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Dive into the research topics where Minato Yokoyama is active.

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Featured researches published by Minato Yokoyama.


European Radiology | 2011

Diagnostic performance of diffusion-weighted magnetic resonance imaging in bladder cancer: potential utility of apparent diffusion coefficient values as a biomarker to predict clinical aggressiveness

Shuichiro Kobayashi; Fumitaka Koga; Soichiro Yoshida; Hitoshi Masuda; Chikako Ishii; Hiroshi Tanaka; Yoshinobu Komai; Minato Yokoyama; Kazutaka Saito; Yasuhisa Fujii; Satoru Kawakami; Kazunori Kihara

ObjectivesThe diagnostic performance of diffusion-weighted magnetic resonance imaging (DW-MRI) in bladder cancer and the potential role of apparent diffusion coefficient (ADC) values in predicting pathological bladder cancer phenotypes associated with clinical aggressiveness were investigated.MethodsOne hundred and four bladder cancer patients underwent DW-MRI and T2-weighted magnetic resonance imaging (T2W-MRI) before transurethral resection. The image sets were reviewed by two independent radiologists. ADC values were measured in 121 eligible tumours.ResultsIn detecting patients with bladder cancer, DW-MRI exhibited high sensitivity equivalent to that of T2W-MRI (>90%). Interobserver agreement was excellent for DW-MRI (κ score, 0.88) though moderate for T2W-MRI (0.67). ADC values were significantly lower in high-grade (vs. low-grade, P < 0.0001) and high-stage (T2 vs. T1 vs. Ta, P < 0.0001) tumours. At a cut-off ADC value determined by partition analysis, clinically aggressive phenotypes including muscle-invasive bladder cancer (MIBC) and high-grade T1 disease were differentiated from less aggressive phenotypes with a sensitivity of 88%, a specificity of 85% and an accuracy of 87%.ConclusionDW-MRI exhibits high diagnostic performance in bladder cancer with excellent objectivity. The ADC value could potentially serve as a biomarker to predict clinical aggressiveness in bladder cancer.


BJUI | 2008

C‐reactive protein level predicts prognosis in patients with muscle‐invasive bladder cancer treated with chemoradiotherapy

Soichiro Yoshida; Kazutaka Saito; Fumitaka Koga; Minato Yokoyama; Yukio Kageyama; Hitoshi Masuda; Tsuyoshi Kobayashi; Satoru Kawakami; Kazunori Kihara

To investigate the effect of C‐reactive protein (CRP) level on the prognosis of patients with muscle‐invasive bladder cancer treated with chemoradiotherapy (ChRT), as it is increasingly recognized that the presence of a systemic inflammatory response is associated with poor survival in various malignancies.


PLOS ONE | 2015

Sarcopenia as a prognostic biomarker of advanced urothelial carcinoma.

Hiroshi Fukushima; Minato Yokoyama; Yasukazu Nakanishi; Ken-ichi Tobisu; Fumitaka Koga

Objectives Sarcopenia, a novel concept reflecting the degenerative loss of skeletal muscle mass, is an objective indicator of cancer cachexia. We investigated its role as a prognostic biomarker in advanced urothelial carcinoma (UC) patients. Methods This retrospective study consisted of 88 UC patients with cT4 and/or metastases to lymph nodes/distant organs. Skeletal muscle index (SMI), an indicator of whole-body muscle mass, was measured from computed tomography (CT) images at the diagnosis. Sarcopenia was defined as SMIs of <43 cm2/m2 for males with body mass index (BMI) <25 cm2/m2, <53 cm2/m2 for males with BMI ≥25 cm2/m2, and <41 cm2/m2 for females. Predictors of overall survival (OS) were examined using Cox proportional hazard models. Results Sixty-seven patients (76%) died during the median follow-up of 13 months. The median OS rate was 13 months. Multivariate analysis revealed that SMI was a significant and independent predictor of shorter OS (hazard ratio (HR) 0.90, P <0.001). In the present cohort, 53 (60%) were diagnosed with sarcopenia. The median OS rates were 11 and 31 months for sarcopenic and non-sarcopenic patients, respectively (P <0.001). On multivariate analysis, sarcopenia was a significant and independent predictor of shorter OS (HR 3.36, P <0.001), along with higher C-reactive protein (CRP) (P = 0.001), upper urinary tract cancer (P = 0.007), higher lactate dehydrogenase (LDH) (P = 0.047), and higher alkaline phosphatase (ALP) (P = 0.048). Conclusion Sarcopenia, which is readily evaluated on routine CT scans, is a useful prognostic biomarker of advanced UC. Non-sarcopenic patients can expect long-term survival. Evaluating sarcopenia can be helpful for decision-making processes in the management of advanced UC patients.


The Journal of Urology | 2013

Usefulness of Pre-biopsy Multiparametric Magnetic Resonance Imaging and Clinical Variables to Reduce Initial Prostate Biopsy in Men with Suspected Clinically Localized Prostate Cancer

Noboru Numao; Soichiro Yoshida; Yoshinobu Komai; C. Ishii; Makoto Kagawa; Toshiki Kijima; Minato Yokoyama; Junichiro Ishioka; Yoh Matsuoka; Fumitaka Koga; Kazutaka Saito; Hitoshi Masuda; Yasuhisa Fujii; Satoru Kawakami; Kazunori Kihara

PURPOSE We evaluated the usefulness of pre-biopsy multiparametric magnetic resonance imaging and clinical variables to decrease initial prostate biopsies. MATERIALS AND METHODS We prospectively evaluated 351 consecutive men with prostate specific antigen between 2.5 and 20 ng/ml, and/or digital rectal examination suspicious for clinically localized disease. All men underwent pre-biopsy multiparametric magnetic resonance imaging and initial 14 to 29-core biopsy, including anterior sampling. Three definitions of significant cancer were defined based on Gleason score and cancer volume (percent positive core and/or maximum cancer length). The overall cohort was divided into men at low risk-prostate specific antigen less than 10 ng/ml and normal digital rectal examination, and high risk-prostate specific antigen 10 ng/ml or greater and/or abnormal digital rectal examination. We evaluated the frequency of significant cancer according to magnetic resonance imaging and risk categories. Clinical variables as significant cancer predictors were analyzed using logistic regression. The sensitivity, specificity, and positive and negative predictive values of magnetic resonance imaging were calculated with or without clinical variables for significant cancer. RESULTS The frequency of significant cancer in men with negative vs positive magnetic resonance imaging was 9% to 13% vs 43% to 50% in the low risk group and 47% to 51% vs 68% to 71% in the high risk group. In men at low risk with negative magnetic resonance imaging prostate volume was the only significant predictor of significant cancer. In the low risk group the negative predictive value for significant cancer of a combination of positive magnetic resonance imaging and lower prostate volume (less than 33 ml) was 93.7% to 97.5%. CONCLUSIONS Pre-biopsy multiparametric magnetic resonance imaging along with prostate volume decreases the number of initial prostate biopsies by discriminating between significant cancer and other cancer in men with prostate specific antigen less than 10 ng/ml and normal digital rectal examination.


BJUI | 2012

Selective bladder-sparing protocol consisting of induction low-dose chemoradiotherapy plus partial cystectomy with pelvic lymph node dissection against muscle-invasive bladder cancer: oncological outcomes of the initial 46 patients

Fumitaka Koga; Kazunori Kihara; Soichiro Yoshida; Minato Yokoyama; Kazutaka Saito; Hitoshi Masuda; Yasuhisa Fujii; Satoru Kawakami

Study Type – Therapy (case series)


Urology | 2008

Low-Dose Chemoradiotherapy Followed by Partial or Radical Cystectomy Against Muscle-Invasive Bladder Cancer: An Intent-to-Treat Survival Analysis

Fumitaka Koga; Soichiro Yoshida; Satoru Kawakami; Yukio Kageyama; Minato Yokoyama; Kazutaka Saito; Yasuhisa Fujii; Tsuyoshi Kobayashi; Kazunori Kihara

OBJECTIVES To evaluate the clinical outcomes of patients with muscle-invasive bladder cancer treated with a prospective institutional protocol composed of induction low-dose chemoradiotherapy (LCRT) plus partial or radical cystectomy. METHODS From March 1997 to March 2006, 102 patients with Stage T2-T4aN0M0 bladder urothelial carcinoma consecutively underwent transurethral resection of the bladder tumor followed by LCRT consisting of radiotherapy to the bladder (radiation dose 40 Gy) concurrent with two cycles of intravenous (20 mg/d for 5 days) or intra-arterial (100 mg) cisplatin. Depending to their post-LCRT tumor status, patients were recommended to undergo partial or radical cystectomy with curative intent. RESULTS LCRT-related toxicity of grade 3 or greater was rare (3%). Of 97 eligible patients, 41 (42%) had a complete response, 29 (30%) a partial response, 24 (25%) had stable disease, and 3 (4%) progressive disease. Of the 97 patients, 19, underwent partial cystectomy, and 58 underwent radical cystectomy, 2 underwent transurethral resection of the bladder tumor, and 18 did not undergo surgery. The 5-year overall survival and cancer-specific survival (CSS) rate was 66% and 74%, respectively. The median follow-up was 43 months (range 3-126). On multivariate analysis, the response to LCRT had the strongest effect on CSS, and CSS was clearly stratified by the response to LCRT (P < .0001), with a 5-year CSS rate of 100% for the 41 patients with a complete response. CONCLUSIONS The results of our study have shown that LCRT is an effective and less-toxic induction therapy against muscle-invasive bladder cancer. Our therapeutic protocol with LCRT plus partial or radical cystectomy yielded favorable survival outcomes. The response to LCRT was the strongest prognostic factor for CSS.


International Journal of Urology | 2007

Absence of prophylactic antibiotics in minimum incision endoscopic urological surgery (MEUS) of adrenal and renal tumors.

Soichiro Yoshida; Hitoshi Masuda; Minato Yokoyama; Tsuyoshi Kobayashi; Satoru Kawakami; Kazunori Kihara

Objective:  Recently, some studies suggested that antimicrobial prophylactics (AMP) are not needed to prevent surgical site infection (SSI) for clean operations despite worldwide acceptance of AMP. However, appropriate use of AMP in urological surgery has not been fully studied. Herein, we report an attempt of gradual decrease of AMP to non‐use of AMP in minimum incision endoscopic urological surgery (MEUS) of adrenal and renal tumors.


The Journal of Urology | 2011

Longitudinal Change in Renal Function After Radical Nephrectomy in Japanese Patients With Renal Cortical Tumors

Minato Yokoyama; Yasuhisa Fujii; Yasumasa Iimura; Kazutaka Saito; Fumitaka Koga; Hitoshi Masuda; Satoru Kawakami; Kazunori Kihara

PURPOSE We investigated the longitudinal change in renal function after radical nephrectomy in Japanese patients with renal cortical tumors and compared it with that after partial nephrectomy. MATERIALS AND METHODS This retrospective study included 416 Japanese patients who underwent radical (341) or partial (75) nephrectomy between 1994 and 2009. We investigated the postoperative duration of freedom from new onset of an estimated glomerular filtration rate of less than 60 and 45 ml/minute/1.73 m(2), and the longitudinal change in renal function after surgery. RESULTS The 3-year probability of freedom from new onset of an estimated glomerular filtration rate of less than 60 ml/minute/1.73 m(2) after radical and partial nephrectomy was 63% and 89%, respectively (p <0.001). The corresponding incidence of an estimated glomerular filtration rate of less than 45 ml/minute/1.73 m(2) was 89% and 95%, respectively (p = 0.247). The estimated glomerular filtration rate decreased by 36% and 13% 1 year after radical and partial nephrectomy, respectively. During the next 5-year followup the estimated glomerular filtration rate after radical nephrectomy slightly but significantly increased by 5% but after partial nephrectomy it did not change significantly. CONCLUSIONS Radical nephrectomy is an independent risk factor for new onset of an estimated glomerular filtration rate of less than 60 ml/minute/1.73 m(2) in Japanese patients. However, relatively few patients have new onset of an estimated glomerular filtration rate of less than 45 ml/minute/1.73 m(2) even after radical nephrectomy. In Japanese patients renal function deteriorates immediately after radical nephrectomy but improves slightly but significantly thereafter.


International Journal of Urology | 2006

Successful management of vesicouterine fistula by luteinizing hormone‐releasing hormone analog

Minato Yokoyama; Chizuru Arisawa; Masao Ando

Abstract  Vesicouterine fistula is a rare complication of cesarean section. Although surgical repair was mandatory for the management of the fistula previously, a recent review showed high efficacy of hormonal manipulation by the induction of amenorrhea. Herein, we report a new case of vesicouterine fistula secondary to cesarean section successfully treated by luteinizing hormone‐releasing hormone analog for 6 months. Conservative hormonal treatment for vesicouterine fistula caused by cesarean section should be considered before surgical repair.


International Journal of Urology | 2012

Impact of renal function on cardiovascular events in patients undergoing radical nephrectomy for renal cancer

Hideki Takeshita; Minato Yokoyama; Yasuhisa Fujii; Koji Chiba; Junichiro Ishioka; Akira Noro; Kazunori Kihara

Objective:  To examine the actual impact of renal dysfunction on cardiovascular events in Japanese patients undergoing radical nephrectomy for renal cancer.

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Kazunori Kihara

Tokyo Medical and Dental University

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Kazutaka Saito

Tokyo Medical and Dental University

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Yasuhisa Fujii

Tokyo Medical and Dental University

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Yoh Matsuoka

Tokyo Medical and Dental University

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Junichiro Ishioka

Tokyo Medical and Dental University

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Soichiro Yoshida

Tokyo Medical and Dental University

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Noboru Numao

Tokyo Medical and Dental University

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Fumitaka Koga

Tokyo Medical and Dental University

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Hitoshi Masuda

Tokyo Medical and Dental University

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Satoru Kawakami

Tokyo Medical and Dental University

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