Risk factors for brain injury after carbon ion radiotherapy for skull base tumors

Background and purpose

This study aimed to determine the risk factors for radiation-induced brain injury (RIBI) after carbon ion radiotherapy (CIRT) for treating skull base tumors.

Materials and methods

Between April 1997 and January 2009, CIRT at a total dose of 48.0–60.8 Gy equivalent (GyE) was administered in 16 fractions to 47 patients with skull base tumors. Of these patients, 39 who were followed up with magnetic resonance imaging (MRI) for more than 24 months were analyzed. RIBI was assessed according to the MRI findings based on the Late Effects of Normal Tissue-Subjective, Objective, Management, Analytic criteria; clinical symptoms were assessed according to the Radiation Therapy Oncology Group/European Organisation for Research and Treatment of Cancer tables. The correlations of clinical and dosimetric parameters with incidence of ?grade 2 RIBI were retrospectively analyzed.

Results

The median follow-up period was 67 months. The 5-year actuarial likelihoods of ?grade 2 RIBI and ?grade 2 clinical symptoms were 24.5% and 7.0%, respectively. Multivariate analysis demonstrated that the brain volume receiving more than 50 GyE (V50) was a significant risk factor for the development of ?grade 2 RIBI (p = 0.004).

Conclusion

V50 was a significant risk factor for ?grade 2 RIBI after CIRT using a 16-fraction regimen.