Enis Ozyar

Enis Ozyar
Acibadem Healthcare Group

Professor of Radiation Oncology

About

198
Publications
17,359
Reads
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2,526
Citations
Citations since 2017
61 Research Items
1072 Citations
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2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
Additional affiliations
February 2008 - present
Acibadem Hospitals Group
Position
  • CEO
January 2008 - present
Acibadem University

Publications

Publications (198)
Article
Purpose/Objective(s) Organs at risk annotation is a strong bottleneck of Magnetic resonance imaging guided radiotherapy (MRgRT) in the context of adaptive treatment. It is a time-consuming task that reduces patient throughput (20% of the fraction duration dedicated to contouring) while suffering standardization and reproducibility across physicians...
Article
Purpose/Objective(s) Organ-at-risk (OAR) delineation is an essential step for radiotherapy treatment (RT) planning. Standard practice during the last decade referred to manual delineation of OARs from medical experts. Manual delineation is the current standard of practice and can be a tedious, time-consuming process, prone to errors due to intra an...
Article
Purpose/Objective(s) Magnetic Resonance is an essential modality in the context of radiotherapy primarily for providing additional information with respect to tumor functional information leading to better target delineation (brain, prostate, etc.) and secondary in the context of emergence of magnetic resonance guided radiotherapy. However, in both...
Article
Purpose/Objective(s) Using moderate or ultra-hypofractionation, which is also known as stereotactic body radiotherapy (SBRT) for treatment of localized prostate cancer patients has been increased. Assessment of the efficacy of treatment response after radiotherapy relies heavily on the monitoring of prostate specific antigen (PSA) levels and PSA ki...
Article
Purpose/Objective(s) Radiotherapy has an important role in management of lung tumors. Online adaptive radiotherapy is a method that provides dosimetric accuracy by considering anatomical and functional changes with real-time images taken during treatment, and MR-guided radiotherapy is the latest technological development in this field. In our study...
Article
Aim: Recommendations for managing patients with nasopharyngeal carcinoma (NPC) in non-endemic areas are largely derived from studies conducted in endemic areas. We analysed the impact of treatment approaches on survival in non-endemic areas. Methods: In an international, multicentre, retrospective study, we analyse consecutive patients with NPC dia...
Article
Purpose/Objective(s) Magnetic resonance imaging guided radiotherapy (MRgRT) offers the ability of daily treatment adaptation: a game changer for various cancers. Contouring of organs at risk (OAR) during adaptation is time-consuming and lacks reproducibility across physicians, hampering the accuracy of high precision MRgRT and diminishing its adopt...
Article
Purpose/Objective(s) Stereotactic MR-guided Adaptive Radiotherapy (SMART) is an appealing treatment option for irradiation of intra-abdominal tumors. Daily adaptation with SMART has the advantage of dose escalation while protecting organs at risk (OARs). We aimed to document dosimetric parameters during SMART and analyze local control for adrenal m...
Article
Full-text available
Purpose/Objective(s) Randomized trials have shown improved local control (LC) but no overall survival (OS) benefit with the addition of non-ablative radiation therapy (RT) dose compared to chemotherapy (CT) alone for pancreas cancer (PCa). Emerging data suggest that dose-escalated RT may improve LC and OS. A few studies suggest that stereotactic ma...
Article
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Purpose/Objective(s) Randomized data show an overall survival (OS) benefit of stereotactic ablative body radiation therapy (SABR) in addition to chemotherapy (CT) in selected patients with oligometastasis (OM). While ablative dose can be safely delivered to some lesions, others in proximity to some organs at risk (OARs) such as bowel may be treated...
Article
Introductio Stereotactic radiosurgery (SRS) is a treatment option in the initial management of patients with brain metastases. While its efficacy has been demonstrated in several prior studies, treatment-related complications, particularly symptomatic radiation necrosis (RN), remains as an obstacle for wider implementation of this treatment modalit...
Article
Full-text available
Background and purpose Magnetic resonance guided radiotherapy (MRgRT) has been successfully implemented for several routine clinical applications in adult patients. The purpose of this study is to map the potential benefit of MRgRT on toxicity reduction and outcome in pediatric patients treated with curative intent for primary and metastatic sites....
Article
Full-text available
Purpose: We aimed to present our initial clinical experience on the implementation of a stereotactic MR-guided online adaptive radiation therapy (SMART) for the treatment of liver metastases in oligometastatic disease. Materials and methods: Twenty-one patients (24 lesions) with liver metastasis treated with SMART were included in this retrospec...
Chapter
Nasopharyngeal cancer (NPC) is a rare condition in pediatric population. Its management poses major challenges to pediatric oncologists due to the significant difference in terms of disease and patient characteristics between pediatric and adult patients diagnosed with NPC. Pediatric NPC (PNCP) almost always have the undifferentiated variant, which...
Article
Extracranial malignant rhabdoid tumors are rare and aggressive tumors that typically occur in the pediatric age group and have a poor prognosis. Herein, we report a case of a one year and five months old male infant who was referred with the diagnosis of malignant rhabdoid tumor of the liver. Magnetic resonance guided stereotactic body radiotherapy...
Article
Purpose Re-irradiation for locally recurrent nasopharyngeal carcinoma (NPC) is challenging as prior radiation dose delivered in the first course is often close to the tolerance limit of surrounding normal structures. A delicate balance between achieving local salvage and minimizing treatment toxicities is needed. However, high-level evidence is lac...
Article
Objective Using moderate or ultra-hypofractionation, which is also known as stereotactic body radiotherapy (SBRT) for treatment of localized prostate cancer patients has been increased. We present our preliminary results on the clinical utilization of MRI-guided adaptive radiotherapy (MRgRT) for prostate cancer patients with the workflow, dosimetri...
Article
Full-text available
First detailed data on time analysis of MR guided radiotgerapy workflow
Article
Introductio Stereotactic radiosurgery (SRS) is a treatment option in the initial management of patients with brain metastases. While its efficacy has been demonstrated in several prior studies, treatment-related complications, particularly symptomatic radiation necrosis (RN), remains as an obstacle for wider implementation of this treatment modalit...
Article
Objective We identified factors influencing outcomes in patients with medically inoperable early‐stage lung cancer (MIESLC) treated with stereotactic ablative radiation therapy (SABR) at 14 centers in Turkey. Methods We retrospectively analyzed 431 patients with stage I‐II MIESLC treated with SABR from 2009 through 2017. Age; sex; performance scor...
Article
Full-text available
PurposeMagnetic resonance-guided radiation therapy (MRgRT) has been incorporated into a growing number of clinical practices world-wide, however, there is limited data on patient experiences with MRgRT. The purpose of this study was to prospectively evaluate patient tolerance of MRgRT using patient reported outcome questionnaires (PRO-Q).Methods Ni...
Article
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Purpose: Approximately 10% of patients who received brain stereotactic radiosurgery (SRS) develop symptomatic radiation necrosis (RN). We sought to determine the effectiveness of treatment options for symptomatic RN, based on patient-reported outcomes. Materials and methods: We conducted a retrospective review of 217 patients with 414 brain meta...
Article
Full-text available
Purpose To document time analysis of detailed workflow steps for the online adaptive magnetic resonance-guided radiotherapy treatments (MRgRT) with ViewRay MRIdian® system (VRS) and to identify the barriers and solutions for shorter treatment times. Methods and Materials A total number of 154 patients were treated with VRS between September 2018 a...
Article
Full-text available
Background Stereotactic ablative radiotherapy (SABR) is effective for thoracic cancer and metastases; however, adverse effects are greater for central tumors. We evaluated factors affecting outcomes and toxicities after SABR for patients with primary lung and oligometastatic tumors. Patients and methods We retrospectively identified consecutive pa...
Article
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Purpose To evaluate the intensity modulated radiotherapy (IMRT) quality assurance (QA) results of the multichannel film dosimetry analysis with single scan method by using Gafchromic™ EBT3 (Ashland Inc., Covington, KY, USA) film under 0.35 T magnetic field. Methods Between September 2018 and June 2019, 70 patients were treated with ViewRay MRIdian®...
Article
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A concomitant chemoradiotherapy followed by brachytherapy is considered to be standard care in patients with locally advanced cervical cancer. Management of the disease becomes a major therapeutic challenge when brachytherapy is not available and the patient declines referral to an expert center. In this case study, we report the case of a 66-year-...
Article
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Purpose: Renal cell carcinoma (RCC) and melanoma have been considered 'radioresistant' due to the fact that they do not respond to conventionally fractionated radiation therapy. Stereotactic radiosurgery (SRS) provides high-dose radiation to a defined target volume and a limited number of studies have suggested the potential effectiveness of SRS i...
Article
Full-text available
Objectives Improved soft-tissue visualization, afforded by magnetic resonance imaging integrated into a radiation therapy linear accelerator-based radiation delivery system (MR-linac) promises improved image-guidance. The availability of MR-imaging can facilitate on-table adaptive radiation planning and enable real-time intra-fraction imaging with...
Article
Purpose: The treatment of nasopharyngeal carcinoma requires high radiation doses. The balance of the risks of local recurrence owing to inadequate tumor coverage versus the potential damage to the adjacent organs at risk (OARs) is of critical importance. With advancements in technology, high target conformality is possible. Nonetheless, to achieve...
Article
Background: The study aimed to assess if adherence to a total-neoadjuvant-treatment (TNT) protocol followed by observation(watch-and-wait) led to the successful nonoperative-management of low-rectal-cancer. Methods: In this study, patients with primary, resectable-T3-T4, N0-N1 distal-rectal-adenocarcinoma underwent-chemoradiotherapy + consolidat...
Article
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Background Paraganglioma of the head and neck (HNPGL) are rare often benign tumors. Surgery and radiation therapy (RT) are the main treatment choices. We present an analysis of outcome and toxicity after RT from 13 institutions of the Rare Cancer Network. Methods Data were collected using a questionnaire concerning patients' characteristics, treat...
Article
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Purpose The electron energy characteristics of mobile intraoperative radiotherapy (IORT) accelerator LIAC® differ from commonly used linear accelerators, thus some of the frequently used detectors can give less accurate results. The aim of this study is to evaluate the output factors (OFs) of several ionization chambers (IC) and solid state detecto...
Data
Table S1. Measured and k sat corrected OFs for flat applicators at 6 MeV with all detectors and OFMC results. Δ% is the percentage difference of measured OFs to OFMC. Table S2. k sat of PPC and CC ion chambers with different applicator sizes for 6 MeV. Table S3. Measured and k sat corrected OFs for flat applicators at 8 MeV of all detectors and O...
Article
Full-text available
The geographical location and differences in tumor biology significantly change the management of gastric cancer. The prevalence of gastric cancer ranks fifth and sixth among men and women, respectively, in Turkey. The international guidelines from the Eastern and Western countries fail to manage a considerable amount of inconclusive issues in the...
Article
Wortel et al (1), reporting the impact of rectal balloon and magnetic resonance imaging delineation on anorectal dose and gastrointestinal toxicity levels. In this study, protocol variations among 4 different centers that have used image-guided hypofractionated radiation therapy in intermediate-or high-risk prostate cancer were analyzed. The author...
Article
Background and purpose: The optimal treatment for adults with newly diagnosed medulloblastoma (MB) has not been defined. We report a large series of cases from the Rare Cancer Network. Material and methods: Thirteen institutions enrolled 206 MB patients who underwent postoperative radiotherapy (RT) between 1976 and 2014. Log-rank univariate and...
Article
Full-text available
Brain metastases are commonly seen complications in non-small cell lung cancer (NSCLC) patients. The incidence of brain metastases is increasing as a result of more effective systemic targeted therapies with prolonged survival. The prognosis is usually poor, and up to six months of median survivals were reported with different therapeutic options....
Article
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Purpose: Stereotactic body radiotherapy (SBRT) is an established treatment technique in the management of medically inoperable early stage non-small cell lung cancer (NSCLC). Different techniques such as volumetric modulated arc (VMAT) and three-dimensional conformal arc (DCA) can be used in SBRT. Previously, it has been shown that VMAT is superio...
Article
Purpose: Target delineation in nasopharyngeal carcinoma (NPC) often proves challenging because of the notoriously narrow therapeutic margin. High doses are needed to achieve optimal levels of tumour control, and dosimetric inadequacy remains one of the most important independent factors affecting treatment outcome. Method: A review of the availa...
Article
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Aim: CyberKnife(®) is a robotic stereotactic radiotherapy system. The aim of this study is to evaluate the effectiveness and the safety of CyberKnife(®) on treating head and neck paragangliomas and to report our results. Methods: Between March 2009 and June 2014, 12 patients with head and neck paragangliomas have been referred to our clinic: in...
Article
Full-text available
Carotid blowout syndrome (CBS) is a rarely seen complication of head-neck surgery and radiation therapy. It may present by massive ear bleeding or epistaxis with high morbidity and mortality rates. Success rate of endovascular therapy or emergency surgery is unfortunately low because of massive bleeding and weakened vessel architecture. Here, we pr...
Article
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Background: The use of patient symptom reports with frequent symptom assessment may be preferred over the more commonly used health-related quality of life questionnaires. Aims: We sought to linguistically validate the Turkish version of the M.D. Anderson Symptom Inventory-Head and Neck module (MDASI-HN) patient reported outcome questionnaire....
Conference Paper
Full-text available
Table of contents A1 Hope and despair in the current treatment of nasopharyngeal cancer IB Tan I1 NPC international incidence and risk factors Ellen T Chang I2 Familial nasopharyngeal carcinoma and the use of biomarkers Chien-Jen Chen, Wan-Lun Hsu, Yin-Chu Chien I3 Genetic susceptibility risk factors for sporadic and familial NPC: recent findings A...
Article
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Purpose: Nasopharyngeal carcinoma (NPC) is a rare but aggressive malignancy in children and adolescents. An international, randomized phase 2 trial was conducted to compare induction chemotherapy with docetaxel plus cisplatin and 5-fluorouracil (TPF) with cisplatin and 5-fluorouracil (PF) in NPC patients under the age of 21. Methods: Patients wi...
Article
Accessory breast tissue is a very rare finding in the general population with an incidence of one to two percent. An even rarer occurrence is accessory mammary-like tissue which developed breast carcinoma. The authors present a case of aggressive and metastatic carcinoma of vulvar originating from mammary-like tissue. A 73-year-old Caucasian female...
Article
Full-text available
PURPOSE: Robotic stereotactic hypofractionated radiotherapy (SRT) become an important modality in the treatment of cranial meningiomas. In this study, we analysed the treatment parameters and outcomes of our cranial meningioma patients treated with SRT. MATERIALS AND METHODS: Between 2009 and 2013, 103 cranial meningioma lesions of 93 patients were...
Article
Full-text available
Approximately, twenty years ago, the Rare Cancer Network (RCN) was formed in Lausanne, Switzerland, to support the study of rare malignancies. The RCN has grown over the years and now includes 130 investigators from twenty-four nations on six continents. The network held its first international symposium in Nice, France, on March 21-22, 2014. The p...
Article
Nasopharyngeal carcinoma (NPC) is a malignant tumor of the nasopharynx arising from the epithelial cells. Extension of the primary tumor to the adjacent tissues can cause cranial nerve (CN) palsies. Although all CNs can be involved, the CN VI, CN V, CN VIII, CN IX, and CN XII are the most commonly affected. Isolated involvement frequently occurs in...
Article
e11539 Background: We aimed to investigate the clinical and pathologic characteristics of patients with breast cancer (BC) who had a non-breast primary tumor and treated in our hospital. Methods: We identified BC patients with a second non-breast primary tumor retrospectively in our database. The tumors arising in a sequence by less than 2 months a...
Article
Full-text available
Background: To evaluate the patient and treatment characteristics of four radiotherapy centers with robotic systems (CyberKnife) in Istanbul. Materials and Methods: Five hundred and ninety-three patients treated with CyberKnife (CK) system during 2010 were included in this study. Data regarding their diagnosis, radiosurgery (SRS) indications, total...
Article
The purpose of this study was to investigate the prognostic factors and treatment results of T1N0M0 glottic laryngeal carcinoma irradiated with 2.3 Gray (Gy) per fraction. A total of 183 patients with glottic carcinoma treated between June 1998 and January 2007 were retrospectively evaluated. Of the 183 patients, 163 patients (89%) had T1a and 20 p...
Article
Full-text available
We compared conformal, intensity-modulated radiotherapy (IMRT) and intensity-modulated arc therapy (IMAT) in early stage glottic cancer in terms of dosimetric features as target coverage, dose to the organs at risk and total treatment time. Five consecutive T1 glottic squamous cell carcinoma patients were selected for the study. Three-dimensional c...