Evaluation of Pinnacle Auto-Planning for Prostate VMAT

Transcription

1 Evaluation of Pinnacle Auto-Planning for Prostate VMAT N. Simpson, G. Simpson, R. Laney, A. Thomson, D. Wheatley, R. Ellis, J. Mcgrane. Medical Physics Royal Cornwall Hospital, Truro, Cornwall United Kingdom

2 Background Plymouth 95 miles. Exeter 120 miles.

3 Background VMAT > 50% workload per month Regional service Catchment population is 450,000 Variability in workload Interest in automation: Increase efficiency Streamline standardized techniques More time for planning complex non-standard techniques

4 Background VMAT Planning RCHT 2015/2016

5 Background AutoPlanning is an integrated IMRT/VMAT module in the Philips Pinnacle TM User Created Treatment experiencedtechnique: skilled planner: Beams Arrangement & AP mimics the workflow of an AP Machine uses Parameters clinical goals to formulate optimisation objectives Clinical optimisation goals for PTV coverage Multiple and dose optimisation limits for loops iteratively reformulate organs risks and (OARs). adjust the optimisation objectives to meet the criteria defined in the template. Global Settings = prioritize sparing of Output: serial organs Clinically over deliverable Plan targets, dose fall-off, max dose Krayenbueh et al (2015) Evaluation of an automated knowledge based treatment planning system for head and neck, Radiat Oncol. Krayenbueh et Nov al (2015) 10;10:226) Evaluation of an automated knowledge based treatment planning system for head and neck, Radiat Oncol. Nov 10;10:226)

6 Methods PRESCRIPTION 74Gy in 37# to PTV2 (Prostate), with an SIB of 66.6Gy in 37# to PTV1 (Prostate+SV) VMAT Single 6MV Arc (356 arcs ( ) 3 o Spacing Dose resolution cm PTV1 (74Gy) = Prostate + 0.5cm margin. PTV2 (66.6Gy) = Prostate + base or full seminal vesicles plus 1.0cm margins SIB Rx 37 fractions IGRT CBCT fractions 1-4, then weekly PLANNING TIME VMAT Planning Experience Experienced 240 Less Experienced 360 Planning Time (Mins)

7 Objectives To evaluate the feasibility of automated single arc VMAT treatment planning for prostate cancer patients using a Pinnacle TM Auto-Planning Module Task Based Approach : 1. Does AP produced plans meet the Institution Plan DVH Protocol? 2. Are generated AP plans comparable to existing manually planned VMAT protocol? 3. Clinicians Evaluation (a) Institutional Criteria (b) Preference 4. Comparison of planning time differences.

8 Study Design Retrospective Planning Study 10 patients Adenocarcinoma Prostate Age Range: Gleason Score: 7-9 Routine (OAR overlaps within protocol) N = 6 Complex (OAR overlaps exceed protocol) N = 4 Apply AP Technique 10 patients Comparison D98, D2, CI, HI, OAR Blinded Clinician Study Planning Time

9 Methods Institutional Protocol PTV1 D(Gy) Vol Min DVH(%) Max DVH(%) AP Technique PTV1_PTV2 Mean Dose Max DVH(%) 77 2 Min DVH(%) PTV2 Mean Dose Max DVH(%) 77 2 OAR Protocol D(Gy) max vol(%) 30 80% 40 70% 50 60% Rectum CHHIP 60 50% 65 30% 70 15% 74 3% % 60 25% Bladder CHHIP % cc Bowel PIVOTAL 50 17cc 55 14cc 60 1cc* 65 0cc AP Technique run on all plans. One optimisation simultaneously. Time taken 40 minutes. Femoral Head CHHIP 50 50%

10 Results Summary AP could produce a comparable clinically deliverable plan in all 10 cases. 6 routine plans met institution constraints 4 complex plans did not meet institution constraints due to overlaps but were comparable to M-VMAT plans 2.4 x Planning Time Saving 240 mins to 100 mins /plan Clinician Blind Evaluation AP produced 100% clinically acceptable plans Difficult to distinguish between plan types Slight preference to M-VMAT plans on routine cases, AP for complex cases

11 Results PTV Coverage No difference in PTV coverage between AP & M- VMAT plans Inverse Planned Auto Planned Data-Point Mean S.D Mean S.D Sig. Min DVH (%) Max DVH (%) PTV PTV1_PTV2 Mean Dose Max Min DVH (%) PTV Mean Dose Max DVH (%)

12 Results PTV HI/CI No difference in plan quality between AP & M- VMAT plans Inverse Planned Auto Planned Data-Point Mean S.D Mean S.D Sig. PTV1 CI PTV1_PTV2 HI PTV2 HI CI

13 Results Rectum Constraints AP Met all constraints in a single run. Slightly higher V74Gy when compared within M-VMAT D(Gy) Inverse Planned Auto Planned Data-Point Mean S.D Mean S.D Sig. V30 <80% V40 < 70% V50<60% V60<50% V65<30% V70<15% V74 <3% ** Statistical significance achieved at the: 95% confidence interval (*) 99% confidence interval (**)

14 Results Bladder Constraints AP Met all constraints in a single run. Slightly higher V74Gy when compared with M-VMAT Inverse Planned Auto Planned Data-Point Mean S.D Mean S.D Sig. V50<50% V60<25% V74<5% * Statistical significance achieved at the: 95% confidence interval (*) 99% confidence interval (**)

15 Results Bowel Constraints (Routine Cases N=6) AP Met all constraints in a single run. Slightly higher V74Gy when compared with M-VMAT Inverse Planned Auto Planned Data-Point Mean S.D Mean S.D Sig. V45 < 78cc V50<17cc V55<14cc V60<1cc V65<0cc

16 Results Bowel Constraints (Complex Cases N=4) AP Met all constraints in a single run. Slightly higher V74Gy when compared with M-VMAT Inverse Planned Auto Planned Data-Point Mean S.D Mean S.D Sig. V45 < 78cc V50<17cc V55<14cc V60<1cc V65<0cc * Statistical significance achieved at the: 95% confidence interval (*) 99% confidence interval (**)

17 Results Bowel overlap with PTV PTV preference over OAR sparing

18 Results Is there a way to improve the plans where there is a large bowel overlap? Develop another Technique? Refine the current Technique? Interact with the plan at the optimiser level?

19 Results: Bowel Overlap Auto Planning Run AP Check overlaps, add DVH point at D60 & D65 points Re-Run the technique Reduced PTV coverage at D98 and D95 (shoulder) Auto Assisted Planning Run AP Modify PTV (minus OAR overlap) Constraint on OAR overlap in the Optimiser Warm Start Reduced high dose tail and maintained coverage at D98 and D95 Increased planning time 40 mins

20 Results: Bowel Overlap Bowel Constraints - (Complex Cases N=4) No change to PTV D98/D95 but significant reduction in V65Gy Bowel Inverse Planned Auto Planned Data-Point Mean S.D Mean S.D Sig. V45 < 78cc V50<17cc V55<14cc V60<1cc V65<0cc * Statistical significance achieved at the: 95% confidence interval (*) 99% confidence interval (**)

21 Case Number Results: Meet Institutional Protocol? For all 10 plans clinicians scored AP as meeting Institutional Protocol in Blinded Study 100% would treat with AP Plans if not given a choice 12 Consultant Blind Evaluation DAW RAE JMG AHT 2 0 IP Plan Type AP

22 Case Number Results: Plan Preference AP. Vs. M-VMAT Plan Preference Given a choice - preference towards M-VMAT plans due to the slightly lower tail DVH for all OARs Consultant Blind Evaluation DAW RAE JMG AHT IP Plan Type AP

23 Number of Cases Results: Plan Preference AP. Vs. M-VMAT Plan Preference Given a choice - preference towards AP plans due to the slight lower tail DVH tail of Bowel in M-VMAT Consultant Blind Evaluation Bowel Overlap Cases DAW RAE JMG AHT IP AP Either Plan Type

24 Results Planning time savings Experienced Planner 2.4 x time saving Less Experienced Planner 3.3 x time saving VMAT Planning Experience Planning Time (Mins) (Manual VMAT) Planning Time (Mins) (Auto Planning) Planning Time(Mins) (Auto Assisted Planning) Experienced Less Experienced

25 Conclusions AP produces highly consistent treatment plans with a single treatment technique for both routine and complex prostate cases. Dose distributions of the target volumes were similar between the AP and M-VMAT OAR sparing was comparable using AP across the DVH curve but slightly increased on the tail.

26 Conclusions Planning time was substantially reduced with AP. Technique can be used by both experienced and less experienced planners. Clinicians would accept either plan but due to DVH tail on all OARs preferred Manually manipulated plans, whether this be the M-VMAT or the auto assisted.

27 Future Work Used Mean Doses for OAR Technique. Refine technique: Add DVH points to shape high dose tail How much further can be OARs be pushed? Assess Auto planning for other clinical sites

28 Acknowledgments Co-Authors: Mr G Simpson Mr R Laney Dr J McGrane Dr D Wheatley Dr R Ellis Dr A Thomson With thanks to: Philips: Greg Perkins and Nigel Deshpande Elaine Buck Claire Cartledge Marina Cousins