The delineation of two target volumes (PTVinitial and PTVBoost) was done for ten patients. Intensity-modulated radiation treatment plans with prescribed doses of 50 Gy(RBE) and 18 Gy(RBE) were generated for photons (IMXT), protons (IMPT) and carbon ions (12C), respectively. For light ion beam treatments, a horizontal fixed beam line without gantry was assumed. The following treatment modality combinations were compared: - IMXT (initial) + IMXT/IMPT/12C (Boost), - IMPT (initial) + IMPT/12C (Boost), - 12C (initial) + 12C (Boost). Treatment plan quality was analyzed and compared on the basis of dosimetric parameters, such as conformity index, homogeneity index, and various dose-volume parameters. Results: Results revealed that sole light ion modalities are the better alternative, considering the reduced integral dose and the higher degrees of homogeneity and conformity, when compared to photon therapy. IMPT and 12C exhibited similar characteristics, with 12C leading to a sharper penumbra around the target volume and reduced integral dose. The light ion treatment modalities demonstrated better sparing of the organs at risk, due to the reduced high-dose areas. Particularly with respect to brainstem, eyes and cerebellum, the dose burden was reduced to a minimum and the dose parameters differed significantly from those of the photon therapy. Conclusion: Even though a fixed horizontal beam with protons and carbon ions was used, various improvements were achieved as compared to the IMXT: higher levels of conformity and homogeneity of the target volumes, and a better sparing of the organs at risk.