Attention to normal brain volumes in glioblastoma radiotherapy: potential role in tumor invasion and vasculogenesis.

Glioblastoma is well known for frequent local recurrences even after radiation therapy. The significance of low-dose normal brain volume analysis is usually ignored by clinical radiotherapist. Recently, several reports have demonstrated that ionizing radiation to surrounding brain tissues augments the secretions of several mediators, including SDF-1α, VEGF and MMPs. They are essential for glioma invasion and vasculogenesis processes. It is hypothesized that irradiated normal brain tissues promotes tumor invasion and vasculogenesis, resulting in glioma recurrence. This prompts new attention on the volumes of "normal" brain in radiation treatment for gliomas. Improvement of radiotherapy techniques is expected to decrease the doses and volumes of irradiated normal brain. The combination of radiation and inhibitors of these mediators would be a promising adjuvant therapy for glioblastoma.