George Stoyanov Stoyanov

Dr. George Stoyanov Stoyanov

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Research Focus & Metrics

Academic Career Length

12Years (2015-Present)

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

Representative Publications

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31 January 2018 in Medical Oncology
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GSGeorge Stoyanov Stoyanov
George Stoyanov Stoyanov
DDDeyan Dzhenkov
Deyan Dzhenkov
PGPeter Ghenev
Peter Ghenev
BIBogomil Iliev
Bogomil Iliev
YEYavor Enchev
Yavor Enchev
ATAnton B. Tonchev
Anton B. Tonchev

1 March 2018 in Folia Medica
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GSGeorge Stoyanov Stoyanov
George Stoyanov Stoyanov
DDDeyan Dzhenkov
Deyan Dzhenkov
Glioblastoma multiforme(GBM) is a grade IV WHO malignant tumor with astrocytic differentiation. As one of the most common clinically diagnosed central nervous system (CNS) oncological entries, there have been a wide variety of historical reports of the description and evolution of ideas regarding these tumors.The first recorded reports of gliomas were given in British scientific reports, by Berns in 1800 and in 1804 by Abernety, with the first comprehensive histomorphological description being given in 1865 by Rudolf Virchow. In 1926 Percival Bailey and Harvey Cushing gave the base for the modern classification of gliomas. Between 1934 and 1941 the most prolific researcher in glioma research was Hans-Joachim Scherer, who postulated some of the clinico-morphological aspects of GBM. With the introduction of molecular and genetic tests the true multifomity of GBM has been established, with different genotypes bearing the same histomorphological and IHC picture, as well as some of the aspects of gliomagenesis. For a GBM to develop, a specific trigger mutation needs to occur in a GBM stem cell – primary GBM, or a slow aggregation of individual mutations, without a distinct trigger mutation – secondary GBM.Knowledge of GBM has been closely related to general medical knowledge of the CNS since these malignancies were first described more than 200 years ago. Several great leaps have been made in that time, in the footsteps of both CNS and advancements in general medical knowledge.

1 February 2022 in Cureus
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GSGeorge Stoyanov Stoyanov
George Stoyanov Stoyanov
ELEmran Lyutfi
Emran Lyutfi
RGReneta Georgieva
Reneta Georgieva
RGRadoslav Georgiev
Radoslav Georgiev
DDDeyan Dzhenkov
Deyan Dzhenkov
PGPeter Ghenev
Peter Ghenev
The 2021 World Health Organization (WHO) classification of tumors of the central nervous system (CNS) has introduced significant changes to tumor taxonomy. One of the most significant changes in the isolation of isocitrate dehydrogenase (IDH) mutant forms of glioblastoma multiforme (GBM) into separate entities, as well as no longer allowing for entries to be classified as not otherwise specified (NOS). As a result, this entity now includes only the most aggressive adult-type tumors. As such, established prognostic factors no longer apply, as they now form the criteria of different disease entries or have been established based on a mixed cohort. Herein, we aimed to reclassify glioblastoma cases diagnosed per the 2016 WHO tumors of the CNS classification into the 2021 WHO tumors of the CNS classification and establish a patient survival pattern based on age, gender, tumor location, and size as well as tumor O‐6‐methylguanine‐DNA methyltransferase (MGMT) mutation. A retrospective, non-clinical approach was utilized. Biopsy specimens of adults diagnosed with GBM, WHO grade 4, NOS in the period February 2018-February 2021 were reevaluated. The data regarding the patient's gender and age were withdrawn from the medical documentation. Immunohistochemistry was performed with mouse monoclonal anti-IDH R132H and rabbit polyclonal anti-MGMT. Radiology data on tumor location and size were pulled from the radiology repository. Data were statistically analyzed for significance, using Kaplan-Meier survival analysis, with a 95% confidence interval and p<0.05 defined as significant. A total of 58 cases fit the set criteria, with eight of them (13.7%) harboring an IDH R132H mutation and were hence reclassified as diffuse astrocytoma IDH-mutant, WHO CNS grade 4. The cases that retained their GBM classification included n=28 males and n=22 females, a male to female ratio of 1.27:1, and a mean age of 65.3 years (range 43-86 years). The MGMT mutational status revealed a total of n=17 positive cases (35%), while the remaining cases were negative. No hemispheric predilection could be established. Lobar predilection was as follows: temporal (37.78%), parietal (28.89%), frontal (24.44%), and occipital (8.89%). The mean tumor size measured on neuroradiology across the cohort was 50.51 mm (range 20-76 mm). The median survival across cases was 255.96 days (8.41 months), with a range of 18-1150 days (0.59-37.78 months). No statistical correlation could be established between patient survival and gender, hemispheric location, lobar location, and tumor size. A significant difference in survival was established only when comparing the 41-50 age groups to the 71-80 and 81-90 age groups and MGMT positive versus negative tumors (p=0.0001). From a practical standpoint, the changes implemented in the new classification of CNS tumors define GBM as the most aggressive adult type of tumor. Based on their significantly more favorable prognosis, the reclassification of IDH mutant forms of astrocytomas has had little epidemiological impact on this relatively common malignancy but has significantly underlined the dismal prognosis. The changes have also led to MGMT promoter methylation status being the only significant prognostic factor for patient survival in clinical use, based on its prediction for response to temozolomide therapy in this nosological unit clinically presenting when it has already reached immense size.

25 July 2020 in Head and Neck Pathology
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GSGeorge Stoyanov Stoyanov
George Stoyanov Stoyanov
DDDeyan Dzhenkov
Deyan Dzhenkov
LPLilyana Petkova
Lilyana Petkova
NSNikolay Sapundzhiev
Nikolay Sapundzhiev
SGSvetoslav Georgiev
Svetoslav Georgiev

2 July 2017 in Cureus
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GSGeorge Stoyanov Stoyanov
George Stoyanov Stoyanov
MKMartina Kitanova
Martina Kitanova
DDDeyan Dzhenkov
Deyan Dzhenkov
PGPeter Ghenev
Peter Ghenev
NSNikolay Sapundzhiev
Nikolay Sapundzhiev
Head and neck cancer (HNC) comprises a diverse group of oncological entities, originating from various tissue types and organ localizations, situated in the topographical regions of the head and neck (H&N). This single institution retrospective study was aimed at establishing the HNC patient demographics and categorizing the individual incidence of H&N malignancies, regarding their organ of origin and main histopathological type. All histologically verified cases of HNC from a single tertiary referral center were reviewed in a descriptive retrospective manner. Data sampling period was 47 months. Male to female ratio of the registered HNC cases was 3.24:1. The mean age of diagnosis was 63.84 ± 12.65 years, median 65 years. The most common HNC locations include the larynx 30.37% (n = 188), lips and oral cavity 29.08% (n = 180), pharynx 20.03% (n = 124) and salivary glands 10.94% (n = 68), with other locations such as the external nose, nasal cavity and sinuses and auricle and external ear canal harboring a minority of the cases. The main histopathological groups include squamous cell carcinoma 76.74% (n = 475) and adenocarcinoma 6.14% (n = 38), with other malignant entries such as other epithelial malignancies, primary tonsillar, mucosa-associated lymphoid tissue or parenchymal lymphomas, connective tissue neoplasias, neuroendocrine and vascular malignancies diagnosed in a minority of cases. Considered to be relatively rare, HNC represents a diverse group of oncological entities with individual and specific demographic characteristics. The reported single institution results appear representative of the national incidence and characteristics of HNC.

5 June 2024 in Gels
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Nadezhda IvanovaNadezhda Ivanova
Nadezhda Ivanova
NENeli Mitkova Ermenlieva
Neli Mitkova Ermenlieva
LSLora Simeonova
Lora Simeonova
NVNeli Milenova Vilhelmova-Ilieva
Neli Milenova Vilhelmova-Ilieva
KBKameliya Bratoeva
Kameliya Bratoeva
Velichka AndonovaVelichka Andonova
Velichka Andonova
A combination of Poloxamer 407 (P407) and hydroxypropyl methylcellulose (HPMC) hydrosols is proposed as an in situ thermo-gelling vehicle for the nasal drug delivery of chlorhexidine–silver nanoparticles conjugates (SN-CX). Optimization of the formulation was carried out by applying varying ratios of P407 and HPMC in the presence and absence of SN-CX so that gelation would occur in the temperature range of the nasal cavity (30–34 °C). Mechanisms for the observed gelation phenomena were suggested based on viscosimetry, texture analysis, and dynamic light scattering. Tests were carried out for sprayability, washout time, in vitro drug release, ex vivo permeation, and antimicrobial activity. When applied separately, HPMC was found to lower the P407 gelation temperature (Tg), whereas SN-CX increased it. However, in the presence of HPMC, SN-CX interfered with the P407 micellar organization in a principally contrasting way while leading to an even further decrease in Tg. SN-CX-loaded nasal formulations composed of P407 16% and HPMC 0.1% demonstrated a desired gelation at 31.9 °C, good sprayability (52.95% coverage of the anterior nasal cavity), mucoadhesion for 70 min under simulated nasal clearance, expedient release and permeation, and preserved anti-infective activity against seasonal Influenza virus and beta-coronavirus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus and other pathogens. Our findings suggest that the current development could be considered a potential formulation of a protective nasal spray against respiratory infections.