Osman Köstek

Dr. Osman Köstek


Research Focus & Metrics

Academic Career Length

14Years (2013-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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29 October 2018 in Cancer Chemotherapy and Pharmacology
Verified
Journal Article
Closed access
PDF file
OKOsman Köstek
Osman Köstek
MHMuhammet Bekir Hacıoğlu
Muhammet Bekir Hacıoğlu
ASAbdullah Sakin
Abdullah Sakin
TDTarık Demir
Tarık Demir
MSMurat Sarı
Murat Sarı
BEBülent Erdoğan
Bülent Erdoğan

7 February 2025 in Journal of Clinical Medicine
Verified
Journal Article
Open access
PDF file
AGAli Kaan Güren
Ali Kaan Güren
MGMurad Guliyev
Murad Guliyev
ÖAÖzkan Alan
Özkan Alan
KÇKıvanç Çadırci
Kıvanç Çadırci
IBİpek Naz Belevi
İpek Naz Belevi
İBİbrahim Vedat Bayoğlu
İbrahim Vedat Bayoğlu
Introduction: CDK 4/6 inhibitors are effectively utilized among patients with hormone-positive, HER-2-negative metastatic breast cancer. The dose reduction for these patients varies between 35% and 57% across multiple trials. We aim to clarify the characteristics of patients who had dosage reduction and the effect of this reduction on survival outcomes. Materials and Methods: The study was designed as a retrospective, multicenter study. Patients who received CDK 4/6 inhibitors in the first-line and subsequent treatment settings were grouped based on dose reductions. Progression-free survival was compared between these groups, and factors influencing dose reduction were analyzed. Results: Multivariate logistic regression study demonstrated that patients aged 65 and older, with a Charlson CI score of 2 or higher, having metastases in three or more sites, and classed as normal weight, had greater dosage reductions. Dose reduction had no impact on progression-free survival (PFS) (p = 0.114 for first-line treatment, p = 0.528 for second and subsequent-line treatment; p > 0.05). Conclusions: Regarding the absence of disparity in progression-free survival between patients with dose reduction and those without, dose reduction should not be avoided in certain patient groups to ensure therapy continuity and mitigate potential adverse effects.

7 June 2021 in Cancer Investigation
Verified
Journal Article
Closed access
ABAykut Bahçeci
Aykut Bahçeci
SPSemra Paydas
Semra Paydas
NANaziye Ak
Naziye Ak
FFFerhat Ferhatoğlu
Ferhat Ferhatoğlu
PSPınar Mualla Saip
Pınar Mualla Saip
NYNilgün Yildirim
Nilgün Yildirim
The aim of this study is to evaluate the efficacy and toxicity of trastuzumab emtansine (T-DM1) in cases with metastatic breast cancer (mBC) in different lines of treatment.Retrospective analysis o...

17 March 2025 in Journal of Clinical Medicine
Verified
Journal Article
Open access
PDF file
NSnadiye sever
nadiye sever
FŞFatih Şimşek
Fatih Şimşek
İOİlknur Deliktaş Onur
İlknur Deliktaş Onur
HAHayati Arvas
Hayati Arvas
TGTural Guliyev
Tural Guliyev
İBİbrahim Vedat Bayoğlu
İbrahim Vedat Bayoğlu
Background: Osteosarcoma is a rare but aggressive bone malignancy. Despite advances in multimodal therapy, survival remains suboptimal, highlighting the need for prognostic markers to guide treatment. Methods: This study included 162 osteosarcoma patients who received neoadjuvant chemotherapy followed by surgery between January 2009 and March 2024. Patients received either double (cisplatin + doxorubicin) or triple (MAP or PEI) chemotherapy. Survival analyses were conducted using Kaplan–Meier curves, log-rank tests, and Cox proportional hazards models. Results: The median age was 20 years (IQR: 18–29), and 53.1% were male. Patients who received triple chemotherapy regimens demonstrated significantly longer overall survival (OS) compared to those on doublet regimens. High tumor necrosis rates (>90%) and negative surgical margins were strongly associated with improved OS, while metastatic disease at diagnosis, elevated alkaline phosphatase (ALP), and male gender were linked to poorer survival. Multivariate analysis identified adjuvant therapy, age under 18, high necrosis rate, negative margins, and normal ALP as significant OS predictors. Conclusions: Triple-agent chemotherapy, necrosis rate ≥90 and negative surgical margins are strongly associated with prolonged survival in osteosarcoma. The key prognostic indicators such as ALP levels, surgical margins and age at diagnosis should guide personalized treatment strategies to improve outcomes in curable patients.

19 February 2025 in The Prostate
Verified
Journal Article
Open access
MHMuhammet Bekir Hacıoğlu
Muhammet Bekir Hacıoğlu
AKAhmet Küçükarda
Ahmet Küçükarda
IGivo gokmen
ivo gokmen
AGAli Fuat Gurbuz
Ali Fuat Gurbuz
MAMurat Araz
Murat Araz
BEBülent Erdoğan
Bülent Erdoğan
Objective: The Prognostic Nutritional Index (PNI), reflects the nutritional and immunological status of the patient and has been associated with outcomes in various cancers. In this study, the prognostic significance of PNI in metastatic hormone‐sensitive prostate cancer (mHSPC) and its potential role in guiding treatment decisions between abiraterone acetate and enzalutamide is investigated.Methods: Retrospective analysis was performed on 167 mHSPC patients treated between 2019 and 2024. PNI was calculated using the formula: 10 × serum albumin (g/dL) + 0.005 × total lymphocyte count (/mm³). Patients were stratified into high and low PNI groups according to a cutoff value of 49.98, determined via receiver operating characteristic (ROC) analysis. Survival outcomes, including overall survival (OS), radiographic progression‐free survival (rPFS), and PSA progression‐free survival (PSA‐PFS), were assessed. Treatment responses to abiraterone acetate and enzalutamide were compared within PNI strata.Results: Patients with PNI > 49.98 had significantly longer median OS than those with PNI ≤ 49.98 (36.6 months vs. 30.0 months, p < 0.01). Multivariate analysis identified high PNI, ECOG performance status 0–1, and absence of visceral metastasis as independent predictors of improved OS. Among patients with low PNI, those treated with enzalutamide had superior OS compared to those receiving abiraterone acetate (p = 0.004), while no significant OS difference was noted between treatments in the high PNI group (p = 0.55).Conclusion: PNI serves as a significant prognostic biomarker in mHSPC, correlating with overall survival and potentially influencing treatment efficacy between abiraterone acetate and enzalutamide. Integrating PNI into clinical practice may aid in tailoring individualized treatment options.

24 January 2019 in Cancer Chemotherapy and Pharmacology
Verified
Journal Article
Closed access
OKOsman Köstek
Osman Köstek
EYErdem Yılmaz
Erdem Yılmaz
MHMuhammet Bekir Hacıoğlu
Muhammet Bekir Hacıoğlu
NDNazım Can Demircan
Nazım Can Demircan
AGAli Gökyer
Ali Gökyer
BEBülent Erdoğan
Bülent Erdoğan