Prog Med Phys.  2022 Dec;33(4):101-107. 10.14316/pmp.2022.33.4.101.

Minimization of Treatment Time Using Partial-Arc Volumetric Modulated Arc Therapy with Bladder Filling Protocol for Prostate Cancer

• Lee H
• Kim DW
• Joo JH
• Ki Y
• Kim W
• Park D
• Nam J
• Kim DH
• Jeon H

• KMID: 2537877
• DOI: http://doi.org/10.14316/pmp.2022.33.4.101

Abstract

Purpose
Radiotherapy after bladder filling protocol (BFP) is known to enhance treatment quality and reduce side effects in prostate cancer, a common male solid cancer globally. However, due to the need to hold back urine during treatment, patients frequently complain of discomfort, and treatment is frequently suspended when patients urinate during treatment and urine penetrates the treatment device, causing malfunction. Therefore, the effect of minimizing treatment time when partial-arc volumetric modulated arc therapy (VMAT) was used instead of full-arc was assessed in this study.
Methods
A total of 70 plans were created in 10 patients using 7 different arc sizes, and the treatment time for each plan was calculated.
Results
Reduced arc size by half resulted in a 54.4% decrease in mean treatment duration, with a proportional tendency observed. Furthermore, the effect of VMAT arc size reduction on target dose homogeneity was significantly limited, and the effect on surrounding organs at risk (OAR) was negligible. It should be noted, however, that when the arc size decreases by >40%, the dose increases in the area without OAR around the target.
Conclusions
The results of this study demonstrated that partial-arc VMAT for enhancing treatment convenience and efficacy of prostate cancer patients undergoing BFP can achieve a considerable reduction in treatment time while preserving treatment quality, and it is expected to be useful for partial-arc VMAT plan design and implementation in practice..

Keyword

Bladder filling protocol; Prostate cancer; Partial-arc volumetric modulated arc therapy; Treatment time

Figure

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  Fig. 1 Size of arcs applied to different plans. VMAT, volumetric modulated arc therapy.

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  Fig. 2 Calculated treatment time by RTP in comparison with (a) sizes of VMAT arcs and (b) actual treatment time. RTP, Radiation Treatment Planning; VMAT, volumetric modulated arc therapy.

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  Fig. 3 Calculated treatment time by RTP in comparison with (a) PTV dose coverage and (b) homogeneity index. PTV, planning target volume; RTP, Radiation Treatment Planning.

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  Fig. 4 Dose distribution near PTV concerning VMAT arc sizes of (a) 360°, (b) 270°, (c) 210°, and (d) 180°. White arrows indicate dose leakage outside PTV. The displayed dose scale is between 75% and 110%.

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  Fig. 5 Calculated treatment time by RTP in comparison with (a) rectum dose at 25% volume and (b) bladder dose at 35% volume. RTP, Radiation Treatment Planning.

Reference

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