High Dose Rate Prostate Research Articles

Development of an HDR Prostate Nomogram as a Secondary Physics Pre-treatment Check With Updated Patient Data

Nomograms are well established in Low Dose Rate (LDR) Brachytherapy to estimate the number of seeds for a prostate volume. This concept can be applied to High Dose Rate (HDR) Brachytherapy to provide a second check of the dose calculation and assess plan and implant quality. In 2011, Pujades et al. published findings on the use of a nomogram in LDR and HDR prostate brachytherapy at 2 separate institutions in Valencia, Spain. This work seeks to validate the use of nomograms in HDR brachytherapy and provide a linear fit correlation from the perspective of another institution.

Can Intermediate Energy Sources Result in Increased Bone Doses for Pelvic and Head-and-Neck Brachytherapy?

Several gamma emitting radionuclides with high (60Co, 75Se) and intermediate (169Yb, 153Gd) energies have been investigated as alternatives to 192Ir for high dose rate (HDR) brachytherapy. The purpose of this study was to evaluate the effect of tissue heterogeneities for 60Co, 192Ir, 75Se, 169Yb and 153Gd for prostate and oral tongue HDR brachytherapy.

Use of Blood Patch as a Spacer in High-Dose Rate Prostate Brachytherapy with Either Co60 or Ir 192, Another Cost-Effective Way to Improve Outcomes

To describe a useful technique to decrease rectal dose during HDR prostate brachytherapy given as boost to EBRT or as monotherapy. Prostate brachytherapy has evolved in recent years together with the technological and computer development. It has become popular to use high dose rate (HDR) and 3D volumetric planning, using computed tomography (CT) and/or magnetic resonance imaging (MRI), which has help improving accuracy and conformation of treatment and also the capabilities to dose scaling, due to the real visualization of the target and organs at risk (OARS), the use of tomographic images allows to take actions and optimize the therapeutic index, escalate dose into the tumor, and protect at the same time OARs. The dosimetric analysis of a multicentric initial Latin American experience from Chile, Peru and Colombia with patients with prostate cancer diagnosis treated with this premise, using blood as OAR spacer, presented as an alternative to this procedure in developing countries with limited resources.

MRI-Based Treatment Planning for Prostate High Dose Rate Brachytherapy Leads to Decreased Target Size and Rectal Dose

MRI-Based Treatment Planning for Prostate High Dose Rate Brachytherapy Leads to Decreased Target Size and Rectal Dose

HDR brachytherapy invivo source position verification using a 2D diode array: A Monte Carlo study.

PurposeThis study aims to assess the accuracy of source position verification during high‐dose rate (HDR) prostate brachytherapy using a novel, in‐house developed two‐dimensional (2D) diode array (the Magic Plate), embedded exactly below the patient within a carbon fiber couch. The effect of tissue inhomogeneities on source localization accuracy is examined.MethodMonte Carlo (MC) simulations of 12 source positions from a HDR prostate brachytherapy treatment were performed using the Geant4 toolkit. An Ir‐192 Flexisource (Isodose Control, Veenendaal, the Netherlands) was simulated inside a voxelized patient geometry, and the dose deposited in each detector of the Magic Plate evaluated. The dose deposited in each detector was then used to localize the source position using a proprietary reconstruction algorithm.ResultsThe accuracy of source position verification using the Magic Plate embedded in the patient couch was found to be affected by the tissue inhomogeneities within the patient, with an average difference of 2.1 ± 0.8 mm (k = 1) between the Magic Plate predicted and known source positions. Recalculation of the simulations with all voxels assigned a density of water improved this verification accuracy to within 1 mm.ConclusionSource position verification using the Magic Plate during a HDR prostate brachytherapy treatment was examined using MC simulations. In a homogenous geometry (water), the Magic Plate was able to localize the source to within 1 mm, however, the verification accuracy was negatively affected by inhomogeneities; this can be corrected for by using density information obtained from CT, making the proposed tool attractive for use as a real‐time in vivo quality assurance (QA) device in HDR brachytherapy for prostate cancer.

Changing trends in prostate brachytherapy practice for clinically localized prostate cancer: Results of a survey in UK and Ireland.

16 Background: High Dose Rate (HDR) and Low Dose Rate ( LDR) prostate brachytherapy (PBT) with or without external beam radiotherapy provide excellent biochemical outcomes with practice adapting to ongoing research and technological advances. We wished to document current PBT practice in the UK and Ireland (UK & I) and compare with previous published audit results. Methods: A link to an online survey was communicated to centres attending the UK & I PBT conference in 2017 (n = 25). Sixty-three questions were grouped into six themed sections which included current experience, staffing, implant numbers (last 3 years), LDR pre / post implant dosimetry and HDR technique. Descriptive analysis was performed. Results: 18 of 25 centres responded (11 LDR only, 6 HDR & LDR, 1 HDR only) with 13 and 3 centres having > 10yrs experience with LDR and HDR respectively. 13 centres have two or more oncologists and 15 centres have two or more medical physics experts (MPE). 61% of lead clinicians performed > 25 implants with 22% performing > 50 in the year 2016. In the preceding 3 years, 44% of centres reported the number of LDR monotherapy cases as stable while 44% noted a reduction in numbers. Similarly 40% of centres reported LDR boost cases as stable, 40% as reduced and 20% with increased cases. The number of centres using HDR treatment as boost, monotherapy and salvage therapy has increased, with increased cases in the year 2016 as compared to 2014. Comparison with the UK 2012 audit showed that post implant LDR dosimetry is more consistently performed and the majority of cases were achieving the 3 defined quality standards of D90, V100 and CT:USS volume ratio. Average post implant D90 was > 145Gy in 63% of centres in 2014 and 2015 compared to 70% in 2016. 50% of centres reported average D90’s of > 155Gy in all three years surveyed. Conclusions: This survey offers a review of PBT practice across UK and I with an apparent fall in LDR monotherapy and boost cases but increase in HDR numbers noted. Surveyed centres report dosimetrically good quality implants. Current research supports PBT as a definitive primary treatment which should be discussed with eligible men at diagnosis.

Process Mapping and Time Study to Improve Efficiency of New Procedure Implementation for High-Dose Rate Prostate Brachytherapy.

New technologies and procedures have the potential to improve outcomes; however, initial implementation is often associated with a steep learning curve, decreased efficiency, and patient safety implications. Implementation of a real-time, ultrasound-based prostate high-dose rate brachytherapy procedure involved a multidisciplinary team composed of approximately 6-8 team members and numerous complex tasks. To characterize time spent on various aspects of the procedure and improve efficiency, the team developed a detailed process map, time study, and team debriefings. A benchmark was created based on an experienced institution which has performed >100 procedures annually. The process map was analyzed based on clinical tasks and treatment planning tasks. Over the course of 17 cases at a single institution, total procedure time ranged from 222 to 107 minutes. Implementation of the process map resulted in a reduction of total time by 52%. The implementation of a new procedure benefits from the integration and utilization of a process map. We were able to reduce procedure time significantly, which resulted in decreased time under general anesthesia, reduced risk of deep vein thrombosis, improved overall patient safety, patient throughput, and decreases in staffing demands.

Pre-implant magnetic resonance and transrectal ultrasound imaging in high-dose-rate prostate brachytherapy: comparison of prostate volumes, craniocaudal extents, and contours.

PurposeThe purpose of this study was to compare the prostate contours drawn by two radiation oncologists and one radiologist on magnetic resonance (MR) and transrectal ultrasound (TRUS) images. TRUS intra- and inter-fraction variability as well as TRUS vs. MR inter-modality and inter-operator variability were studied.Material and methodsThirty patients affected by localized prostate cancer and treated with interstitial high-dose-rate (HDR) prostate brachytherapy at the National Cancer Institute in Milan were included in this study. Twenty-five patients received an exclusive two-fraction (14 Gy/fraction) treatment, while the other 5 received a single 14 Gy fraction as a boost after external beam radiotherapy. The prostate was contoured on TRUS images acquired before (virtual US) and after (real US) needle implant by two radiation oncologists, whereas on MR prostate was independently contoured by the same radiation oncologists (MR1, MR2) and by a dedicated radiologist (MR3). Absolute differences of prostate volumes (│ΔV│) and craniocaudal extents (│Δdz│) were evaluated. The Dice’s coefficient (DC) was calculated to quantify spatial overlap between MR contours.ResultsSignificant difference was found between Vvirtual and Vlive (p < 0.001) for the first treatment fractions and between VMR1 and VMR2 (p = 0.043). Significant difference between cranio-caudal extents was found between dzvirtual and dzlive (p < 0.033) for the first treatment fractions, between dzvirtual of the first treatment fractions and dzMR1 (p < 0.001) and between dzMR1 and dzMR3 (p < 0.01). Oedema might be responsible for some of the changes in US volumes. Average DC values resulting from the comparison MR1 vs. MR2, MR1 vs. MR3 and MR2 vs. MR3 were 0.95 ± 0.04 (range, 0.82-0.99), 0.87 ± 0.04 (range, 0.73-0.91) and 0.87 ± 0.04 (range, 0.72-0.91), respectively.ConclusionsOur results demonstrate the importance of a multiprofessional approach to TRUS-guided HDR prostate brachytherapy. Specific training in MR and US prostate imaging is recommended for centers that are unfamiliar with HDR prostate brachytherapy.

Dosimetric impact of inter-observer catheter reconstruction variability in ultrasound-based high-dose-rate prostate brachytherapy

PurposeTo investigate the dosimetric impact of interobserver catheter reconstruction variability in transrectal ultrasound–guided prostate high-dose-rate (HDR) brachytherapy. Methods and MaterialsTwenty consecutive patients with intermediate- or high-risk prostate cancer were treated with a single, 15-Gy HDR brachytherapy boost as part of this study. The treated plan was used as the study reference plan (PR). Three expert treatment planners (observers) manually reconstructed the catheter paths on the static three-dimensional transrectal ultrasound images, and new plans were generated from the updated positions (POBS); subsequently, the dwell time and positions from the POBS plans were superimposed on the PR catheter paths to evaluate the dosimetric effect of the interobserver variations (PEVAL). Plans from each group were stratified by observer and by number of catheters (12 or 16) and then compared using a one-way Kruskal–Wallis H test with post hoc Mann–Whitney U tests reserved for significant variations (α = 0.05). ResultsGreater than 98.9% of catheter reconstruction variations were <3 mm. When stratified by observer, there was a significant decrease (p << 0.05) in planning target volume (PTV) V100% and increases in the urethral Dmax between the POBS plans propagated to the PR catheter paths and dosimetry evaluated and PR plans only. Stratification of plans by catheter number showed nonclinically significant decreases in PTV V100%, and D90% and increases in urethral Dmax for the 12-catheter plans. ConclusionsLimiting interobserver variability, and its effects on prostate HDR brachytherapy plan quality, is critical to achieving good dosimetric outcomes; small variations in catheter reconstruction may translate to inadequate PTV coverage, excessive urethral dose, or both.

Updated Retrospective Dose Volume Histogram Analysis of High Dose Rate Prostate Brachytherapy Patients With Hydrogel Spacer Implantation

A commercially available bioabsorbable hydrogel system—a mixture of a precursor (trilysine buffer solution and polyethylene glycol powder) and accelerator (salt buffer)—is implanted between the prostate and rectum of men undergoing radiation therapy for prostate cancer. Use of this device provides additional separation between the prostate and rectum, ostensibly reducing rectal injury due to proximity of the high dose target. This study investigates rectal sparing achieved in high dose rate (HDR) prostate brachytherapy patients with hydrogel spacer implantation. One hundred and fifty two monotherapy HDR prostate brachytherapy cases were selected from the patient population treated from July 2015 to February 13, 2017. Patients were selected based on a treatment regimen of 13.5 Gy per fraction. Of these cases, 120 fractions were delivered to patients with implanted hydrogel rectal spacers while 32 fractions were treated without the use of this or any other rectal sparing device. For this patient cohort, the dose volume histogram (DVH) from the previously calculated plan was used to obtain D1cc, D2cc, and maximum rectal dose statistics based on rectum contours drawn on the planning CT dataset by the dosimetrist at the time of treatment planning. To compare to conventionally fractionated external beam radiation therapy (EBRT), the equivalent dose in 2 Gy fractions (EQD2) was calculated for each rectal dose statistic. Statistical analysis software was employed for data analysis. The D1cc, D2cc, and maximum dose to the rectum for cases in which the hydrogel spacer was implanted prior to treatment were compared to cases treated without rectal sparing devices. Results with and without hydrogel spacer implantation were as follows: D1cc was 7.9±0.2 Gy and 8.4±0.4 Gy, respectively; D2cc was 7.1±0.2 Gy and 7.5±0.4 Gy, respectively; and the maximum dose to the rectum as 10.7±0.3 Gy and 11.9±0.6 Gy, respectively. Reduction in maximum (p < 0.001) and small volumetric doses (p = 0.027 and 0.113 for D1cc and D2cc) to the rectum is observed in cases implementing the hydrogel rectal spacer. Considering a typical HDR prostate brachytherapy dose prescription of 27.0 Gy (two 13.5 Gy fractions) and an α/β = 3.0 for rectum, the average maximum EQD2 point dose for patients receiving hydrogel implants was 59.9±3.1 Gy compared to 71.9±2.8 Gy (p < 0.001) for those treated without the device. DVH analysis for the patient sampling with hydrogel implantation demonstrated statistically significant reduction in Dmax and D1cc metrics. When compared to plans without hydrogel implants, the average EQD2 of the max point dose to rectum for patients receiving hydrogel implants was lower and fell within the TD5/5 of 60 Gy, as recommended by Emami et al. Future clinical evaluation of these patients may allow for a statistical relationship between the observed dose reduction and clinical toxicity.

Comparing Acute Toxicity Profiles for High Dose Rate Prostate Brachytherapy Patients Receiving Two Implants Separated by a One-Week Versus Two-Week Interval

Multiple dose/fractionations and implant intervals have been used for patients undergoing definitive prostate high dose rate (HDR) brachytherapy (BT) as monotherapy, but limited data exist identifying the impact of interval duration on acute toxicity. We use 13.5 Gy x 2, given as one fraction per implant performed 1-2 weeks apart based on patient and OR availability at our institution. Our objective was to compare the acute toxicity profiles between patients receiving implants at a one-week or two-week interval. All patients were treated on a prospective institutional IRB-approved protocol by the same 2 brachytherapists. Patients completed IPSS and EPIC-26 questionnaires at their pre-treatment visit and at 1 and 3 months after BT. Physician-reported genitourinary (GU) and gastrointestinal (GI) CTCAE v4.03 toxicity grades at these same time points were recorded. IPSS and EPIC-26 values and physician-reported toxicity grades were compared for patients stratified into two interval duration groups, ≤10 days vs. >10 days between implants. Linear mixed effects models were used to estimate patients’ mean IPSS and EPIC-26 values over time based on their implant interval duration. Similarly, generalized linear mixed effects models were used to estimate the odds of higher physician-reported GU or GI toxicity grades over the same period for both groups. Median follow-up was 5 months (interquartile range [IQR]: 3 – 8 months). A total of 39 patients were analyzed, in which 21 had ≤10 days between implants and 18 had >10 days between implants with a median implant interval time of 7 (IQR: 7-7) and 14 (IQR: 12-14) days, respectively. There was no difference in IPSS and EPIC-26 values between the groups at pre-treatment, 1 month, and 3 months (Table). Similarly, when comparing the two interval duration groups, the physician-reported GI toxicity grades (p=.86) and GU toxicity grades (p=.30) were not meaningfully different at any time point. For patients with ≤10 days and >10 days between implants, 43% and 58% had grade ≥2 GU toxicity, respectively, and no patients had grade ≥2 GI toxicity. The interval duration between implants for patients undergoing HDR BT as monotherapy using a two implant regimen does not appear to be associated with patient-reported or physician-graded acute toxicity. Longer term follow-up is needed to assess for late toxicity and disease-control outcomes.Abstract 2595Mean IPSS (Standard Error [SE])p-valueMean EPIC GU (SE)p-valueMean EPIC GI (SE)p-value≤10 days>10 days≤10 days>10 days≤10 days>10 daysPre-treatment3.92 (1.29)5.79 (1.34).237.08 (1.10)7.11 (1.58).9916.67 (1.27)22.25 (2.10).481 Month13.15 (1.38)13.86 (1.52).699.06 (1.02)9.75 (1.49).7119.83 (1.18)18.96 (1.74).793 Months6.37 (1.48)8.70 (1.64).247.69 (1.09)7.09 (1.31).7317.81 (1.26)17.21 (1.52).77 Open table in a new tab

Starting a Prostate HDR Program in a Young Cancer Center - 1st Year Experience

The radiation oncology department at CISSS Laval (Laval, Canada) was inaugurated in February 2012. Our prostate High Dose Rate (PHDR) brachytherapy program began in September 2015 with the commissioning of Oncentra Prostate. The first PHDR patient was treated on January 12 2016 with success.

Reducing Prostate High Dose Rate Brachytherapy Treatment Planning Duration Through Targeted Interventions

Reducing Prostate High Dose Rate Brachytherapy Treatment Planning Duration Through Targeted Interventions

An Evaluation of Needle Translations and Their Dosimetric Impact in CT Based Prostate High Dose Rate Brachytherapy Treatments

An Evaluation of Needle Translations and Their Dosimetric Impact in CT Based Prostate High Dose Rate Brachytherapy Treatments

A novel adaptive needle insertion sequencing for robotic, single needle MR-guided high-dose-rate prostate brachytherapy

MR-guided high-dose-rate (HDR) brachytherapy has gained increasing interest as a treatment for patients with localized prostate cancer because of the superior value of MRI for tumor and surrounding tissues localization. To enable needle insertion into the prostate with the patient in the MR bore, a single needle MR-compatible robotic system involving needle-by-needle dose delivery has been developed at our institution. Throughout the intervention, dose delivery may be impaired by: (1) sub-optimal needle positioning caused by e.g. needle bending, (2) intra-operative internal organ motion such as prostate rotations or swelling, or intra-procedural rectum or bladder filling. This may result in failure to reach clinical constraints. To assess the first aforementioned challenge, a recent study from our research group demonstrated that the deposited dose may be greatly improved by real-time adaptive planning with feedback on the actual needle positioning. However, the needle insertion sequence is left to the doctor and therefore, this may result in sub-optimal dose delivery. In this manuscript, a new method is proposed to determine and update automatically the needle insertion sequence. This strategy is based on the determination of the most sensitive needle track. The sensitivity of a needle track is defined as its impact on the dose distribution in case of sub-optimal positioning. A stochastic criterion is thus presented to determine each needle track sensitivity based on needle insertion simulations. To assess the proposed sequencing strategy, HDR prostate brachytherapy was simulated on 11 patients with varying number of needle insertions. Sub-optimal needle positioning was simulated at each insertion (modeled by typical random angulation errors). In 91% of the scenarios, the dose distribution improved when the needle was inserted into the most compared to the least sensitive needle track. The computation time for sequencing was less than 6 s per needle track. The proposed needle insertion sequencing can therefore assist in delivering an optimal dose in HDR prostate brachytherapy.

Long-term outcomes of high-dose-rate brachytherapy for intermediate- and high-risk prostate cancer with a median follow-up of 10 years.

To evaluate the long-term outcomes of high-dose-rate (HDR) brachytherapy for patients with intermediate- and high-risk prostate cancer. We retrospectively analysed a prospective longitudinal cohort database including a single-surgeon series of 507 consecutive men treated with external beam radiotherapy and an HDR prostate brachytherapy boost between August 2000 and December 2009. The risk factors used were based on the D'Amico classification. We measured the incidence of no biochemical evidence of disease (bNED) based on the Phoenix definition of failure (nadir PSA + 2 ng/mL). We also reviewed the incidence of urethral stricture in this cohort. With minimum and median follow-ups of 6 and 10.3 years, respectively, the bNED rates for men with intermediate- and high risk disease were 93.3% and 74.2%, respectively, at 5 years and 86.9% and 56.1%, respectively, at 10 years. The 10-year bNED rate for men with only one intermediate-risk factor was 94%, whereas for patients with all three high-risk factors it was 39.5%. The overall urethral stricture rate was 13.6%. Before 2005, the urethral stricture rate was 28.9% and after January 2005 it was 4.2%. For the 271 men with a minimum follow-up of 10 years the actuarial 10-year prostate cancer-specific survival rate was 90.8% and the actuarial overall survival rate was 86.7%. For men with intermediate- or high-risk prostate cancer features, who are considered not suitable for, or wish to avoid a radical prostatectomy, HDR prostate brachytherapy remains an appropriate treatment option. From December 2004, prevention strategies decreased the risk of post-brachytherapy urethral strictures.

Monte Carlo study of the impact of a magnetic field on the dose distribution in MRI-guided HDR brachytherapy using Ir-192

In the process of developing a robotic MRI-guided high-dose-rate (HDR) prostate brachytherapy treatment, the influence of the MRI scanner’s magnetic field on the dose distribution needs to be investigated. A magnetic field causes a deflection of electrons in the plane perpendicular to the magnetic field, and it leads to less lateral scattering along the direction parallel with the magnetic field. Monte Carlo simulations were carried out to determine the influence of the magnetic field on the electron behavior and on the total dose distribution around an Ir-192 source. Furthermore, the influence of air pockets being present near the source was studied. The Monte Carlo package Geant4 was utilized for the simulations. The simulated geometries consisted of a simplified point source inside a water phantom. Magnetic field strengths of 0 T, 1.5 T, 3 T, and 7 T were considered. The simulation results demonstrated that the dose distribution was nearly unaffected by the magnetic field for all investigated magnetic field strengths. Evidence was found that, from a dose perspective, the HDR prostate brachytherapy treatment using Ir-192 can be performed safely inside the MRI scanner. No need was found to account for the magnetic field during treatment planning. Nevertheless, the presence of air pockets in close vicinity to the source, particularly along the direction parallel with the magnetic field, appeared to be an important point for consideration.

Clinical application of MOSkin dosimeters to rectal wall in vivo doismetry in gynecological and prostate HDR brachytherapy

Introduction MOSkins are MOSFET dosimeters designed and developed at the Centre for Medical Radiation Physics (University of Wollongong, Australia), optimized to measure the dose in steep dose gradients. In this work, their clinical application to rectal wall in vivo dosimetry (IVD) during gynecological and prostate high dose rate brachytherapy (HDR-BT) was studied. Purpose To evaluate the discrepancies between planned and measured doses to the rectal wall and to investigate the impact of the duration of the treatment planning procedure on these discrepancies. Materials and methods In gynecological HDR-BT, three MOSkins were assembled over a semi-flexible rectal probe and 51 IVD measurements were performed. In prostate HDR-BT, two MOSkins were assembled on the trans-rectal ultrasound probe and 36 IVD measurements were performed. The absolute differences ΔD between measured and calculated doses in the estimated dosimeters positions were quantified and a possible correlation with the treatment planning time was investigated. Results Grouping ΔD according to the time elapsed between imaging and treatment (i.e., group 1: ⩽90 min; group 2: >90 min), average ΔD for groups 1 and 2 were 5.1 ± 3.0% and 8.3 ± 6.2% for prostate and 3.8 ± 3.5% and 6.5 ± 4.3% for gynecology HDR-BT, respectively. Average ΔD were in both cases lower for group 1, demonstrating higher uncertainties of the calculated dose with higher treatment planning times (i.e., probability of morphological changes increases with time). Conclusion MOSkin dosimeters coupled to rectal probes may be used for rectal IVD during gynecological/prostate HDR-BT. Planning time should be kept as low as possible to reduce uncertainties in calculated doses. Disclosure none

Modelling second malignancy risks from low dose rate and high dose rate brachytherapy as monotherapy for localised prostate cancer

Background and purposeTo estimate the risks of radiation-induced rectal and bladder cancers following low dose rate (LDR) and high dose rate (HDR) brachytherapy as monotherapy for localised prostate cancer and compare to external beam radiotherapy techniques. Materials and methodsLDR and HDR brachytherapy monotherapy plans were generated for three prostate CT datasets. Second cancer risks were assessed using Schneider’s concept of organ equivalent dose. LDR risks were assessed according to a mechanistic model and a bell-shaped model. HDR risks were assessed according to a bell-shaped model. Relative risks and excess absolute risks were estimated and compared to external beam techniques. ResultsExcess absolute risks of second rectal or bladder cancer were low for both LDR (irrespective of the model used for calculation) and HDR techniques. Average excess absolute risks of rectal cancer for LDR brachytherapy according to the mechanistic model were 0.71 per 10,000 person-years (PY) and 0.84 per 10,000 PY respectively, and according to the bell-shaped model, were 0.47 and 0.78 per 10,000 PY respectively. For HDR, the average excess absolute risks for second rectal and bladder cancers were 0.74 and 1.62 per 10,000 PY respectively. The absolute differences between techniques were very low and clinically irrelevant. Compared to external beam prostate radiotherapy techniques, LDR and HDR brachytherapy resulted in the lowest risks of second rectal and bladder cancer. ConclusionsThis study shows both LDR and HDR brachytherapy monotherapy result in low estimated risks of radiation-induced rectal and bladder cancer. LDR resulted in lower bladder cancer risks than HDR, and lower or similar risks of rectal cancer. In absolute terms these differences between techniques were very small. Compared to external beam techniques, second rectal and bladder cancer risks were lowest for brachytherapy.

MO‐B‐BRC‐04: MRI‐Based Prostate HDR

Brachytherapy has proven to be an effective treatment option for prostate cancer. Initially, prostate brachytherapy was delivered through permanently implanted low dose rate (LDR) radioactive sources; however, high dose rate (HDR) temporary brachytherapy for prostate cancer is gaining popularity. Needle insertion during prostate brachytherapy is most commonly performed under ultrasound (U/S) guidance; however, treatment planning may be performed utilizing several imaging modalities either in an intra‐ or post‐operative setting. During intra‐operative prostate HDR, the needles are imaged during implantation, and planning may be performed in real time. At present, the most common imaging modality utilized for intra‐operative prostate HDR is U/S. Alternatively, in the post‐operative setting, following needle implantation, patients may be simulated with computed tomography (CT) or magnetic resonance imaging (MRI). Each imaging modality and workflow provides its share of benefits and limitations.Prostate HDR has been adopted in a number of cancer centers across the nation. In this educational session, we will explore the role of U/S, CT, and MRI in HDR prostate brachytherapy. Example workflows and operational details will be shared, and we will discuss how to establish a prostate HDR program in a clinical setting. Learning Objectives: Review prostate HDR techniques based on the imaging modality Discuss the challenges and pitfalls introduced by the three imagebased options for prostate HDR brachytherapy Review the QA process and learn about the development of clinical workflows for these imaging options at different institutions