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. 2016 Jun;8(3):201-7.
doi: 10.5114/jcb.2016.60499. Epub 2016 Jun 13.

Robustness of IPSA optimized high-dose-rate prostate brachytherapy treatment plans to catheter displacements

Joel Poder  1 , May Whitaker  2
Affiliations

Robustness of IPSA optimized high-dose-rate prostate brachytherapy treatment plans to catheter displacements

Joel Poder et al. J Contemp Brachytherapy. 2016 Jun.

Abstract

Purpose: Inverse planning simulated annealing (IPSA) optimized brachytherapy treatment plans are characterized with large isolated dwell times at the first or last dwell position of each catheter. The potential of catheter shifts relative to the target and organs at risk in these plans may lead to a more significant change in delivered dose to the volumes of interest relative to plans with more uniform dwell times.

Material and methods: This study aims to determine if the Nucletron Oncentra dwell time deviation constraint (DTDC) parameter can be optimized to improve the robustness of high-dose-rate (HDR) prostate brachytherapy plans to catheter displacements. A set of 10 clinically acceptable prostate plans were re-optimized with a DTDC parameter of 0 and 0.4. For each plan, catheter displacements of 3, 7, and 14 mm were retrospectively applied and the change in dose volume histogram (DVH) indices and conformity indices analyzed.

Results: The robustness of clinically acceptable prostate plans to catheter displacements in the caudal direction was found to be dependent on the DTDC parameter. A DTDC value of 0 improves the robustness of planning target volume (PTV) coverage to catheter displacements, whereas a DTDC value of 0.4 improves the robustness of the plans to changes in hotspots.

Conclusions: The results indicate that if used in conjunction with a pre-treatment catheter displacement correction protocol and a tolerance of 3 mm, a DTDC value of 0.4 may produce clinically superior plans. However, the effect of the DTDC parameter in plan robustness was not observed to be as strong as initially suspected.

Keywords: DTDC; IPSA; brachytherapy; catheter displacement; prostate cancer.

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Figures

Fig. 1
Fig. 1
The change in PTV V100% as a function of catheter displacement for plans optimized with DTDC set to 0 and 0.4 (error bars showing 95% confidence interval)
Fig. 2
Fig. 2
The change in PTV V200% as a function of catheter displacement for plans optimized with DTDC set to 0 and 0.4 (error bars showing 95% confidence interval)
Fig. 3
Fig. 3
The change in CI as a function of catheter displacement for plans optimized with DTDC set to 0 and 0.4 (error bars showing 95% confidence interval)
Fig. 4
Fig. 4
The change in ODI as a function of catheter displacement for plans optimized with DTDC set to 0 and 0.4 (error bars showing 95% confidence interval)
See this image and copyright information in PMC

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