John Byun

All Publications

• Efficacy and Safety of CyberKnife Stereotactic Radiosurgery for Occipital Condyle Metastasis NEUROSURGERY PRACTICE Park, D. J., Voruganti, H., Annagiri, S., Shaghaghian, E., Hori, Y. S., Persad, A. R., Yoo, K. H., Abu-Reesh, D., Lam, F. C., Tayag, A., Ustrzynski, L., Emrich, S. C., Han, S. S., Gu, X., Byun, J., Rahimy, E., Pollom, E. L., Soltys, S. G., Gephart, M., Li, G., Chang, S. D. 2025; 6 (4)

  View details for DOI 10.1227/neuprac.0000000000000169

  View details for Web of Science ID 001577502000001

• Efficacy and Safety of CyberKnife Stereotactic Radiosurgery for Occipital Condyle Metastasis. Neurosurgery practice Park, D. J., Voruganti, H., Annagiri, S., Shaghaghian, E., Hori, Y. S., Persad, A. R., Yoo, K. H., Abu-Reesh, D., Lam, F. C., Tayag, A., Ustrzynski, L., Emrich, S. C., Han, S. S., Gu, X., Byun, J., Rahimy, E., Pollom, E. L., Soltys, S. G., Gephart, M. H., Li, G., Chang, S. D. 2025; 6 (4): e000169

  Abstract

  Occipital condyle metastasis (OCM) is a rare condition characterized by severe occipital pain and neurological symptoms due to lower cranial nerve (CN) deficits, stemming from its anatomic location. Despite the widespread use of stereotactic radiosurgery (SRS) for cranial metastases, its specific impact on OCM remains underexplored. This study evaluates the efficacy and safety of CyberKnife SRS in treating OCM, focusing on occipital pain, dysfunctions of lower CNs, and local tumor control.We retrospectively analyzed cases of OCM treated with SRS at our institute from 2012 to 2023, evaluating patient demographics, presenting symptoms, treatment parameters, and outcomes.Eighteen patients (10 females) with a mean age of 64 years (SD: 10.4) were treated. Common presentations included occipital pain (44.4%) and lower CN deficits (27.8%). The median target volume was 6.95 cc (IQR: 4.64-21.2). The mean single-fraction equivalent dose was 18.7 Gy10 (SD: 1.9). Ten tumors received 15-20 Gy in 1 fraction (50%), 2 tumors received 20-28 Gy in 2 fractions (10%), 4 tumors received 27 Gy in 3 fractions (20%), and 4 tumors received 30-40 Gy in 5 fractions (20%). Based on Kaplan-Meier estimate, SRS achieved 93.8% local tumor control rate over 3 years, with a median overall survival of 13 months (95% CI: 0-32.2). Among patients presenting with symptoms, 87.5% reported occipital pain relief (P = .04), and 80% observed improvements in CN function (P = .003). Four patients experienced local recurrence.CyberKnife SRS is a promising treatment of OCM, offering significant pain relief and improvement in neurological symptoms, along with favorable local control rates. This noninvasive therapy provides a valuable alternative to surgery, potentially enhancing the quality of life for patients with limited treatment options due to this challenging condition.

  View details for DOI 10.1227/neuprac.0000000000000169

  View details for PubMedID 41163734

  View details for PubMedCentralID PMC12560716

• Repeat stereotactic radiosurgery for treatment of brain metastases locally recurrent following initial radiosurgery. Journal of neuro-oncology Hall, J. C., Goel, K., Lozko, Y., Chang, S. D., Park, D. J., Hori, Y. S., Lam, F. C., AbuReesh, D., Jackson, S., Li, G., Hayden-Gephart, M., Kaneko, T., Nagpal, S., Gibbs, I. C., Rahimy, E., Byun, J., Jin, K., Pollom, E., Soltys, S. G. 2025

  Abstract

  We report outcomes of repeat stereotactic radiosurgery (rSRS) to sites of tumor progression following initial SRS. Additionally, we sought to determine if, at the time of recurrence following initial SRS, surgical resection of the tumor followed by SRS (surgery + rSRS) provided benefit compared to rSRS alone.We retrospectively reviewed patients treated with rSRS for local recurrence after initial SRS. The cumulative incidences of LF and adverse radiation effect (ARE), with death as a competing risk, were estimated.From 2004 to 2022, we identified 77 patients with 429 brain metastases treated with initial SRS, of which 97 metastases were treated with rSRS for salvage of LF following initial SRS; 49 metastases had resection prior to rSRS. Of the 429 brain metastases treated with initial SRS, the cumulative incidence of LF was 12.6% [95% confidence interval (CI) 9.7-15.9] at 1 year; in 97 sites treated with rSRS, LF was 14.6% (95%CI 8.4-22.4) at 1 year. There was no significant difference (p = 0.3) in 1-year LF after surgery + rSRS [11.1% (95%CI 4.0-22.31)] versus rSRS alone [18.4% (95%CI 9.0-30.5)]. The 1-year rates of ARE were: 3.0% (95%CI 1.7-5.0%) for initial SRS (overall grade 1-4), 15.6% (95%CI 9.2-23.6) for rSRS (overall grade 1-4), and 12.6% (95%CI 6.8-20.1%) for rSRS (symptomatic grade 2-4).Given that the 1-year local progression of 15% with rSRS is similar to the 13% of initial SRS, our data do not support that tumors recurrent after initial SRS are inherently radioresistant to salvage SRS. Tumor control must be balanced by the 1-year rates of adverse radiation effect (16% overall, 13% symptomatic).

  View details for DOI 10.1007/s11060-025-05201-y

  View details for PubMedID 40914931

  View details for PubMedCentralID 5737512

• Perilesional Edema as a Predictor of Local Failure in Metastatic Brain Lesions Treated with Stereotactic Radiosurgery: A Systematic Review and Meta-Analysis: Perilesional Edema and Local Failure. International journal of radiation oncology, biology, physics Akhavan-Sigari, A., Sbaih, O., Hori, Y. S., Mathieu, D., Byun, J., Pollom, E. L., Soltys, S. G., Park, D. J., Chang, S. D. 2025

  Abstract

  Identifying prognostic factors to improve local tumor control (LTC) after SRS for brain metastases (BM) is crucial for optimizing patient outcomes. This study synthesizes evidence on the impact of perilesional edema (PLE) on local tumor control in brain metastases managed with SRS.A systematic search was conducted in Pubmed, Scopus, Embase, and Web of Science, to identify relevant studies reporting PLE as a prognostic factor for LTC in BM treated with SRS.Nine studies, comprising 829 patients treated for 1,742 BM treated with SRS, met the inclusion criteria. For the primary analysis, eight studies involving 1,455 BM were included. A random effects model (REM) demonstrated that higher or present PLE was associated with an increased risk of local failure (HR=1.82, 95% CI: 1.42-2.34, I2=13.8%). Subgroup analyses using a fixed-effect model (FEM) revealed further insights: studies defining PLE using numeric cutoffs showed a higher risk of local failure (HR=1.71, 95% CI: 1.39-2.10; I²=0%), while studies dichotomizing PLE as present versus absent observed an even greater risk (HR=2.78, 95% CI: 1.65-4.69; I²=33.5%). Sensitivity analysis incorporating all nine studies confirmed a significant association between PLE and local failure but introduced notable heterogeneity (HR=1.68, 95% CI: 1.17-2.43, I2=81.3%).Pre-treatment PLE in BM is associated with an increased risk of local failure following SRS, with local failure rates more than doubling in lesions exhibiting edema at the time of treatment. Future research should explore the potential of edema-reducing therapies administered at the time of SRS to improve treatment outcomes.

  View details for DOI 10.1016/j.ijrobp.2025.06.3878

  View details for PubMedID 40588068

• Understanding the Radiobiology of Central Nervous System Diseases in the Golden Age of Radiosurgery-Does It Matter? Brain sciences Lam, F. C., Byun, J., Guru, S., AbuReesh, D., Hori, Y. S., Rahimy, E., Pollom, E. L., Soltys, S., Park, D. J., Chang, S. D. 2025; 15 (6)

  Abstract

  Stereotactic radiosurgery (SRS) deploys image-guidance to deliver multiple beams of highly focused ionizing radiation to tightly conformed anatomical targets, leading to precise dosing of radiation-induced cellular injury and predictable biological responses that can be applied to treat a multitude of central nervous system (CNS) disorders. Herein we review the principles of CNS radiobiology, comparing differences between SRS and conventional radiation therapy. We then review the radiobiology of SRS as it pertains to the treatment of CNS tumors and vascular malformations and the emerging application of SRS for the treatment of functional and psychiatric neurological disorders. Finally, we look toward the future in combining SRS with other novel technologies to improve treatment outcomes for patients with CNS disorders.

  View details for DOI 10.3390/brainsci15060649

  View details for PubMedID 40563819

• Use of Carbon Fiber Implants to Improve the Safety and Efficacy of Radiation Therapy for Spine Tumor Patients. Brain sciences Lam, F. C., Guru, S., AbuReesh, D., Hori, Y. S., Chuang, C., Liu, L., Wang, L., Gu, X., Szalkowski, G. A., Wang, Z., Wohlers, C., Tayag, A., Emrich, S. C., Ustrzynski, L., Zygourakis, C. C., Desai, A., Hayden Gephart, M., Byun, J., Pollom, E. L., Rahimy, E., Soltys, S., Park, D. J., Chang, S. D. 2025; 15 (2)

  Abstract

  Current standard of care treatment for patients with spine tumors includes multidisciplinary approaches, including the following: (1) surgical tumor debulking, epidural spinal cord decompression, and spine stabilization techniques; (2) systemic chemo/targeted therapies; (3) radiation therapy; and (4) surveillance imaging for local disease control and recurrence. Titanium pedicle screw and rod fixation have become commonplace in the spine surgeon's armamentarium for the stabilization of the spine following tumor resection and separation surgery. However, the high degree of imaging artifacts seen with titanium implants on postoperative CT and MRI scans can significantly hinder the accurate delineation of vertebral anatomy and adjacent neurovascular structures to allow for the safe and effective planning of downstream radiation therapies and detection of disease recurrence. Carbon fiber-reinforced polyetheretherketone (CFR-PEEK) spine implants have emerged as a promising alternative to titanium due to the lack of artifact signals on CT and MRI, allowing for more accurate and safe postoperative radiation planning. In this article, we review the tenants of the surgical and radiation management of spine tumors and discuss the safety, efficacy, and current limitations of CFR-PEEK spine implants in the multidisciplinary management of spine oncology patients.

  View details for DOI 10.3390/brainsci15020199

  View details for PubMedID 40002531

  View details for PubMedCentralID PMC11852773