Figure 1.

Schematic concept of the time course of radiation-induced reactions in cancer patients treated with ionizing radiation via portals exposing some part of the central nervous system (CNS). The tumor is expected to become eradicated within a few weeks. The severity and latency of CNS reactions are dose-dependent. Three different levels are shown. Acute CNS reactions often remain below the level of clinical detection and resolve early. A second wave of so-called late reactions might develop after several months or years and after higher radiation doses. The upper curve with or without additional comorbidity shows how certain factors might influence damage progression or make intervention more difficult. The dotted line below the threshold level represents succesful therapeutic intervention, which was started at the time indicated by the arrow.