By Sunnia Shafiq (Medical Physicist)
Abstract:
Objective:
This study aimed to determine whether an optimized
Three-Dimensional Conformal Radiotherapy (3D-CRT)
technique could achieve dosimetric outcomes comparable to
Intensity-Modulated Radiotherapy (IMRT) in patients with
grade IV glioblastoma.
Materials and Methods:
Treatment plans of 127 patients with
grade IV glioblastoma, treated between January 2020 and
September 2025, were retrospectively analyzed. Each case was
planned using both 3D-CRT and IMRT techniques. The
3D-CRT plans incorporated three to five fields with dynamic
wedges and field-in-field modulation, while IMRT utilized
seven fields with equidistant beam angles. Planning objectives
required that 97% of the prescribed dose cover 98% of the
Planning Target Volume (PTV). Dosimetric parameters,
including homogeneity index (HI), conformity index (CI), and
organ-at-risk (OAR) doses, were compared.
Results:
Target coverage was comparable between both techniques. IMRT demonstrated superior dose homogeneity
(HI: 0.053 vs. 0.097) and conformity (CI: 1.187 vs. 1.663)
compared to 3D-CRT. It provided enhanced sparing of normal
brain tissue and nearby organs, except for the contralateral eye.
However, IMRT required longer delivery times and higher
monitor units (MUs). Optimized 3D-CRT resulted in slightly
increased low-dose exposure to normal brain regions.
Conclusion:
While IMRT remains superior in conformity,
homogeneity, and OAR protection, optimized 3D-CRT can
approximate its performance for tumors away from critical
structures. This approach may serve as a feasible alternative in
resource-limited settings where advanced modulation
techniques are unavailable.