I-125 Prostate Research Articles

Dual-energy metal artefact reduction for iodine-125 seed identification in postimplant CT after prostate brachytherapy.

To assess the metal artefact reductions of dual-energy CT high-energy virtual monochromatic images (VMI) combined with the Single-Energy Metal Artifact Reduction (SEMAR) (CANON MEDICAL SYSTEMS, Otawara, Japan) processing techniques for iodine (I)-125 seed identification in postimplant CT after prostate brachytherapy. Dual-energy acquisition with fast tube voltage switching was performed on a prostate phantom with simulated seeds and six clinical cases treated with I-125 prostate brachytherapy. The images were retrospectively reconstructed at VMI energy levels of 65-200 keV and with and without SEMAR (SEMAR and non-SEMAR images). To estimate seed swelling, the calibre of iodine-125 seed was calculated as the full width at half maximum. The metal artefacts were evaluated using the artefact index (AI). The dose distributions were calculated and were compared among the high-energy VMI (SEMAR and non-SEMAR images) and low-energy VMI (SEMAR images). The blooming artefacts decreased at higher energy levels. In addition, the SEMAR process markedly reduced AI, which helped reduce overestimation of high dose ranges in the treatment planning dose map. The locations and number of iodine-125 seed were clearly identified in the dose distribution map of the treatment planning using 200 keV VMI with SEMAR. The high-energy VMI of the dual-energy CT in combination with SEMAR is appropriate for the postimplant planning process of I-125 prostate brachytherapy.

A precise and simple isodose-volume-based verification method for HDR and LDR brachytherapy plans

The American Association of Physicists in Medicine (AAPM) code of practice for brachytherapy physics recommends performing an independent treatment time calculation. For this we implemented an easy to use isodose-based verification method for HDR (high-dose-rate) and LDR (low-dose-rate) brachytherapy plans. Dose-volume-based methods have been developed for Ir-192-based high-dose-rate (HDR) and I-125 prostate low-dose-rate (LDR) brachytherapy. They allow checking the integral dwell time or activity when the volume of a suitable isodose is known. The verification method was validated for 55 clinical HDR and 243 clinical LDR plans. For HDR brachytherapy, the mean absolute difference between the estimated and calculated integral dwell time was 0.8% ± 1.0% (n = 30) with a single-source path and 2.7% ± 1.1% (n = 25) for multiple source paths. The corresponding value for LDR brachytherapy was 1.8% ± 2.0% (n = 243). In HDR brachytherapy, the verification method depends slightly on the plan class when considering one or more than one source paths. Good agreement between the estimated and calculated integral dwell times was obtained based on the 2Gy isodose. Unlike HDR brachytherapy, the parameters used in the verification method for LDR brachytherapy plan verification strongly depend on the type of seed distribution. So, we recommend using an isodose at the prescribed dose for prostate HDR therapy. Isodose-based verification methods are precise, do not presuppose dedicated tools, and are simple to implement in clinical practice.

Radiation dose rate variations in different measurement scenarios after prostate 125I brachytherapy

This study aimed to directly compare different measurement scenarios using a supplemental radiation exposure measurement data set. Two sets of measurement scenarios comparing different body postures, such as standing and chair sitting positions, and different measurement directions, such as anterior and posterior directions, were assessed for radiation dose rate variations in this study at the Tokyo Medical Center, Japan. The estimated precaution time for holding children in the spoon position while sitting was also calculated. Different radiation dose rate measurement scenarios showed different variation tendencies. Radiation dose rate measurement showed higher mean values of measured radiation dose tendency in the standing position than in the sitting positions. The measurement from the anterior direction showed a slightly lower tendency than that from the posterior direction. Assuming a dose limit of 1 mSv, the precaution time calculated for children being held in the spoon position for a certain duration every day was 51.5 (range, 12.5-152.2) minutes. Our study presented a supplemental radiation exposure measurement data set and directly compared different measurement scenarios. Several trends in radiation exposure variations were found in the measurement scenarios at different body postures and different measurement directions. Our study data set could be a useful source of concrete information regarding radiation safety and contribute to the review and revision of public guidance in the future.

Intraprostatic calcification and biochemical recurrence in men treated with Cs-131 prostate brachytherapy.

237 Background: Vigneault et al. reported that baseline intraprostatic calcification (IC) was associated with a higher risk of biochemical recurrence (BCR) in men treated with I-125 prostate brachytherapy (PB). Cs-131 has different physical properties than I-125. We assessed whether baseline IC was associated with BCR in men treated with Cs-131 PB. Methods: We retrospectively reviewed the records of all low-risk (LR), favorable intermediate-risk (FIR), and unfavorable IR (UIR) prostate cancer patients treated with Cs-131 PB +/- external beam radiotherapy (EBRT) from 2/2011 to 7/2018 at our institution. Patients who received hormone therapy or those with < 24 months follow-up were excluded. Baseline IC status (defined as 1 or more ICs ≥ 5 mm) and characteristics were determined on post-PB CT scans. Baseline patient characteristics were compared via χ2, Mann–Whitney U, or Student’s t-test. Predictors of BCR (Phoenix definition) were analyzed via Cox proportional hazards model and Kaplan–Meier survival curves were generated. Results: Two hundred and sixteen LR, FIR, and UIR prostate cancer patients treated with Cs-131 PB +/- EBRT were included. Median follow up was 56.9 months (range 24.1–111.4 months). 76 patients (35.2%) had baseline IC and 140 patients (64.8%) did not. Baseline disease characteristics did not differ significantly between patients with vs. without ICs. In patients with baseline IC, the median number of ICs was 1 (range 1–3), median length of largest IC was 9.1 mm (range 5.0–33.1), and median peak density of largest IC was 884 Hounsfield units (range 283–1744). ICs were most commonly present in the midgland (88.2%) and central (97.4%) regions. On univariate Cox analysis of all baseline disease, treatment, and IC characteristics, only initial PSA (p = 0.016) and NCCN risk group (p = 0.047) were significant predictors of BCR, whereas baseline IC was not (p = 0.11). The 5-year BCR-free survival in patients with vs. without baseline IC was 97.7% vs. 93.8% (p = 0.40), respectively. Conclusions: In a cohort of LR and IR prostate cancer patients treated with Cs-131 PB, the rate of BCR in men with baseline IC was low and baseline IC was not associated with a higher risk of BCR.

OC-1027: Comparing GU toxicity of LDR I-125 prostate brachytherapy by robotic and manual loading techniques

OC-1027: Comparing GU toxicity of LDR I-125 prostate brachytherapy by robotic and manual loading techniques

Outcomes of combined radiotherapy in high-risk prostate cancer

Radiotherapy is one of the radical treatment options used in patients with prostate cancer (PC). Many studies of combined radiotherapy (CRT) for PC have demonstrated good results in respect of response to treatment; however, the sequence of CRT steps and optimal interval between them have not been determined so far. Few randomized studies have been conducted in order to confirm the advantages of brachytherapy at the first or second step or determine the most effective interval between the contact and external beam RT. Therefore, it appears reasonable to evaluate different CRT techniques.Purpose. The goal of the study was to evaluate the outcomes of PC treatment depending on the sequence of CRT steps and the interval between them.Materials and methods. 53 patients with PC received 125I radiation therapy in combination with long-term hormone therapy (HT). Median follow-up was 38 months. Patients’ age varied from 54 to 81 years. All patients were in a high-risk group according to the D’Amico Risk Classification System. The patients were allocated to two groups: in Group 1, brachytherapy was used as the first step (n=31); in Group 2, it was applied after external beam therapy (EBT). The interval between the CRT steps could be less than 4 weeks (n=6), 4 – 7 weeks (n=17) and more than 8 weeks (n=30). Standard fractionation EBT with a total dose of 46 Gy using the VMAT technique was conducted. 125I prostate implants were inserted to reach a total dose of 110 Gy. Neoadjuvant (2 – 4 months) and adjuvant (not less than 24 months) regimens of HT were applied.Results. Five (9.4 %) patients had disease progression; two of them experienced only biochemical recurrence; distant metastases were diagnosed in three patients. Median time to disease progression was 29.9 months. One patient with a biochemical relapse died of acute myocardial infarction (1.9 %). Median five-year disease-free survival was 84.5±11.7 % in Group 1 and 83.5±9.1 (p=0.73) in Group 2. There were no significant differences in the incidence of toxicity depending on the sequence of CRT steps.Conclusion. EBT using 125I radiation sources in combination with long-term hormone therapy is an effective and safe treatment option for high-risk PC patients. No significant increase in the incidence of disease progression was observed when the interval between the CRT steps was increased to more than 8 weeks. Changes in the sequence of CRT steps do not affect response to treatment or incidence of radiation-related complications.

Ten-year longitudinal health-related quality of life following iodine-125 brachytherapy monotherapy for localized prostate cancer.

PurposeThis prospective longitudinal study quantifies health-related quality of life (HRQoL) up to 10 years following permanent iodine-125 (125I) prostate brachytherapy alone for localized prostate cancer.Material and methodsIn total, 120 patients completed a validated expanded prostate cancer index composite (EPIC) questionnaire pre-treatment and at 8 time points after treatment (6 weeks, 6, 10, 18 months, and 2, 3, 5, 10 years). At each time point, clinically relevant small, moderate, and severe declines in HRQoL were defined as 0.2-0.5 SD, 0.5-0.8 SD, and > 0.8 SD of baseline function for each of urinary, bowel, and sexual domains, respectively.ResultsResponse rates in the first two years were > 90%, but thereafter dropped to 75% and 48% at 5 and 10 years, respectively. 50 patients (41.6%) responded at all stages. Maximal deterioration in mean urinary and sexual summary scores was noted 6 weeks after implant, with severe urinary symptoms and moderate bowel/sexual symptoms. At 6 months, urinary and bowel quality of life (QoL) had improved to mild impairment, which then fully resolved at 10 months. Sexual QoL remained mildly impaired throughout the 10 years of follow-up. At 10 years, new mild impairment of urinary and bowel QoL was found.ConclusionsClinically mild changes in urinary, bowel, and sexual QoL are found 10 years after 125I monotherapy. The impairment in sexual function persists from treatment, but urinary and bowel symptoms are new at 10 years.

A history of transurethral resection of the prostate should not be a contra-indication for low-dose-rate 125I prostate brachytherapy: results of a prospective Uro-GEC phase-II trial.

PurposeEarly reports suggested that transurethral resection (TURP) prior to permanent seed brachytherapy (BT) results in high incontinence rates. Guidelines consider prior TURP as a contra-indication to treatment, but improvements in imaging and treatment planning may reduce this risk, and are investigated in this prospective study.Material and methods99 men with histologically proven low- to intermediate-risk, localized prostate cancer, with a history of TURP performed at least 3 months before BT procedure were enrolled. All patients received a permanent seed implant between March 2009 and June 2015. Intra-operative interactive planning was recommended to ensure optimal accuracy of seed placement during the procedure. No supplemental external beam was allowed. Target and organ at risk contouring, definition of clinical target volume (CTV), and dosimetric parameters followed the modified GEC-ESTRO guidelines for permanent seed implants, as described an earlier report of our group. Follow-up was scheduled every 3 months for the first year, and every 6 months afterwards, with minimum follow-up of 2 years.Study endpointsThe primary endpoint was the incidence of post-implant urinary incontinence. Secondary endpoints were the incidence of urinary and gastro-intestinal toxicity, the eventual impact on the sexual function, and the freedom from biochemical failure.ResultsThe median follow-up time for these 99 patients was 49 months (min. 24, max. 96). In this series, the incontinence rate was 2% after TURP + BT and 2% in case of TURP + BT + re-TURP, ending up with a total urinary incontinence rate of 4%. Acute and late urinary toxicities were extremely low. No significant late gastro-intestinal toxicity was seen, and the 5-year biochemical non-evidence of disease (bNED) was 93%.ConclusionsThe excellent long-term results and low morbidity presented as well as many advantages of prostate brachytherapy over other treatments demonstrates that brachytherapy is an effective treatment for patients with transurethral resection and organ-confined prostate cancer.

A New Approach to the Risk Classification of Patients with Prostate Cancer Treated with I-125 Prostate Seed Implantation in a Japanese Nationwide Prospective Cohort Study

A New Approach to the Risk Classification of Patients with Prostate Cancer Treated with I-125 Prostate Seed Implantation in a Japanese Nationwide Prospective Cohort Study

Impact of a dominant intraprostatic lesion (DIL) boost defined by sextant biopsy in permanent I-125 prostate implants on biochemical disease free survival (bDFS) and toxicity outcomes

Background and purposeTo compare bDFS and toxicity outcomes in a population of intermediate risk prostate cancer patients treated using I-125 LDR brachytherapy with or without DIL boost based on multiple core biopsy maps. Materials and methodsBetween January 2005 and December 2013, all our intermediate risk prostate cancer patients treated with LDR I-125 brachytherapy were reviewed. All patients were given 144 Gy to the prostate. A pathologic DIL distribution (defined by sextant biopsy) was contoured prospectively prior to planning, to be covered by the 150% isodose line. Of the 165 patients treated, 55 received a DIL boost. Patients completed prospectively the IPSS questionnaire, a sexual and bowel function questionnaire. Gastro-intestinal toxicities were graded according to CTCAE v4.03. A patient was considered to have erectile dysfunction if he was unable to achieve erection to perform intercourse. BDFS was determined according to the Phoenix consensus definitions. ResultsThe median follow-up was 78 months. The estimated 7-year bDFS rate was 96% (95% CI, 74–99%) in the DIL group versus 89% (95% CI, 79–94%) in the control group (p = 0.188). There was no difference between groups in urinary, gastro-intestinal or sexual toxicities up to 5 years of follow-up. There was no difference in urinary obstruction with catheterization between DIL versus control groups (3,6 vs 2,8 %, p = 1.00). Only 1 patient in the DIL group had ≥grade 3 toxicity (TURP) and none in the control group. ConclusionsBoost to DIL defined by sextant biopsy with permanent seed prostate implant shows a trend toward improvement of biochemical control in intermediate risk prostate cancer patient without increasing toxicity.

Can a Dominant Intraprostatic Lesion (DIL) Boost with Permanent I-125 Prostate Implants, Altered Outcomes and Improve Biochemical Disease-Free Survival (bDFS) in Intermediate Risk Prostate Cancer?

To compare bDFS and toxicity outcomes in population of intermediate risk prostate cancer patients treated using I-125 LDR brachytherapy with or without DIL boost based on multiple core biopsy maps.

Some Decline Of Urinary Toxicity In Patients Treated With I-125 Prostate Brachytherapy Boost During A 10-Year Period

To determine whether overall, acute and late urinary toxicity rates improved with a prostate brachytherapy boost program at a single institution over 10 years.

PV-0371: Analysis of seed loss at day of implant for I-125 prostate brachytherapy. Can we skip the CT scan?

PV-0371: Analysis of seed loss at day of implant for I-125 prostate brachytherapy. Can we skip the CT scan?

OC-0272: Long-term rectal toxicity following I-125 prostate brachytherapy in 1,260 patients

OC-0272: Long-term rectal toxicity following I-125 prostate brachytherapy in 1,260 patients

Predictive Factors of Long-Term Rectal Toxicity Following I-125 Prostate Brachytherapy with or without External Beam Radiotherapy

Predictive Factors of Long-Term Rectal Toxicity Following I-125 Prostate Brachytherapy with or without External Beam Radiotherapy

PO-0946: Entropic model for real-time dose calculation: I-125 prostate brachytherapy application

PO-0946: Entropic model for real-time dose calculation: I-125 prostate brachytherapy application

PO-0932: Prostate-specific Antigen bounce in patients treated with 125I prostate brachytherapy: Keep calm

PO-0932: Prostate-specific Antigen bounce in patients treated with 125I prostate brachytherapy: Keep calm

Towards clinical application of RayStretch for heterogeneity corrections in LDR permanent 125I prostate brachytherapy

PurposeRayStretch is a simple algorithm proposed for heterogeneity corrections in low-dose–rate brachytherapy. It is built on top of TG-43 consensus data, and it has been validated with Monte Carlo (MC) simulations. In this study, we take a real clinical prostate implant with 71 125I seeds as reference and we apply RayStretch to analyze its performance in worst-case scenarios. Methods and MaterialsTo do so, we design two cases where large calcifications are located in the prostate lobules. RayStretch resilience under various calcification density values is also explored. Comparisons against MC calculations are performed. ResultsDose–volume histogram–related parameters like prostate D90, rectum D2cc, or urethra D10 obtained with RayStretch agree within a few percent with the detailed MC results for all cases considered. ConclusionsThe robustness and compatibility of RayStretch with commercial treatment planning systems indicate its applicability in clinical practice for dosimetric corrections in prostate calcifications. Its use during intraoperative ultrasound planning is foreseen.

A Monte Carlo study of I-125 prostate brachytherapy with gold nanoparticles: dose enhancement with simultaneous rectal dose sparing via radiation shielding

We investigate via Monte Carlo simulations a new 125I brachytherapy treatment technique for high-risk prostate cancer patients via injection of Au nanoparticle (AuNP) directly into the prostate. The purpose of using the nanoparticles is to increase the therapeutic index via two synergistic effects: enhanced energy deposition within the prostate and simultaneous shielding of organs at risk from radiation escaping from the prostate. Both uniform and non-uniform concentrations of AuNP are studied. The latter are modeled considering the possibility of AuNP diffusion after the injection using brachy needles. We study two extreme cases of coaxial AuNP concentrations: centered on brachy needles and centered half-way between them.Assuming uniform distribution of 30 mg g−1 of AuNP within the prostate, we obtain a dose enhancement larger than a factor of 2 to the prostate. Non-uniform concentration of AuNP ranging from 10 mg g−1 and 66 mg g−1 were studied. The higher the concentration in a given region of the prostate the greater is the enhancement therein. We obtain the highest dose enhancement when the brachytherapy needles are coincident with AuNP injection needles but, at the same time, the regions in the tail are colder (average dose ratio of 0.7). The best enhancement uniformity is obtained with the seeds in the tail of the AuNP distribution. In both uniform and non-uniform cases the urethra and rectum receive less than 1/3 dose compared to an analog treatment without AuNP.Remarkably, employing AuNP not only significantly increases dose to the target but also decreases dose to the neighboring rectum and even urethra, which is embedded within the prostate. These are mutually interdependent effects as more enhancement leads to more shielding and vice-versa. Caution must be paid since cold spot or hot spots may be created if the AuNP concentration versus seed position is not properly distributed respect to the seed locations.

Adaptive cone-beam CT planning improves long-term biochemical disease-free survival for 125I prostate brachytherapy

PurposeDetermining the independent effect of additional intraoperative adaptive C-arm cone-beam CT (CBCT) planning vs. transrectal ultrasound (TRUS)-guided interactive planning alone in 125I brachytherapy for prostate cancer (PCa) on biochemical disease-free survival (BDFS). Methods and materialsT1/T2-stage PCa patients receiving TRUS-guided brachytherapy from 2000 to 2014 were analyzed. From October 2006, patients received additional intraoperative adaptive CBCT planning for dosimetric evaluation and subsequent remedial seed placement in underdosed areas. Patients were stratified according to the National Comprehensive Cancer Network (NCCN) risk classification. Kaplan–Meier analysis was used to estimate BDFS (primary outcome), overall survival, and PCa-specific survival (secondary outcomes). Cox regression was used to assess the relation between CBCT use and biochemical failure (BF) and overall mortality. ResultsIn all, 1623 patients were included. Median followup was 99 months (interquartile range 70–115) for TRUS patients (n = 613) and 51 months (interquartile range 29–70) for CBCT patients (n = 1010). BF occurred 203 times and 206 patients died, 26 from PCa. For TRUS and CBCT patients, 7-year BDFS was 87.2% vs. 93.5% (log rank: p = 0.04) for low, 75.9% vs. 88.5% (p < 0.001) for intermediate, and 57.1% vs. 85.0% for high-risk patients (p < 0.001). For TRUS and CBCT patients, 7-year PCa-specific survival was 96.0% vs. 100% (p < 0.0001). After Cox regression, CBCT patients had lower hazard of BF: hazard ratio (HR) 0.25 (95% confidence interval [CI]: 0.18–0.33; p < 0.0001). Corrected for confounders, CBCT remained a predictor of BF: HR 0.51 (95% CI: 0.31–0.86; p = 0.01) but not for overall mortality: HR 0.66 (95% CI: 0.40–1.07; p = 0.09). ConclusionsAdditional intraoperative adaptive CBCT planning in 125I prostate brachytherapy leads to a significant increase in BDFS in all NCCN risk groups.