Researcher: Peker, Selçuk
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Peker, Selçuk
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Publication Metadata only Transient ageusia and dysgeusia following thalamic cyst drainage(Turkish Neurosurgical Society, 2024) N/A; Nokay, Aziz Emre; Erden, Mert Emre; Samancı, Mustafa Yavuz; Peker, Selçuk; School of MedicineTaste consists of sensation and perception. Specific neural structures transmit a stimulus from the taste buds to the gustatory cortex to generate taste sensation. Any disruption of this pathway, whether it affects sensation or perception, can result in taste disorders. Stereotactic procedures involving the thalamus may result in gustatory complications. A 41-year-old female patient who underwent stereotactic drainage of a thalamic cyst suffered transient ageusia. Subsequently, she developed metallic taste perception. When her stereotactic plan was re-evaluated, it was noted that the posteromedial ventral thalamus nucleus was in the path of the needle tract and the needle had passed through it. Follow-up was recommended and her symptoms completely resolved within 2 months following surgery. Modern imaging techniques allow for the visualization of neural structures related to the sense of taste. Additionally, care must be taken when planning stereotactic procedures for such lesions.Publication Metadata only Risk of new tumor, carotid stenosis, and stroke after stereotactic radiosurgery for pituitary tumor: a multicenter study of 2254 patients with imaging follow-up(Oxford Univ Press, 2024) Dumot, C.; Mantziaris, G.; Dayawansa, S.; Brantley, C.; Lee, C. C.; Yang, H. C.; Mathieu, D.; Tourigny, J. N.; Moreno, N. M.; Álvarez, R. M.; Chytka, T.; Liscák, R.; Speckter, H.; Lazo, E.; Brito, A.; Picozzi, P.; Franzini, A.; Alzate, J.; Mashiach, E.; Bernstein, K.; Kondziolka, D.; Tripathi, M.; Bowden, G. N.; Warnick, R. E.; Sheehan, D.; Sheehan, K.; Fuentes, A.; Jane, J. A. Jr.; Lee Vance, M.; Sheehan, J. P.; Peker, Selçuk; Samancı, Mustafa Yavuz; ; School of Medicine;Background A higher risk of secondary brain tumor, carotid stenosis, and stroke has been reported after conventional sella irradiation for pituitary neuroendocrine tumors (PitNET). Stereotactic radiosurgery (SRS), which is a more focused approach, is now increasingly used instead. The aim was to assess the risk of secondary brain tumor, carotid stenosis/occlusion, and stroke after SRS. Methods In this multicentric retrospective study, 2254 patients with PitNET were studied, 1377 in the exposed group, and 877 in the control group. Results There were 9840.1 patient-years at risk for the SRS and 5266.5 for the control group. The 15-year cumulative probability of secondary intracranial tumor was 2.3% (95% CI: 0.5%, 4.1%) for SRS and 3.7% (95% CI: 0%, 8.7%) for the control group (P = .6), with an incidence rate of 1.32 per 1000 and 0.95 per 1000, respectively. SRS was not associated with an increased risk of tumorigenesis when stratified by age (HR: 1.59 [95% CI: 0.57, 4.47], Pp = .38). The 15-year probability of new carotid stenosis/occlusion was 0.9% (95% CI: 0.2, 1.6) in the SRS and 2% (95% CI: 0, 4.4) in the control group (P = .8). The 15-year probability of stroke was 2.6% (95% CI: 0.6%, 4.6%) in the SRS and 11.1% (95% CI: 6%, 15.9%) in the control group (P < .001). In Cox multivariate analysis stratified by age, SRS (HR 1.85 [95% CI:0.64, 5.35], P = .26) was not associated with risk of new stroke. Conclusions No increased risk of long-term secondary brain tumor, new stenosis or occlusion, and stroke was demonstrated in the SRS group compared to the control in this study with imaging surveillance.Publication Metadata only Adjuvant versus on-progression Gamma Knife radiosurgery for residual nonfunctioning pituitary adenomas: A matched-cohort analysis(Amer Assoc Neurological Surgeons, 2023) Mantziaris, Georgios; Pikis, Stylianos; Chytka, Tomas; Liscak, Roman; Sheehan, Kimball; Sheehan, Darrah; Bindal, Shray K.; Niranjan, Ajay; Lunsford, L. Dade; Kaur, Rupinder; Madan, Renu; Tripathi, Manjul; Pangal, Dhiraj J.; Strickland, Ben A.; Zada, Gabriel; Langlois, Anne-Marie; Mathieu, David; Warnick, Ronald E.; Patel, Samir; Minier, Zayda; Speckter, Herwin; Xu, Zhiyuan; Anand, Rithika Kormath; Sheehan, Jason P.; Peker, Selçuk; Samancı, Mustafa Yavuz; School of MedicineOBJECTIVE Radiological progression occurs in 50%-60% of residual nonfunctioning pituitary adenomas (NFPAs). Stereotactic radiosurgery (SRS) is a safe and effective management option for residual NFPAs, but there is no consen-sus on its optimal timing. This study aims to define the optimal timing of SRS for residual NFPAs. METHODS This retrospective, multicenter study involved 375 patients with residual NFPAs managed with SRS. The patients were divided into adjuvant (ADJ;treated for stable residual NFPA within 6 months of resection) and progression (PRG) cohorts (treated for residual NFPA progression). Factors associated with tumor progression and clinical deteriora-tion were analyzed.RESULTS Following propensity-score matching, each cohort consisted of 130 patients. At last follow-up, tumor con-trol was achieved in 93.1% of patients in the ADJ cohort and in 96.2% of patients in the PRG cohort (HR 1.6, 95% CI 0.55-4.9, p = 0.37). Hypopituitarism was associated with a maximum point dose of > 8 Gy to the pituitary stalk (HR 4.5, 95% CI 1.6-12.6, p = 0.004). No statistically significant difference was noted in crude new-onset hypopituitarism rates (risk difference [RD] = -0.8%, p > 0.99) or visual deficits (RD = -2.3%, p = 0.21) between the two cohorts at the last follow-up. The median time from resection to new hypopituitarism was longer in the PRG cohort (58.9 vs 29.7 months, p = 0.01).CONCLUSIONS SRS at residual NFPA progression does not appear to alter the probability of tumor control or hormon-al/visual deficits compared with adjuvant SRS. Deferral of radiosurgical management to the time of radiological progres- sion could significantly prolong the time to radiosurgically induced pituitary dysfunction. A lower maximum point dose (< 8 Gy) to the pituitary stalk portended a more favorable chance of preserving pituitary function after SRS. https://thejns.org/doi/abs/10.3171/2022.10.JNS221873Publication Metadata only Stereotactic radiosurgery for brain metastases from human epidermal receptor 2 positive breast Cancer: An international, multi-center study(Springer, 2024) Pikis, Stylianos; Mantziaris, Georgios; Protopapa, Maria; Tos, Salem M.; Kowalchuk, Roman O.; Ross, Richard Blake; Rusthoven, Chad G.; Tripathi, Manjul; Langlois, Anne-Marie; Mathieu, David; Lee, Cheng-Chia; Yang, Huai-Che; Zhang, Michael Yu; Braunstein, Steve E.; Wei, Zhishuo; Niranjan, Ajay; Lunsford, Dade L.; Sheehan, Jason; Peker, Selçuk; Samancı, Mustafa Yavuz; School of MedicinePurpose: To report patient outcomes and local tumor control rates in a cohort of patients with biopsy-proven HER-2 positive breast cancer treated with stereotactic radiosurgery (SRS) for brain metastases (BM). Methods: This international, retrospective, multicenter study, included 195 female patients with 1706 SRS-treated BM. Radiologic and clinical outcomes after SRS were determined and prognostic factors identified. Results: At SRS, median patient age was 55 years [interquartile range (IQR) 47.6–62.0], and 156 (80%) patients had KPS ≥ 80. The median tumor volume was 0.1 cm3 (IQR 0.1–0.5) and the median prescription dose was 16 Gy (IQR 16–18). Local tumor control (LTC) rate was 98%, 94%, 93%, 90%, and 88% at six-, 12-, 24-, 36- and 60-months post-SRS, respectively. On multivariate analysis, tumor volume (p = < 0.001) and concurrent pertuzumab (p = 0.02) improved LTC. Overall survival (OS) rates at six-, 12-, 24-, 36-, 48-, and 60-months were 90%, 69%, 46%, 27%, 22%, and 18%, respectively. Concurrent pertuzumab improved OS (p = 0.032). In this patient subgroup, GPA scores ≥ 2.5 (p = 0.038 and p = 0.003) and rare primary tumor histologies (p = 0.01) were associated with increased and decreased OS, respectively. Asymptomatic adverse radiation events (ARE) occurred in 27 (14.0%) and symptomatic ARE in five (2.6%) patients. Invasive lobular carcinoma primary (p = 0.042) and concurrent pertuzumab (p < 0.001) conferred an increased risk for overall but not for symptomatic ARE. Conclusion: SRS affords effective LTC for selected patients with BM from HER-2 positive breast cancer. Concurrent pertuzumab improved LTC and OS but at the same time increased the risk for overall, but not symptomatic, ARE. © The Author(s) 2024.Publication Metadata only Pediatric cerebral cavernous malformations and stereotactic radiosurgery: An analysis of 50 cases from a multicentric study(American Association of Neurological Surgeons, 2024) Mantziaris, Georgios; Dumot, Chloe; Pikis, Stylianos; Nabeel, Ahmed M.; Reda, Wael A.; Tawadros, Sameh R.; Abdel Karim, Khaled; El-Shehaby, Amr M.N.; Emad Eldin, Reem M.; Elazzazi, Ahmed H.; Sheehan, Darrah; Sheehan, Kimball; Moreno, Nuria Martinez; Alvarez, Roberto Martinez; Liscak, Roman; May, Jaromir; Tripathi, Manjul; Rajput, Akshay; Kumar, Narendra; Kaur, Rupinder; Alzate, Juan Diego; Kondziolka, Douglas; Dayawansa, Sam; Sheehan, Jason P.; Peker, Selçuk; Samancı, Mustafa Yavuz; Ardor, Gökçe Deniz; School of Medicine; Koç University HospitalOBJECTIVE Cerebral cavernous malformations (CCMs) are the second most common vascular anomaly affecting the CNS in children. Although stereotactic radiosurgery (SRS) has been proposed as an alternative to microsurgery in the management of selected cases in adults, there is a paucity of studies focusing on pediatric patients. The aim of this study was to present the outcomes and associated risks of SRS in this subgroup of patients. METHODS This retrospective multicenter study included pediatric patients treated with single-session SRS for CCMs. The annual hemorrhage rate (AHR) was calculated before and after SRS in hemorrhagic lesions. The Engel classification was used to describe post-SRS epileptic control. Adverse radiation effects (AREs) and the occurrence of new neurological deficits were recorded. RESULTS The study included 50 patients (median age 15.1 [IQR 5.6] years) harboring 62 CCMs. Forty-two (84%) and 22 (44%) patients had a history of hemorrhage or epilepsy prior to SRS, respectively. The AHR from diagnosis to SRS excluding the first hemorrhage was 7.19 per 100 CCM-years, dropping to 3.15 per 100 CCM-years after treatment. The cumulative risk of first hemorrhage after SRS was 7.4% (95% CI 0%–14.3%) at 5 years and 23.6% (95% CI 0%–42.2%) at 10 years. Eight hemorrhagic events involving 6 CCMs in 6 patients were recorded in the post-SRS follow-up period;4 patients presented with transient symptoms and 4 with permanent symptoms. Of the 22 patients with pre-SRS seizures, 11 were seizure free at the last follow-up (Engel class I), 6 experienced improvement (Engel class II or III), 5 had no improvement (Engel class IVA or IVB), and 1 experienced worsening (Engel class IVC). Radiographic AREs were documented in 14.5% (9/62) of CCMs, with 4 being symptomatic. CONCLUSIONS Single-session SRS reduces the CCM hemorrhage rate in the pediatric population and provides adequate seizure control. © 2024 American Association of Neurological Surgeons. All rights reserved.Publication Metadata only Repeat stereotactic radiosurgery for persistent cerebral arteriovenous malformations in pediatric patients(American Association of Neurological Surgeons, 2024) Garcia, Gracie; Mantziaris, Georgios; Pikis, Stylianos; Dumot, Chloe; Lunsford, L. Dade; Niranjan, Ajay; Wei, Zhishuo; Srinivasan, Priyanka; Tang, Lilly W.; Liscak, Roman; May, Jaromir; Lee, Cheng-Chia; Yang, Huai-Che; Nabeel, Ahmed M.; Reda, Wael A.; Tawadros, Sameh R.; Karim, Khaled Abdel; El-Shehaby, Amr M.N.; Eldin, Reem Emad; Elazzazi, Ahmed Hesham; Moreno, Nuria Martínez; Álvarez, Roberto Martínez; Padmanaban, Varun; Jareczek, Francis J.; McInerney, James; Cockroft, Kevin M.; Alzate, Juan Diego; Kondziolka, Douglas; Tripathi, Manjul; Sheehan, Jason P.; Peker, Selçuk; Samancı, Mustafa Yavuz; School of MedicineOBJECTIVE The purpose of this study was to describe the long-term outcomes and associated risks related to repeat stereotactic radiosurgery (SRS) for persistent arteriovenous malformations (AVMs) in pediatric patients. METHODS Under the auspices of the International Radiosurgery Research Foundation, this retrospective multicenter study analyzed pediatric patients who underwent repeat, single-session SRS between 1987 and 2022. The primary outcome variable was a favorable outcome, defined as nidus obliteration without hemorrhage or neurological deterioration. Secondary outcomes included rates and probabilities of hemorrhage, radiation-induced changes (RICs), and cyst or tumor formation. RESULTS The cohort included 83 pediatric patients. The median patient age was 11 years at initial SRS and 15 years at repeat SRS. Fifty-seven children (68.7%) were managed exclusively using SRS, and 42 (50.6%) experienced hemorrhage prior to SRS. Median AVM diameter and volume were substantially different between the first (25 mm and 4.5 cm3, respectively) and second (16.5 mm and 1.6 cm3, respectively) SRS, while prescription dose and isodose line remained similar. At the 5-year follow-up evaluation from the second SRS, nidus obliteration was achieved in 42 patients (50.6%), with favorable outcome in 37 (44.6%). The median time to nidus obliteration and hemorrhage was 35.5 and 38.5 months, respectively. The yearly cumulative probability of favorable outcome increased from 2.5% (95% CI 0.5%–7.8%) at 1 year to 44% (95% CI 32%–55%) at 5 years. The probability of achieving obliteration followed a similar pattern and reached 51% (95% CI 38%–62%) at 5 years. The 5-year risk of hemorrhage during the latency period after the second SRS reached 8% (95% CI 3.2%–16%). Radiographically, 25 children (30.1%) had RICs, but only 5 (6%) were symptomatic. Delayed cyst formation occurred in 7.2% of patients, with a median onset of 47 months. No radiation-induced neoplasia was observed. CONCLUSIONS The study results showed nidus obliteration in most pediatric patients who underwent repeat SRS for persistent AVMs. The risks of symptomatic RICs and latency period hemorrhage were quite low. These findings suggest that repeat radiosurgery should be considered when treating pediatric patients with residual AVM after prior SRS. Further study is needed to define the role of repeat SRS more fully in this population. © 2024 American Association of Neurological Surgeons. All rights reserved.Publication Metadata only Comparative analysis of the spatial distribution of brain metastases across several primary cancers using machine learning and deep learning models(Springer, 2024) Mahmoodifar, Saeedeh; Pangal, Dhiraj J.; Neman, Josh; Zada, Gabriel; Mason, Jeremy; Salhia, Bodour; Kaisman-Elbaz, Tehila; Hamel, Andreanne; Mathieu, David; Tripathi, Manjul; Sheehan, Jason; Pikis, Stylianos; Mantziaris, Georgios; Newton, Paul K.; Peker, Selçuk; Samancı, Mustafa Yavuz; School of MedicineObjectiveBrain metastases (BM) are associated with poor prognosis and increased mortality rates, making them a significant clinical challenge. Studying BMs can aid in improving early detection and monitoring. Systematic comparisons of anatomical distributions of BM from different primary cancers, however, remain largely unavailable.MethodsTo test the hypothesis that anatomical BM distributions differ based on primary cancer type, we analyze the spatial coordinates of BMs for five different primary cancer types along principal component (PC) axes. The dataset includes 3949 intracranial metastases, labeled by primary cancer types and with six features. We employ PC coordinates to highlight the distinctions between various cancer types. We utilized different Machine Learning (ML) algorithms (RF, SVM, TabNet DL) models to establish the relationship between primary cancer diagnosis, spatial coordinates of BMs, age, and target volume.ResultsOur findings revealed that PC1 aligns most with the Y axis, followed by the Z axis, and has minimal correlation with the X axis. Based on PC1 versus PC2 plots, we identified notable differences in anatomical spreading patterns between Breast and Lung cancer, as well as Breast and Renal cancer. In contrast, Renal and Lung cancer, as well as Lung and Melanoma, showed similar patterns. Our ML and DL results demonstrated high accuracy in distinguishing BM distribution for different primary cancers, with the SVM algorithm achieving 97% accuracy using a polynomial kernel and TabNet achieving 96%. The RF algorithm ranked PC1 as the most important discriminating feature.ConclusionsIn summary, our results support accurate multiclass ML classification regarding brain metastases distribution.Publication Metadata only Efficacy of hypofractionated Gamma Knife radiosurgery in treating surgical beds of metastatic brain tumors(Elsevier Sci Ltd, 2024) Samancı, Mustafa Yavuz; Tepebaşılı, Mehmet Ali; Ardor, Gökçe Deniz; Düzkalır, Ali Haluk; Askeroğlu, Mehmet Orbay; Peker, Selçuk; School of Medicine; Koç University HospitalObjective: Surgery alone for metastatic brain tumors (METs) often results in local recurrence due to microscopic residual tumor tissue. While stereotactic radiosurgery (SRS) is commonly used post-surgery, hypofractionation may be required for large surgical beds. This study evaluated the efficacy and safety of hypofractionated Gamma Knife radiosurgery (hf-GKRS) for the first time as a post-operative adjuvant therapy. Methods: This retrospective study involved 24 patients (28 surgical beds) who underwent hf-GKRS within four weeks after surgery. The study primarily focused on local control (LC) rate and analyzed distant intracranial failure (DICF), intracranial progression-free survival (PFS), leptomeningeal disease (LMD), overall survival (OS), and radiation necrosis (RN). Results: During a median follow-up of 9 months, LC was achieved in 89.3 % of surgical beds. LC estimates at 6, 12, and 24 months were 96.4 %, 82.7 %, and 82.7 %, respectively. DICF was observed in 45.8 % of patients, and LMD was identified in two patients (8.3 %). At the end of the follow-up, 58.3 % of patients were alive, and the median OS was 20 months. RN occurred in only one surgical bed (3.6 %). No grade 5 toxicity was observed. The univariate analysis identified a longer interval to GKRS (HR 11.842, p = 0.042) and a larger treatment volume (HR 1.103, p = 0.037) as significant factors for local failure. Conclusions: hf-GKRS shows potential as an effective and safe adjuvant treatment for surgical beds. It offers an alternative to SRS, SRT, or WBRT, particularly for larger volumes or tumors near critical structures. Further research is needed to confirm these results and optimize treatment approaches.Publication Metadata only Gamma Knife radiosurgery for multiple sclerosis-associated trigeminal neuralgia(Elsevier Sci Ltd, 2024) Özlük, Gülşah Özturk; Samancı, Mustafa Yavuz; Düzkalır, Ali Haluk; Şenyürek, Şükran; Askeroğlu, Mehmet Orbay; Peker, Selçuk; School of Medicine; Koç University HospitalBackground: Gamma Knife radiosurgery (GKRS) has well-known efficacy in the treatment of idiopathic trigeminal neuralgia (TN). However, few studies have evaluated the effects of GKRS in the treatment of multiple sclerosis (MS)-related TN. This study analyzed the efficacy and complications of GKRS for MS-related TN. Methods: This retrospective study included 28 MS-related TN patients who underwent GKRS with a median follow-up of 27 (range, 12-181) months. The cisternal segment of the trigeminal nerve was targeted with a median radiation dose of 80 (80-90) Gy. Pain intensity was assessed using Barrow Neurological Institute (BNI)Pain Intensity Scores (BNI-PIS). Before GKRS, all patients suffered from BNI pain levels of 4 or 5. A reduction in pain to BNI 3b or below was deemed as adequate pain relief. Results: The initial proportion of patients who experienced adequate pain relief was 71.4%, with a median interval of 21 (1-45) days. At the final follow-up, 50% of patients had achieved adequate pain relief. Ten patients (35.7%) suffered from complications, including four with facial sensorial dysfunctions, four with a decline in their corneal reflexes, and two with jaw weakness. Among the 20 initial responders, six (30%) patients suffered pain recurrence after a median interval of 35 (12-180) months. Conclusions: GKRS is an effective means of pain relief in MS-related TN, but has side effects that are relevant to other ablative treatments. The benefits and risks of GKRS should be discussed with patients who wish to avoid surgery or when previous treatments fail.Publication Metadata only Clinical outcomes following stereotactic radiosurgery for cerebral cavernous malformations of the basal ganglia and thalamus(American Association of Neurological Surgeons, 2023) Singh, R.; Dumot, C.; Mantziaris, G.; Dayawansa, S.; Xu, Z.; Pikis, S.; Nabeel, A.M.; Reda, W.A.; Tawadros, S.R.; Abdel, Karim, K.; El-Shehaby, A.M.N.; Emad, Eldin, R.M.; Sheehan, D.; Sheehan, K.; Elazzazi, A.H.; Martínez, Moreno, N.; Martínez, Álvarez, R.; Liscak, R.; May, J.; Mathieu, D.; Tourigny, J.N.; Tripathi, M.; Rajput, A.; Kumar, N.; Kaur, R.; Picozzi, P.; Franzini, A.; Speckter, H.; Hernandez, W.; Brito, A.; Warnick, R.E.; Alzate, J.D.; Kondziolka, D.; Bowden, G.N.; Patel, S.; Sheehan, J.P.; Peker, Selçuk; Samancı, Mustafa Yavuz; Ardor, Gökçe Deniz; School of Medicine; Koç University HospitalOBJECTIVE There are few reports of outcomes following stereotactic radiosurgery (SRS) for the management of cerebral cavernous malformations (CCMs) of the basal ganglia or thalamus. Therefore, the authors aimed to clarify these outcomes. METHODS Centers participating in the International Radiosurgery Research Foundation were queried for CCM cases managed with SRS from October 2001 to February 2021. The primary outcome of interest was hemorrhage-free survival (HFS) with a secondary outcome of symptomatic adverse radiation events (AREs). Assessment of the association of prognostic factors with HFS was conducted via Kaplan-Meier analysis and log-rank test. Chi-square tests were conducted to assess potential factors associated with the incidence of AREs. RESULTS Seventy-three patients were identified. The median patient age was 43.5 years (range 4.4–79.5 years). Fifty-nine (80.8%) patients had hemorrhage prior to SRS. The median treatment volume was 0.9 cm3 (range 0.07–10.1 cm3) with a median margin prescription dose (MPD) of 12 Gy (range 10–20 Gy). One-, 3-, 5-, and 10-year HFS were 93.0%, 89.9%, 89.9%, and 83.0%, respectively, with one hemorrhage-related death approximately 1 year after SRS and nearly 60% and 30% of patients having improvement or stability of symptoms, respectively. There was no correlation between lesion size or MPD and HFS. Seven (9.6%) patients experienced AREs (MPDs > 12 Gy in all cases). Lesion size > 1.0 cm3 was correlated with the incidence of an ARE (p = 0.019). Forty-two (93.3%) of 45 patients treated with an MPD ≤ 12 Gy experienced neither hemorrhage nor AREs following SRS versus 17 (60.7%) of 28 patients treated with an MPD > 12 Gy (p = 0.0006). CONCLUSIONS SRS is a reasonable treatment strategy and confers clinical stability or improvement and hemorrhage avoidance in patients harboring CCMs of the basal ganglia or thalamus. An MPD of approximately 12 Gy is recommended for the management of CCM.