Prostate and Lymph Node VMAT Treatment Planning

Transcription

1 Prostate and Lymph Node VMAT Treatment Planning Jess France, Alison McVey, Graham McVey, Jaap Vaarkamp 1

2 Presentation Outline Old planning method multi-phase New planning method single-phase Comparison of 6 patients Additional improvements to the new method How is the new class solution performing? 2

3 Overview Comparison of six patients treated for high risk prostate cancer. The treatment volume includes the prostate, seminal vesicles (SV) and pelvic lymph nodes (PLN). Multi-phase technique (old method) Phase one VMAT (2 full arcs) Phase two 3D conformal (4 fields) Phase three 3D conformal (4 fields) Single phase technique (new method) VMAT (2 full arcs) 3

4 Old Technique - Multi-phase Phase 1 Phase 2 Phase 3 CTV Prostate + SV PLN Prostate + SV Prostate Margin for the PTV 1cm, 0.8cm posteriorly 0.5cm 1cm, 0.8cm posteriorly 0.5cm, 0cm posteriorly Image Dose Prescription 46Gy in 23#s 18Gy in 9#s 10Gy in 5#s Technique RapidArc (VMAT) 3D conformal 3D conformal SV Seminal vesicles PLN Pelvic lymph nodes 4

5 New Technique - Single-phase PTV_55 PTV_67 PTV_74 All three volumes are treated in a single VMAT plan over 37#s. 5

6 Single Phase 2Gy equivalent dose Multi-Phase Single-Phase Planned Dose Planned Dose 2Gy equivalent dose* Prostate 74Gy (2.0Gy/#) 74Gy (2.0Gy/#) 74.0Gy Seminal Vesicles 64Gy (2.0Gy/#) 67Gy (1.8Gy/#) 64.2Gy Lymph Nodes 46Gy (2.0Gy/#) 55Gy (0.7Gy/#) 48.7Gy * Using an α/β ratio of 2.5 [1] Dose to prostate, and seminal vesicles remain similar when comparing the 2Gy equivalent doses. Dose to lymph nodes has been increased slightly. [1] Reference; Oliveira et al, What do we know about the α/β ratio for prostate cancer? Medical Physics 39, 3189 (2012) 6

7 Old Technique - Multi-phase Phase 1 Phase 3 Phase 2 7

8 New Technique - Single-phase PTV_55 PTV_67 PTV_74 8

9 PTV coverage Multi-phase technique Single-phase technique PTV V 95% Phase 1 100% Phase % Phase % PTV V 95% PTV_74 100% PTV_67 100% PTV_55 100% 9

10 Organs at risk (OARs) Bladder Rectum 10

11 60Gy Colourwash Multi-phase Single-phase 11

12 50Gy Colourwash Multi-phase Single-phase NB increased dose to LNs in new single-phase method. 12

13 Organ at risk - Rectum Dose CHHiP trial Multi Phase Single Phase Difference 50Gy 60% 39.0% 34.2% 4.8% 60Gy 50% 27.6% 22.0% 5.6% 65Gy 30% 21.3% 15.2% 6.1% 70Gy 15% 12.2% 4.5% 7.7% 74Gy 3% 0.7% 0.1% 0.6% Volume (%) Multi-Phase Single-Phase Dose (Gy) 13

14 Organ at risk - Bladder Dose CHHiP trial Multi Phase Single Phase Difference 50Gy 50% 22.9% 24.7% + 1.8% 60Gy 25% 16.0% 12.2% 3.8% 74Gy 5% 2.0% 1.2% 0.8% Volume (%) Multi-Phase Single-Phase Dose (Gy) 14

15 Organ at risk - Bowel An additional improvement to the single-phase technique including the bowel structure in the VMAT optimisation process. Bowel 15

16 Organ at risk - Bowel PIVOTAL Trial Dose Optimal Not included in VMAT optimisation Included in VMAT optimisation 45Gy 78cc 30.7 cc 17.8 cc 50Gy 17cc 17.5 cc 11.5 cc 55Gy 14cc 4.4 cc 4.4 cc 60Gy 0.5cc 0.5 cc 0.4 cc 65Gy 0cc 0.2 cc 0.1 cc 16

17 New method - performance The new single-phase technique has been in clinical use since October As of 1 st June patients have been planned using the new single-phase VMAT technique Number of patients Bowel overlap Small Bladder Artificial Hip 0 Priorities unchanged Priorities changed 17

18 Summary On average a reduction in dose to rectum and bladder, therefore a benefit for the patient due to reduced toxicity. Bowel now included in optimisation reduced toxicity. Robust optimisation process 83% of patients require no optimisation interaction (89% if artificial hip patients are excluded from this). A more streamlined planning and treatment process (only one plan, rather than three). 18

19 Thank you for listening Any questions? 19