Korean Society of Endourology and Robotics (KSER) recommendation on the diagnosis, treatment, and prevention of urolithiasis.

This article provides evidence-based recommendations and expert opinions to aid urologists in making optimal decisions regarding managing urolithiasis in various clinical scenarios. The most frequently asked questions by urologists in their clinical practice have been collected and answered in the form of FAQs; based on the latest evidence and expert opinions. The natural history of urolithiasis is divided into active treatment and silent phases, with the active treatment stage divided into typical and special situations and peri-treatment management. The authors address 28 key questions, offering practical guidance for the proper diagnosis, treatment, and prevention of urolithiasis in clinical practice. This article is expected to be served as a valuable resource for urologists.

The prognostic impact of downgrading and upgrading from biopsy to radical prostatectomy among men with Gleason score 7 prostate cancer.

BACKGROUND: Recently, a new prostate cancer (PC) grading system was introduced, where Gleason score (GS) 7 was divided into 3 + 4 = 7 and 4 + 3 = 7 due to the different prognoses associated with each tumor type. However, whether downgrading or upgrading from needle biopsy (NB) to radical prostatectomy (RP) affects oncologic outcomes is currently unknown. Herein, we investigated the prognostic impact of downgrading and upgrading from NB to RP among men with GS 7 PC. METHODS: We retrospectively reviewed the medical records of 3003 patients with localized PC who underwent RP between 2005 and 2014. We included 692 patients with GS 7 PC on both NB and RP specimens. We analyzed the data using Kaplan-Meier methods and Cox proportional hazard models. RESULTS: Of the 692 patients enrolled in this study, 389 (56.2%) and 303 (43.8%) patients had RP GS 3 + 4 = 7 and RP GS 4 + 3 = 7 PC, respectively. On the basis of NB and RP GS, 264 (38.1%), 125 (18.1%), 142 (20.5%), and 161 (23.3%) patients were classified as 3 + 4/3 + 4, 4 + 3/3 + 4, 3 + 4/4 + 3, and 4 + 3/4 + 3, respectively. Kaplan-Meier curves showed significant differences in biochemical recurrence (BCR)-free survival across the groups (P < .001). In the multivariate analyses, these groups were significantly associated with BCR (4 + 3/3 + 4: hazard ratio [HR], 1.675; 3 + 4/4 + 3: HR, 1.908; and 4 + 3/4 + 3: HR, 2.699). CONCLUSIONS: Downgrading and upgrading from NB to RP was an independent predictor of BCR in men with GS 7 PC, which could be due to the amount of Gleason pattern 4.

Pure single-site robot-assisted pyeloplasty with the da Vinci SP surgical system: Initial experience.

Purpose: Laparoendoscopic single-site surgery (LESS) reduces the limited invasiveness of conventional laparoscopy while providing superior cosmetic results. However, LESS remains a challenging surgical technique, even in robotic surgery, primarily due to the lack of triangulation and limited instrument movement. The da Vinci SP surgical system (Intuitive Surgical) was recently introduced to overcome these limitations. We describe our initial experience with pure single-site robot-assisted pyeloplasty (RAP) for ureteropelvic junction obstruction (UPJO) using the da Vinci SP surgical system. Materials and Methods: Three consecutive patients who were diagnosed with UPJO underwent RAP with the da Vinci SP surgical system from December 2018 to February 2019 at our institution. The surgical technique involved reproducing the steps of multi-port RAP. A 30-mm umbilical incision was made and the GelPOINT was inserted. The multichannel robotic port and the assistant's port were placed through the GelSeal cap. In all patients, Anderson-Hynes dismembered pyeloplasty was performed. The ureteral double J stent was inserted antegrade, and the drain was not placed. Results: The procedures were successfully completed using a pure single-site approach. There was no need for additional port placement or conversion to laparoscopic or open surgery. Total operative time in the three patients was 139, 180, and 213 minutes, respectively. No intraoperative complications occurred, and blood loss was minimal. The postoperative course of all patients was uneventful with no complications greater than Clavien-Dindo grade I surgical complications. Conclusions: Pure single-site RAP using the da Vinci SP surgical system is feasible and safe.

Effect of Diabetes Mellitus on Acute Kidney Injury after Minimally Invasive Partial Nephrectomy: A Case-Matched Retrospective Analysis.

Postoperative acute kidney injury (AKI) is still a concern in partial nephrectomy (PN), even with the development of minimally invasive technique. We aimed to compare AKI incidence between patients with and without diabetes mellitus (DM) and to determine the predictive factors for postoperative AKI. This case-matched retrospective study included 884 patients with preoperative creatinine levels ≤1.4 mg/dL who underwent laparoscopic or robot-assisted laparoscopic PN between December 2005 and May 2018. Propensity score matching was employed to match patients with and without DM in a 1:3 ratio (101 and 303 patients, respectively). Of 884 patients, 20.4% had postoperative AKI. After propensity score matching, the incidence of postoperative AKI in DM and non-DM patients was 30.7% and 14.9%, respectively (P < 0.001). In multivariate analysis, male sex and warm ischemia time (WIT) >25 min were significantly associated with postoperative AKI in patients with and without DM. In patients with DM, hemoglobin A1c (HbA1c) >7% was a predictive factor for AKI, odds ratio (OR) = 4.59 (95% CI, 1.47⁻14.36). In conclusion, DM increased the risk of AKI after minimally invasive PN; male sex, longer WIT, and elevated HbA1c were independent risk factors for AKI in patients with DM.

Clinical Significance of Multiparametric Magnetic Resonance Imaging as a Preoperative Predictor of Oncologic Outcome in Very Low-Risk Prostate Cancer

Currently, multiparametric magnetic resonance imaging (mpMRI) is not an indication for patients with very low-risk prostate cancer. In this study, we aimed to evaluate the usefulness of mpMRI as a diagnostic tool in these patients. We retrospectively analyzed the clinical and pathological data of individuals with very low-risk prostate cancer, according to the NCCN guidelines, who underwent mpMRI before radical prostatectomy at our institution between 2010 and 2016. Patients who did not undergo pre-evaluation with mpMRI were excluded. We analyzed the factors associated with biochemical recurrence (BCR) using Cox regression model, logistic regression analysis, and Kaplan⁻Meier curve. Of 253 very low-risk prostate cancer patients, we observed 26 (10.3%) with BCR during the follow-up period in this study. The median follow-up from radical prostatectomy was 53 months (IQR 33⁻74). The multivariate Cox regression analyses demonstrated that the only factor associated with BCR in very low-risk patients was increase in the pathologic Gleason score (GS) (HR: 2.185, p-value 0.048). In addition, multivariate logistic analyses identified prostate specific antigen (PSA) (OR: 1.353, p-value 0.010), PSA density (OR: 1.160, p-value 0.013), and suspicious lesion on mpMRI (OR: 1.995, p-value 0.019) as the independent preoperative predictors associated with the pathologic GS upgrade. In our study, the pathologic GS upgrade after radical prostatectomy in very low-risk prostate cancer patients demonstrated a negative impact on BCR and mpMRI is a good prognostic tool to predict the pathologic GS upgrade. We believe that the implementation of mpMRI would be beneficial to determine the treatment strategy for these patients.

Predictive Factors and Oncologic Outcome of Downgrade to Pathologic Gleason Score 6⁻7 after Radical Prostatectomy in Patients with Biopsy Gleason Score 8⁻10.

Gleason score (GS) 8⁻10 is associated with adverse outcomes in prostate cancer (PCa). However, biopsy GS (bGS) may be upgraded or downgraded post-radical prostatectomy (RP). We aimed to investigate predictive factors and oncologic outcomes of downgrade to pathologic GS (pGS) 6⁻7 after RP in PCa patients with bGSs 8⁻10. We retrospectively reviewed clinical data of patients with bGS ≥ 8 undergoing RP. pGS downgrade was defined as a pGS ≤ 7 from bGS ≥ 8 post-RP. Univariate and multivariate cox regression analysis, logistic regression analysis, and Kaplan⁻Meier curves were used to analyze pGS downgrade and biochemical recurrence (BCR). Of 860 patients, 623 and 237 had bGS 8 and bGS ≥ 9, respectively. Post-RP, 332 patients were downgraded to pGS ≤ 7; of these, 284 and 48 had bGS 8 and bGS ≥ 9, respectively. Prostate-specific antigen (PSA) levels; clinical stage; and adverse pathologic features such as extracapsular extension, seminal vesicle invasion and positive surgical margin were significantly different between patients with pGS ≤ 7 and pGS ≥ 8. Furthermore, bGS 8 (odds ratio (OR): 0.349, p < 0.001), PSA level < 10 ng/mL (OR: 0.634, p = 0.004), and ≤cT3a (OR: 0.400, p < 0.001) were identified as significant predictors of pGS downgrade. pGS downgrade was a significant positive predictor of BCR following RP in patients with high bGS (vs. pGS 8, hazard radio (HR): 1.699, p < 0.001; vs. pGS ≥ 9, HR: 1.765, p < 0.001). In addition, the 5-year BCR-free survival rate in patients with pGS downgrade significantly differed from that in patients with bGS 8 and ≥ 9 (52.9% vs. 40.7%, p < 0.001). Among patients with bGS ≥ 8, those with bGS 8, PSA level < 10 ng/mL, and ≤cT3a may achieve pGS downgrade after RP. These patients may have fewer adverse pathologic features and show a favorable prognosis; thus we suggest that active treatment is needed in these patients. In addition, patients with high-grade bGS should be managed aggressively, even if they show pGS downgrade.

Probe-Based Confocal Laser Endomicroscopy During Transurethral Resection of Bladder Tumors Improves the Diagnostic Accuracy and Therapeutic Efficacy.

PURPOSE: This study was designed to assess the diagnostic accuracy and therapeutic efficacy of probe-based confocal laser endomicroscopy (pCLE), which provides real-time, in vivo histological information during transurethral resection of bladder tumors. METHODS: We performed a prospective study between August 2013 and August 2014. pCLE was performed on a total of 119 lesions in 75 patients. We analyzed the diagnostic accuracy of pCLE by comparing the confocal image reports with the pathology reports of surgical specimen. Confocal images were interpreted by a single urologist blinded to the pathology reports. The therapeutic efficacy was analyzed by comparing the outcomes in pCLE and non-pCLE groups. RESULTS: In a total of 119 lesions, 23 were benign and 96 were malignant. The detection accuracy for malignant lesions with pCLE was determined with a sensitivity and a positive predictive value (PPV) of 91.7% and 93.6%, respectively. For high-grade versus low-grade bladder cancer, sensitivity and PPV of pCLE were 94.5% and 89.7%, respectively. Distinguishing carcinoma in situ from inflammatory lesions also was accurate with sensitivity, specificity, and PPV of 71.4%, 81.3%, and 83.3%, respectively. The Kaplan-Meier curves revealed that the recurrence-free survival rate was significantly higher in the pCLE group than in the non-pCLE group (p = 0.031). CONCLUSIONS: Probe-based confocal laser endomicroscopy is a promising method to provide the surgeon during the transurethral resection of a bladder tumor with real-time tumor histology, regardless of the tumor's gross appearance. Furthermore, it also may improve the therapeutic efficacy with longer recurrence-free periods.

Effect of prostate gland weight on the surgical and oncological outcomes of extraperitoneal robot-assisted radical prostatectomy.

BACKGROUND: Robot-assisted radical prostatectomy (RARP) is performed by urologists as one of the surgical procedures for treating prostate cancer. Numerous studies have been published with regard to the impact of prostate weight on performing RARP but were limited by the insufficient number of patients and use of the transperitoneal approach. This study aimed to determine the effect of prostate gland weight on the surgical and short-term oncological outcomes of RARP using the extraperitoneal approach. METHODS: In total, 1168 patients who underwent extraperitoneal RARP (EP-RARP) performed by a single surgeon at Yonsei University Severance Hospital between May 2009 and May 2016 were included in the study. The patients were divided into 4 groups according to the prostate weight measured by transrectal ultrasonography preoperatively. Intraoperative and postoperative outcomes were analyzed retrospectively. One-way analysis of variance and the chi-square test were used in the statistical analyses. RESULTS: Age, the Gleason score, clinical stage, and pathological stage were significantly different. Patients with a larger prostate size had a longer console time and higher estimated blood loss (P < 0.05). There were no significant differences between the 4 groups in length of hospital stay, duration of catheterization, blood transfusion, body mass index, prostate-specific antigen (PSA) level, history of abdominal surgery, intraoperative complications, positive surgical margin, incidence of lymphocele, and PSA recurrence after 1 year. CONCLUSIONS: The console time and estimated blood loss were significantly increased with a larger prostate size. However, there were no significant differences in the oncologic outcome and intraoperative complications, suggesting that EP-RARP requires meticulous bleeding control in patients with a prostate weighing > 75 g, and if appropriate management is implemented for blood loss intraoperatively, EP-RARP can be performed regardless of the prostate size.

Clinical significance of multiparametric MRI and PSA density as predictors of residual tumor (pT0) following radical prostatectomy for T1a-T1b (incidental) prostate cancer.

PURPOSE: The aim of this study was to evaluate predictors of residual tumor and clinical prognosis in T1a-T1b (incidental) prostate cancer by analysis of specimens from men undergoing surgery for benign prostatic hyperplasia. MATERIALS AND METHODS: We retrospectively reviewed medical records of incidental prostate cancer patients who had undergone radical prostatectomy. Patients whose tumor statuses were further confirmed by prostate biopsy, or who had used androgen deprivation therapy before radical prostatectomy, were excluded. Clinical and pathological parameters were analyzed to evaluate residual tumor and clinical prognosis. We used univariate and multivariate logistic regression analyses, as well as receiver operator characteristics, to predict residual tumor (pT0). RESULTS: The final analysis included 95 patients. Among these patients, 67 (70.53%) exhibited residual tumor, whereas 28 (29.47%) did not (pT0). Pathology findings showed that 44 (65.67%), 16 (23.88%), and 7 patients (10.45%) exhibited Gleason scores of G6, G7, and ≥G8, respectively. Fifty-seven and 10 patients exhibited pathologic T stages T2 and T3, respectively. Mean follow-up duration was 70.26 (±34.67) months. Biochemical recurrence was observed in 11 patients; none were pT0 patients. Multivariate logistic regression showed that low prostate-specific antigen density after benign prostatic hyperplasia surgery and invisible lesion on multiparametric magnetic resonance imaging were significantly associated with pT0. Additionally, a combination of these factors showed an increase in the diagnostic accuracy of pT0, compared with mpMRI alone (AUC 0.805, 0.767, respectively); this combination showed sensitivity, specificity, and positive predictive values of 71.6%, 89.3%, and 94.1%, respectively. CONCLUSION: Our results suggest that patients with incidental prostate cancer who have both prostate-specific antigen density ≤0.08 after benign prostatic hyperplasia surgery as well as invisible cancer lesion on multiparametric magnetic resonance imaging should be considered for active surveillance.

Clinical significance and predictors of oncologic outcome after radical prostatectomy for invisible prostate cancer on multiparametric MRI.

BACKGROUND: The objective of our study was to evaluate the clinical significance of invisible prostate cancer (iPCa) on multiparametric magnetic resonance imaging (mpMRI) by analyzing clinical parameters and oncologic outcomes. METHODS: We retrospectively reviewed the records of patients treated with radical prostatectomy (RP) from 2010 to 2015 at our institution. Before RP, all patients were confirmed to have prostate cancer based on prostate biopsy. We excluded patients who underwent neoadjuvant therapy. Additionally, we excluded patients who had incomplete mpMRI based on PI-RADS (Prostate Imaging Reporting and Data System). iPCa was defined as having no grade 3 or higher region of interests using a scoring system established by PI-RADS without limitations on interpretation from mpMRI by radiologists. We selected patients with iPCa using this protocol. We analyzed data using univariate and multivariate cox regression analysis, logistic analysis, Kaplan-Meier curves, and receiver operator characteristic curves to predict biochemical recurrence (BCR). RESULTS: A total of 213 patients with iPCa were selected according to the patient selection protocol. Among them, pathological findings showed that Gleason score (GS) G6, G7 and ≥ G8 were present in 115 cases (54.0%), 78 cases (36.6%), and 20 cases (9.4%), respectively. Further, extracapsular extension (ECE), positive surgical margins (PSM), and lymphovascular invasion (LVI) were present in 28 (13.1%), 18 (8.5%), and 3 cases (1.4%), respectively. Seminal vesicle invasion (SVI) was observed in one case (0.5%). During a median follow-up time of 51 months, BCR was observed 29 cases. Adverse pathology (AP) was defined as GS ≥8, ECE, SVI and LVI. AP and prostate specific antigen (PSA) were significantly associated with BCR. Moreover, PSA > 6.2 ng/ml was suggested as a cut-off value for predicting BCR. CONCLUSIONS: In our results, cases of iPCa had clinically significant PCa, and AP and poor prognosis were also observed in some. Additionally, we found that PSA is the most clinically reliable predictor of oncologic outcome. We suggest that active treatment and diagnosis should be considered for patients with iPCa with PSA > 6.2 ng/ml.

Efficacy and Safety of Robotic Procedures Performed Using the da Vinci Robotic Surgical System at a Single Institute in Korea: Experience with 10000 Cases.

PURPOSE: To evaluate the efficacy and safety of robotic procedures performed using the da Vinci Robotic Surgical System at a single institute. MATERIALS AND METHODS: We analyzed all robotic procedures performed at Severance Hospital, Yonsei University Health System (Seoul, Korea). Reliability and mortality rates of the robotic surgeries were also investigated. RESULTS: From July 2005 to December 2013, 10267 da Vinci robotic procedures were performed in seven different departments by 47 surgeons at our institute. There were 5641 cases (54.9%) of general surgery, including endocrine (38.0%), upper (7.7%) and lower gastrointestinal tract (7.5%), hepato-biliary and pancreatic (1.2%), and pediatric (0.6%) surgeries. Urologic surgery (33.0%) was the second most common, followed by otorhinolaryngologic (7.0%), obstetric and gynecologic (3.2%), thoracic (1.5%), cardiac (0.3%), and neurosurgery (0.1%). Thyroid (40.8%) and prostate (27.4%) procedures accounted for more than half of all surgeries, followed by stomach (7.6%), colorectal (7.5%), kidney and ureter (5.1%), head and neck (4.0%), uterus (3.2%), thoracic (1.5%), and other (2.9%) surgeries. Most surgeries (94.5%) were performed for malignancies. General and urologic surgeries rapidly increased after 2005, whereas others increased slowly. Thyroid and prostate surgeries increased rapidly after 2007. Surgeries for benign conditions accounted for a small portion of all procedures, although the numbers thereof have been steadily increasing. System malfunctions and failures were reported in 185 (1.8%) cases. Mortality related to robotic surgery was observed for 12 (0.12%) cases. CONCLUSION: Robotic surgeries have increased steadily at our institution. The da Vinci Robotic Surgical System is effective and safe for use during surgery.

Age-adjusted Charlson Comorbidity Index as a prognostic factor for radical prostatectomy outcomes of very high-risk prostate cancer patients.

PURPOSE: Prostate cancer (PC) is a devastating and heterogeneous condition with diverse treatment options. When selecting treatments for patients with very high-risk PC, clinicians must consider patient comorbidities. We investigated the efficacy of the age-adjusted Charlson Comorbidity Index (ACCI) as a prognostic factor for patient outcomes after radical prostatectomy (RP). MATERIALS AND METHODS: We retrospectively investigated the medical records of PC patients at our institution who underwent RP from 1992 to 2010. Very high-risk PC was defined according to National Comprehensive Cancer Network guidelines. Patients with incomplete medical records or who had received neoadjuvant therapy were excluded. Preoperative comorbidity was evaluated by the ACCI, and the prognostic efficacy of the ACCI was analyzed using univariable and multivariable Cox regression, competing risk regression model and Kaplan-Meier curves. RESULTS: Our final analysis included 228 men with a median age of 66 years (interquartile range 62-71) and median prostate specific antigen of 10.7 ng/mL. There were 41 (18%) patients with an ACCI score >3 and 88 (38.6%) patients with a biopsy Gleason score >8. Preoperative evaluation revealed that 159 patients (69.7%) had a non-organ confined tumor (≥T3). Following RP, 8-year prostate cancer-specific survival (PCSS) and overall survival (OS) rates were 91.6% and 83.4%, respectively. Competing risk regression analysis revealed that ACCI was significantly associated with other-cause survival and OS (p<0.05). CONCLUSION: The ACCI is an effective prognostic factor for other-cause survival and OS in very high-risk PC patients. RP should be considered carefully for patients with an ACCI score >3.

Impact of Early Salvage Androgen Deprivation Therapy in Localized Prostate Cancer after Radical Prostatectomy: A Propensity Score Matched Analysis.

PURPOSE: Androgen deprivation therapy (ADT) is used as a salvage treatment for men with biochemical recurrence (BCR) of prostate cancer (PCa) following initial radical prostatectomy (RP). The optimal time at which to begin salvage ADT (sADT) remains controversial. In this retrospective study, we evaluated the efficacy of initiating sADT in patients before prostate-specific antigen (PSA) values met the clinical definition of BCR. MATERIALS AND METHODS: We identified 484 PCa patients who received sADT for BCR after RP. Median follow-up was 82 months. Propensity score matching was performed based on preoperative PSA level, pathologic T stage, and Gleason score. Patients were assigned to two groups of 169 patients each, based on PSA levels at the time of sADT: Group A (without meeting of the definition of BCR) and Group B (after BCR). Kaplan-Meier survival analyses and Cox regression analyses were performed. RESULTS: The median PSA level at sADT initiation was 0.12 ng/mL in group A and 0.42 ng/mL in group B. Kaplan-Meier analyses showed that group A had favorable disease progression-free survival (DPFS) and distant metastasis-free survival (DMFS), but did not have better cancer-specific survival (CSS) than group B. In subgroup analyses, group A showed better CSS rates in the non-organ confined PCa group. In Cox regression analyses, early sADT was associated significantly with DPFS and DMFS rates, however, did not correlate with CSS (p=0.107). CONCLUSION: Early sADT after RP improved DPFS and DMFS. Furthermore, early sADT patients demonstrated better CSS in non-organ confined PCa.

Predictors of adverse pathologic features after radical prostatectomy in low-risk prostate cancer.

BACKGROUND: Prostate-specific antigen (PSA) screening more frequently detects early stage prostate cancer (PC). However, adverse pathologic features (APFs) after radical prostatectomy (RP) in low-risk PC occur. Previous related studies had utilized outdated staging criteria or small sample cohorts. In this study, we analyzed predictors of APFs after RP in low-risk PC using classification under the current criteria. MATERIALS AND METHODS: We retrospectively reviewed medical records of 546 low-risk PC patients who had undergone RP. Low-risk PC was defined as PC with clinical T1-T2a, Gleason score ≤ 6, and PSA levels < 10 ng/mL. Clinical and pathological parameters were analyzed to predict APFs. APFs were defined as extracapsular extension (ECE), seminal vesicle invasion (SVI), or positive surgical margins (PSM). We analyzed our data using univariable and multivariable logistic regression analyses, as well as receiver operator characteristics to predict APFs. RESULTS: Among 546 patients, ECE, SVI, and PSM were present in 199 (36.4%), 8 (1.5%), and 179 cases (32.8%), respectively. PSM had a significant correlation with preoperative high PSA levels and number of positive cores obtained. ECE/SVI was also significantly correlated with PSA levels and number of positive cores. As a result, presence of APFs after RP was associated with high PSA levels and large number of positive cores. PSA > 4.5 ng/mL and number of positive cores > 2 in low-risk PC were significantly associated with APFs, and suggested as cut-off values for predicting APFs. CONCLUSIONS: PSA > 4.5 ng/mL and number of positive cores > 2 in low-risk PC were associated with presence of APFs and patients with such records should be considered carefully to provide active surveillance.

Clinical Outcomes of CyberKnife Radiotherapy in Prostate Cancer Patients: Short-term, Single-Center Experience.

PURPOSE: In this retrospective study, we analyzed the outcomes of prostate cancer patients treated with the CyberKnife radiotherapy system (Accuray). MATERIALS AND METHODS: Between 2007 and 2010, 31 patients were treated for prostate cancer by use of the CyberKnife radiotherapy system. After excluding six patients who were lost to follow-up, data for the remaining 25 patients were analyzed. Patients were divided into the CyberKnife monotherapy group and a postexternal beam radiotherapy boost group. Clinicopathologic features and treatment outcomes were compared between the groups. The primary endpoint was biochemical recurrence-free survival period based on the Phoenix definition. Toxicities were evaluated by using the Radiation Therapy Oncology Group scoring criteria. RESULTS: Of 25 patients, 17 (68%) and 8 (32%) were classified in the monotherapy and boost groups, respectively. With a median follow-up of 29.3 months, most of the toxicities were grade 1 or 2 except for one patient in the boost group who experienced late grade 3 gastrointestinal toxicity. The overall biochemical recurrence rate was 20% (5/25) and the median time to biochemical recurrence was 51.9 months. None of the patients with low or intermediate risk had experienced biochemical recurrence during follow-up. Among D'Amico high-risk populations, 16.7% (1/6) in the monotherapy group and 50.0% (4/8) in the boost group experienced biochemical recurrence. CONCLUSIONS: Our data support that prostate cancer treatment by use of the CyberKnife radiotherapy system is feasible. The procedure can be a viable option for managing prostate cancer either in a monotherapy setting or as a boost after conventional radiotherapy regardless of the patient's risk stratification.