The effects of edema on urethral dose following palladium-103 prostate brachytherapy.

The effects of edema on urethral dose after interstitial prostate brachytherapy with palladium-103 (103Pd) were studied. Fifty patients underwent a 90-Gy 103Pd implant followed by dosimetric computed tomography (CT). Twenty-one days later, a Foley catheter was reinserted and a dosimetric CT was repeated. The mean reduction in prostate volume between day 0 and day 21 was 16%. Median prostate D90 on day 0 was 89.7 Gy (range 59.5 to 127) and 99.5 Gy (range 62.5 to 130) on day 21. Median prostate V100 was 90% (range 63 to 98%) on day 0 and 96% (range 66 to 99%) on day 21. Median V150 was 61% (range 31 to 85%) on day 0 and 75% (range 39 to 93%) on day 21. Median urethral D50 was 107 Gy (range 57 to 201) on day 0 and 126 Gy (range 64 to 193) on day 21. Regression analysis demonstrated a significant correlation between the decrease in the prostate volume and the increased urethral D50 (r 0.58, p < 0.05). Acute urinary toxicity was 32% grade 0, 38% grade 1, and 30% grade 2. The median urethral D50 increased by a mean of 18% with a correlation coefficient of 0.58 (p < 0.05). Catheterization of the urethra was well tolerated and was of value in better characterizing urethral dose after 103Pd brachytherapy.     

PET-CT检查致前列腺癌患者辐射剂量研究

目的 评估¹⁸F-Choline、¹¹C-Choline和⁶⁸Ga-PSMA PET-CT检查致前列腺癌患者的有效剂量和器官剂量。方法 回顾性研究2017年5月至2018年6月广西医科大学附属肿瘤医院接受PET-CT检查的150例前列腺癌患者,按照注射正电子放射性药物类型分为3组,每组50例。CT定位扫描电压和电流分别为120 kV和35 mA,全身CT扫描电和电流分别为120 kV和（135.6±9.4） mA。PET部分的剂量利用基于医学内照射剂量（MIRD）计算方法的OLINDA/EXM （version 1.1）软件行计算。利用有效剂量转换因子和ImPACT （version 1.0.4） CT剂量计算器计算CT部分剂量,CT剂量指数（CTDI）利用标准体模测量和ImPACT CT计算,组织权重因子取自国际放射防护委员会（ICRP）103号报告,PET和CT剂量之和为患者总有效剂量。结果 注射¹⁸F-Choline、¹¹C-Choline和⁶⁸Ga-PSMA的活度分别为（279.2±13.2）、（350.2±39.9）和（186.8±19.4） MBq,有效剂量分别为（5.0±0.2）、（1.6±0.2）和（3.0±0.3） mSv,差异有统计学意义（F=837.0,P<0.001）。CT有效剂量为（11.4±0.2） mSv。3组总有效剂量分别为（16.4±0.3）、（13.0±0.3）和（14.4±0.4） mSv。PET检查3组器官当量剂量平均值比较,差异有统计学意义（F=381.2~1 637.7,P<0.001）。¹⁸F-Choline和⁶⁸Ga-PSMA PET-CT检查器官当量剂量最高为肾脏,而¹¹C-Choline PET-CT检查最高为甲状腺。结论 PET-CT检查致前列腺癌患者的有效剂量为13.0~16.4 mSv,其中绝大部分的剂量来自CT扫描。¹¹C-Choline PET-CT检查致患者的辐射剂量最低,有望成为潜在的前列腺癌PET显像药物。     

Biochemical disease-free survival rates following definitive low-dose-rate prostate brachytherapy with dose escalation to biologic target volumes identified with SPECT/CT capromab pendetide

PURPOSE: To report biochemical disease-free survival (bDFS) after conformal brachytherapy with dose escalation to biological target volumes (BTVs) identified by Capromab Pendetide with single photon emission computed tomography and computed tomography image fusion (SPECT/CT). METHODS AND MATERIALS: Two hundred thirty-nine (T1c-T3b NxM0) consecutive patients were evaluated by SPECT/CT before treatment. Intraprostatic SPECT/CT BTVs were identified and targeted for 150% dose escalation during brachytherapy seed implant (SI). Patients received either SI alone (n = 150) or external beam radiation therapy (EBRT) plus SI boost (EBRT+SI) (n = 89), with (n = 50) and without (n = 189) neoadjuvant hormone ablation therapy. Risk factors (RF) (prostate-specific antigen [PSA] >10 ng/mL, Stage > or = T2b, and Gleason grade > or = 7) defined risk group (RG) categories [none, 1, and > or = 2 RF define low, intermediate, and high RG] for bDFS calculations using four failure criteria: American Society for Therapeutic Radiology and Oncology (ASTRO) consensus definition, PSA >1.0 ng/mL (PSA >1), PSA >0.5 ng/mL after nadir (PSA >0.5), and PSA nadir+2 ng/mL rise in PSA clinical nadir (CN+2). Median followup was 47.2 months (range, 24.8-96.1). RESULTS: Seven-year actuarial bDFS rates were 88.0%, 82.1%, 80.4%, and 79.9% using the ASTRO, PSA >1, PSA >0.5, and CN+2 failure criteria, respectively. ASTRO-defined bDFS rates were 96.0%, 87.0%, and 72.5% for low, intermediate, and high RG's. CONCLUSION: The data presented here demonstrate the feasibility of performing SPECT/CT BTV dose escalation in a mature series.     

The effect of constipation on rectal dosimetry following prostate brachytherapy

The purpose of this study is to report the effect of dilatation of the anorectum on rectal dosimetry following an ¹²⁵I prostate implant. Three months following prostate brachytherapy, 2 computed tomography (CT) scans of the prostate gland were obtained within 90 minutes of each other. The first CT scan revealed a dilated anorectum secondary to constipation. The second CT was obtained following the administration of an enema with a successfully evacuated rectum. Differences in radiation doses to the distended and empty rectum were computed via the mean dose, the maximum dose per slice, the distance from the base, and in terms of the surface of the anterior quadrant of the rectum receiving 100%, 125%, 150%, 175%, 200%, and 250% of the prescribed dose. The dose to the rectal wall was substantially increased in the distended state for all evaluated parameters. In general, the mean dose to the rectal wall was increased by a factor of 1.5 in the distended state. In both scenarios, the dose to the rectal wall peaked near midgland. In terms of 10° rectal wall sectors receiving a given percentage of the prescribed minimal peripheral dose, S%mPD, the S₁₀₀, S₁₂₅, S₁₅₀, S₁₇₅, S₂₀₀, and S₂₅₀ were substantially greater for the distended versus the empty rectum. The magnitude of the percentage difference in dose between the distended and evacuated rectum increased with dose level while the difference in the number of sectors receiving a given dose level was greatest at 125% and 150% of the prescribed dose. We recommend detailed postimplant attention to bowel habits for at least 2 half-lives of the implanted isotope to minimize rectal distention, decrease radiation dose to the anterior rectal wall, and subsequently minimize potential constipation related rectal toxicity.     

Image-guided brachytherapy following external-beam radiation therapy for patients with inoperable endometrial cancer

ObjectiveTo investigate the outcomes of definitive external-beam radiation therapy (EBRT) plus image-guided brachytherapy (IGBT) in patients with endometrial cancer (EC) unsuitable for surgery.MethodsA total of 50 patients with inoperable EC were included. The patients received EBRT in a median dose of 45 Gy to the pelvis over 5 weeks. Thereafter, the patients received brachytherapy using tandem and ovoid applicators. High-risk clinical target volume (HR-CTV) and gross tumor volume in brachytherapy (GTVp) were defined by the assistance of patients’ pre-IGBT magnetic resonance imaging.ResultsThe medical records of the 50 patients were analyzed. The main causes of inoperability were anesthesia contraindications, namely medical comorbidities and obesity. The median cumulative D90s (the minimum dose delivered to 90% of the volume) in EQD2 (equivalent dose in 2-Gy fractions) to the HR-CTV and GTVp were 72.9 Gy10 (range, 64.9 to 80.3) and 166.2 Gy10 (range, 123.0 to 189.8), respectively. Over a median follow-up period of 27 months, 8 of the patients died of cancer. The 2-year overall and cancer-specific survival rates were 75% and 83%, respectively. The cumulative incidences of pelvic and distant failure were 4% (n = 2) and 16% (n = 8), respectively. Gastrointestinal complications of grade 2 or above were noted in 2 patients (4%), and a grade 2 genitourinary complication was noted in one.ConclusionsFor patients with inoperable EC, EBRT followed by IGBT is an effective approach for achieving high local control without a high risk of complications.     

Interfractional fluctuation of rectal dose in high dose rate brachytherapy for prostate cancer

Purpose The aim of the study was to explore the cause of the difference in the maximal rectal dose between the first and second high dose rate (HDR) brachytherapy applications by comparing the thickness of the anterior rectal wall. Materials and methods The rectal dose and the thickness of the anterior rectal wall were analyzed in 26 patients with prostate cancer. After undergoing external beam radiation treatment with a total isocenter dose of 50 Gy, they were treated with HDR brachytherapy of 7.5 Gy/fraction, two fractions daily. The interval between the first HDR brachytherapy session and the second was 5 h. The rectal doses were directly surveyed during irradiation of the HDR brachytherapy. Thickening of the anterior rectal wall was measured at the same level by axial computed tomography scans obtained before the first and second HDR brachytherapy applications. Results The maximal surveyed rectal doses during the first and second HDR brachytherapy applications were 188 ± 51 cGy and 220 ± 35 cGy, respectively (P < 0.01). The fluctuation ratio exceeded 1 in each case. The thickness of the anterior rectal wall before the first and second HDR brachytherapy applications was 18.78 ± 4.34 mm and 14.95 ± 4.09 mm (P < 0.01), respectively. The fluctuation difference exceeded 0 in each case. Conclusion The different rectal dose is attributable to thinning of the anterior rectal wall. The total rectal dose is within the range of doses at risk of exerting a toxic effect on the rectum.     

Dosimetry of anal radiation in high-dose-rate brachytherapy for prostate cancer

PURPOSE: The objective of this study is to determine the radiation dose to the anus during brachytherapy using high-dose-rate Ir-192 sources. METHODS AND MATERIALS: Thermoluminescence dosimeters were used for measuring the dose to the distal part of the anus in 10 patients, and in a prostate phantom to measure the radiation dose during the transport of the radiation source. RESULTS: The measured dose to the anus in vivo was on average 0.85 Gy (range, 0.48-1.37 Gy) per treatment. The transport dose using 15 and 19 needles in the prostate phantom was 0.07 and 0.08 Gy, respectively. CONCLUSIONS: The dose delivered to the anus using high-dose-rate brachytherapy with Ir-192 sources is quite low. There is a contribution to the anal radiation dose during the transport of the Ir-192 source into the needles. However, in clinical practice when using 15-20 needles, the dose from transporting the Ir-192 source can be ignored.     

Evolution of brachytherapy treatment planning to deterministic radiation transport for calculation of cardiac dose

Brachytherapy was among the first methods of radiotherapy and has steadily continued to evolve. Here we present a brief review of the progression of dose calculation methods in brachytherapy to the current state-of-the art computerized methods for heterogeneity correction. We further review the origin and development of the BrachyVision (Varian Medical Systems, Inc., Palo Alto, CA) treatment planning system and evaluate dosimetric results from 12 patients implanted with the strut-assisted volumetric implant (SAVI) applicator (Cianna Medical, Aliso Viejo, CA) for accelerated partial breast irradiation (APBI). Dosimetric results from plans calculated using homogenous and heterogeneous algorithms have been compared to investigate the impact of heterogeneity corrections. Our study showed large percent difference between mean cardiac doses 11.8?±?6.2% (p?=?0.0007) calculated with and without heterogeneity corrections. Our findings are consistent with those of others, indicating an overestimation of the distal dose to organs-at-risk by traditional methods, especially at interfaces between air and tissue.     

The effect of hormonal manipulation on urinary function following permanent prostate brachytherapy

PURPOSE: To evaluate the effect of hormonal manipulation on catheter dependency, the resolution of urinary symptomatology, and the need for postbrachytherapy transurethral/transincisional resection (TURP/TUIP). METHODS AND MATERIALS: Seven hundred sixteen consecutive patients (median follow-up, 29 months) underwent brachytherapy for clinical T1b-T3a (1997 AJCC) prostate cancer from January 1998 through August 2002. Of the evaluated cohort, 400 patients were hormone na?ve, 227 received short-course cytoreductive (< or = 6 months) hormonal therapy, and 89 received extended (>6 months) hormonal therapy. An alpha-blocker was initiated prior to implantation and continued at least until the International Prostate Symptom Score (I-PSS) returned to baseline levels. Evaluated parameters included age, T-stage, preimplant I-PSS, ultrasound volume, treatment planning volume, hormonal status, supplemental external beam radiation therapy (XRT), isotope, urethral dose, total implant activity, D90, and V100/150/200. Catheter dependency and the incidence of TURP/TUIP were also evaluated. RESULTS: Six hundred fifty three patients (91.2%) had the urinary catheter permanently removed on day 0 with 15 patients (2.1%) requiring a catheter beyond 4 days. The I-PSS returned to within 1 point of the antecedent value at a median of 4 months. Sixteen patients (2.2%) underwent postimplant TURP/TUIP. A Cox regression indicated that preimplant I-PSS, supplemental XRT, planning target volume, hormonal therapy, and number of seeds were the strongest predictors for I-PSS resolution. Using all available data, the strongest predictors for I-PSS at 18 months following brachytherapy included variants of I-PSS, isotope, and days of catheter dependency. The maximum I-PSS, planning target volume, and XRT best predicted for prolonged (#10878;4 days) catheter dependency. The need for postimplant TURP/TUIP was most closely associated with days of catheter dependency and the maximum increase in I-PSS. However, when only data available prior to implantation was entered into the model, hormonal therapy predicted for postsurgical intervention. CONCLUSIONS: In this retrospective evaluation, hormonal manipulation did not statistically impact short-term or prolonged urinary catheter dependency or I-PSS at 18 months, but did influence time to I-PSS normalization and the need for postbrachytherapy surgical intervention.     

Temporal effect of neoadjuvant androgen deprivation therapy on PSA kinetics following permanent prostate brachytherapy with or without supplemental external beam radiation

PURPOSE: To evaluate the effect of neoadjuvant androgen deprivation therapy on PSA kinetics following brachytherapy with or without supplemental external beam radiation therapy (XRT), to evaluate the magnitude and duration of the peak PSA, and to compare potential differences in PSA response curves between biochemically disease-free and failed patients. MATERIALS AND METHODS: From November 1995 through August 2000, 179 consecutive patients with clinical T1b-T3a NxM0 (2002 AJCC) prostate cancer received neoadjuvant androgen deprivation therapy (median, 4 months) prior to brachytherapy using (103)Pd or (125)I with or without supplemental XRT. The median follow-up was 56 months. Following brachytherapy, PSA determinations were obtained at 3 months and then every 6 months thereafter. A median and mean of 9 and 9.5 PSA determinations, respectively, were obtained per patient. Biochemical disease-free survival was defined by the ASTRO and Houston definitions with both definitions used to determine the rate of overestimation of early biochemical failure secondary to testosterone recovery. RESULTS: Although a trend for higher baseline and peak PSA was noted in (125)I monotherapy patients, the difference between the 4 groups was not statistically significant (p = 0.088). Changes in PSA over time, however, were statistically significant (p = 0.042). For all 4 groups, the peak PSA occurred approximately 15-21 months following brachytherapy. For biochemically disease-free patients, the median PSA increase above nadir was 0.1 ng/mL, and the median number of consecutive rises in PSA was 1. Using the ASTRO and Houston definitions, only 2.3% and 0.6% of patients would have been inadvertently scored as failures. CONCLUSIONS: In brachytherapy patients receiving 3-6 months of neoadjuvant androgen deprivation therapy, the median PSA increase above nadir was 0.1 ng/mL. The ASTRO and Houston definitions of biochemical failure inadvertently scored only 2.3% and 0.6% of patients as failures.     

Predictive factors of long-term rectal toxicity following permanent iodine-125 prostate brachytherapy with or without supplemental external beam radiation therapy in 2216 patients

PurposeWe analyzed factors associated with rectal toxicity after iodine-125 prostate brachytherapy (BT) with or without external beam radiation therapy (EBRT).Methods and MaterialsIn total, 2216 prostate cancer patients underwent iodine-125 BT with or without EBRT between 2003 and 2013. The median followup was 6.9 years. Cox proportional hazards modeling was used for univariate and multivariate analyses to assess clinical and dosimetric factors associated with rectal toxicity. Dosimetric parameters from 1 day after implantation (Day 1) and 1 month after implantation (Day 30) were included in the analyses.ResultsThe 7-year cumulative incidence of Grade 2 or higher rectal toxicity was 5.7% in all patients. The multivariate analysis revealed that antiplatelet or anticoagulant therapy, neoadjuvant androgen deprivation therapy, treatment modality, Day 1 rectal volume receiving 100% of the prescribed dose (RV₁₀₀), and the Day 30 minimal percent of the prescribed dose delivered to 30% of the rectum (RD₃₀) were associated with rectal toxicity. Day 1 RV₁₀₀ was a common predictor in both BT-alone and the BT + EBRT groups. The 5-year cumulative incidence of Grade 2 or higher rectal toxicity was 12.6%, 5.9%, and 1.7% for BT + 3-dimensional conformal radiation therapy, BT + intensity-modulated radiation therapy, and the BT-alone groups, respectively (p < 0.001).ConclusionsRectal dosimetric parameters in BT were associated with late rectal toxicity. Although the risk of rectal toxicity was higher when EBRT was combined with BT, with proper and achievable rectal dose constraints intensity-modulated radiation therapy yielded less toxicity than 3-dimensional conformal radiation therapy.     

Dynamic swallowing study and radiation dose to patients

PURPOSE: The purpose of this study was to define an optimal radiological procedure to evaluate the results of rehabilitation therapy for swallowing disorders and to calculate both the effective and organ dose to the patient to provide a measure of the radiation risk associated with the procedure. MATERIALS AND METHODS: In order to define the optimal radiological procedure, kerma-area product (KAP) measurements and evaluations of image quality in fluoroscopy and fluorography mode were made using dedicated phantoms. Twenty-two patients were included in the study, and the values of KAP, screening time and average voltage selected were individually recorded. The recorded KAP values were used to estimate radiation risk with the use of dedicated calculation software. RESULTS: Median, first and third quartiles of the KAP distribution were, respectively, 2.1, 1.5 and 2.7 Gy cm2, with a corresponding effective dose of 0.35, 0.26 and 0.46 mSv. A good correlation between KAP and exposure time was also found (R2=0.85). Exposure of the thyroid, which is inside the radiation field, accounts for the greatest share to the effective dose, with a calculated median dose of 6 mGy. CONCLUSIONS: With the defined radiological procedure, the obtained KAP values are lower than recorded doses in interventional radiology, and the corresponding values of entrance skin dose are lower than the threshold dose for deterministic effects. Considering the effective dose at the median KAP value, the probability for stochastic effects is shown to be low, at approximately 1 in 39,000.     

Relationship of the International Prostate Symptom score with urinary flow studies, and catheterization rates following 125I prostate brachytherapy

PURPOSE: Prostate cancer patients undergoing 125I brachytherapy were reviewed. A relationship between pretreatment risk factors including International Prostate Symptom (IPS) score, urinary flow studies, and posttreatment urinary morbidity was assessed. METHODS AND MATERIALS: Pretreatment IPS scores and urinary flow studies on 207 patients were reviewed. Relationship between scores and acute urinary morbidity was evaluated. RESULTS: Median age, 64 years; median baseline IPS score, 9; median prostate volume, 36 cc. Catheterization was required in 18% of patients. Baseline IPS score and peak flow rate (PFR) varied inversely, demonstrating that PFR for patients requiring a catheter was lower than that for those not requiring catheterization. Univariate regression showed that prostate volume, prior hormone therapy, and PFR were statistically predictive of postimplant urinary retention. For every one-unit increase in PFR, the odds of catheterization decreased by 6%. Multivariate analysis demonstrated that only PFR and prostate volume were predictive of postimplant urinary retention. CONCLUSIONS: Pretreatment IPS questionnaire and urinary flow studies assist in predicting risk of urinary morbidity and retention post-125I brachytherapy for prostate cancer.