Elekta 2017 Australasian User Meeting 12 th November 2017, Newcastle, NSW

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3 This work aims to compare ITVs defined using 4DCBCT data in two treatment planning systems (TPS) and to assess their impact on planned dose Elekta 2017 Australasian

4 Background: Lung SABR in NT Introduction: ITV in lung SABR Method: ITV definition using 4DCBCT Validation: Validation of 2 methods Results: Volume Analysis + Plan Evaluation Discussion: Uncertainty + Adv./Disadv. Conclusion: Major findings + implications

5 Alan Walker Cancer Care Centre - AWCCC Only RT centre in NT Low population patients per day High Indigenous population High incidence lung cancer Advanced presentations High COPD CT TPS Linac Toshiba Wide Bore No 4DCT Pinnacle 2 Elekta Synergy MLCi2 4D CBCT XVI Symmetry

6 SABR for lung only First patient treated October 2016 Total 16 patients treated to date 3DCRT + non-coplanar beams 48Gy / 4 Fx Dose escalation planned for 2018

7 SABR for lung cancer relies on accurate definition of tumour motion using an internal target volume (ITV). Typically 4DCT is utilised to define the ITV Two methods of ITV definition using 4- dimensional cone-beam CT (4DCBCT) data are described.

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9 Manual Method - Pinnacle

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11 MIP Method - Monaco

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14 End-to-end testing Localisation of moving target Tumour remains within ITV Moving/static dose <1% difference

15 ITV Volume (cm 3 ) ITV Manual ITV MIP Patient Patient Ratio Elekta 2017 Australasian All ITVs reduced

16 PTV Volume (cm 3 ) PTV Manual PTV MIP Patient Patient Ratio Elekta 2017 Australasian 9/15 > 10% difference

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18 Replans in Pinnacle Isocentre Beam angles Target coverage maintained 2 patients excluded - PTV coverage could not be met

19 Number OAR Constraints Decreased Increased Unchanged Elekta 2017 Australasian Patient

20 All 13 patients experienced dose reduction for one or more OAR constraints Average 75% OAR doses decreased by replan 6/13 patients had one or more OAR reduced 10% Most clinically insignificant 3 cases reviewed

21 Volume (%) Elekta 2017 Australasian 18 Lungs - GTV: V20 <10% ITV Manual ITV MIP Patient

22 Patient 11 48Gy/4Fx PTV Manual cm 3 Patient 11 Constraint Planning Aim ITV Manual ITV MIP CI 100 % 1.2 / CI 50 % <3.35 / < LUNGS -GTV V20 < Mean (Gy) < Point max (Gy) < SPINAL CANAL 0.35cc Vol. max (<20.8Gy) cc Vol. max (<13.6Gy) PTV MIP cm 3 HEART GREAT VESSELS OESOPHAGUS SKIN TRACHEA & LARGE BRONCHUS Point max (Gy) < cc Vol. max (<28Gy) Point max (Gy) < cc Vol. max (<43Gy) Point max (Gy) < cc Vol. max (<18.8Gy) Point max (Gy) < cc Vol. max (<33.2Gy) Point max (Gy) < cc Vol. max (<15.6Gy) Elekta 2017 Australasian CHEST WALL/RIBS NORMAL TISSUE % Point max (Gy) < cc Vol. max (<32Gy) <68.97 / <

23 Patient 5 60Gy/8Fx PTV Manual cm 3 Patient 5 Constraint Planning Aim ITV Manual ITV MIP CI 100 % 1.2 / CI 50 % <3.67 / < LUNGS -GTV V20 < Mean (Gy) < Point max (Gy) < SPINAL CANAL 0.25cc Vol. max (<22.5Gy) cc Vol. max (<13.5Gy) PTV MIP cm 3 HEART GREAT VESSELS OESOPHAGUS SKIN TRACHEA & LARGE BRONCHUS Point max (Gy) < cc Vol. max (<28Gy) Point max (Gy) < cc Vol. max (<47Gy) Point max (Gy) < cc Vol. max (<27.5Gy) Point max (Gy) < cc Vol. max (<30Gy) Point max (Gy) < cc Vol. max (<18Gy) Elekta 2017 Australasian CHEST WALL/RIBS NORMAL TISSUE % Point max (Gy) < cc Vol. max (<32Gy) <64.62 / <

24 Patient 4 48Gy/4Fx PTV Manual 9.34cm 3 Patient 4 Constraint Planning Aim ITV Manual ITV MIP CI 100 % 1.2 / CI 50 % <4.97 / < LUNGS -GTV V20 < Mean (Gy) < Point max (Gy) < SPINAL CANAL 0.35cc Vol. max (<20.8Gy) cc Vol. max (<13.6Gy) PTV MIP 8.15cm 3 HEART GREAT VESSELS OESOPHAGUS SKIN TRACHEA & LARGE BRONCHUS Point max (Gy) < cc Vol. max (<28Gy) Point max (Gy) < cc Vol. max (<43Gy) Point max (Gy) < cc Vol. max (<18.8Gy) Point max (Gy) < cc Vol. max (<33.2Gy) Point max (Gy) < cc Vol. max (<15.6Gy) Elekta 2017 Australasian Point max (Gy) < CHEST WALL/RIBS 1cc Vol. max (<32Gy) NORMAL TISSUE % <50 / <

25 Contouring assessed through team meeting Motion artefacts in CT and CBCT Different position/breathing pattern from CT to CBCT Fusion

26 Advantages No 4DCT required Tumour motion captured in treatment position Adequate tumour coverage Tumour motion verified at treatment Disadvantages Poor Image quality Additional fusion Additional machine time Dose calculation on free breathing Increased QA

27 Image quality Target coverage OAR doses Time Accuracy Manual X X X MIP X

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29 ITV definition using Symmetry validated for Lung SABR Manual + MIP Pinnacle + Monaco MIP method produces smaller volumes more indicative of true tumour motion most of the time Exceptions lateral or inferior located tumours Manual method more likely to over-contour MIP ITVs resulting in smaller PTVs reduced OAR dose in all cases although reduced target coverage in some cases Although majority of OAR doses were subsequently reduced, clinically significant plan changes were rare and therefore overall plan acceptability was comparable

30 Jeremy Plawecki, Senior RT planning Dr. Thanuja Thachil, RO contouring Elekta Monaco education station