Comparison of Prostate IMRT and VMAT Biologically Optimised Treatment Plans

Hardcastle, Nicholas; Tomé, Wolfgang A.; Foo, Kerwyn; Miller, Andrew; Carolan, Martin; Metcalfe, Peter

doi:10.1016/j.meddos.2010.06.001

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Volume 36, Issue 3 , Pages 292-298, Autumn 2011

Comparison of Prostate IMRT and VMAT Biologically Optimised Treatment Plans

Nicholas Hardcastle, Ph.D.
- Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia
- Department of Human Oncology and Medical Physics, University of Wisconsin-Madison, WI, USA
- Reprint requests to: Nicholas Hardcastle, Ph.D., Department of Human Oncology and Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, CSC K4/347, 600 Highland Ave., Madison, WI 53792
Wolfgang A. Tomé, Ph.D.
- Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia
- Department of Human Oncology and Medical Physics, University of Wisconsin-Madison, WI, USA
Kerwyn Foo, FRANZCR
- Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia
- Illawarra Cancer Care Centre, Wollongong Hospital, Wollongong, NSW, Australia
- Graduate School of Medicine, University of Wollongong, Wollongong, NSW, Australia
Andrew Miller, FRANZCR
- Illawarra Cancer Care Centre, Wollongong Hospital, Wollongong, NSW, Australia
- Graduate School of Medicine, University of Wollongong, Wollongong, NSW, Australia
Martin Carolan, Ph.D.
- Illawarra Cancer Care Centre, Wollongong Hospital, Wollongong, NSW, Australia
Peter Metcalfe, Ph.D.
- Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia

Received 8 October 2009; accepted 10 June 2010. published online 30 August 2010.

Abstract

Recently, a new radiotherapy delivery technique has become clinically available—volumetric modulated arc therapy (VMAT). VMAT is the delivery of IMRT while the gantry is in motion using dynamic leaf motion. The perceived benefit of VMAT over IMRT is a reduction in delivery time. In this study, VMAT was compared directly with IMRT for a series of prostate cases. For 10 patients, a biologically optimized seven-field IMRT plan was compared with a biologically optimized VMAT plan using the same planning objectives. The Pinnacle RTPS was used. The resultant target and organ-at-risk dose-volume histograms (DVHs) were compared. The normal tissue complication probability (NTCP) for the IMRT and VMAT plans was calculated for 3 model parameter sets. The delivery efficiency and time for the IMRT and VMAT plans was compared. The VMAT plans resulted in a statistically significant reduction in the rectal V25Gy parameter of 8.2% on average over the IMRT plans. For one of the NTCP parameter sets, the VMAT plans had a statistically significant lower rectal NTCP. These reductions in rectal dose were achieved using 18.6% fewer monitor units and a delivery time reduction of up to 69%. VMAT plans resulted in reductions in rectal doses for all 10 patients in the study. This was achieved with significant reductions in delivery time and monitor units. Given the target coverage was equivalent, the VMAT plans were superior.

Key Words: VMAT, IMRT, Prostate, Biological Optimisation