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Carbon fiber–reinforced PEEK spinal implants for primary and metastatic spine tumors: a systematic review on implant complications and radiotherapy benefits

Presented at the 2023 AANS/CNS Joint Section on Disorders of the Spine and Peripheral Nerves

Hammad A. Khan, Roee Ber, Sean N. Neifert, David B. Kurland, Ilya Laufer, Douglas Kondziolka, Arpit Chhabra, Anthony K. Frempong-Boadu, and Darryl Lau

OBJECTIVE

By minimizing imaging artifact and particle scatter, carbon fiber–reinforced polyetheretherketone (CF-PEEK) spinal implants are hypothesized to enhance radiotherapy (RT) planning/dosing and improve oncological outcomes. However, robust clinical studies comparing tumor surgery outcomes between CF-PEEK and traditional metallic implants are lacking. In this paper, the authors performed a systematic review of the literature with the aim to describe clinical outcomes in patients with spine tumors who received CF-PEEK implants, focusing on implant-related complications and oncological outcomes.

METHODS

A systematic review of the literature published between database inception and May 2022 was performed in accordance with the 2020 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The PubMed database was queried using the terms "carbon fiber" and "spine" or "spinal." The inclusion criteria were articles that described patients with CF-PEEK pedicle screw fixation and had a minimum of 5 patients. Case reports and phantom studies were excluded.

RESULTS

This review included 11 articles with 326 patients (237 with CF-PEEK–based implants and 89 with titanium-based implants). The mean follow-up period was 13.5 months, and most tumors were metastatic (67.1%). The rates of implant-related complications in the CF-PEEK and titanium groups were 7.8% and 4.7%, respectively. The rate of pedicle screw fracture was 1.7% in the CF-PEEK group and 2.4% in the titanium group. The rates of reoperation were 5.7% (with 60.0% because of implant failure or junctional kyphosis) and 4.8% (all because of implant failure or junctional kyphosis) in the CF-PEEK and titanium groups, respectively. When reported, 72.5% of patients received postoperative RT (41.0% stereotactic body RT, 30.8% fractionated RT, 25.6% proton, 2.6% carbon ion). Four articles suggested that implant artifact was reduced in the CF-PEEK group. Local recurrence occurred in 14.4% of CF-PEEK and 10.7% of titanium-implanted patients.

CONCLUSIONS

While CF-PEEK harbors similar implant failure rates to traditional metallic implants with reduced imaging artifact, it remains unclear whether CF-PEEK implants improve oncological outcomes. This study highlights the need for prospective, direct comparative clinical studies.

In Journal of Neurosurgery: Spine Publish Before Print

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Letter to the Editor. Blood flow analysis for obliteration of AVMs

Ruinan Li, Yu Chen, Zhipeng Li, Heze Han, Pingting Chen, Xiaolin Chen, and Yuanli Zhao

In Journal of Neurosurgery Volume 138: Issue 4 (Apr 2023)

Free access

Imaging-defined necrosis after treatment with single-fraction stereotactic radiosurgery and immune checkpoint inhibitors and its potential association with improved outcomes in patients with brain metastases: an international multicenter study of 697 patients

Eric J. Lehrer, Manmeet S. Ahluwalia, Jason Gurewitz, Kenneth Bernstein, Douglas Kondziolka, Ajay Niranjan, Zhishuo Wei, L. Dade Lunsford, Kareem R. Fakhoury, Chad G. Rusthoven, David Mathieu, Claire Trudel, Timothy D. Malouff, Henry Ruiz-Garcia, Phillip Bonney, Lindsay Hwang, Cheng Yu, Gabriel Zada, Samir Patel, Christopher P. Deibert, Piero Picozzi, Andrea Franzini, Luca Attuati, Rahul N. Prasad, Raju R. Raval, Joshua D. Palmer, Cheng-Chia Lee, Huai-Che Yang, Brianna M. Jones, Sheryl Green, Jason P. Sheehan, and Daniel M. Trifiletti

OBJECTIVE

Immune checkpoint inhibitors (ICIs) and stereotactic radiosurgery (SRS) are commonly utilized in the management of brain metastases. Treatment-related imaging changes (TRICs) are a frequently observed clinical manifestation and are commonly classified as imaging-defined radiation necrosis. However, these findings are not well characterized and may predict a response to SRS and ICIs. The objective of this study was to investigate predictors of TRICs and their impact on patient survival.

METHODS

This retrospective multicenter cohort study was conducted through the International Radiosurgery Research Foundation. Member institutions submitted de-identified clinical and dosimetric data for patients with non–small cell lung cancer (NSCLC), melanoma, and renal cell carcinoma (RCC) brain metastases that had been treated with SRS and ICIs. Data were collected from March 2020 to February 2021. Univariable and multivariable Cox and logistic regression analyses were performed. The Kaplan-Meier method was used to evaluate overall survival (OS). The diagnosis-specific graded prognostic assessment was used to guide variable selection. TRICs were determined on the basis of MRI, PET/CT, or MR spectroscopy, and consensus by local clinical providers was required.

RESULTS

The analysis included 697 patients with 4536 brain metastases across 11 international institutions in 4 countries. The median follow-up after SRS was 13.6 months. The median age was 66 years (IQR 58–73 years), 54.1% of patients were male, and 57.3%, 36.3%, and 6.4% of tumors were NSCLC, melanoma, and RCC, respectively. All patients had undergone single-fraction radiosurgery to a median margin dose of 20 Gy (IQR 18–20 Gy). TRICs were observed in 9.8% of patients. The median OS for all patients was 24.5 months. On univariable analysis, Karnofsky Performance Status (KPS; HR 0.98, p < 0.001), TRICs (HR 0.67, p = 0.03), female sex (HR 0.67, p < 0.001), and prior resection (HR 0.60, p = 0.03) were associated with improved OS. On multivariable analysis, KPS (HR 0.98, p < 0.001) and TRICs (HR 0.66, p = 0.03) were associated with improved OS. A brain volume receiving ≥ 12 Gy of radiation (V12Gy) ≥ 10 cm3 (OR 2.78, p < 0.001), prior whole-brain radiation therapy (OR 3.46, p = 0.006), and RCC histology (OR 3.10, p = 0.01) were associated with an increased probability of developing TRICs. The median OS rates in patients with and without TRICs were 29.0 and 23.1 months, respectively (p = 0.03, log-rank test).

CONCLUSIONS

TRICs following ICI and SRS were associated with a median OS benefit of approximately 6 months in this retrospective multicenter study. Further prospective study and additional stratification are needed to validate these findings and further elucidate the role and etiology of this common clinical scenario.

In Journal of Neurosurgery Volume 138: Issue 5 (May 2023)

Free access

Preoperative flow analysis of arteriovenous malformations and obliteration response after stereotactic radiosurgery

Juan Diego Alzate, Assaf Berger, Kenneth Bernstein, Reed Mullen, Tanxia Qu, Joshua S. Silverman, Maksim Shapiro, Peter K. Nelson, Eytan Raz, Jafar J. Jafar, Howard A. Riina, and Douglas Kondziolka

OBJECTIVE

Morphological and angioarchitectural features of cerebral arteriovenous malformations (AVMs) have been widely described and associated with outcomes; however, few studies have conducted a quantitative analysis of AVM flow. The authors examined brain AVM flow and transit time on angiograms using direct visual analysis and a computer-based method and correlated these factors with the obliteration response after Gamma Knife radiosurgery.

METHODS

A retrospective analysis was conducted at a single institution using a prospective registry of patients managed from January 2013 to December 2019: 71 patients were analyzed using a visual method of flow determination and 38 were analyzed using a computer-based method. After comparison and validation of the two methods, obliteration response was correlated to flow analysis, demographic, angioarchitectural, and dosimetric data.

RESULTS

The mean AVM volume was 3.84 cm3 (range 0.64–19.8 cm3), 32 AVMs (45%) were in critical functional locations, and the mean margin radiosurgical dose was 18.8 Gy (range 16–22 Gy). Twenty-seven AVMs (38%) were classified as high flow, 37 (52%) as moderate flow, and 7 (10%) as low flow. Complete obliteration was achieved in 44 patients (62%) at the time of the study; the mean time to obliteration was 28 months for low-flow, 34 months for moderate-flow, and 47 months for high-flow AVMs. Univariate and multivariate analyses of factors predicting obliteration included AVM nidus volume, age, and flow. Adverse radiation effects were identified in 5 patients (7%), and 67 patients (94%) remained free of any functional deterioration during follow-up.

CONCLUSIONS

AVM flow analysis and categorization in terms of transit time are useful predictors of the probability of and the time to obliteration. The authors believe that a more quantitative understanding of flow can help to guide stereotactic radiosurgery treatment and set accurate outcome expectations.

In Journal of Neurosurgery Volume 138: Issue 4 (Apr 2023)

Open access

Diplopia outcomes following stereotactic radiosurgery for petroclival or cavernous sinus meningiomas: patient series

Bennett R. Levy, Assaf Berger, and Douglas Kondziolka

BACKGROUND

Skull base meningiomas (SBM) often present with diplopia due to compression of the abducens cranial nerve (CN VI). The authors evaluated outcomes in 13 patients diagnosed with SBMs who were experiencing diplopia to determine if Gamma Knife surgery (GKS) resulted in resolution of their symptoms.

OBSERVATIONS

Fourteen patients who were diagnosed with SBMs located in the cavernous sinus, clivus, or petroclival regions and presented with diplopia were treated by GKS. Demographic and clinical data as well as the duration of diplopia prior to GKS were documented. Of the 13 patients included in the study, 1 was excluded because he was lost to follow-up. For the remaining 12, diplopia was resolved in 10 (83%) and no change was noted in 2 (17%). Time to resolution was measured in months, varying from 1 to 30 months, with a median resolution time of 4.5 ± 9.7 months. Of the patients with documented postradiosurgical resolution (n = 10), the median amount of time with diplopia prior to GKS was 1.5 months (range, 1 to 20).

LESSONS

This study showed that diplopia, related to a basal meningioma, may improve following GKS. An earlier time course to radiosurgery after diplopia onset was associated with better outcomes.

In Journal of Neurosurgery: Case Lessons Volume 3 (2022): Issue 25 (Jun 2022)

Free access

Stereotactic radiosurgery for Rathke’s cleft cysts: an international multicenter study

Douglas Kondziolka, Kenneth Bernstein, Cheng-Chia Lee, Huai-Che Yang, Roman Liscak, Jaromir May, Roberto Martínez-Álvarez, Nuria Martínez-Moreno, Adomas Bunevicius, and Jason P. Sheehan

OBJECTIVE

Rathke’s cleft cysts (RCCs) are sellar collections from an incompletely regressed Rathke’s pouch. Common symptoms of RCCs can include headaches, visual loss, and endocrinopathy. Surgery is required in some cases of symptomatic or growing RCCs. Recurrence after surgery is common (range 10%–40%). Stereotactic radiosurgery (SRS) has been used in an attempt to control growth and symptoms, but outcomes are not well known. The authors sought to study the outcomes of RCCs following Gamma Knife surgery for both salvage and initial treatment.

METHODS

The outcomes of 25 patients with RCCs who underwent SRS between 2001 and 2020 were reviewed. Four patients received initial SRS and 21 were treated with salvage SRS. Diagnosis was based on imaging or histopathology. Cyst control was defined as stability or regression of the cyst. Kaplan-Meier analysis was used to determine time to recurrence and determine potential factors for recurrence.

RESULTS

The respective median clinical follow-up and margin dose were 6.5 years and 12 Gy. Overall control was achieved in 19 (76%) of 25 patients, and 4 recurrences required further intervention. The average time to recurrence was 35.6 months in those RCCs that recurred. Visual recovery occurred in 14 (93.3%) of 15 patients and no new post-SRS visual deficits occurred. The presence of a pretreatment visual deficit was often an indicator of RCC regrowth. All 3 patients with pretreatment hyperprolactinemia experienced resolution after SRS. New endocrinopathy related to SRS was noted in 5 (20%) of 25 patients, all of which were thyroid and/or cortisol axis related. Upfront SRS was used in 4 patients. No new endocrinopathies or visual deficits developed after upfront SRS, and the 1 patient with a pretreatment visual deficit recovered. One of the 4 patients with upfront SRS experienced a recurrence after 7.5 years.

CONCLUSIONS

SRS produced effective recovery of visual deficits and carries a low risk for new visual deficits. Cyst control was achieved in approximately three-fourths of the patients. Following SRS, patients without pretreatment visual deficits are less likely to have RCC regrowth. Endocrinopathy can occur after SRS, similar to other sellar mass lesions. Initial SRS shows the potential for long-term cyst control, with improvement of symptoms and a low risk for complications.

In Journal of Neurosurgery Volume 137: Issue 4 (Oct 2022)

Free access

Stereotactic radiosurgery for intracranial chordomas: an international multiinstitutional study

Stylianos Pikis, Georgios Mantziaris, Selcuk Peker, Yavuz Samanci, Ahmed M. Nabeel, Wael A. Reda, Sameh R. Tawadros, Amr M. N. El-Shehaby, Khaled Abdelkarim, Reem M. Emad Eldin, Darrah Sheehan, Kimball Sheehan, Roman Liscak, Tomas Chytka, Manjul Tripathi, Renu Madan, Herwin Speckter, Wenceslao Hernández, Gene H. Barnett, Yusuke S. Hori, Nisha Dabhi, Salman Aldakhil, David Mathieu, Douglas Kondziolka, Kenneth Bernstein, Zhishuo Wei, Ajay Niranjan, Charles R. Kersh, L. Dade Lunsford, and Jason P. Sheehan

OBJECTIVE

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 cm3 (SD 7.3), and the mean prescription volume was 9.1 cm3 (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.

In Journal of Neurosurgery Volume 137: Issue 4 (Oct 2022)

Open access

Absence of residual tumor tissue after Gamma Knife radiosurgery followed by resection of a vestibular schwannoma: illustrative case

Assaf Berger, Kristyn Galbraith, Matija Snuderl, John G. Golfinos, and Douglas Kondziolka

BACKGROUND

Late pathology after vestibular schwannoma radiosurgery is uncommon. The authors presented a case of a resected hemorrhagic mass 13 years after radiosurgery, when no residual tumor was found.

OBSERVATIONS

A 56-year-old man with multiple comorbidities, including myelodysplastic syndrome cirrhosis, received Gamma Knife surgery for a left vestibular schwannoma. After 11 years of stable imaging assessments, the lesion showed gradual growth until a syncopal event occurred 2 years later, accompanied by progressive facial weakness and evidence of intralesional hemorrhage, which led to resection. However, histopathological analysis of the resected specimen showed hemorrhage and reactive tissue but no definitive residual tumor.

LESSONS

This case demonstrated histopathological evidence for the role of radiosurgery in complete elimination of tumor tissue. Radiosurgery for vestibular schwannoma carries a rare risk for intralesional hemorrhage in select patients.

In Journal of Neurosurgery: Case Lessons Volume 3 (2022): Issue 2 (Jan 2022)

Free access

Survival and outcomes in patients with ≥ 25 cumulative brain metastases treated with stereotactic radiosurgery

Carolina Gesteira Benjamin, Jason Gurewitz, Ami Kavi, Kenneth Bernstein, Joshua Silverman, Monica Mureb, Bernadine Donahue, and Douglas Kondziolka

OBJECTIVE

In the era in which more patients with greater numbers of brain metastases (BMs) are being treated with stereotactic radiosurgery (SRS) alone, it is critical to understand how patient, tumor, and treatment factors affect functional status and overall survival (OS). The authors examined the survival outcomes and dosimetry to critical structures in patients treated with Gamma Knife radiosurgery (GKRS) for ≥ 25 metastases in a single session or cumulatively over the course of their disease.

METHODS

A retrospective analysis was conducted at a single institution. The institution’s prospective Gamma Knife (GK) SRS registry was queried to identify patients treated with GKRS for ≥ 25 cumulative BMs between June 2013 and April 2020. Ninety-five patients were identified, and their data were used for analysis. Treatment plans for dosimetric analysis were available for 89 patients. Patient, tumor, and treatment characteristics were identified, and outcomes and OS were evaluated.

RESULTS

The authors identified 1132 patients with BMs in their institutional registry. Ninety-five patients were treated for ≥ 25 cumulative metastases, resulting in a total of 3596 tumors treated during 373 separate treatment sessions. The median number of SRS sessions per patient was 3 (range 1–12 SRS sessions), with nearly all patients (n = 93, 98%) having > 1 session. On univariate analysis, factors affecting OS in a statistically significant manner included histology, tumor volume, tumor number, diagnosis-specific graded prognostic assessment (DS-GPA), brain metastasis velocity (BMV), and need for subsequent whole-brain radiation therapy (WBRT). The median of the mean WB dose was 4.07 Gy (range 1.39–10.15 Gy). In the top quartile for both the highest cumulative number and highest cumulative volume of treated metastases, the median of the mean WB dose was 6.14 Gy (range 4.02–10.15 Gy). Seventy-nine patients (83%) had all treated tumors controlled at last follow-up, reflecting the high and durable control rate. Corticosteroids for tumor- or treatment-related effects were prescribed in just over one-quarter of the patients. Of the patients with radiographically proven adverse radiation effects (AREs; 15%), 4 were symptomatic. Four patients required subsequent craniotomy for hemorrhage, progression, or AREs.

CONCLUSIONS

In selected patients with a large number of cumulative BMs, multiple courses of SRS are feasible and safe. Together with new systemic therapies, the study results demonstrate that the achieved survival rates compare favorably to those of larger contemporary cohorts, while avoiding WBRT in the majority of patients. Therefore, along with the findings of other series, this study supports SRS as a standard practice in selected patients with larger numbers of BMs.

In Journal of Neurosurgery Volume 137: Issue 2 (Aug 2022)

Free access

The incidence and predictors of new brain metastases in patients with non–small cell lung cancer following discontinuation of systemic therapy

Dennis London, Dev N. Patel, Bernadine Donahue, Ralph E. Navarro, Jason Gurewitz, Joshua S. Silverman, Erik Sulman, Kenneth Bernstein, Amy Palermo, John G. Golfinos, Joshua K. Sabari, Elaine Shum, Vamsidhar Velcheti, Abraham Chachoua, and Douglas Kondziolka

OBJECTIVE

Patients with non–small cell lung cancer (NSCLC) metastatic to the brain are living longer. The risk of new brain metastases when these patients stop systemic therapy is unknown. The authors hypothesized that the risk of new brain metastases remains constant for as long as patients are off systemic therapy.

METHODS

A prospectively collected registry of patients undergoing radiosurgery for brain metastases was analyzed. Of 606 patients with NSCLC, 63 met the inclusion criteria of discontinuing systemic therapy for at least 90 days and undergoing active surveillance. The risk factors for the development of new tumors were determined using Cox proportional hazards and recurrent events models.

RESULTS

The median duration to new brain metastases off systemic therapy was 16.0 months. The probability of developing an additional new tumor at 6, 12, and 18 months was 26%, 40%, and 53%, respectively. There were no additional new tumors 22 months after stopping therapy. Patients who discontinued therapy due to intolerance or progression of the disease and those with mutations in RAS or receptor tyrosine kinase (RTK) pathways (e.g., KRAS, EGFR) were more likely to develop new tumors (hazard ratio [HR] 2.25, 95% confidence interval [CI] 1.33–3.81, p = 2.5 × 10−3; HR 2.51, 95% CI 1.45–4.34, p = 9.8 × 10−4, respectively).

CONCLUSIONS

The rate of new brain metastases from NSCLC in patients off systemic therapy decreases over time and is uncommon 2 years after cessation of cancer therapy. Patients who stop therapy due to toxicity or who have RAS or RTK pathway mutations have a higher rate of new metastases and should be followed more closely.

In Journal of Neurosurgery Volume 137: Issue 2 (Aug 2022)