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Topic 7: Radionecrosis in Single & Multi-Fraction Radiosurgery -…
Topic 7: Radionecrosis in Single & Multi-Fraction Radiosurgery
Methods
Data Collection and Imaging
Data were sourced from the CyberKnife database (Juravinski Cancer Centre, Hamilton, ON).
MRI scans were reviewed at 3-month intervals to assess lesion size, radionecrosis (LQ < 0.3), and recurrence (LQ > 0.6). Perfusion MRI was used when available for confirmation.
Treatment and Variables Assessed
Treatments were delivered with CyberKnife radiosurgery, with dose and fractionation based on lesion size.
Treatment variables analyzed: maximum dose, lesion volume, whole-brain radiotherapy (WBRT), and fractionation.
Prescription covered 95% of the planning target volume with isodose lines ranging from 69%-86%.
Analysis and Ethics
A paired design was used, comparing SSRS and FSRS within the same patients
Logistic regression assessed associations of variables (volume, dose, WBRT, fractionation) with radionecrosis.
Study approval: Hamilton Integrated Research Ethics Board.
Study Design and Participants
Patients with multiple brain metastases treated with simultaneous single-fraction (SSRS) and three-fraction (FSRS) stereotactic radiosurgery (SRS) between 2012–2015 were included.
Eligibility criteria: Biopsy-confirmed malignancy originating outside the CNS and a minimum 6-month MRI follow-up for assessing radionecrosis.
Main Result
Radionecrosis developed in 16 patients, which corresponds to
34% of the lesions
treated (21 out of 62 lesions). Among these,
4 lesions were symptomatic
(20%).
Of the lesions that developed radionecrosis,
11
were treated with
multi-fraction
stereotactic radiosurgery and
10 with single-fraction
stereotactic radiosurgery.
A 10-unit increase in lesion volume was associated with a higher risk of developing radionecrosis (with an
odds ratio of 3.1
)
The analysis showed
no significant association
between the maximum dose delivered and the incidence of radionecrosis (odds ratio of 1.0, 95% CI: 0.9 to 1.1)
The
median follow-up
for the patients was 320 days, with a
median survival
of 352 days.
Introduction
Purpose
Investigates the impact of fractionation (single-fraction vs. multi-fraction radiosurgery) on RN incidence, aiming to clarify risk factors and optimize treatment strategies.
Background
SRS offers high local control for brain metastases, avoiding some toxicities of whole-brain radiotherapy (WBRT).
RN can range from incidental imaging findings to debilitating symptoms.
Factors like dose, volume, and prior WBRT are linked to RN risk.
Hypofractionation is suggested to reduce RN risk compared to single-fraction SRS.
Focus
The study addresses radionecrosis (RN), a severe side effect of stereotactic radiosurgery (SRS) for brain metastases.
Conclusion
Key Findings
Tumor volume was a major factor associated with increased RN risk.
Fractionation showed potential in reducing RN severity in large-volume lesions but did not completely eliminate the risk.
Patients with multiple brain metastases receiving SRS had higher RN rates and worse survival outcomes than expected.
Clinical and Research Implications
Fractionated SRS could help manage RN risk in large lesions.
Further studies are needed to refine dose and fractionation strategies to optimize treatment effectiveness while minimizing risks.
Discussion
Radiation necrosis in a single radiotherapy operation
Features:
High dose single irradiation: A single radiation surgery usually uses a high dose (>12-20 Gy) to produce a strong local killing effect on the tumor target.
• High risk of necrosis: Due to the concentrated dose and no time for normal tissue repair, the surrounding normal tissue is subjected to greater radiation damage.
• Proximity of the target to sensitive tissue: The risk of radiation necrosis is significantly increased if the target is close to highly radiation-sensitive organs, such as the brain stem or optic nerve.
mechanism
• Direct cell damage: High doses of radiation directly cause irreversible cell damage and death.
• Vascular injury: fibrosis and occlusion of small blood vessels, resulting in ischemia and necrosis.
• Inflammatory response: The release of pro-inflammatory factors exacerbates local tissue damage.