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. 2013 Oct 2:8:228.
doi: 10.1186/1748-717X-8-228.

Prostate stereotactic body radiotherapy with simultaneous integrated boost: which is the best planning method?

Alison Tree  1 , Caroline Jones, Aslam Sohaib, Vincent Khoo, Nicholas van As
Affiliations

Prostate stereotactic body radiotherapy with simultaneous integrated boost: which is the best planning method?

Alison Tree et al. Radiat Oncol. .

Abstract

Background: The delivery of a simultaneous integrated boost to the intra-prostatic tumour nodule may improve local control. The ability to deliver such treatments with hypofractionated SBRT was attempted using RapidArc (Varian Medical systems, Palo Alto, CA) and Multiplan (Accuray inc, Sunnyvale, CA).

Materials and methods: 15 patients with dominant prostate nodules had RapidArc and Multiplan plans created using a 5 mm isotropic margin, except 3 mm posteriorly, aiming to deliver 47.5 Gy in 5 fractions to the boost whilst treating the whole prostate to 36.25 Gy in 5 fractions. An additional RapidArc plan was created using an 8 mm isotropic margin, except 5 mm posteriorly, to account for lack of intrafraction tracking.

Results: Both RapidArc and Multiplan can produce clinically acceptable boost plans to a dose of 47.5 Gy in 5 fractions. The mean rectal doses were lower for RapidArc plans (D50 13.2 Gy vs 15.5 Gy) but the number of missed constraints was the same for both planning methods (11/75). When the margin was increased to 8 mm/5 mm for the RapidArc plans to account for intrafraction motion, 37/75 constraints were missed.

Conclusions: RapidArc and Multiplan can produce clinically acceptable simultaneous integrated boost plans, but the mean rectal D50 and D20 with RapidArc are lower. If the margins are increased to account for intrafraction motion, the RapidArc plans exceed at least one dose constraint in 13/15 cases. Delivering a simultaneous boost with hypofractionation appears feasible, but requires small margins needing intrafraction motion tracking.

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Figures

Figure 1
Figure 1
Planning schema.
Figure 2
Figure 2
Mean rectal DVH data by planning method.
Figure 3
Figure 3
Number of missed rectal constraints by dose (43/75 for RapidArc larger margins, 11/75 for RapidArc standard margins, 11/75 for Cyberknife standard margins).
Figure 4
Figure 4
Mean bladder DVH data by planning method.
See this image and copyright information in PMC

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