ONE SHOT - single shot radiotherapy for localized prostate cancer: 18-month results of a single arm, multicenter phase I/II trial.

PURPOSE: To assess in a prospective, multicenter, single-arm phase I/II study the early safety and efficacy profile of single fraction urethra-sparing stereotactic body radiotherapy (SBRT) for men with localized prostate cancer. MATERIAL AND METHODS: Patients with low- and intermediate-risk localized prostate cancer without significant tumor in the transitional zone were recruited. A single-fraction of 19 Gy was delivered to the prostate, with 17 Gy dose-reduction to the urethra. Intrafraction motion was monitored using intraprostatic electromagnetic transponders with intra-fraction correction of displacements exceeding 3 mm. Genitourinary (GU), gastrointestinal (GI), and sexual toxicity during the first 18 months were evaluated using the CTCAE v4.0 grading scale. Quality of life was assessed using the International Prostate Symptom Score, the Expanded Prostate Cancer Index composite 26 score, and the International Index of Erectile Function score. RESULTS: Among the 45 patients recruited in 5 centers between 2017 and 2022, 43 received the single fraction without protocol deviations, and 34 had a minimal follow-up of 18 months. The worst GU toxicity was observed at day-5 after SBRT (42.5 % and 20 % with grade 1 and 2, respectively), returning to baseline at week-12 and month-6 (<3% with grade 2), with a 12 % grade 2 flare at month 18. Gl toxicity was mild in the acute phase, with no grade ≥ 2 events (12 % grade 1 at month 6). Grade-3 proctitis was observed in one patient at month 12, with < 3 % grade 2 toxicity at month 18. Mean GU and GI bother scores showed a decline at day 5, a complete recovery at month 6, and a flare between month 12 and 18. Mean PSA dropped from 6.2 ng/ml to 1.2 ng/ml at month 18 and 0.7 ng/ml at month 24. After a median follow-up time of 26 months, 3 biochemical failures (7 %) were observed at month 17, 21 and 30. CONCLUSIONS: In this multicenter phase I/II trial, we demonstrated that a 19 Gy single-fraction urethra-sparing SBRT is feasible and associated with an acceptable toxicity rate, mostly returning to the baseline at week-12 and with a symptoms flare between months 12 and 18. Longer follow-up is needed to assess the potential long-term adverse effects and the disease control efficacy.

Urethral and bladder dose-effect relations for late genitourinary toxicity following external beam radiotherapy for prostate cancer in the FLAME trial.

PURPOSE OR OBJECTIVES: The FLAME trial (NCT01168479) showed that by adding a focal boost to conventional fractionated EBRT in the treatment of localized prostate cancer, the five-year biochemical disease-free survival increased, without significantly increasing toxicity. The aim of the present study was to investigate the association between radiation dose to the bladder and urethra and genitourinary (GU) toxicity grade ≥2 in the entire cohort. MATERIAL AND METHODS: The dose-effect relations of the urethra and bladder dose, separately, and GU toxicity grade ≥2 (CTCAE 3.0) up to five years after treatment were assessed. A mixed model analysis for repeated measurements was used, adjusting for age, diabetes mellitus, T-stage, baseline GU toxicity grade ≥1 and institute. Additionally, the association between the dose and separate GU toxicity subdomains were investigated. RESULTS: Dose-effect relations were observed for the dose (Gy) to the bladder D2 cm3 and urethra D0.1 cm3, with adjusted odds ratios of 1.14 (95% CI 1.12-1.16, p < 0.0001) and 1.12 (95% CI 1.11-1.14, p < 0.0001), respectively. Additionally, associations between the dose to the urethra and bladder and the subdomains urinary frequency, urinary retention and urinary incontinence were observed. CONCLUSION: Further increasing the dose to the bladder and urethra will result in a significant increase in GU toxicity following EBRT. Focal boost treatment plans should incorporate a urethral dose-constraint. Further treatment optimization to increase the focal boost dose without increasing the dose to the urethra and other organs at risk should be a focus for future research, as we have shown that a focal boost is beneficial in the treatment of prostate cancer.

Prostate Stereotactic Body Radiation Therapy: An Overview of Toxicity and Dose Response.

PURPOSE: Ultrahypofractionationed radiation therapy for prostate cancer is increasingly studied and adopted. The American Association of Physicists in Medicine Working Group on Biological Effects of Hypofractionated Radiotherapy therefore aimed to review studies examining toxicity and quality of life after stereotactic body radiation therapy (SBRT) for prostate cancer and model its effect. METHODS AND MATERIALS: We performed a systematic PubMed search of prostate SBRT studies published between 2001 and 2018. Those that analyzed factors associated with late urinary, bowel, or sexual toxicity and/or quality of life were included and reviewed. Normal tissue complication probability modelling was performed on studies that contained detailed dose/volume and outcome data. RESULTS: We found 13 studies that examined urinary effects, 6 that examined bowel effects, and 4 that examined sexual effects. Most studies included patients with low-intermediate risk prostate cancer treated to 35-40 Gy. Most patients were treated with 5 fractions, with several centers using 4 fractions. Endpoints were heterogeneous and included both physician-scored toxicity and patient-reported quality of life. Most toxicities were mild-moderate (eg, grade 1-2) with a very low overall incidence of severe toxicity (eg, grade 3 or higher, usually <3%). Side effects were associated with both dosimetric and non-dosimetric factors. CONCLUSIONS: Prostate SBRT appears to be overall well tolerated, with determinants of toxicity that include dosimetric factors and patient factors. Suggested dose constraints include bladder V(Rx Dose)Gy <5-10 cc, urethra Dmax <38-42 Gy, and rectum Dmax <35-38 Gy, though current data do not offer firm guidance on tolerance doses. Several areas for future research are suggested.

Toxicity and clinical outcomes of single-fraction high-dose-rate brachytherapy combined with external beam radiotherapy for high-/very high-risk prostate cancer: A dosimetric analysis of toxicity.

PURPOSE: The purpose of this study was to investigate the clinical outcomes, urinary function, quality of life (QOL), and toxicities in high- or very high-risk prostate cancer patients undergoing single-fraction high-dose-rate brachytherapy (HDR-BT) with external beam radiotherapy (EBRT) and analyze the relationship between dosimetric parameters and toxicities. MATERIALS AND METHODS: Between April 2014 and April 2019, 124 patients underwent 13-Gy HDR-BT followed by EBRT (46 Gy/23 fractions). Urinary function and QOL were evaluated using IPSS and 7-grade QOL Scale, respectively. Biochemical progression-free survival (bPFS) was calculated. RESULTS: Median follow-up period was 35.8 months; all patients received neoadjuvant hormonal therapy and very high-risk patients received adjuvant hormonal therapy. Only one patient developed a grade 3 toxicity (hematuria). Multivariate analysis showed the dose covering 30% of the urethral volume, bladder volume receiving 75% of the dose, and dose covering 2 cc of rectum were independent predictors of acute G2 urinary frequency, acute G2 urinary retention, and late G2 rectal hemorrhage. IPSS and QOL scores significantly increased following HDR-BT and returned to baseline within 6 months. The 2-year bPFS was 99.2%. CONCLUSION: The single-fraction HDR-BT with EBRT is a safe treatment for quicker recovery of urinary symptoms and QOL. The dose of at-risk organs correlated with toxicities. Single-fraction high-dose-rate brachytherapy (HDR-BT) combined with external beam radiotherapy (EBRT) for prostate cancer is a safe treatment allowing for quicker recovery of urinary symptoms and QOL. The dose of at-risk organs correlated with toxicities.

Rectal and Urethro-Vesical Subregions for Toxicity Prediction After Prostate Cancer Radiation Therapy: Validation of Voxel-Based Models in an Independent Population.

PURPOSE: Recent voxel-based studies have shown that the dose to specific rectal and urethro-vesical subregions is predictive of toxicities after prostate cancer intensity modulated radiation therapy. The objective of this study was to validate the discriminatory power of these subregions with respect to the whole organs in a large independent population. METHODS AND MATERIALS: The validation cohort consisted of 450 patients from the TROG03.04-RADAR trial treated with 3-dimensional conformal radiation therapy at 66 to 74 Gy. Previous voxel-based analyses identified an inferoanterior rectal subregion as predictive of rectal bleeding and 5 subregions in the urethra and the posterior and superior part of the bladder as predictive of urinary incontinence, dysuria, retention, and hematuria. In the validation cohort, these subregions were segmented in each patient's anatomy. Dose-volume histograms (DVHs) of the whole organs and the 6 subregions were compared bin-wise between patients with and without toxicities. The discriminatory power of DVHs for grade ≥2 toxicity endpoints was assessed using the area under the receiver operating characteristic curve (AUC). RESULTS: Subregion DVHs were significantly different between patients with and without toxicities for late rectal bleeding (V44-V74), acute urinary incontinence (V68-V72), late dysuria (V56-V68), and late retention (V14-V64). The dose to the rectal subregion and the whole rectum were equally predictive of rectal bleeding (V68; AUC = 0.61). The doses to 3 out of the 5 urethro-vesical subregions were found to be more predictive than the dose to the whole bladder: in the urethra for acute incontinence (V71 AUC = 0.69 vs V71 AUC = 0.66), in the posterior part of the bladder for late dysuria (V65 AUC = 0.66 vs V68 AUC = 0.59), and late retention (V39 AUC = 0.74 vs no significant AUC). CONCLUSIONS: Three subregions located in the urethra and the bladder were successfully validated as more predictive of urinary toxicity than the whole bladder for urinary incontinence, retention, and dysuria. Sparing the posterior part of the bladder in particular in treatment planning may reduce the risk of late urinary retention.

A UK wide study of current prostate planning practice.

OBJECTIVES: The objective of this work was to undertake a non-judgemental study of prostate planning practice across the UK by inviting all departments to undertake the same case. METHODS: An invitation to take part in the study was sent to the Heads of all UK radiotherapy departments and posted on the UK Medical Physics mailbase. Individuals interested in participating were able to access a single anonymised CT dataset for download with the prostate gland, seminal vesicles, bladder, rectum, bowel, femoral heads, and penile bulb outlined. A brief patient history was also supplied. Participants were asked to create planning target volumes (PTVs) according to their local clinical protocol and plan to give 60 Gy in 20 fractions to the PTV receiving the highest dose. No guidance was given for acceptable organ at risk doses. Dicom plan and dose information was loaded back into ProKnow for analysis by contributors. RESULTS: There were 102 plan submissions made to the study representing 48 different UK radiotherapy departments. Seventeen distinct methodologies for creating the prescription PTV from the prostate and seminal vesicles were identified with the ethos of the CHHIP trial protocol for margin growing followed in nearly two-thirds of cases. Positive correlations were found when assessing the doses received by the bladder and rectum against the volume of the PTV to which 60 Gy was prescribed. CONCLUSIONS: A national planning study whereby staff from a multitude of radiotherapy departments create plans based solely on a single dataset is feasible. The cohort of data was made available to all participants following the study to enable self-assessment and benchmarking against that of their peers. ADVANCES IN KNOWLEDGE: This is the first UK wide treatment planning study to investigate local clinical prostate planning practice. This has given UK departments the opportunity to evaluate their planning practices against those of their peers.

Evaluation of the urethral α/ß ratio and tissue repair half-time for iodine-125 prostate brachytherapy with or without supplemental external beam radiotherapy.

PURPOSE: To assess the correlation between postimplant dosimetric quantifiers and the genitourinary (GU) toxicity of low-dose rate brachytherapy for prostate cancer. METHODS AND MATERIALS: The minimum urethral dose (UD10, 30, and 90) and the percent volume of the urethra receiving the prescription dose (V100, V150) were calculated from the postimplant dose-volume histograms of 182 patients. We then calculated various urethral biologically equivalent doses (uBEDs) using different values of the α/ß ratio and tissue repair half-time (t1/2) and examined the correlations with GU toxicity. RESULTS: Common dosimetric quantifiers, such as UD90 (brachytherapy) + UD50 (external beam radiotherapy), showed no correlation with Grade ≥ 2 GU toxicity. There was a significant correlation between Grade ≥2 GU toxicity and uBED when the α/ß value was 0.5 or 1 Gy and t1/2 was 0.5-2.5 h. An uBED (α/ß = 1.0, t1/2 = 0.5) had the largest hazard ratio for GU toxicity, and it was also significantly correlated with Grade ≥ 2 GU toxicity according to multivariate analysis. CONCLUSIONS: We observed a significant correlation of uBED with GU toxicity when α/ß was 0.5 or 1.0 Gy and t1/2 was 0.5-2.5 h. As the simple formula we used has not been verified in basic experiments, more data are needed to validate our results.

A pilot study on dosimetric and radiomics analysis of urethral strictures following HDR brachytherapy as monotherapy for localized prostate cancer.

OBJECTIVE: A cohort of high dose-rate (HDR) monotherapy patients was analyzed to (i) establish the frequency of non-malignant urethral stricture; (ii) explore the relation between stricture formation with the dose distribution along the length of the urethra, and MRI radiomics features of the prostate gland. METHODS: A retrospective review of treatment records of patients who received 19 Gy single fraction of HDR brachytherapy (BT) was carried out. A matched pair analysis used one control for each stricture case matched with pre-treatment International Prostate Symptom Score (IPSS) score, number of needles used and clinical target volume volume for each stricture case identified.For all data sets, pre-treatment T2 weighted MRI images were used to define regions of interests along the urethra and within the whole prostate gland. MRI textural radiomics features-energy, contrast and homogeneity were selected. Wilcoxon signed-rank test was performed to investigate significant differences in dosimetric parameters and MRI radiomics feature values between cases and controls. RESULTS: From Nov 2010 to July 2017, there were 178 patients treated with HDR BT delivering 19 Gy in a single dose. With a median follow-up of 28.2 months, a total of 5/178 (3%) strictures were identified.10 patients were included in the matched pair analysis. The urethral dosimetric parameters investigated were not statistically different between cases and controls (p > 0.05). With regards to MRI radiomics feature analysis, significant differences were found in contrast and homogeneity between cases and controls (p < 0.05). However, this did not apply to the energy feature (p = 0.28). CONCLUSION: In this matched pair analysis, no association between post-treatment stricture and urethral dosimetry was identified. Our study generated a preliminary clinical hypothesis suggesting that the MRI radiomics features of homogeneity and contrast of the prostate gland can potentially identify patients who develop strictures after HDR BT. Although the sample size is small, this warrants further validation in a larger patient cohort. ADVANCES IN KNOWLEDGE: Urethral stricture has been reported as a specific late effect with prostate HDR brachytherapy. Our study reported a relatively low stricture rate of 3% and no association between post-treatment stricture and urethral dosimetry was identified. MRI radiomics features can potentially identify patients who are more prone to develop strictures.

Single fraction urethra-sparing prostate cancer SBRT: Phase I results of the ONE SHOT trial.

The ONE SHOT trial is the first phase I/II prospective, multicenter, single-arm study assessing the efficacy and safety of a single-dose SBRT for men with localized prostate cancer. Aim of this paper is to present the phase I results of a 19 Gy single fraction urethra-sparing SBRT with real-time electromagnetic tracking.

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

PURPOSE: This study characterizes prostatic urethra cross-section to develop a surrogate urethra for accurate prediction of urethral dose during real-time high-dose-rate prostate brachytherapy. MATERIALS AND METHODS: Archived preoperative transrectal ultrasound images from 100 patients receiving low-dose-rate prostate brachytherapy were used to characterize the prostatic urethra, contoured on ultrasound using aerated gel. Consensus contours, defined using majority vote, described commonalities in cross-sectional shape across patients. Potential simplified surrogates were defined and evaluated against the true urethra. The best performing surrogate, a circle of varying size (CS) was retrospectively contoured on 85 high-dose-rate prostate brachytherapy treatment plans. Dose to this recommended surrogate was compared with urethral doses estimated by the standard 6 mm circle surrogate. RESULTS: Clear variation in urethral cross-sectional shape was observed along its length and between patients. The standard circle surrogate had low predictive sensitivity (61.1%) compared with true urethra because of underrepresentation of the verumontanum midgland. The CS best represented the true urethra across all validation metrics (dice: 0.73, precision: 67.0%, sensitivity: 83.2%, conformity: 0.78). Retrospective evaluation of planned doses using the CS surrogate resulted in significant differences in all reported urethral dose parameters compared with the standard circle, with the exception of D100%. The urethral dose limit (115%) was exceeded in 40% of patients for the CS surrogate. CONCLUSIONS: The proposed CS surrogate, consisting of circles of varying diameter, is simple yet better represents the true urethra compared with the standard 6 mm circle. Higher urethral doses were predicted using CS, and the improved accuracy of CS may offer increased predictive power for urethral toxicity, a subject of future work.

[Urethral sarcoma 14 years after brachytherapy of the prostate gland]. / Urethrasarkom 14 Jahre nach Prostata-Brachytherapie.

We report a case of an 83-year-old male patient with the rare diagnosis of a urethral sarcoma.

Dose to the bladder neck in MRI-guided high-dose-rate prostate brachytherapy: Impact on acute urinary toxicity and health-related quality of life.

PURPOSE: To assess the impact of the dose to the bladder neck (BN) on acute urinary toxicity (AUT) and health-related quality of life (uHRQoL) in patients with prostate cancer treated with MRI-guided high-dose-rate brachytherapy combined to external beam radiotherapy. METHODS AND MATERIALS: Sixty-one patients were treated with a single 15-Gy MRI-guided high-dose-rate brachytherapy followed by external beam radiotherapy as part of a prospective Phase II trial. The BN was delineated in retrospect on T2-weighted images. AUT and uHRQoL data were collected prospectively using Common Terminology Criteria for Adverse Events version 4.0 and the expanded prostate index composite. A minimally important difference (MID) was defined as a deterioration of uHRQoL scores at 3 months ≥ 0.5 standard deviation of baseline score. Linear and logistic regression models were used. RESULTS: The median BN volume was 0.6 cc. The median BN and urethral maximum dose (BNDmax and UDmax) were 22 Gy and 20 Gy, respectively. BNDmax was significantly associated with UDmax (p = 0.03). AUT Grade 2 + was observed in 32% of patients. Among those, 4 patients had an acute urinary retention (AUR). No Grade 4 + toxicity was reported. At 3 months, 47% of patients reported an MID in urinary uHRQoL. None of the dosimetric parameters including BNDmax was associated with acute Grade 2 + urinary toxicity or MID. However, 3 of 4 patients with AUR had a BNDmax in the highest quartile; >175% of prescription dose. CONCLUSIONS: Although a high BN dose was observed in patients who had an AUR, the predictive value of this parameter is yet to be determined in a larger cohort.

Interobserver variability of 3.0-tesla and 1.5-tesla magnetic resonance imaging/computed tomography fusion image-based post-implant dosimetry of prostate brachytherapy.

This study aimed to compare the interobserver variabilities in magnetic resonance imaging (MRI)/computed tomography (CT) fusion image-based post-implant dosimetry of permanent prostate brachytherapy (PPB) between 1.5-T and 3.0-T MRI. The study included 60 patients. Of these patients, 30 underwent 1.5-T MRI and CT 30 days after seed implantation (1.5-T group), and 30 underwent 3.0-T MRI and CT 30 days after seed implantation (3.0-T group). All patients received PPB alone. Two radiation oncologists performed MRI/CT fusion image-based post-implant dosimetry, and the interobserver variabilities of dose-volume histogram (DVH) parameters [dose (Gy) received by 90% of the prostate volume (prostate D90)], percentage of the prostate volume receiving at least the full prescribed dose (prostate V100), percentage of the prostate volume receiving at least 150% of the prescribed dose (prostate V150), dose (Gy) received by 5% of the urethral volume (urethral D5) and the urethral volume receiving at least 150% of the prescribed dose (urethral V150)] were retrospectively estimated using the paired Student's t test and Pearson's correlation coefficient. The Pearson's correlation coefficients of all DVH parameters were higher in the 3.0-T group than in the 1.5-T group (1.5-T vs 3.0-T: prostate D90, 0.65 vs 0.93; prostate V100, 0.62 vs 0.82; prostate V150, 0.97 vs 0.98; urethral D5, 0.92 vs 0.93; and urethral V150, 0.88 vs 0.93). In the paired Student's t test, no significant differences were observed in any of the DVH parameters between the two radiation oncologists in the 3.0-T group (0.068 ≤ P ≤ 0.842); however, significant differences were observed in prostate D90 (P = 0.004), prostate V100 (P = 0.011) and prostate V150 (P = 0.002) between the oncologists in the 1.5-T group. The interobserver variability of DVH parameters in the MRI/CT fusion image-based post-implant dosimetry analysis of brachytherapy was lower with 3.0-T MRI than with 1.5-T MRI.

Expanded validation of the EPIC bowel and urinary domains for use in women with gynecologic cancer undergoing postoperative radiotherapy.

OBJECTIVE: Women with endometrial or cervical cancer at risk for recurrence receive postoperative radiation therapy (RT). A patient reported outcomes (PRO) instrument to assess bowel and urinary toxicities is the Expanded Prostate Cancer Index Composite (EPIC), which has been validated in men with prostate cancer. As this instrument specifically measures bowel toxicity and the degree to which this is a problem, it was used in NRG Oncology/RTOG 1203 to compare intensity modulated RT (IMRT) to standard RT. This paper reports on the expanded validation of EPIC for use in women receiving pelvic RT. METHODS: In addition to the EPIC bowel domain, urinary toxicity (EPIC urinary domain), patient reported bowel toxicities (PRO-CTCAE) and quality of life (Functional Assessment of Cancer Therapy (FACT)) were completed before, during and after treatment. Sensitivity, reliability and concurrent validity were assessed. RESULTS: Mean bowel and urinary scores among 278 women enrolled were significantly worse during treatment and differed between groups. Acceptable to good reliability for bowel and urinary domain scores were obtained at all time points with the exception of one at baseline. Correlations between function and bother scores within the bowel and urinary domains were consistently stronger than those across domains. Correlations between bowel domain scores and PRO-CTCAE during treatment were stronger than those with the FACT. CONCLUSION: Correlations within and among the instruments indicate EPIC bowel and urinary domains are measuring conceptually discrete components of health. These EPIC domains are valid, reliable and sensitive instruments to measure PRO among women undergoing pelvic radiation.

Observation and mechanism study of bladder wound healing after transurethral holmium laser resection of bladder tumor.

This research aims to observe and compare the wound healing process of urethral bladder after transurethral holmium laser resection of bladder tumor (HoLRBT) and transurethral resection of bladder tumor (TURBT) and explore the possible mechanism of wound healing and bladder re-epithelialization after HoLRBT. An animal model of canine achieving HoLRBT and TURBT was established. Cystoscopy was performed at different time points (3 days and 1, 2, 3, and 4 weeks) after operation to observe the wound healing and re-epithelialization of bladder epithelium. Bladder mucosa specimens were obtained and histopathological changes of the bladder epithelium were observed under light microscope after HE staining. Immunochemistry was used to determine the cell expression ofCK5, CK14, EGF, EGFR; microRNA expressions of CK5, CK14, EGF, and EGFR were measured by qRT-PCR. The changes of urinary EGF concentration were detected by ELISA. The bladder epithelial wound was repaired and re-epithelialized at 1 week after HoLRBT. At the 4th week, the bladder wound was basically completed and re-epithelialized; repair of bladder epithelial wounds recapitulates the wounds with the proliferation and migration of residual epithelial cells under the wound and the bladder epithelium that proliferates alongside the wound surface to complete re-epithelialization. The process begins at 1 week after surgery and basically completes at 4 weeks after surgery. CK5 and CK14 positive cells were detected in the basal cells of the bladder epithelium after HoLRBT, and the expression of CK5 and CK14 mRNA in the basal cells of the bladder epithelium under hyperplasia was significantly higher than that of the normal bladder epithelial basal cells. Bladder epithelial wound repair of TURBT group was performed by the proliferative differentiation of the peri-bladder epithelium adjacent to the wound edge and crawled to the wound surface to complete the re-epithelialization process. The wound repair and re-epithelialization were significantly slower than HoLRBT group. The CK5 and CK14 positive cells can also be detected in the basal cells of marginal hyperplasia of basal margin, and the expression of CK5 and CK14 mRNA in the basal cells of the peri-bladder hyperplasia is obviously higher than that of the normal bladder epithelial basal cells. The expression of EGF in bladder regenerating epithelium gradually increased with time after HoLRBT. Bladder basal cells and bladder regenerating epithelium express high levels of EGFR after HoLRBT. The concentration of EGF in urine after HoLRBT and TURBT increased significantly after surgery, and peaked at 3 days after operation. The urinary EGF concentration in HoLRBT group was higher than that in TURBT group at 3 and 4 weeks after operation. The re-epithelialization process can be seen 1 week after the cystectomy with holmium laser cystectomy, and the epithelialization rate is faster than the traditional transection surgery. This is because the residual bladder epithelial stem cells and wound marginal epithelial cells are involved in the process of wound repair and re-epithelialization following HoLRBT. But only the marginal epithelial tissue participates in the re-epithelialization process after TURBT, so the repair rate of TURBT is slower. The repair of bladder epithelium after HoLRBT is related to the stimulation of tissue factor EGF. The regenerated bladder epithelium also participates in the wound repair process by means of autocrine of EGF.

A stochastic frontier analysis for enhanced treatment quality of high-dose-rate brachytherapy plans.

The purpose of the present study is to develop patient specific unbiased quality control (QC) models for high dose rate (HDR) brachytherapy plans. The proposed models are based on the stochastic frontier analysis formalism, a method of economic modeling. They act as a QC tool by predicting before the treatment planning process starts, the dosimetric coverage achievable for a HDR brachytherapy prostate plan. The geometric parameters considered in developing the models were: patient clinical target volume (CTV), organs at risk (OAR) volume, the bidirectional Hausdorff distance between CTV and OARs, and a fourth parameter measuring the catheters degree of non-parallelism within the target volume. Dosimetry parameters of interest are V100 for the CTV, V75 (bladder, rectum) and D10 (urethra). Results show that the built models can provide valuable information on the personalization of the optimization process based on the patient geometric parameters. The impact on the quality plan due to the planner's experience variability and judgment can be reduced by using those models, since the planner will attempt to achieve dosimetric parameters predicted by the models. Furthermore, the models provide information on the better trade-off between the target volume coverage and OARs sparing that can be achieved, regardless of the planner's experience; the latter being achieved by moving each plan at least around their respective frontier for V100, V75 and D10. The shortfall of the dosimetric parameters values computed by the treatment planning system (TPS) from those predicted by the models for a proportion of plans in the dataset reveals that optimized plans from a TPS, even clinically acceptable, are not necessarily the best that could be achieved. These represent 83% of plans in the training set for the target volume coverage (V100), ∼50% for the bladder (V75) and ∼72% for the urethra (D10).

Voxel-Based Analysis for Identification of Urethrovesical Subregions Predicting Urinary Toxicity After Prostate Cancer Radiation Therapy.

PURPOSE: To apply a voxel-based analysis to identify urethrovesical symptom-related subregions (SRSs) associated with acute and late urinary toxicity in prostate cancer radiation therapy. METHODS AND MATERIALS: Two hundred seventy-two patients with prostate cancer treated with intensity-modulated radiation therapy/image-guided radiation therapy were analyzed prospectively. Each patient's computed tomography imaging was spatially normalized to a common coordinate system via nonrigid registration. The obtained deformation fields were used to map the dose of each patient to the common coordinate system. A voxel-based statistical analysis was applied to generate 3-dimensional dose-volume maps for different urinary symptoms, allowing the identification of corresponding SRSs with statistically significant dose differences between patients with or without toxicity. Each SRS was propagated back to each individual's native space, and dose-volume histograms (DVHs) for the SRSs and the whole bladder were computed. Logistic and Cox regression were used to estimate the SRS's prediction capability compared with the whole bladder. RESULTS: A local dose-effect relationship was found in the bladder and the urethra. SRSs were identified for 5 symptoms: acute incontinence in the urethra, acute retention in the bladder trigone, late retention and dysuria in the posterior part of the bladder, and late hematuria in the superior part of the bladder, with significant dose differences between patients with and without toxicity, ranging from 1.2 to 9.3 Gy. The doses to the SRSs were significantly predictive of toxicity, with maximum areas under the receiver operating characteristic curve of 0.73 for acute incontinence, 0.62 for acute retention, 0.70 for late retention, 0.81 for late dysuria, and 0.67 for late hematuria. The bladder DVH was predictive only for late retention, dysuria, and hematuria (area under the curve, 0.65-0.72). CONCLUSIONS: The dose delivered to the urethra and the posterior and superior parts of the bladder was predictive of acute incontinence and retention and of late retention, dysuria, and hematuria. The dose to the whole bladder was moderately predictive.

Institutional patient accrual volume and the treatment quality of I­125 prostate seed implantation in a Japanese nationwide prospective cohort study.

PURPOSE: It is unclear whether experience at high-volume institute improves the treatment quality of prostate seed implantation. The aim of this study was to evaluate the effect of institutional experience on postimplant dosimetric parameters in a nationwide prospective cohort study. METHODS: From July 2005 to June 2007, 2354 patients were registered in the Japanese Prostate Cancer Outcome Study of Permanent I­125 Seed Implantation (J-POPS), and 1126 patients treated with seed implantation alone were evaluated. As a surrogate for institutional experience, we classified the J­POPS institutions as high-volume (patient accrual volume was ≥120 patients per institution) or low-volume institutions (patient accrual volume was <120 patients per institution). To compare treatment quality between institutions, we evaluated the postimplant dosimetric parameters including D90, V100/150 (prostatic dose parameters), UD5/90, U200 (urethral dose parameters), and rectum R100/150 (rectal dose parameters). RESULTS: In the 5 high-volume institutions (n = 601 patients), most of the patients were treated with >144 Gy of D90, whereas in the 20 low-volume institutions (n = 525) some of the patients were treated with <144 Gy. The V100 of most of the high-volume institution patients were >90%, whereas in the low-volume institutions a considerable percentage of patients showed lower V100. Although there was no correlation between D90 and rectal dose parameters, UD90 had a moderate positive correlation with D90 in both the high- and low-volume institutions. U200 varied more widely in the low-volume institutions. CONCLUSIONS: Our findings indicate that the institutional patient accrual volume is associated with the treatment quality of I­125 prostate seed implantation.

Health-related Quality of Life and Toxicity After Single-fraction High-dose-rate Brachytherapy With External Beam Radiotherapy for Localized and Locally Advanced Prostate Cancer.

BACKGROUND/AIM: To evaluate the treatment outcomes, toxicity and health-related quality of life (HRQOL) in prostate cancer (PCa) patients who underwent single-fraction high-dose-rate brachytherapy (single-fraction HDR-BT) with external beam radiotherapy (EBRT). MATERIALS AND METHODS: From April 2014 to October 2017, treatment outcomes and toxicity of 85 patients who underwent single-fraction HDR-BT of 13 Gy, followed by 46 Gy EBRT in 23 fractions, were examined. HRQOL of 53 patients was evaluated using the Expanded Prostate Cancer Index Composite (EPIC), International Prostate Symptom Score (IPSS)/QOL index, International Index of Erectile Function 5 (IIEF-5), and 36-Item Short Form Survey (SF-36) scores through one year. RESULTS: The median follow-up period was 28.8 months. Only three patients had biochemical recurrence. Toxicities included less than grade 3 lower urinary tract symptoms and grade 1 diarrhea. Urethral stricture, a problem related to late toxicity in conventional HDR-BT, was not observed. The urinary and bowel functions in EPIC scores significantly worsened until three or six months after treatment, respectively. CONCLUSION: Single-fraction HDR-BT with EBRT showed promising biochemical control, tolerant toxicities, and preservation of HRQOL, and can be efficiently performed in a shorter time than conventional HDR-BT.