Prog Med Phys.  2022 Dec;33(4):121-128. 10.14316/pmp.2022.33.4.121.

Evaluation of Treatment Plan Quality between Magnetic Resonance-Guided Radiotherapy and Volumetric Modulated Arc Therapy for Prostate Cancer

• Choi CH
• Kim JH
• Son J
• Park JM
• Kim Ji

• KMID: 2537880
• DOI: http://doi.org/10.14316/pmp.2022.33.4.121

Abstract

Purpose
This study evaluated the quality of plans based on magnetic resonance-guided radiotherapy (MRgRT) tri-Co-60, linac, and conventional linac-based volumetric modulated arc therapy (linac-VMAT) for prostate cancer.
Methods
Twenty patients suffering from prostate cancer with intermediate risk who were treated by MAT were selected. Additional treatment plans (primary and boost plans) were generated based on MRgRT-tri-Co-60 and MRgRT-linac. The planning target volume (PTV) of MRgRT-based plans was created by adding a 3 mm margin from the clinical target volume (CTV) due to high soft-tissue contrast and real-time motion imaging. On the other hand, the PTV of conventional linac was generated based on a 1 cm margin from CTV. The targets of primary and boost plans were prostate plus seminal vesicle and prostate only, respectively. All plans were normalized to cover 95% of the target volume by 100% of the prescribed dose. Dosimetric characteristics were evaluated for each of the primary, boost, and sum plans.
Results
For target coverage and conformity, the three plans showed similar results. In the sum plans, the average value of V _65Gy of the rectum of MRgRT-linac (2.62%±2.21%) was smaller than those of MRgRT tri-Co-60 (9.04%±3.01%) and linac-VMAT (9.73%±7.14%) (P<0.001). In the case of bladder, the average value of V _65Gy of MRgRT-linac was also smaller.
Conclusions
In terms of organs at risk sparing, MRgRT-linac shows the best value while maintaining comparable target coverage among the three plans.

Keyword

MRgRT; VMAT; Tri-Co-60; MR linac; Prostate