Volumetric-modulated arc therapy in postprostatectomy radiotherapy patients: a planning comparison study

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment Planning

Background:

• Accurate radiation delivery is crucial for postprostatectomy cancer treatment.
• Volumetric-modulated arc therapy (VMAT) is an advanced radiotherapy technique.
• Intensity-modulated radiotherapy (IMRT) is a conventional technique for precise dose distribution.

Purpose of the Study:

• To compare the efficacy of single arc (SA) VMAT and double arc (DA) VMAT against dynamic sliding window IMRT for postprostatectomy planning.
• To evaluate dose coverage, organ-at-risk sparing, and treatment efficiency.

Main Methods:

• Ten postprostatectomy patient cases were planned using IMRT, SA VMAT, and DA VMAT.
• All plans aimed for a minimum dose of 68Gy to 95% of the planning target volume (PTV).
• Specific dose constraints were set for rectal and bladder volumes, and plans were compared for dose metrics and monitor units (MU).

Main Results:

• SA VMAT plans resulted in a significantly higher mean dose to the clinical target volume and PTV compared to DA VMAT and IMRT.
• Rectal V40 was lowest with DA VMAT, and both VMAT techniques significantly reduced rectal V20 compared to IMRT.
• IMRT plans required substantially more monitor units (1400 MU) compared to DA VMAT (745 MU) and SA VMAT (708 MU).

Conclusions:

• SA and DA VMAT provide comparable target coverage to IMRT but with significantly reduced treatment delivery time (lower MU).
• VMAT techniques, particularly DA, offer improved sparing of the rectum at lower dose levels.
• The increased dose heterogeneity in VMAT plans is balanced by reduced rectal dose and improved efficiency.