Researcher: Peker, Selçuk
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Peker, Selçuk
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Publication Metadata only Stereotactic radiosurgery and local control of brain metastases from triple-negative breast cancer(American Association of Neurological Surgeons, 2022) Kowalchuk, Roman O.; Niranjan, Ajay; Hess, Judith; Antonios, Joseph P.; Zhang, Michael Y.; Braunstein, Steve; Ross, Richard B.; Pikis, Stylianos; Deibert, Christopher P.; Lee, Cheng-Chia; Yang, Huai-Che; Langlois, Anne-Marie; Mathieu, David; Rusthoven, Chad G.; Chiang, Veronica; Wei, Zhishuo; Dade Lunsford L.; Trifiletti, Daniel M.; Sheehan, Jason P.; N/A; Peker, Selçuk; Samancı, Mustafa Yavuz; Faculty Member; Faculty Member; School of Medicine; School of Medicine; 11480; 275252Objective: stereotactic radiosurgery (SRS) is an effective treatment for intracranial metastatic disease, but its role in triple-negative breast cancer requires further study. Herein, the authors report overall survival (OS) and local tumor control in a multiinstitutional cohort with triple-negative breast cancer metastases treated with SRS. Methods: patients treated from 2010 to 2019 at 9 institutions were included in this retrospective study if they had biopsy-proven triple-negative breast cancer with intracranial metastatic lesions treated with SRS. Patients were excluded if they had undergone prior SRS, whole-brain radiation therapy, or resection of the metastatic lesions. A retrospective chart review was conducted to determine OS, local control, and treatment efficacy. Results: sixty-eight patients with 315 treated lesions were assessed. Patients had a median Karnofsky Performance Status of 80 (IQR 70-90) and age of 57 years (IQR 48-67 years). Most treated patients had 5 or fewer intracranial lesions, with 34% of patients having a single lesion. Treated lesions were small, having a median volume owf 0.11 cm3 (IQR 0.03-0.60 cm3). Patients were treated with a median margin dose of 18 Gy (IQR 18-20 Gy) to the median 71% isodose line (IQR 50%-84%). Overall, patients had a 1-year OS of 43% and 2-year OS of 20%. Most patients (88%) were followed until death, by which time local tumor progression had occurred in only 7% of cases. Furthermore, 76% of the lesions demonstrated regression. Tumor volume was correlated with local tumor progression (p = 0.012). SRS was very well tolerated, and only 3 patients (5%) developed symptomatic radiation necrosis. Conclusions: SRS is a safe and efficacious treatment for well-selected patients with triple-negative breast cancer, especially for those with a favorable performance status and small- to moderate-volume metastatic lesions.Publication Metadata only Gamma knife radiosurgery for hemorrhagic brainstem cavernomas(Turkish Neurosurgical Soc, 2019) Üçüncü Kefeli, Ayşegül; Şengöz, Meriç; N/A; Peker, Selçuk; Faculty Member; School of Medicine; Koc University Hospital; 11480AIM: To assess treatment results of gamma knife radiosurgery (GKRS) for hemorrhagic brainstem cavernous malformations (BSCMs). MATERIAL and METHODS: A retrospective review of patients with hemorrhagic BSCMs, who were treated at the Acibadem Kozyatagi Hospital GKRS unit from May 2007 to October 2015 was performed. RESULTS: In total, 82 patients were identified. All patients had experienced at least one hemorrhagic event (range 1-3), and all of them presented with radiological evidence of hemorrhage. The median target volume was 0.3 ml, and the median marginal radiation dose was 12 Gy. The mean durations before and after surgery were 25.5 (range 1-204) months, and 50.3 (range 13-113) months, respectively. Pre-treatment hemorrhage rates were calculated from the date of first hemorrhage to the date of radiosurgery. There were 97 bleeds over 174.4 patient-years during the observation period, with an annual hemorrhage rate of 55.7%. If the first bleed is excluded, the annual hemorrhage rate was 8.6%. Only three patients demonstrated re-bleeding, which occurred at 3, 12 and 79 months after radiosurgery. Over a total follow up time of 344 patient-years the annual re-bleeding rate was therefore 0.87%, indicating that the risk of BSCM hemorrhage was significantly decreased by radiosurgery. CONCLUSION: GKRS was a safe and effective treatment for symptomatic low volume BSCMs when a low marginal dose is used. A randomized controlled trial is needed that compares GKRS to observation if we want to establish the true efficacy of this treatment.Publication Metadata only Stereotactic radiosurgery for intracranial chordomas: an international multiinstitutional study(American Association of Neurological Surgeons (AANS), 2022) Pikis, Stylianos; Mantziaris, Georgios; Nabeel, Ahmed M.; Reda, Wael A.; Tawadros, Sameh R.; El-Shehaby, Amr M. N.; Abdelkarim, Khaled; Eldin, Reem M. Emad; Sheehan, Darrah; Sheehan, Kimball; Liscak, Roman; Chytka, Tomas; Tripathi, Manjul; Madan, Renu; Speckter, Herwin; Hernandez, Wenceslao; Barnett, Gene H.; Hori, Yusuke S.; Dabhi, Nisha; Aldakhil, Salman; Mathieu, David; Kondziolka, Douglas; Bernstein, Kenneth; Wei, Zhishuo; Niranjan, Ajay; Kersh, Charles R.; Lunsford, L. Dade; Sheehan, Jason P.; N/A; Peker, Selçuk; Samancı, Mustafa Yavuz; Faculty Member; Faculty Member; School of Medicine; School of Medicine; 11480; 275252Objective: the object of this study was to evaluate the safety, efficacy, and long-term outcomes of stereotactic radiosurgery (SRS) in the management of intracranial chordomas. Methods: this retrospective multicenter study involved consecutive patients managed with single-session SRS for an intracranial chordoma at 10 participating centers. Radiological and neurological outcomes were assessed after SRS, and predictive factors were evaluated via statistical methodology. Results: a total of 93 patients (56 males [60.2%], mean age 44.8 years [SD 16.6]) underwent single-session SRS for intracranial chordoma. SRS was utilized as adjuvant treatment in 77 (82.8%) cases, at recurrence in 13 (14.0%) cases, and as primary treatment in 3 (3.2%) cases. The mean tumor volume was 8 cm(3) (SD 7.3), and the mean prescription volume was 9.1 cm(3) (SD 8.7). The mean margin and maximum radiosurgical doses utilized were 17 Gy (SD 3.6) and 34.2 Gy (SD 6.4), respectively. on multivariate analysis, treatment failure due to tumor progression (p = 0.001) was associated with an increased risk for post-SRS neurological deterioration, and a maximum dose > 29 Gy (p = 0.006) was associated with a decreased risk. A maximum dose > 29 Gy was also associated with improved local tumor control (p = 0.02), whereas the presence of neurological deficits prior to SRS (p = 0.04) and an age > 65 years at SRS (p = 0.03) were associated with worse local tumor control. The 5- and 10-year tumor progression-free survival rates were 54.7% and 34.7%, respectively. An age > 65 years at SRS (p = 0.01) was associated with decreased overall survival. The 5- and 10-year overall survival rates were 83% and 70%, respectively. Conclusions: SRS appears to be a safe and relatively effective adjuvant management option for intracranial chordomas. The best outcomes were obtained in younger patients without significant neurological deficits. Further well-designed studies are necessary to define the best timing for the use of SRS in the multidisciplinary management of intracranial chordomas.Publication Metadata only Hormonal and radiologic outcomes after gamma knife radiosurgery for nonfunctioning pituitary adenomas(Taylor & Francis Ltd) Kara, Mujdat; Yilmaz, Meltem; Sengoz, Meric; N/A; Peker, Selçuk; Faculty Member; School of Medicine; Koç University Hospital; 11480Background Gamma knife radiosurgery (GKRS) is an established treatment option for residual and recurrent nonfunctioning pituitary adenoma (NFPA). This investigation assessed hormonal and radiologic outcomes after adjuvant and primary GKRS for NFPAs. Methods This retrospective study included 252 patients with NFPA who underwent GKRS at a single center between 2005 and 2016. GKRS was performed as adjuvant procedure in 216 (85.8%) patients and as primary procedure in 36 (14.2%) patients. Characteristics of these two groups were compared. Results Mean age was comparable between adjuvant and primary GKRS groups (48.3 +/- 12.6 vs. 52.2 +/- 13.2 years, respectively, p > 0.05). Adjuvant GKRS and primary GKRS groups were similar in terms of the mean prescribed radiation dose and tumor volume (15.1 +/- 2.7 vs. 15.3 +/- 1.9 Gy and 4.2 +/- 3.6 vs. 3.1 +/- 2.5 cm(3), respectively, p > 0.05 for both). The rate of endocrine deficiency during 5-year follow-up showed similar trend in adjuvant and primary GKRS groups (3.7%, 8.7%, and 14.8% vs. 5.6%, 13.9%, and 27.8% at first, third, and fifth year time points, respectively). Tumor control rates were also similar (98.6%, 96.3%, and 93% vs. 100%, 97.3%, and 94.5% at first, third, and fifth year time points, respectively). In both groups, tumor volume >5 cm(3) was associated with higher rate of hypopituitarism and tumor progression. Conclusions GKRS was effective both as adjuvant and primary procedure in patients with NFPA. Radiation dose of <= 13.5 Gy was associated with lower tumor control rate and tumor volume >5 cm(3) was associated with higher rates of hypopituitarism and tumor progression.Publication Metadata only Management of pediatric cerebral cavernous malformations with gamma knife radiosurgery: a report of 46 cases(Springer, 2022) Samancı, Mustafa Yavuz; Ardor, Gökçe Deniz; Peker, Selçuk; Faculty Member; Researcher; Faculty Member; School of Medicine; N/A; School of Medicine; Koç University Hospital; 275252; N/A; 11480Introduction: Pediatric cerebral cavernous malformations (CCMs) are commonly treated vascular anomalies with different clinical characteristics than their adult counterparts. Outcomes of Gamma Knife Radiosurgery (GKRS) for pediatric CCMs have not explicitly been reported. This paper reports our experience in managing pediatric CCMs with GKRS. Methods We retrospectively reviewed the clinical features, GKRS parameters, and clinical and radiological outcomes of 46 children with 64 CCMs. Results A total of 46 children, including 19 girls and 27 boys, with a median age of 16 years (3-17 years), were enrolled in the study. The median age at first CCM diagnosis was 13 years (range, 2-17 years). Twenty-two patients (47.8%) had more than one neurological symptom at the time of diagnosis, and the most common presenting symptom was seizure (28.3%). The most common location was supratentorial superficial (53.1%), and 17.4% of patients had multiple CCMs. A developmental venous anomaly was detected in 5 patients (10.9%). During a total of 52.4 retrospective patient-years in patients with> 1 hemorrhage episode, the calculated annual hemorrhage rate was 40.1%. The median post-GKRS follow-up was 79 months (range, 19-175 months), with an overall 306.2 prospective patient years. The annual hemorrhage rate (AHR) during the first 2 years after GKRS and after the initial 2 years was 1.11% and 0.46%, respectively. Regarding clinical factors and GKRS parameters, univariate analysis revealed a significant association with post-GKRS AHR and volume (p = 0.023) only. Patients with pre-GKRS seizures showed favorable seizure control (Engel class I and II) in 8 children (61.5%). There was no mortality in our series. Conclusion: Low AHR following GKRS with no radiation-induced toxicity makes GKRS a therapeutic alternative for pediatric CCMs.Publication Metadata only Long-term results of Gamma Knife radiosurgery for facial nerve schwannomas(Taylor & Francis, 2020) Şirin, Alperen; Yılmaz, Meltem; Şengöz, Meriç; N/A; N/A; Akyoldaş, Göktuğ; Peker, Selçuk; Faculty Member; Faculty Member; School of Medicine; School of Medicine; 203677; 11480Objective: Long-term outcomes of eleven cases of facial nerve schwannoma were evaluated and the related literature was reviewed to determine the efficacy of Gamma Knife radiosurgery for treating patients with facial nerve schwannoma. Methods: Eleven patients with facial nerve schwannoma (7 women and 4 men; mean age, 44.2 years; range, 19-73 years) underwent Gamma Knife radiosurgery. The most common symptoms were facial palsy (n = 10) and hearing loss (n = 7). Five patients presented with headache. Two patients had undergone prior resection. The patients' clinical and radiographic data were evaluated retrospectively. Results: For the 11 cases of facial nerve schwannoma, mean tumor volume was 3.1 cm(3) (range, 0.4-7.4 cm(3)) and the mean marginal dose applied was 11.9 Gy (range, 11-13 Gy). The mean follow-up period was 84.3 months (range, 66-117 months). Tumor control was achieved in all patients. At the time of writing, four patients experienced tumor volume regression and the other seven were in stable condition. During follow-up, nine patients experienced no change in their facial function, two experienced deteriorated facial function, and none developed new facial palsy. Ten patients who had serviceable hearing prior to Gamma Knife radiosurgery retained their hearing. Conclusions: Gamma Knife radiosurgery achieves excellent results with respect to tumor control for 7 years on average. In addition, Gamma Knife radiosurgery provides good results in facial nerve and hearing function at long term. Our series demonstrates that Gamma Knife radiosurgery is an effective and safe treatment for patients with either primary or residual facial nerve schwannoma.Publication Metadata only Long-term results of Gamma Knife radiosurgery for foramen magnum meningiomas(Springer, 2021) Yılmaz, Meltem; Şengöz, Meriç; Akyoldaş, Göktuğ; Samancı, Mustafa Yavuz; Peker, Selçuk; Faculty Member; Faculty Member; Faculty Member; School of Medicine; School of Medicine; School of Medicine; 203677; 275252; 11480Outcomes of 37 patients of foramen magnum meningioma (FMM) were evaluated, and the related literature was reviewed to determine the efficacy of Gamma Knife radiosurgery (GKRS) for treating patients with FMM. We present the largest series reported from a single institution with the longest follow-up to date. The database of patients who underwent GKRS for FMM between 2007 and 2019 was evaluated retrospectively. A total of 37 patients with radiological and pathological features consistent with FMM were included in this series. Thirty-three patients were female, and 4 were male. The median age was 58 years (range, 23-74 years). The most common symptom at diagnosis was headache (64.9%). Twelve patients had a history of microsurgical resection. The median duration from the initial onset of symptoms to GKRS was 12 months (range 1-140 months). Among the 37 tumors, eight (21.6%) were located ventrally, 24 (64.9%) laterally, and five (13.5%) dorsally. The median target volume was 3.30 cm(3) (range, 0.6-17.6 cm(3)). Thirty-five patients (95%) were treated with single fraction GKRS, and two patients (5%) were treated with hypofractionated GKRS. The median clinical follow-up was 80 months (range, 18-151 months), while the median radiological follow-up was 84 months (range, 18-144 months). At the last clinical follow-up after GKRS, 27 patients (73%) had improved symptoms, and none had worsened pre-GKRS symptoms. At the last radiological follow-up after GKRS, 23 tumors (62.2%) remained stable, 13 (35.1%) decreased in size, and 1 (2.7%) increased in size. Tumor control, including stable and regressed tumors, was achieved in 97.3% of patients. Our cohort demonstrates that GKRS is an effective and safe treatment for patients with either primary or recurrent/residual FMM.Publication Metadata only Effects of neuroanatomic structural distances on pituitary function after stereotactic radiosurgery: a multicenter study(Lippincott Williams and Wilkins (LWW), 2023) Ironside, Natasha; Chen, Ching-Jen; Xu, Zhiyuan; Schlesinger, David; Lee Vance, Mary; Hong, Gregory K.; Jane, John A.; Patel, Samir; Bindal, Shray K.; Niranjan, Ajay; Lunsford, L Dade; Liscak, Roman; Chytka, Thomas; Jezkova, Jana; Saifi, Omran; Trifiletti, Daniel M.; Berger, Assaf; Alzate, Juan; Bernstein, Kenneth; Kondziolka, Douglas; Speckter, Herwin; Hernandez, Wenceslao; Lazo, Erwin; Zacharia, Brad E.; Mau, Christine; Wegner, Rodney E.; Shepard, Matthew J.; Mathieu, David; Maillet, Michel; Sheehan, Jason P; N/A; Peker, Selçuk; Samancı, Mustafa Yavuz; Faculty Member; Faculty Member; School of Medicine; School of Medicine; 11480; 275252Background: Delayed hypopituitarism is the most common complication after stereotactic radiosurgery (SRS) for pituitary adenomas. Objective: To investigate the relationship between neuroanatomic structure distances from the radiation target and anterior pituitary function preservation after SRS through multicenter study. Methods: We retrospectively reviewed the International Radiosurgery Research Foundation database from January 2002 to December 2021 for adult patients undergoing SRS for pituitary adenomas with >6 months of follow-up. Distances between centers or edges of hypothalamic-pituitary axis structures and SRS target volumes were measured using MRI. The primary outcome was anterior pituitary function preservation. Predictors were analyzed using multivariable logistic regression and area under the receiver operating curve (AUROC) curve analyses. Results: Four hundred eighty-seven patients were categorized by preservation (n = 384) and no preservation (n = 103) of anterior pituitary function. The mean margin dose was 19.1(6.2) Gy. Larger distance from the center of the stalk to the tumor margin isodose was a positive predictor (adjusted odds ratio [aOR] = 1.162 [1.046-1.291], P = .005), while pre-SRS hypopituitarism (aOR = 0.646 [0.405-1.031], P = .067) and larger treatment volume (aOR = 0.965 [0.929-1.002], P = .061) were near negative predictors of the primary outcome. An interaction between the treatment volume and center stalk to margin isodose distance was found (aOR = 0.980 [0.961-0.999], P = .045). Center stalk to margin isodose distance had an AUROC of 0.620 (0.557-0.693), at 3.95-mm distance. For patients with treatment volumes of <2.34 mL, center stalk to margin isodose distance had an AUROC of 0.719 (0.614-0.823), at 2.95-mm distance. Conclusion: Achieving a distance between the center of the pituitary stalk and the tumor margin isodose ≥3.95 mm predicted anterior pituitary function preservation. For smaller treatment volumes <2.34 mL, the optimal distance was ≥2.95 mm. This may be modifiable during trans-sphenoidal resection to preserve pituitary function.Publication Metadata only Acute-onset hemiparkinsonism secondary to subacute-chronic subdural hematoma(Turkish Neurosurgical Soc, 2022) Özekmekçi, Sibel; Şenel, Gülçin Benbir; N/A; Ertan, Fatoş Sibel; Çakmak, Özgür Öztop; Peker, Selçuk; Faculty Member; Faculty Member; Faculty Member; School of Medicine; School of Medicine; School of Medicine; Koç University Hospital; 112829; 299358; 11480Subdural hematomas constitute rare causes of secondary Parkinsonism in elderly. Subacute or chronic subdural hematomas occur in the elderly following minor head trauma or even without a remarkable history of trauma. A 69-year-old woman admitted with a rapidly progressive acute-onset hemiparkinsonism on the left side of her body. She denied any precipitating event before the onset of her symptoms, and her medical history was unremarkable. The anti-Parkinsonian therapy showed no benefit, but gradually worsening of the symptoms was observed. Her brain magnetic resonance imaging revealed a large subacute-chronic subdural hematoma on the right side with a mass effect on the basal ganglia structures, contralateral to her symptomatology. On thorough questioning, she confessed to having fallen out of the bed at night almost four weeks ago, three-weeks before the onset of her symptomatology. She had no complications associated with this fall and merely remembered this event. She denied any history of rapid eye movements (REM) sleep behavior disorder. The anti-Parkinsonian treatment was discontinued; the subdural hematoma was evacuated via burr hole drainage surgery. Her symptoms disappeared instantly after the surgery, with a normal neurologic examination one week after the surgery.Publication Metadata only Frameless hypofractionated gamma knife radiosurgery for residual or recurrent craniopharyngioma(Lippincott Williams and Wilkins (LWW), 2023) N/A; Samancı, Mustafa Yavuz; Essibayi, Muhammed Amir; Askeroğlu, Mehmet Orbay; Budak, Mustafa; Karaköse, Fatih; Peker, Selçuk; Faculty Member; Other; Other; Other; Other; Faculty Member; School of Medicine; N/A; N/A; N/A; N/A; School of Medicine; Koç University Hospital; 275252; N/A; N/A; N/A; N/A; 11480Background: The management of craniopharyngiomas is challenging, usually requiring multidisciplinary care. Gamma Knife radiosurgery (GKRS) is an essential technique for residual/recurrent craniopharyngiomas. Objective: To evaluate the efficacy of frameless hypofractionated GKRS (hfGKRS) for craniopharyngioma and factors which affect tumor control and complications. Methods: This retrospective study involved 24 patients managed with hfGKRS. Clinical and radiological data, tumor characteristics, and procedural details were analyzed. Results: There were 15 (62.5%) female patients. The median age was 38.5 years (range, 3-66 years). The mean tumor volume was 2.4 (1.93) cm3, with a mean solid volume of 1.6 (1.75) cm3. The median marginal dose was 20 Gy (range, 18-25 Gy) delivered in a median of 5 fractions (range, 3-5). During a median radiological follow-up of 23.5 months (range, 12-50 months), tumor progression was noted in 5 (20.8%) patients. The 2-year and 4-year progression-free survival were 81.8% and 61.4%, respectively. No deaths were identified at a median clinical follow-up of 31.3 months (range, 12-54 months). Visual deficits attributable to progression were noted in 3 (12.5%) patients with pre-GKRS visual field defects. An additional 4 (16.7%) patients with pre-GKRS visual deficit developed new minor visual field defects. Four (16.7%) patients showed improvement of vision after GKRS. There were no new-onset post-GKRS hormonal deficits. Conclusion: The management of craniopharyngioma requires a multidisciplinary approach, and irradiation represents effective treatment option for residual/recurrent tumors after surgery. To the best of our knowledge, this is the first study that addresses the efficacy of frameless hfGKRS in managing craniopharyngiomas over sufficient follow-up.