A matched-pair analysis of clinical outcomes after intracavitary cesium-131 brachytherapy versus stereotactic radiosurgery for resected brain metastases.

OBJECTIVE: Adjuvant radiation therapy (RT), such as cesium-131 (Cs-131) brachytherapy or stereotactic radiosurgery (SRS), reduces local recurrence (LR) of brain metastases (BM). However, SRS is less efficacious for large cavities, and the delay between surgery and SRS may permit tumor repopulation. Cs-131 has demonstrated improved local control, with reduced radiation necrosis (RN) compared to SRS. This study represents the first comparison of outcomes between Cs-131 brachytherapy and SRS for resected BM. METHODS: Patients with BM treated with Cs-131 and SRS following gross-total resection were retrospectively identified. Thirty patients who underwent Cs-131 brachytherapy were compared to 60 controls who received SRS. Controls were selected from a larger cohort to match the patients treated with Cs-131 in a 2:1 ratio according to tumor size, histology, performance status, and recursive partitioning analysis class. Overall survival (OS), LR, regional recurrence, distant recurrence (DR), and RN were compared. RESULTS: With a median follow-up of 17.5 months for Cs-131-treated and 13.0 months for SRS-treated patients, the LR rate was significantly lower with brachytherapy; 10% for the Cs-131 cohort compared to 28.3% for SRS patients (OR 0.281, 95% CI 0.082-0.949; p = 0.049). Rates of regional recurrence, DR, and OS did not differ significantly between the two cohorts. Kaplan-Meier analysis with log-rank testing showed a significantly higher likelihood of freedom from LR (p = 0.027) as well as DR (p = 0.018) after Cs-131 compared to SRS treatment (p = 0.027), but no difference in likelihood of OS (p = 0.093). Six (10.0%) patients who underwent SRS experienced RN compared to 1 (3.3%) patient who received Cs-131 (p = 0.417). CONCLUSIONS: Postresection patients with BM treated with Cs-131 brachytherapy were more likely to achieve local control compared to SRS-treated patients. This study provides preliminary evidence of the potential of Cs-131 to reduce LR following gross-total resection of single BM, with minimal toxicity, and suggests the need for a prospective study to address this question.

University of California Replacement of Cesium Irradiators with Alternative Technologies.

The University of California possesses a large number of Cs irradiators that are used in a wide variety of medical and research applications. The university president made a system-wide decision to reduce the potential threat of malevolent use of Cs by switching wherever feasible to x-ray irradiators over a 3-y period of time. A Radioactive Source Replacement Working Group of involved faculty was formed to study the topic and to make recommendations as to when alternative technologies could offer equivalency. The Working Group concluded that x-ray irradiators could replace Cs irradiators in most applications, with some likely exceptions. They found that the depth dose curve for the 320 kVp x-ray irradiator was found to be nearly identical to that of Cs down to a depth in tissue of 4 cm. It was concluded that x rays (energies ≤320 keV) are more biologically effective than Cs gamma rays, suggesting that lower doses of x rays will be required to achieve the same biological endpoint as Cs gamma rays. A simple conversion factor for equating x-ray effects to Cs effects was not recommended because relative biological effectiveness depends on multiple factors. They concluded that each experiment should be individually calibrated when converting from Cs irradiators to x-ray irradiators. The lessons learned from implementing the project to date have shown the importance of having senior management buy-in, involving the research community in the decision making process and allowing for exceptions where equivalency of Cs to x ray cannot be established.

Long-term biochemical outcomes using cesium-131 in prostate brachytherapy.

PURPOSE: Long-term outcomes reveal equivalent biochemical outcomes with low-dose-rate (LDR) brachytherapy (BT) compared with radical prostatectomy and external-beam radiotherapy for the management of prostate cancer. Iodine-125, the most commonly used isotope, may be associated with long-term urinary consequences. Cesium-131 (131Cs) has a higher dose rate and shorter dose delivery time, predicting a shorter duration of urinary morbidity. We report our institution's high-volume experience and the most mature data to date on outcomes with 131Cs prostate BT. METHODS AND MATERIALS: 571 men (median age: 65.38 years) with low (55%)-, intermediate (36%)-, and high-risk disease (9%) received monobrachytherapy, dual-modality, or trimodality using 131Cs at a single institution. Risk groups were defined according to the National Comprehensive Cancer Network definition. Median prescription dose for definitive LDR-BT and LDR-BT boost was 115 Gy and 70 Gy, respectively. Median initial PSA was 6.1 ng/mL (IQR: 4.6-8.7). RESULTS: Median followup time was 5 years. 5/7-year overall survival for low-, intermediate-, and high-risk patients was 96.9%/96/9%, 92.8%/89.7%, and 95.8%/87.1%, respectively (p = 0.02). 5/7-year freedom from biochemical failure for low-, intermediate-, and high-risk patients was 98.5%/96.3%, 94.1%/86.4%, and 93.2%/74.5%, respectively (p < 0.01). 5/7-year prostate cancer -specific survival was 100%/100%, 99.3%/99.3%, and 98.0%/98.0% for low-, intermediate-, and high-risk patients, respectively (p < 0.01). CONCLUSIONS: 131Cs is a viable alternative isotope for prostate brachytherapy for organ-confined disease. Long-term biochemical control and survival outcomes are excellent and on par with those attained with the use of 125I or 103Pd. This report therefore supports the continued use of 131Cs as an effective and comparable alternative isotope.

Effect of dose and dose rate on temporal γ-H2AX kinetics in mouse blood and spleen mononuclear cells in vivo following Cesium-137 administration.

BACKGROUND: Cesium-137 (137Cs) is one of the major and most clinically relevant radionuclides of concern in a radiological dispersal device, "dirty bomb" scenario as well as in nuclear accidents and detonations. In this exposure scenario, a significant amount of soluble radionuclide(s) may be dispersed into the atmosphere as a component of fallout. The objectives of the present study were to investigate the effect of protracted 137Cs radionuclide exposures on DNA damage in mouse blood and spleen mononuclear cells (MNCs) in vivo using the γ-H2AX biomarker, and to develop a mathematical formalism for these processes. RESULTS: C57BL/6 mice were injected with a range of 137CsCl activities (5.74, 6.66, 7.65 and 9.28 MBq) to achieve total-body committed doses of ~ 4 Gy at Days 3, 5, 7, and 14. Close to 50% of 137Cs was excreted by day 5, leading to a slower rate of decay for the remaining time of the study; 137Cs excretion kinetics were independent of activity level within the tested range, and the absorbed radiation dose was determined by injected activity and time after injection. Measurements of γ-H2AX fluorescence in blood and spleen MNCs at each time point were used to develop a new biodosimetric mathematical formalism to estimate injected activity based on γ-H2AX fluorescence and time after injection. The formalism performed reasonably well on blood data at 2-5 days after injection: Pearson and Spearman's correlation coefficients between actual and predicted activity values were 0.857 (p = 0.00659) and 0.929 (p = 0.00223), respectively. CONCLUSIONS: Despite the complicated nature of the studied biological system and the time-dependent changes in radiation dose and dose rate due to radionuclide excretion and other processes, we have used the γ-H2AX repair kinetics to develop a mathematical formalism, which can relatively accurately predict injected 137Cs activity 2-5 days after initial exposure. To determine the assay's usefulness to predict retrospective absorbed dose for medical triage, further studies are required to validate the sensitivity and accuracy of the γ-H2AX response after protracted exposures.

Resection and permanent intracranial brachytherapy using modular, biocompatible cesium-131 implants: results in 20 recurrent, previously irradiated meningiomas.

OBJECTIVE: Effective treatments for recurrent, previously irradiated intracranial meningiomas are limited, and resection alone is not usually curative. Thus, the authors studied the combination of maximum safe resection and adjuvant radiation using permanent intracranial brachytherapy (R+BT) in patients with recurrent, previously irradiated aggressive meningiomas. METHODS: Patients with recurrent, previously irradiated meningiomas were treated between June 2013 and October 2016 in a prospective single-arm trial of R+BT. Cesium-131 (Cs-131) radiation sources were embedded in modular collagen carriers positioned in the operative bed on completion of resection. The Cox proportional hazards model with this treatment as a predictive term was used to model its effect on time to local tumor progression. RESULTS: Nineteen patients (median age 64.5 years, range 50-78 years) with 20 recurrent, previously irradiated tumors were treated. The WHO grade at R+BT was I in 4 (20%), II in 14 (70%), and III in 2 (10%) cases. The median number of prior same-site radiation courses and same-site surgeries were 1 (range 1-3) and 2 (range 1-4), respectively; the median preoperative tumor volume was 11.3 cm3 (range 0.9-92.0 cm3). The median radiation dose from BT was 63 Gy (range 54-80 Gy). At a median radiographic follow-up of 15.4 months (range 0.03-47.5 months), local failure (within 1.5 cm of the implant bed) occurred in 2 cases (10%). The median treatment-site time to progression after R+BT has not been reached; that after the most recent prior therapy was 18.3 months (range 3.9-321.9 months; HR 0.17, p = 0.02, log-rank test). The median overall survival after R+BT was 26 months, with 9 patient deaths (47% of patients). Treatment was well tolerated; 2 patients required surgery for complications, and 2 experienced radiation necrosis, which was managed medically. CONCLUSIONS: R+BT utilizing Cs-131 sources in modular carriers represents a potentially safe and effective treatment option for recurrent, previously irradiated aggressive meningiomas.

Characterization of Ivoclar Vivadent Dental Restoration Material for 137CS Retrospective Radiation Dosimetry.

Retrospective dosimetry is the method of using materials on or near a person who is exposed to ionizing radiation to determine the amount of radiation received by the person. A possible candidate material for retrospective dosimetry is Ivoclar Vivadent IPS e.max® CAD ceramic dental restoration material, which exhibits radiation-induced thermoluminescence when exposed to gamma- and x-ray radiation from a Cs source. The purpose of this paper is to characterize the material and study the behavior of the thermoluminescence signal with radiation dose and with delay time between radiation exposure and thermoluminescence measurement. The first glow peak is well-modeled by a first-order glow curve deconvolution formula. The height of the first glow peak is approximately linear with dose. The fading of the signal with time is approximately described by a power law curve with cutoff. The material appears to be suitable for retrospective radiation dosimetry.

Screening Internal Contamination of Inhaled and Ingested Radionuclides with Hand-held Survey Meters.

During the aftermath of a radiological accident or attack, the rapid identification of individuals who have internalized medically significant amounts of material is paramount to guide medical and public health decisions. This paper explores the utility of hand-held, pancake GM detectors to determine if an individual has inhaled Sr, Cs, Pu, Pu, or Am in quantities requiring treatment. Additionally, ingestion of Sr or Cs was considered. Both Sr and Cs were modeled in equilibrium with their progeny, but the progeny of Pu, Pu, and Am were excluded. Treatment thresholds are defined using the National Council on Radiation Protection & Measurements' (NCRP) clinical decision guides (CDGs). Using Monte Carlo N-Particle (MCNP) modeling software, a human phantom and detector were modeled to determine the activity required to achieve a detector reading of twice background 1, 7, or 30 d post-ingestion or post-inhalation. Modeling found that inhaled Pu, Pu, and Am are detectable only if the contaminated individual inhaled thousands-fold more material than the CDG. This lack of detectability means that hand-held GM detectors are inappropriate for initial screening for americium or plutonium and that more intensive screening is necessary to confirm suspected contamination. Cesium-137, by contrast, could be detected at levels 10- to 100-fold lower than the amount requiring treatment, allowing quick differentiation between contaminated and uncontaminated individuals. Surprisingly, Sr was detectable within a factor of 2 of the amount requiring treatment. Detection of Sr was due primarily to bremsstrahlung radiation from beta interactions with calcium in bone. While rapid screening could identify individuals contaminated by Cs and possibly with Sr, further screening of identified individuals is necessary to establish medical need. However, these contaminated individuals could still be prioritized for further testing and possible presumptive treatment. Based on the findings of this study, concepts of operation for the use of hand-held survey meters should be developed for the screening of individuals potentially internally contaminated with Cs and Sr.

Biological characterization of a novel in vitro cell irradiator.

To evaluate the overall robustness of a novel cellular irradiator we performed a series of well-characterized, dose-responsive assays to assess the consequences of DNA damage. We used a previously described novel irradiation system and a traditional 137Cs source to irradiate a cell line. The generation of reactive oxygen species was assessed using chloromethyl-H2DCFDA dye, the induction of DNA DSBs was observed using the comet assay, and the initiation of DNA break repair was assessed through γH2AX image cytometry. A high correlation between physical absorbed dose and biologic dose was seen for the production of intracellular reactive oxygen species, physical DNA double strand breaks, and modulation of the cellular double stand break pathway. The results compared favorably to irradiation with a traditional 137Cs source. The rapid, straightforward tests described form a reasonable approach for biologic characterization of novel irradiators. These additional testing metrics go beyond standard physics testing such as Monte Carlo simulation and thermo-luminescent dosimeter evaluation to confirm that a novel irradiator can produce the desired dose effects in vitro. Further, assessment of these biological metrics confirms that the physical handling of the cells during the irradiation process results in biologic effects that scale appropriately with dose.

Complexes of myo-Inositol-Hexakisphosphate (IP6) with Zinc or Lanthanum for the Decorporation of Radiocesium.

Radioactive nuclides leak into the surrounding environment after nuclear power plant disasters, such as the Chernobyl accident and the Fukushima Daiichi Nuclear Power Plant disaster. Cesium-137 (137Cs) (t1/2=30.1 year), a water-soluble radionuclide with a long physical half-life, contaminates aquatic ecosystems and food products. In humans, 137Cs concentrates in muscle tissue and has a long biological half-life, indicating it may be harmful. myo-Inositol-hexakisphosphate (IP6) is a compound found in grain, beans, and oil seeds. IP6 has the ability to form insoluble complexes with metals, including lanthanum (La) and zinc (Zn). We hypothesized that La-IP6 and Zn-IP6 may promote the elimination of 137Cs from the body through the adsorption of La-IP6 and Zn-IP6 to 137Cs in the gastrointestinal tract. Therefore, in this study, we evaluated the adsorptive capacity of La-IP6 and Zn-IP6 complexes with 137Cs in vitro and in vivo. La-IP6 and Zn-IP6 complexes were stable in acidic solution (pH 1.2) at 37°C. In vitro binding assays indicated that La-IP6 and Zn-IP6 complexes adsorbed 137Cs, with the adsorption capacity of Zn-IP6 to 137Cs greater than that of La-IP6. To evaluate the usefulness of La-IP6 and Zn-IP6 in vivo, La-IP6 or Zn-IP6 was administrated to mice after intravenous injection of 137Cs. However, the biodistribution of 137Cs in the La-IP6 treated group and the Zn-IP6 treated group was nearly identical to the non-treated control group, indicating that La-IP6 and Zn-IP6 were not effective at promoting the elimination of 137Cs in vivo.

Surgical Technique and Clinically Relevant Resection Cavity Dynamics Following Implantation of Cesium-131 (Cs-131) Brachytherapy in Patients With Brain Metastases.

BACKGROUND: Cesium-131 (Cs-131) brachytherapy is used to reduce local recurrence of resected brain metastases. In order to ensure dose homogeneity and reduce risk of radiation necrosis, inter-seed distance and cavity volume must remain stable during delivery. OBJECTIVE: To investigate the efficacy of the "seeds-on-a-string" technique with intracavitary fibrin glue in achieving cavity volume stability. METHODS: We placed intra-operative Cs-131 brachytherapy in 30 cavities post-resection of brain metastases. Seeds-on-a-string were placed like barrel staves within the cavity with fibrin glue. Serial MRI imaging occurred post-operatively. Pre-operative tumor volumes were compared with post-operative cavity volumes to evaluate volume stability. Thirty patients who underwent post-resective stereotactic radiosurgery (SRS) were used as a control group for volumetric comparison. RESULTS: Cs-131 and SRS patients exhibited consistent cavity shrinkage over the median 110-day follow-up (p<.001), with total median shrinkage of 56.5% (Cs-131) and 84.8% (SRS). During the first month when ~88% of Cs-131 dosage is delivered, however, there was non-significant volume decrease in the Cs-131 group (median 22.0%; p=.063), while SRS patients showed significantly more shrinkage (46.7%; p=.042). No events of radiation necrosis occurred in either group. CONCLUSION: Cs-131 patients exhibited significantly less cavity shrinkage than SRS patients during the first critical month with 88% Cs-131 dose delivery. This significant difference in shrinkage suggests that the intracavitary seeds-on-a-string technique facilitates increased cavity stability, promoting more homogenous dose delivery.

[Impact of Radioactive Elements on Microbial Complexes in Cryogenic Soils of Yakutia].

It has been found that microorganisms in cryogenic soils of Yakutia are resistant to the long-term impact of cesium and thorium. The number of microorganisms in the studied ecological-trophic groups does not depend on the concentrations of radioactive elements. Differences in the number of microorganisms are determined by the physicochemical conditions that are created in different horizons of the soils studied. The long-term impact of radiation (for 36 and 66 years) on microorganisms inhabiting the permafrost soils of Yakutia has developed their adaptive capacity to high concentrations of these radioactive elements.

Comparison of Cesium-137 and X-ray Irradiators by Using Bone Marrow Transplant Reconstitution in C57BL/6J Mice.

Mice are used extensively in transplantation studies involving bone marrow ablation. Due to the increasing security issues and expenses involved with γ irradiators, self-contained X-ray irradiators have been increasing in popularity. We hypothesized that bone marrow ablation by irradiation of mice with a (137)Cs irradiator would be comparable to that from an X-ray source irradiator. A lethal-dose curve was obtained by irradiating C57BL/6J mice with 500, 700, 900, and 1100 cGy from either source. These data were used to determine the lethal radiation exposure range for a noncompetitive bone marrow engraftment curve for each source. At 90 d after reconstitution, the bone marrow engraftment curves revealed significant differences between the 2 sources in the establishment of B cell, myeloid, and T cell lineages. Murine B cell reconstitution after exposure to a (137)Cs source was greater than that after X-ray exposure at each dose level, whereas the converse was true for myeloid cell reconstitution. At the 1050- and 1100-cGy doses, mice irradiated by using the X-ray source demonstrated higher levels of T cell reconstitution but decreased survival compared with mice irradiated with the (137)Cs source. We concluded that although both sources ablated endogenous bone marrow sufficiently to enable stem cell engraftment, there are distinct physiologic responses that should be considered when choosing the optimal source for use in a study and that irradiation from the (137)Cs source was associated with lower overall morbidity due to opportunistic infection.

Considerations on the ICRP model predictions of the transfer of (137)Cs from food to the milk and urine of lactating mothers.

A recent work has shown that the current ICRP biokinetic model for the transfer of caesium radionuclides from food to human breast milk was able to describe with satisfactory accuracy (137)Cs activity concentrations in human breast samples collected a few weeks after the Chernobyl accident as well as in samples collected some years later. However, systematic discrepancies were observed for the predictions of the activity concentrations in urine samples. In the present work, modifications to the model were investigated with the aim of improving the agreement between model predictions and data. It turned out that the disagreement for the urine data was ascribable to the mathematical simplifications used by the ICRP to describe urinary excretion in the first few days after delivery. However, the predictive performances of the model remained unchanged even when differences in the bioavailability of caesium from the ingested food types were considered or metabolic interactions between caesium and potassium were introduced into the model formulation.

Reconstruction of long-lived radionuclide intakes for Techa riverside residents: 137Cs.

Radioactive contamination of the Techa River (Southern Urals, Russia) occurred from 1949-1956 due to routine and accidental releases of liquid radioactive wastes from the Mayak Production Association. The long-lived radionuclides in the releases were Sr and Cs. Contamination of the components of the Techa River system resulted in chronic external and internal exposure of about 30,000 residents of riverside villages. Data on radionuclide intake with diet are used to estimate internal dose in the Techa River Dosimetry System (TRDS), which was elaborated for the assessment of radiogenic risk for Techa Riverside residents. The Sr intake function was recently improved, taking into account the recently available archival data on radionuclide releases and in-depth analysis of the extensive data on Sr measurements in Techa Riverside residents. The main purpose of this paper is to evaluate the dietary intake of Cs by Techa Riverside residents. The Cs intake with river water used for drinking was reconstructed on the basis of the Sr intake-function and the concentration ratio Cs-to-Sr in river water. Intake via Cs transfer from floodplain soil to grass and cows' milk was evaluated for the first time. As a result, the maximal Cs intake level was indicated near the site of releases in upper-Techa River settlements (8,000-9,000 kBq). For villages located on the lower Techa River, the Cs intake was significantly less (down to 300 kBq). Cows' milk was the main source of Cs in diet in the upper-Techa River region.

Radiocesium distribution in the tissues of Japanese Black beef heifers fed fallout-contaminated roughage due to the Fukushima Daiichi Nuclear Power Station accident.

This study examined the accumulation and tissue distribution of radioactive cesium nuclides in Japanese Black beef heifers raised on roughage contaminated with radioactive fallout due to the accident at the Fukushima Daiichi Nuclear Power Station on March 2011. Radiocesium feeding increased both (134)Cs and (137)Cs levels in all tissues tested. The kidney had the highest level and subcutaneous adipose had the lowest of radioactive cesium in the tissues. Different radioactive cesium levels were not found among parts of the muscles. These results indicate that radiocesium accumulated highly in the kidney and homogenously in the skeletal muscles in the heifers.

Thyroid doses for evacuees from the Fukushima nuclear accident.

A primary health concern among residents and evacuees in affected areas immediately after a nuclear accident is the internal exposure of the thyroid to radioiodine, particularly I-131, and subsequent thyroid cancer risk. In Japan, the natural disasters of the earthquake and tsunami in March 2011 destroyed an important function of the Fukushima Daiichi Nuclear Power Plant (F1-NPP) and a large amount of radioactive material was released to the environment. Here we report for the first time extensive measurements of the exposure to I-131 revealing I-131 activity in the thyroid of 46 out of the 62 residents and evacuees measured. The median thyroid equivalent dose was estimated to be 4.2 mSv and 3.5 mSv for children and adults, respectively, much smaller than the mean thyroid dose in the Chernobyl accident (490 mSv in evacuees). Maximum thyroid doses for children and adults were 23 mSv and 33 mSv, respectively.

The metabolomic approach identifies a biological signature of low-dose chronic exposure to cesium 137.

Reports have described apparent biological effects of (137)Cs (the most persistent dispersed radionuclide) irradiation in people living in Chernobyl-contaminated territory. The sensitive analytical technology described here should now help assess the relation of this contamination to the observed effects. A rat model chronically exposed to (137)Cs through drinking water was developed to identify biomarkers of radiation-induced metabolic disorders, and the biological impact was evaluated by a metabolomic approach that allowed us to detect several hundred metabolites in biofluids and assess their association with disease states. After collection of plasma and urine from contaminated and non-contaminated rats at the end of the 9-months contamination period, analysis with a LC-MS system detected 742 features in urine and 1309 in plasma. Biostatistical discriminant analysis extracted a subset of 26 metabolite signals (2 urinary, 4 plasma non-polar, and 19 plasma polar metabolites) that in combination were able to predict from 68 up to 94% of the contaminated rats, depending on the prediction method used, with a misclassification rate as low as 5.3%. The difference in this metabolic score between the contaminated and non-contaminated rats was highly significant (P = 0.019 after ANOVA cross-validation). In conclusion, our proof-of-principle study demonstrated for the first time the usefulness of a metabolomic approach for addressing biological effects of chronic low-dose contamination. We can conclude that a metabolomic signature discriminated (137)Cs-contaminated from control animals in our model. Further validation is nevertheless required together with full annotation of the metabolic indicators.

Influence on the mouse immune system of chronic ingestion of 137Cs.

The aim of this work was to determine the possible occurrence of damage to the immune system during the course of chronic ingestion of (137)Cs. BALB/C mice were used, with (137)Cs intake via drinking water at a concentration of 20 kBq l(-1). Adults received (137)Cs before mating and offspring were sacrificed at various ages between birth and 20 weeks. Phenotypic analysis of circulating blood cells and thymocytes did not show any significant modification of immune cell populations in animals ingesting (137)Cs as compared with control animals, with the exception of a slight increase in Treg percentage at the age of 12 weeks. Functional tests, including proliferative response to mitogens such as phytohaemagglutinin, response to alloantigens in mixed lymphocyte reaction and immunoglobulin response to vaccine antigens such as tetanus toxin and keyhole limpet haemocyanin did not show any significant functional modification of the immune system in (137)Cs-ingesting animals as compared with control animals. Overall, our results suggest that chronic ingestion of a low concentration of (137)Cs in drinking water in the long term does not have any biologically relevant effect on the immune system.

Acute bowel morbidity after prostate brachytherapy with cesium-131.

PURPOSE: The present study evaluates the severity and time to resolution of bowel symptoms in men undergoing prostate brachytherapy (PB) with cesium-131 ((131)Cs). METHODS AND MATERIALS: A longitudinal, prospective study of patients who had undergone PB with (131)Cs at a single institution was performed. All patients were asked to complete the Expanded Prostate Cancer Index Composite preoperatively and at 2 weeks and 1, 3, and 6 months postoperatively. Outcomes were analyzed using descriptive statistics and Student's t test. RESULTS: The first 142 patients to have undergone PB with (131)Cs at our institution were included in the study. The mean Expanded Prostate Cancer Index Composite bowel summary score at baseline was 90.1±11.0 compared with 71.5±22.8 (p=0.000), 70.1±20.7, 87.1±13.8 (p=0.01), and 90.7±9.2 (p=0.70) at 2 weeks and 1, 3, and 6 months postoperatively, respectively. CONCLUSIONS: In men undergoing PB as monotherapy with (131)Cs, bowel symptoms returned to baseline by 3 months after the procedure. For patients undergoing PB with (131)Cs as part of combination therapy, bowel symptoms return to their post-external beam radiotherapy, pre-PB baseline by 3 months after the procedure.