Browsing by Author "Obek, Can"

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5-Hydroxyuracil Incision Activity Varies According to the Histological Grade of Non-muscle-invasive Bladder Cancer
(GALENOS YAYINCILIK, 2021-01-01) Keskin, Selcuk; Antmen, Fatma Merve; Somuncu, Berna; Saglican, Yesim; Doganca, Tunkut; Obek, Can; Ince, Umit; Kural, Ali Riza; Muftuoglu, Meltem
Objective: High levels of endonuclease III-like 1 (NTHL1) DNA glycosylase, which plays a role in the first step of the base excision repair pathway, has been related to cancer initiation and progression. 5-hydroxyuracil (5-OHU) oxidative base damage is a substrate for NTHL1 and endonuclease VIII-like 1 enzyme 1 (NEIL1) DNA glycosylases. This study investigates the association of 5-OHU incision activity with the risk of disease progression in patients with non-muscle-invasive bladder cancer (NMIBC) regarding grade and stage. Materials and Methods: During transurethral resection of 17 NMIBC patients, the papillary tumour before monopolar resection and healthy bladder mucosal tissue from the same person were obtained using cold cup biopsy. Both the normal mucosa and NMIBC tumour were pathologically confirmed. The histological grade and stage were also determined. The 5-OHU incision activity of all tissues was measured using a radiolabelled 5-OHU modified base containing DNA substrate. Results: 5-OHU incision activity was significantly higher in all high-grade NMIBC tissue extracts compared with the corresponding normal tissues (p=0.001). However, we found no significant difference in 5-OHU incision activity in low-grade NMIBC tissues (p=0.89). There was also a significant increase in 5-OHU incision activity at the Ta/T1 stage compared with the corresponding normal tissue (p=0.001). Conclusion: The increase in 5-OHU incision activity according to the histological grade of NMIBC tissue indicates that this activity (mainly performed by NTHL1 and NEIL1 DNA glycosylases) might play a role in NMIBC prognosis. Thus, it could be used as a potential prognostic biomarker for NMIBC.
Can SUVmax values of Ga-68-PSMA PET/CT scan predict the clinically significant prostate cancer?
(LIPPINCOTT WILLIAMS \& WILKINS, 2019-01-01) Demirci, Emre; Kabasakal, Levent; Sahin, Onur E.; Akgun, Elife; Gultekin, Mehmet Hamza; Doganca, Tunkut; Tuna, Mustafa B.; Obek, Can; Kilic, Mert; Esen, Tarik; Kural, Ali R.
Purpose The intensity of prostate-specific membrane antigen (PSMA) expression increases as the tumor grade increases and the uptake of Ga-68-PSMA is higher in high-grade tumors. The aim of the present study was to evaluate the correlation of preoperative tracer uptake of primary tumor to Gleason Score in patients who underwent prostatectomy. Patients and methods We retrospectively evaluated 141 patients who had Ga-68-PSMA positron emission tomography/computed tomography (PET/CT) imaging and who underwent prostatectomy. All patients had a diagnosis of prostate cancer on the basis of 10-24 cores transrectal ultrasound-guided biopsy (TRUS-Bx). Histological assessment was performed according to the New Contemporary Prostate Cancer Grading System. All patients had a prostate-specific antigen (PSA) level measurement within maximum of 28 days before Ga-68-PSMA PET/CT. Region of interests were drawn manually around the prostate gland, avoiding the bladder activity, to calculate the maximum standardized uptake values (SUVmax) values. Results The median PSA values for all patients were 10.0 ng/ml. PSA values for low-risk patients were significantly lower than those of high-risk patients (P<0.001). There were 41.1\% upgrades and 7.8\% downgrades following prostatectomy in terms of Grade Groups. According to the final pathology reports, 21\% (n=16) of patients moved from a low-risk level (grade groups 1+2) to a high-risk level (grade groups 3+4+5). The median SUVmax value was 8.8, ranging from 2.1 to 62.4. There was a strong correlation between SUVmax values and grade groups (Pearson rho=0.66) (P<0.001). The mean SUVmax values of high-risk patients were significantly higher than those of low-risk patients (18.9 +/- 12.1 vs. 7.16 +/- 6.2, respectively) (P<0.001). Receiver operation characteristic curve analysis of SUVmax at the cut-off value of 9.1 showed a high sensitivity (78\%) and specificity (81\%) for detection of high risk disease. Conclusion SUVmax values correlate significantly with the grade groups of the primary tumor. The intraprostatic accumulation sites may predict clinically significant cancer and potentially serve as a target for biopsy sampling in conjunction with mpMRI in selected patients.
Can We Accomplish Better Oncological Results with Robot-Assisted Radical Prostatectomy?
(MARY ANN LIEBERT, INC, 2017-01-01) Kural, Ali Riza; Obek, Can; Doganca, Tunkut
Surgical removal with radical prostatectomy has been a cornerstone for the treatment of prostate cancer and is associated with level 1 evidence for survival advantage compared with watchful waiting. Since the first structured robotic program was launched in 2000, robot-assisted radical prostatectomy (RARP) has had a rapid diffusion and surpassed its open radical prostatectomy (ORP) and laparoscopic radical prostatectomy (LRP) counterparts in the United States and is progressively expanding in other countries. Interestingly, this common acceptance of RARP was initially driven in the paucity of robust clinical evidence. There is still lack of level 1 evidence with prospective randomized trials on the oncologic outcomes of RARP. In that scenario, the clinician has to rely on retrospective data and systemic and meta-analyses. In comparison with ORP and LRP, RARP has proven to reach at least equivalent oncological outcomes. Lower rate of positive surgical margins may probably be achieved with RARP in pT2 patients. Although urologists were initially reluctant to embrace RARP in highrisk patients and lymph node yield was low, contemporary series have revealed that RARP and extended lymphadenectomy may be safely performed with obtaining similar (or better) nodal yields compared with ORP. Surgeon experience is universally of utmost importance in obtaining good outcomes. We will need to wait for long-term results of contemporary series to comprehend the impact of RARP on cancer-specific survival and overall survival. Using novel imaging before surgery and frozen section analysis during surgery may allow for superior oncological outcomes.
Impact of Refractive Errors on Da Vinci SI Robotic System
(SOC LAPAROENDOSCOPIC SURGEONS, 2020-01-01) Tuna, Mustafa Bilal; Kilavuzoglu, Ayse Ebru; Mourmouris, Panogiotis; Argun, Omer Burak; Doganca, Tunkut; Obek, Can; Ozisik, Ozan; Kural, Ali Riza
Objective: To investigate the impact of refractive errors on binocular visual acuity while using the Da Vinci SI robotic system console. Methods: Eighty volunteers were examined on the Da Vinci SI robotic system console by using a near vision chart. Refractive errors, anisometropia status, and Fly Stereo Acuity Test scores were recorded. Spherical equivalent (SE) were calculated for all volunteers' right and left eyes. Visual acuity was assessed by the logarithm of the minimal angle of resolution (LogMAR) method. Binocular uncorrected and best corrected (with proper contact lens or glasses) LogMAR values of the subjects were recorded. The difference between these values (DiffLogMAR) are affected by different refractive errors. Results: In the myopia and/or astigmatism group, uncorrected SE was found to have significant impact on the DiffLogMAR (P < 0.001) and myopia greater than 1.75 diopter had significantly higher DiffLogMAR values (p < 0.05). Subjects with presbyopia had significantly higher DiffLogMAR values (p < 0.01), and we observed positive correlation between presbyopia and DiffLogMAR values (p = 0.33, p < 0.01). The cut off value of presbyopia that correlated the most with DiffLogMAR differences was found to be 1.25 diopter (P< 0.001). In 13 hypermetropic volunteers, we found significant correlation between hypermetropia value and DiffLogMAR (p > 0.7, p < 0.01). The statistical analysis between Fly test and SE revealed a significant impact of presbyopia and hypermetropia to the stereotactic view of the subject (p = -0.734, p < 0.05). Conclusion: Surgeons suffering from myopia greater than 1.75 diopter, presbyopia greater than 1.25 diopter (D), and hypermetropia regardless of grade must always perform robotic surgeries with the proper correction.
Magnetic Resonance - Transrectal Ultrasound Fusion Guided Prostate Biopsy
(GALENOS YAYINCILIK, 2016-01-01) Argun, Omer Burak; Obek, Can; Kural, Ali Riza
Prostate has remained as the single solid organ for which biopsy cannot be performed from a lesion for decades. Lately, the groundbreaking magnetic resonance imaging (MRI) techniques have emerged to scan prostate cancer and have become an important diagnostic tool in the diagnosis of prostate cancer. Efforts to improve the accuracy of the standard biopsy methods have led to the emergence of target-oriented biopsy methods. Today, MRI-transrectal ultrasound (TRUS) fusion guided biopsy methods are being used increasingly, especially for patients with an increasing prostate specific antigen level after a previous negative biopsy result and for patients under follow-up with active surveillance protocols. Even though it is not yet suggested in guidelines, our view and practice are in line with the fact that MRI-TRUS fusion guided biopsy is the most ideal biopsy method in any patient scheduled for a prostate biopsy with a significant lesion on MRI.
Management of prostate cancer patients during COVID-19 pandemic
(SPRINGERNATURE, 2020-01-01) Obek, Can; Doganca, Tunkut; Argun, Omer Burak; Kural, Ali Riza
Prostate cancer patients' management demands prioritization, adjustments, and a tailored approach during the unprecedented SARS-CoV-2 pandemic. Benefit of care from treatment must be carefully weighed against the potential of infection and morbidity from COVID-19. Furthermore, urologists need to be cognizant of their obligation for wise consumption of restricted healthcare resources and protection of the safety of their coworkers. Nonurgent in-person clinic visits should be postponed or conducted remotely via phone or teleconference. Prostate cancer screening, imaging, and biopsies may be suspended in general. Treatment may be safely deferred in low and intermediate risk patients. Surgery may be delayed in most high-risk patients and neoadjuvant ADT is generally not advocated prior to surgery. Initiation of long-term ADT coupled with EBRT subsequent to the pandemic may be favored as a feasible alternative in high-risk and very high-risk disease. In patients with cN1 disease, treatment within 6 weeks is advocated. Presurgery assessment should include testing for COVID-19 and preferably a chest imaging. In the presence of SARS-CoV-2 infection, surgery should be postponed whenever possible. All protective measurements suggested by national/international authorities must to be diligently followed during perioperative period. Strict precautions specific to laparoscopic/robotic surgery are required, considering the unproven but potential risk of aerosolization of SARS-CoV-2 virus and spillage with pneumoperitoneum. Regarding radiotherapy, shortest safe EBRT regimen should be favored and prophylactic whole pelvic RT and brachytherapy avoided. Chemotherapy should be avoided whenever possible.
Minimizing Ports During Robotic Partial Nephrectomy
(SOC LAPAROENDOSCOPIC SURGEONS, 2016-01-01) Argun, Omer Burak; Mourmouris, Panagiotis; Tufek, Ilter; Obek, Can; Tuna, Mustafa Bilal; Keskin, Selcuk; Kural, Ali Riza
Background and Objective: Robotic upper urinary tract surgery is in most of the cases performed utilizing a standard 5 port configuration. Fewer ports can potentially produce a less invasive operation. Taking in consideration the above we report a novel technique for robot assisted laparoscopic partial nephrectomy utilizing fewer ports and we test its feasibility and safety profile. Methods: Data on 11 robot-assisted laparoscopic partial nephrectomies performed by using our technique from February 2015 through June 2015 were retrospectively analyzed. The robotic platform used was DaVinci Xi (Intuitive Surgical, Inc., Sunnyvale, California, USA) with a 3-arm setup. The AirSeal system (SurgiQuest, Milford, Connecticut, USA) was used as a port allowing simultaneous introduction of 2 instruments for the bedside surgeon, obviating the need for an additional (fourth) robotic arm. A long suction-and-irrigation device and atraumatic grasping forceps were used. Both instruments were introduced through the trocar of the AirSeal system, making simultaneous introduction and use possible. We preferred the long suction-and-irrigation device, because it minimizes collision of the instruments. Results: Mean age and BMI of the patients were 55 +/- 14.6 y and 29.18 +/- 6.85, respectively. Seven tumors were on the right side and 4 were on the left. The mean size of the tumors was 32.45 mm (+/- 11.31). Surgical time was 132.2 minutes (+/- 37.17), with an estimated blood loss and ischemia time of 103.63 mL (+/- 65.92) and 16.72 minutes (+/- 9.52), respectively. One patient had postoperative bleeding that was resolved without transfusion. The median hospitalization period was 3.9 d (+/- 0.53). Loss of intra-abdominal pressure was not observed, and pressure was stable at 10 mm Hg. Conclusion: The AirSeal System and its valveless trocar eliminated the need for an additional port placement in our series. The technique is feasible, safe, and reproducible
Non-muscle invasive bladder cancer tissues have increased base excision repair capacity
(NATURE PORTFOLIO, 2020-01-01) Somuncu, Berna; Keskin, Selcuk; Antmen, Fatma Merve; Saglican, Yesim; Ekmekcioglu, Aysegul; Ertuzun, Tugce; Tuna, Mustafa Bilal; Obek, Can; Wilson, David M.; Ince, Umit; Kural, Ali Riza; Muftuoglu, Meltem
The molecular mechanisms underlying the development and progression of bladder cancer (BC) are complex and have not been fully elucidated. Alterations in base excision repair (BER) capacity, one of several DNA repair mechanisms assigned to preserving genome integrity, have been reported to influence cancer susceptibility, recurrence, and progression, as well as responses to chemotherapy and radiotherapy. We report herein that non-muscle invasive BC (NMIBC) tissues exhibit increased uracil incision, abasic endonuclease and gap-filling activities, as well as total BER capacity in comparison to normal bladder tissue from the same patient (p<0.05). No significant difference was detected in 8-oxoG incision activity between cancer and normal tissues. NMIBC tissues have elevated protein levels of uracil DNA glycosylase, 8-oxoguanine DNA glycosylase, AP endonuclease 1 and DNA polymerase beta protein. Moreover, the fold increase in total BER and the individual BER enzyme activities were greater in high-grade tissues than in low-grade NMIBC tissues. These findings suggest that enhanced BER activity may play a role in the etiology of NMIBC and that BER proteins could serve as biomarkers in disease prognosis, progression or response to genotoxic therapeutics, such as Bacillus Calmette-Guerin.
Water Vapor Thermal Therapy (RezumTM) for Benign Prostate Hyperplasia: Initial Experience from Turkiye
(GALENOS PUBL HOUSE, 2022-01-01) Tuna, Mustafa Bilal; Doganca, Tunkut; Argun, Omer Burak; Pirdal, Betul Zehra; Tufek, Ilter; Obek, Can; Kural, Ali Riza
Objective: Rezumn{''} system is a safe minimal invasive treatment modality for benign prostate hyperplasia (BPH) treatment. The aim of this study was to evaluate the short-term results of Rezumn{''} therapy in our center.Materials and Methods: We retrospectively collected the data of 28 patients with symptomatic BPH who underwent RezumTM therapy in our center. All patients' pre-operative and post-operative