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Comparison of Plan Quality Using RapidPlan and a Multi Criteria Optimisation Tool for Lung SABR

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s smith

s smith*, G Currie , R Valentine , NHS Greater Glasgow & Clyde, Glasgow, Strathclyde


SU-I-GPD-T-565 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To investigate whether multi-criteria optimisation (MCO) can produce improved treatment plans, in terms of reduction in dose to organs at risk and/or improved planning target volume coverage, for VMAT radiotherapy treatment of Lung SABR when compared with a plan generated using RapidPlanᵀᴹ alone.

Methods: A retrospective planning study was performed for ten lung SABR patients. Each patient treatment was planned as standard using RapidPlanᵀᴹ. The plans were then re-optimised within the Eclipse Treatment Planning System [Varian Medical Systems] using a pre clinical release of an MCO tool (E-MCO). Both plans were normalised to ensure that 95% of the target received 100% of the prescribed dose and the resulting plans were then compared. Differences in dose volume histogram parameters were calculated to assess plan quality. Significance was assessed by two-tailed t-test (p<0.01).

Results: The E-MCO generated plans exhibited significant organ at risk (OAR) reductions for the dose at 2cm from PTV (mean: 12.9%; range: 9.6% - 24.0%), the maximum spinal cord dose (mean: 3.2 Gy; range: 0.3 Gy – 6.7 Gy), the dose to 1cc of oesophagus (mean: 1.2 Gy; range: 0.3 Gy – 3.2 Gy) and percentage of lung minus GTV to receive 20Gy (mean: 12.8%; range: 0.0% - 25.0%). There was no significant difference observed for the remaining organs at risk. As the plans were normalised to achieve the same target coverage, there was no significant difference in PTV coverage. The plans generated by both RapidPlanᵀᴹ and RapidPlanᵀᴹ with E-MCO were all clinically acceptable and met local OAR and PTV dosimetric objectives.

Conclusion: Using E-MCO to re-optimise RapidPlanᵀᴹ generated plans was shown to decrease significantly the dose to organs at risk without adverse affect on tumour coverage. E-MCO demonstrated the ability to further enhance plans that were already of a high standard.

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