The aim of the present study is to evaluate the dosimetric analysis of doses received by planning target volume and organs at risks by using intensity-modulated radiation therapy (IMRT) and three-dimensional conformal radiation therapy (3D-CRT) techniques in patients treated for glioblastoma multiforme. A total of ten patients underwent computed tomography treatment planning in conjunction with magnetic resonance imaging fusion.Prescription dose and normal-tissue constraints were identical for the 3DCRT and IMRT plans. All the Patients were treated on Clinac DHX Linear Accelerator. The prescribed dose was 60 Gy delivered at 2.0 Gy per fraction using 6 MV photons. The tolerance level for maximum dose was 7.0 Gy for lenses and 54.0 Gy for brain stem, optical chiasm and optical nerves as per RTOG criteria. The Target volumes, organ at risk (OAR), dose volume constrains were used for planning. Cumulative dose volume histogram of target volumes and organ at risk (OAR), normal brain tissue integral dose, target coverage, target homogeneity, target conformity, and normal tissue sparing with
3DCRT and IMRT planning were compared. Statistical analysis was performed to determine the differences. A statistically significant difference between 3DCRT and IMRT and in the mean dose to the PTV (p < 0.519) has been observed. The mean value of the PTV was 61.04 ± 1.152 in 3DCRT and 60.72 ± 1.005 in IMRT. The maximum dose
to the PTV in 3DCRT (64.26 ± 2.36) and in IMRT (62.95 ± 2.33) had a lower maximum dose to the PTV (p = 0.228). This result indicates that IMRT was better than 3DCRT. The average minimum dose in IMRT was (46.80 ± 3.89) compared to (49.06 ± 4.98) in 3DCRT, (p = 0.285). The dose to 95% of the PTV was (57.73 ± 1.55) in IMRT to (58.20
± 0.97) in 3DCRT, (p = 0.423). Conformity index (CI) was approximately equal in both modalities with an average value of 0.962 ± 0.041 in IMRT compared to (0.969 ± 0.039) in 3DCRT, (p = 0.481). The average homogeneity index(HI) in IMRT was 0.187±0.176 and 0.099 ± 0.050 in 3DCRT, (p = 0.165). Therefore, IMRT achieved an improvement
in HI. Target coverage index (TCI) in IMRT was 0.7213 ± 0.2050 and 0.5970± 0.194 in 3DCRT. The IMRT plan yielded superior target coverage and reduced radiation dose to the brain, brainstem, and optic chiasm. With the availability of new cancer imaging tools and more effective systemic agents, IMRT may be used to intensify tumor doses while minimizing toxicity, therefore potentially improving outcomes in patients with high-grade glioma.

Keywords: Glioblastoma multiforme (GBM); Intensity modulated radiation therapy (IMRT); Three dimentional conformal radiation therapy (3DCRT)