Irradiated volume as a predictor of brain radionecrosis after linear accelerator stereotactic radiosurgery

Int J Radiat Oncol Biol Phys. 2010 Jul 15;77(4):996-1001. doi: 10.1016/j.ijrobp.2009.06.006. Epub 2009 Sep 23.


Purpose: To investigate the correlation between volume of brain irradiated by stereotactic radiosurgery (SRS) and the incidence of symptomatic and asymptomatic brain radionecrosis (RN).

Methods and materials: 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.

MeSH terms

  • Adult
  • Aged
  • Analysis of Variance
  • Brain / pathology*
  • Brain / radiation effects*
  • Brain Neoplasms / secondary
  • Brain Neoplasms / surgery*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Necrosis / etiology
  • Necrosis / pathology
  • Radiation Injuries / pathology*
  • Radiosurgery / adverse effects*
  • Radiotherapy Dosage
  • Retrospective Studies
  • Survival Analysis
  • Tumor Burden