Irradiated volume as a predictor of brain radionecrosis after linear accelerator stereotactic radiosurgery.
OBJECTIVE
To investigate the correlation between volume of brain irradiated by stereotactic radiosurgery (SRS) and the incidence of symptomatic and asymptomatic brain radionecrosis (RN).


METHODS
A retrospective analysis was performed of patients treated with single-fraction SRS for brain metastases at our institution. Patients with at least 6-month imaging follow-up were included and diagnosed with RN according to a combination of criteria, including appearance on serial imaging and histology. Univariate and multivariate analyses were performed to determine the predictive value of multiple variables, including volume of brain receiving a specific dose (V8 Gy-V18 Gy).


RESULTS
Sixty-three patients were reviewed, with a total of 173 lesions. Most patients (63%) had received previous whole-brain irradiation. Mean prescribed SRS dose was 18 Gy. Symptomatic RN was observed in 10% and asymptomatic RN in 4% of lesions treated. Multivariate regression analysis showed V8 Gy-V16 Gy to be most predictive of symptomatic RN (p < 0.0001). Threshold volumes for significant rise in RN rates occurred between the 75th and 90th percentiles, with a midpoint volume of 10.45 cm(3) for V10 Gy and 7.85 cm(3) for V12 Gy.


CONCLUSIONS
Analysis of patient and treatment variables revealed V8 Gy-V16 Gy to be the best predictors for RN using linear accelerator-based single-fraction SRS for brain metastases. We propose that patients with V10 Gy >10.5 cm(3) or V12 Gy >7.9 cm(3) be considered for hypofractionated rather than single-fraction treatment, to minimize the risk of symptomatic RN.
Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
Brian J
BJ
Blonigen
Ryan D
RD
Steinmetz
Linda
L
Levin
Michael A
MA
Lamba
Ronald E
RE
Warnick
John C
JC
Breneman
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001921:Brain / Q000473:pathology* / Q000528:radiation effects*; D001932:Brain Neoplasms / Q000556:secondary / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009336:Necrosis / Q000209:etiology / Q000473:pathology; D011832:Radiation Injuries / Q000473:pathology*; D016634:Radiosurgery / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D016019:Survival Analysis; D047368:Tumor Burden