12 Gy gamma knife radiosurgical volume is a predictor for radiation necrosis in non-AVM intracranial tumors

doi:10.1016/j.ijrobp.2005.07.980

International Journal of Radiation OncologyBiologyPhysics

Volume 64, Issue 2, 1 February 2006, Pages 419-424

Presented in poster format at the Annual Meeting of the Society of Neuro-Oncology, November 20, 2004, Toronto, Ontario, Canada.

https://doi.org/10.1016/j.ijrobp.2005.07.980 Get rights and content

Purpose: To determine whether the 12-Gy radiosurgical volume (12-GyV) correlates with the development of postradiosurgical imaging changes suggestive of radiation necrosis in patients treated for non–arteriovenous malformation (non-AVM) intracranial tumors with gamma knife stereotactic radiosurgery (GKSRS).

Methods and Materials: A retrospective single-institution review of 129 patients with 198 separate non-AVM tumors was performed. Patients were followed with magnetic resonance imaging (MRI) and physical examinations at 3- to 6-month intervals. Patients who developed postradiosurgical MRI changes suggestive of radiation necrosis were labeled as having either symptomatic radiation necrosis (S-NEC) if they experienced any decline in neurologic examination associated with the imaging changes, or asymptomatic radiation necrosis (A-NEC) if they had a stable or improving neurologic examination.

Results: 12-GyV correlated with risk of S-NEC, which was 23% (for 12-GyV of 0–5 cc), 20% (5–10 cc), 54% (10–15 cc), and 57% (>15 cc). The risk of A-NEC did not significantly change with 12-GyV. Logistic regression analyses showed that the following factors were associated with the development of S-NEC: 12-GyV (p < 0.01), occipital and temporal lesions (p < 0.01), previous whole-brain radiotherapy (p = 0.03), and male sex (p = 0.03). Radiosurgical plan conformality did not correlate with the development of S-NEC.

Conclusion: The risk of S-NEC, but not A-NEC after GKSRS for non-AVM tumors correlates with 12-GyV, and increases significantly for 12-GyV >10 cc.

Introduction

Gamma knife stereotactic radiosurgery (GKSRS) treatment planning is a complex process balancing the dose necessary to treat an intracranial lesion with the perception of toxicity from the treatment. Although a significant number of studies have been published pertaining to the efficacy of treatment for both malignant and nonmalignant lesions, there are relatively few reports pertaining to the predominant late toxicity of radiosurgery, radiation necrosis. Radiation necrosis is defined in the literature both as a pathologic endpoint with biopsy as a gold standard and as a clinical entity using physical examination and radiographic imaging with magnetic resonance imaging (MRI) findings including increased T2 changes likely representing blood–brain barrier disruption and accompanying cerebral edema, increased T1 central hypointensity, and a “feathery” contrast enhancement pattern on T1 sequences as the basis for diagnosis (1, 2). Case series studies of patients receiving radiosurgical treatment for arteriovenous malformations (AVMs) (3, 4, 5) have reported a model for predicting post-GKSRS radiation necrosis based on the radiosurgical treatment volume receiving 12 Gy (12-GyV). The aim of our study was to determine whether this 12-GyV correlated with the development of symptomatic or asymptomatic postradiosurgical imaging changes suggestive of radiation necrosis in patients with non-AVM central nervous system tumors.

Section snippets

Methods and materials

In a retrospective review of 338 consecutive patients treated at our Gamma Knife Clinic from January 1, 2001 to March 30, 2003, 198 separate lesions from 129 patients were analyzed after applying the following inclusion criteria: age >18 years, treatment for central nervous system tumor (vs. functional radiosurgery), follow-up >3 months, and no repeat radiosurgery to same lesion.

Patients were treated with standard of care therapy on our Gamma Knife Unit Model B (Elekta Instruments, Stockholm,

Results

A summary of patient characteristics is shown in Table 1. 12-GyV was shown to be a statistically significant predictor of S-NEC, in polytomous logistic regression with statistically significant slope coefficients β = 0.08 (Z = 3.53) for S-NEC, a finding that is highly compatible with the previously estimated value of β = 0.073 found in AVM radiosurgical treatment (5). There was no significant association between 12-GyV and development of A-NEC. For graphical representation, tumors were divided

Discussion

Despite the extensive use of radiosurgery for the treatment of many intracranial tumors, relatively little data have been published regarding its primary late toxicity, radiation necrosis. Of the published toxicity data, the majority has been acquired from patients treated for AVMs with few studies investigating patients with non-AVM tumors. In addition, most have reported only risks of symptomatic postradiosurgical imaging changes with little mention of asymptomatic postradiosurgical imaging

Conclusion

We found that the risk of developing S-NEC, but not A-NEC after gamma knife radiosurgery for non-AVM tumors correlates with 12-GyV. The risk of S-NEC increased significantly for 12-GyV >10 cc, regardless of plan conformality. These observations add to the knowledge base of postradiosurgical toxicity and can be used when planning and optimizing gamma knife radiosurgical treatments.

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Clinical investigationBrain12 Gy gamma knife radiosurgical volume is a predictor for radiation necrosis in non-AVM intracranial tumors

Introduction

Section snippets

Methods and materials

Results

Discussion

Conclusion

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Radiother Oncol

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Clinical investigation
Brain
12 Gy gamma knife radiosurgical volume is a predictor for radiation necrosis in non-AVM intracranial tumors