and professional bodies, such as the Australasian Brachytherapy Group, in formulating recommendations, setting standards and future planning.