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Y. Flanagan
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P1.14 - Radiotherapy (ID 700)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: Radiotherapy
- Presentations: 1
- Moderators:
- Coordinates: 10/16/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
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P1.14-018 - Construction and Evaluation of RapidPlanTM Models for Radical Lung Planning (ID 10303)
09:30 - 16:00 | Author(s): Y. Flanagan
- Abstract
Background:
A Volume Modulated Arc Therapy (VMAT) service for our radical lung patients has been offered since 2011. Attention has now turned towards how this service can be improved further. The RapidPlan[TM] package has already been used to great effect in our Prostate service so was assessed for its potential in radical lung planning.
Method:
RapidPlanTM models were created using the Eclipse Treatment Planning System [Varian Medical Systems] v13.6: consisting of 50 randomly selected radcial right lung patients (M_R), left lung patients (M_L) and a combined model using all 100 of these same patients (M_COM). The models were assessed using the standard RapidPlanTM tools. A retrospective planning study was performed for 10 right lung and 10 left lung patients. Each of the 20 patient treatments were replanned using each model. All plans were normalised to ensure that the target mean was 100% and compared to the manually optimised plan (O_P) The PTV coverage was assessed using dose homogeneity indices. Differences in organ at risk (OAR) dose volume histogram parameters were calculated to assess plan quality. The plans were compared on a variety of criteria including but not limited to whole lung V5 (with tolerance considered 70%) and V20 (with tolerance considered 30%) and the maximum dose to spinal canal (tolerance considered to be 80 %). Significance was assessed by two-tailed t-test (p<0.01).
Result:
Although all models gave a clinically acceptable plan differences in the homogoeneity indices were observed with M_COM values showing an improvement on the other models. M_COM plans had a statistically significant increase in maximum spinal cord dose when compared to the other plans set, however doses were within tolerance. An increase in mean whole lung and whole lung minus PTV V20Gy was also observed. There was no significant difference in contra lateral lung V5Gy or whole lung minus PTV V5Gy. There was no statistical difference observed when comparing right sided tumour patient calculated with M_L and left sided tumour patients planned with M_R.
Conclusion:
M_COM outperformed the other models and O_P in relation to PTV coverage without impacting clinically acceptable OAR constraints. This model demonstrated improvement when compared to M_L and M_R suggesting that 50 plans are insufficient to perfect a lung model and that 100 plans is more effective. When compared with manually optimised plans the M_COM model demonstrates an improved relationship between balancing OAR objectives and PTV conformity.
