A dosimetric comparison of volumetric modulated arc therapy with step-and-shoot intensity modulated radiation therapy for prostate cancer, "Beyond the Abstract," by Richard Wilder, MD, MS, MBA

BERKELEY, CA (UroToday.com) - In our recent study, 2-arc volumetric modulated arc therapy (VMAT) statistically significantly decreased median beam-on time from 4.3 to 3.4 minutes (p=0.03) relative to 7-field, step-and-shoot intensity-modulated radiation therapy (IMRT). Decreased radiation beam-on time improves one’s confidence that the dose distribution is being delivered as planned.[1, 2] Hall et al.[3] also observed that VMAT statistically significantly reduced beam-on time compared with 7-field, step-and-shoot IMRT. Adamson et al.[1] have suggested that a shorter beam-on time may allow one to reduce margins on the clinical target volume, thereby decreasing the dose of radiation delivered to adjacent normal tissues.

VMAT plans had a lower maximum planning target volume dose (p=0.002) resulting in improved homogeneity (p=0.003). There was no statistically significant difference in bladder and rectal V65, V70, and V75 for VMAT compared with step-and-shoot IMRT.

In conclusion, VMAT constitutes a new and improved method of delivering IMRT.


  1. Adamson J, Wu Q. Prostate intrafraction motion assessed by simultaneous kilovoltage fluoroscopy at megavoltage delivery I: clinical observations and pattern analysis. Int J Radiat Oncol Biol Phys 2010;78:1563-1570.
  2. Reggiori G, Mancosu P, Tozzi A, et al. Cone beam CT pre- and post-daily treatment for assessing geometrical and dosimetric intrafraction variability during radiotherapy of prostate cancer. J Appl Clin Med Phys 2011;12:3371.
  3. Hall WA, Fox TH, Jiang X, et al. Treatment efficiency of volumetric modulated arc therapy in comparison with intensity-modulated radiotherapy in the treatment of prostate cancer. J Am Coll Radiol 2013;10:128-134.

Written by:
Richard Wilder, MD, MS, MBA as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.

Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL USA

A dosimetric comparison of volumetric modulated arc therapy with step-and-shoot intensity modulated radiation therapy for prostate cancer - Abstract

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