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Prostate stereotactic body radiotherapy with simultaneous integrated boost: which is the best planning method?
Alison Tree1, Caroline Jones, Aslam Sohaib
1Royal Marsden NHS Foundation Trust, Fulham Road, London SW3 6JJ, UK. alison.tree@rmh.nhs.uk.
Radiation Oncology (London, England)
|October 4, 2013
Summary
Simultaneous integrated boost radiotherapy for prostate cancer is feasible with RapidArc and Multiplan. RapidArc showed lower rectal doses, but larger margins for motion control compromised plan acceptability.
Area of Science:
- Radiation Oncology
- Medical Physics
Background:
- Simultaneous integrated boost (SIB) delivery to intra-prostatic nodules may enhance local control in prostate cancer.
- Hypofractionated stereotactic body radiation therapy (SBRT) delivery was explored using RapidArc and Multiplan planning systems.
Purpose of the Study:
- To evaluate the feasibility and dosimetric outcomes of SIB for prostate cancer using RapidArc and Multiplan.
- To compare rectal dose and plan acceptability between the two planning systems with varying margins.
Main Methods:
- RapidArc and Multiplan plans were created for 15 prostate cancer patients, delivering 47.5 Gy in 5 fractions to the boost and 36.25 Gy to the prostate.
- Margins of 5 mm isotropic (3 mm posterior) were used, with an additional RapidArc plan using 8 mm isotropic (5 mm posterior) margins to assess intrafraction motion impact.
Main Results:
- Both systems produced clinically acceptable SIB plans. RapidArc plans demonstrated lower mean rectal doses (D50: 13.2 Gy vs. 15.5 Gy).
- Missed dose constraints occurred in 11/75 instances for both methods with standard margins.
- Increasing margins to 8 mm/5 mm for RapidArc plans to account for intrafraction motion resulted in 37/75 missed constraints.
Conclusions:
- RapidArc and Multiplan are capable of generating clinically acceptable SIB plans for prostate cancer.
- RapidArc offers dosimetric advantages regarding rectal sparing. However, increased margins for intrafraction motion compromise plan quality significantly.
- Feasible SIB delivery with hypofractionation necessitates small margins and effective intrafraction motion tracking.
