A rose is a rose by any name

Transcription

1 SABR Tomas Kron

2 A rose is a rose by any name W. Shakespeare What is in a name? Hypofractionated Image Guided Motion Managed High Precision Radiation Therapy (HIGMHPRT not a good acronym) Stereotactic Body Radiation Therapy (SBRT) Stereotactic Ablative Body Radiotherapy (SABR)

3 A rose is a rose by any name W. Shakespeare What is in a name? Stereotactic is a term widely used in interventional radiology and surgery. Hypofractionated It does Image imply Guided high precision Motion and does not come with the connotation of Managed High Precision Radiation Therapy radiation (HIGMHPRT not a good acronym) Stereotactic Body Radiation Therapy (SBRT) Stereotactic Ablative Body Radiotherapy (SABR) Ablative implies a different method of cell kill and as such a paradigm shift giving radiotherapy a new and exciting look

4 Two presentations Implementing SBRT for physicists ( ) Challenges and issues for SBRT ( ) Refresher Time for questions

5 may I introduce myself History: Phd Germany 12 year clinical radiotherapy physics in Australia 4 years tomotherapy co-ordinator in London, Ontario Since 8 years Research Physicist at Peter Mac Past President ACPSEM Interests: Dosimetry (TLD, gels, MOSFETs) Treatment verification and clinical trials (TROG) Adaptive/image guided radiotherapy Education of radiotherapy staff

6 Disclosures Our hospital is about to enter into a research collaborative agreement with Varian Medical Systems I am grateful to Varian Medical Systems for supporting my travel to SEACOMP through a Varian Speaker Agreement Varian as a medical device manufacturer cannot and does not recommend specific treatment approaches. The presentation does reflect the practice at Peter Mac and my personal experience.

7 Peter MacCallum Cancer Centre Only hospital dedicated to cancer in Australia Operates on 5 sites Total 18 linacs About 7000 new RT patients/year Organised in tumour streams (subspecialisation)

8 SABR program at PeterMac Program commenced in 2009 Since 2011 special chart rounds dedicated to SABR Programs for lung, liver, kidney, spine, mets from prostate and breast cancer > 50% of patients on clinical trials

9 Our tools Varian Trilogy and 21iX linac CBCT essential Mosaiq ROI Elekta XiO planning for lung Varian Eclipse planning for all others (particular if IMRT is needed) Very few gated deliveries No VMAT On-board imaging EPID

10 Objectives of the presentations Provide a background of SABR Introduce the technological features required for commencing a SABR program Discuss different clinical scenarios and the challenges associated with them Touch on dosimetry issues (small fields) Explore what medical physicists can add in terms of Quality Assurance Program development and evaluation

11 Contents of the two presentations 1. Background for SABR 2. Technology requirements Imaging for planning Planning Delivery Quality Assurance 3. Clinical scenarios 4. Conclusion (what does it mean for physicists?)

12 1. Background

13 What is Stereotactic Radiotherapy? Neurosurgeon Lars Leksell from Karolinska Institute in Stockholm, Sweden pioneered stereotactic treatments Developed procedure in late 1940s to destroy dysfunctional loci in the brain Coined the term radiosurgery (1951) Stereotactic radiosurgery (SRS) Intracranial lesions Single fraction Stereotactic radiotherapy (SRT) Multiple dose fractions

14 The term stereotactic "Stereotactic" in Greek means movement in space Stereotactic surgery works on the basis of three main components: 1. A stereotactic atlas of the targeted anatomical structures (internal reference system: CT images). 2. A stereotactic device or apparatus rigidly connected with the patient. It has discernable reference points in the CT images (external reference system). 3. A stereotactic localization and placement procedure

15 Stereotactic procedures Targets were usually brain lesions External head frame used to ensure accurate patient positioning Invasive or re-locatable Dedicated units Cyberknife Gamma knife

16 Linac based X-ray knife Cones Mini MLC

17 Stereotactic procedures Concept now also applied to extracranial lesions in the body Frames are possible Image guidance is more common

18 More problems in body than in brain A. More variety in targets B. Immobilization more difficult C. Target definition requires usually the inclusion of motion D. Less experience regarding fractionation and dose per fraction E. Non-coplanar beams harder to fit F. Irregular lesions MLC, IMRT/VMAT? G. Dose calculation requires good algorithm small fields H. Image guidance required I. Motion management during treatment required 18

19 General features Small lesions Small margins Competes with surgery Set-up and Motion margin CTV Set-up margin PTV TUMOUR ITV PTV

20 A. Target variety: Radical treatment Non-operable patients Lung Liver Renal cancer Pancreas others 20

21 21 Martel Dose-Response Curve for NSCLC

22 Palliative treatment? Bone pain Oligo metastases Few metastases in the context of inactive primary

23 Oligo metastases Site of primary Colorectal Prostate Breast Renal Sarcoma? Melanoma? Site of metastases Liver Lung Adrenal Kidney Vertebra/spine Lymph nodes Adapted from L Dawson

24 Oligo metastases Site of primary Colorectal Prostate Breast Renal Sarcoma? Melanoma? Site of metastases Liver Lung Adrenal Kidney Vertebra/spine Lymph nodes Not only the site of metastasis but also the primary determines treatment options

25 AAPM SBRT Task Group (2006) Number of fractions: <=5 Treatment intent: ablation Dose per fraction: >> 5Gy Conformity: high Immobilisation: essential Verification: IGRT

26 AAPM SBRT Task Group (2006) Number of fractions: <=5 Treatment intent: ablation Dose per fraction: >> 5Gy Conformity: high Immobilisation: essential Verification: IGRT Reflects billing in US

27 A. More variety in targets Imaging for treatment planning is important Require: Wide bore planning CT with 4D option Access to PET and MR

28 4D CT does not only allow for motion determination it also reduces artefacts that affect our ability to contour From AAPM TG 76 (2006)

29 From AAPM TG 76 (2006)

30 From AAPM TG 76 (2006)

31 A comment on imaging Importance cannot be underestimated Eg: PET required for staging, assessment of oligo mets status Required for target definition Required for critical structure contouring eg MRI for spine Fusion is essential Requires additional quality assurance

32 3D 4D MIP 4D PET could be helpful (PMCC experience in lung, J Callahan)

33 Require guidelines for contouring 33

34 34 For example brachial plexus

35 B. Immobilization in the brain.... vs the body

36 Need to verify immobilisation Pre treatment CBCT --> align Mid treatment CBCT

37 Need to verify immobilisation Cone Beam CT Mean shift Range Standard Deviation Initial 2.1 mm 0-4 mm 1.5 mm Check setup 0.03 mm 0-1 mm 0.2 mm Midtreatment 0.4 mm 0-2 mm 0.6 mm Nine patients Mid-treatment CBCT median time of 21 minutes

38 Features of immobilization Same at CT and treatment Must be comfortable May reduce motion 38

39 C. Motion management Often required in SABR Several different options: Assess in planning ITV or mid breathing position Reduce compression, breath hold Gating Motion adaptive treatment

40 The internal target volume (ITV) Tumor Motion encompassing volume Tumor 40 Exhale Courtesy of Paul Keall Inhale

41 Generating an ITV Based on maximum intensity projection (MIP) image set derived from 4D CT Cannot be used for dose calculation the average image set derived from 4D CT or mid phase must be used. 4D CT MIP ITV ITV + 5 mm = PTV Philips Brilliance Big Bore + bellows system

42 Elekta Bodyfix + drape SABR immobilisation

43 Comparison of 2 4DCTs

44

45 Fiducial marker placement? Visicoil 0.75mm diameter Superdimension 0.9mm diameter (the only patient with two marker implant)

46 Fiducial marker placement? Visicoil 0.75mm diameter Superdimension 0.9mm diameter (the only patient with two marker implant)

47 May need surrogate marker also in treatment

48 More problems in body than in brain A. More variety in targets B. Immobilization more difficult C. Target definition requires usually the inclusion of motion D. Less experience regarding fractionation and dose per fraction E. Non-coplanar beams harder to fit F. Irregular lesions MLC, IMRT/VMAT? G. Dose calculation requires good algorithm small fields H. Image guidance required I. Motion management during treatment required 48

49 F. Irregular lesions MLC, IMRT/VMAT? MLC how small is small enough? Our experience is that there is no simple solution: We use 5mm for nearly everything Using jaws between leafs can help (and sharpens the penumbra) Isocentre placement and collimator rotation is important jaw

50 Courtesy P Hoban Importance of leaf resolution For fixed fields Beam edge is affected For IMRT Whole beam is affected MLC IMRT MMLC mimrt

51 F. IMRT / VMAT considerations Needed for steep dose gradients Needed for concave targets Interplay effect with motion (only very few fractions) Treatment time QA Hotspots

52 Highly Conformal Dose Distribution Hotspots are part of stereotactic procedures

53 Example: Prescription 26Gy Max dose: 34Gy

54 Prescription To covering isodose line As in Intracranial SRS to an isodose line between 65 and 85% Hotspots between 20 and 50% are not unusual Choice depends on preference and lesion size: the smaller the lesion less uniform the dose

55 Prescription To covering isodose line As in Intracranial SRS to an isodose line between 65 and 85% Hotspots between 20 and 50% are not unusual Need to read papers very carefully: 48Gy in 4 fraction may be something quite different

56 Implications for IMRT Is the hotspot clinically important? In this case we would need to create it with IMRT by using additional smaller structures in the PTV In 3D conformal the cold spot is always at the edge of the PTV in IMRT it can be anywhere

57 Related consideration Conformity Index: Many definitions Depends on prescription No hard and fast rules We use CI100 (VprescribedD/PTV) and CI50 (V50%dose/PTV) to guide plan optimisation CI50 depends on target size (aim for 5, settle for 10 in very small lesions)

58 G. Dose calculation Example: 51.4Gy in 3 fractions, 9 nonopposed non-coplanar beams, prescribed to PTV Skin covering dose isodose (which happens to be in lung) Chest wall 58

59 Dose calculation algorithm Lung 59 Beam Utilises a 3D dose calculation algorithm (eg convolution / superposition algorithm) capable of performing calculations which account for variations in lateral scatter in the presence of 3D-(CT) defined heterogeneities. Systems that have this capability include Philips Pinnacle, CMS XiO and Varian Eclipse (AAA algorithm NOT pencil beam). If centres intend to use a different algorithm or are unsure about the performance of their system they should contact the physicist or radiation therapist on the trial management committee (AAPM/RPC/RTOG). Electrons go wider in Low Density

60 A few personal comments Pencil beam typically NOT suited for most SABR Even good algorithms have shortcomings Quality depends on algorithm AND beam model

61 Lateral Equilibrium not established tissue 61

62 62 Lateral Equilibrium not established

63 More problems in body than in brain A. More variety in targets B. Immobilization more difficult C. Target definition requires usually the inclusion of motion D. Less experience regarding fractionation and dose per fraction E. Non-coplanar beams harder to fit F. Irregular lesions MLC, IMRT/VMAT? G. Dose calculation requires good algorithm small fields H. Image guidance required I. Motion management during treatment required 63

64 H. Image guidance Goldmarkers Image guidance is required Must visualise the target fiducial markers are an option Should provide an indication of the effect of motion Can be used more than once during delivery 64

65 Image guidance essential CBCT (or other volumetric imaging) at treatment for verification required Need reference image 65

66 Isocentre placed in midline to facilitate CBCT acquisition Isocentre placement and CBCT

67 Isocentre placed in midline to facilitate CBCT acquisition Isocentre placement and CBCT This will be more problematic for flattening filter free beams

68 68 IGRT

69 IGRT In our view: CBCT is great for lung, acceptable for kidneys and not very useful for liver and might be replaced with kv/kv for bony lesions. 69

70 Motion assessment should be part of IGRT Verification of internal target volume (ITV) margin by assessment of superior-inferior diaphragm motion during mock-up appointment. ITV verification done for kidney and liver clinical targets For Kidney SBRT daily pretreatment verification of breathing range is performed. Courtesy D Pham

71 Motion assessment should be part of IGRT Profile from planning Verification of internal target volume (ITV) margin by assessment of superior-inferior diaphragm motion during mock-up appointment. ITV verification done for kidney and liver clinical targets Profile from CBCT For Kidney SBRT daily pretreatment verification of breathing range is performed. Total Number = 35 (from 13 pts)

72 A note on gating

73 A note on gating Requires extensive additional QA ANT 0 One patient done at PMCC Special case (single lung) No routine QA as yet

74 Image guidance and motion management Both are linked Image guidance Determines that location is correct at one point Essential each time the patient is treated Motion management Makes sure it stays that way throughout the delivery Not necessarily standard in all departments 74

75 Many X-ray image guidance solutions Brainlab Exactrac Siemens in-room CT Protons at PSI Tomotherapy MVCT

76 MRI linac Utrecht MRI linac project

77 More problems in body than in brain A. More variety in targets B. Immobilization more difficult C. Target definition requires usually the inclusion of motion D. Less experience regarding fractionation and dose per fraction E. Non-coplanar beams harder to fit F. Irregular lesions MLC, IMRT/VMAT? G. Dose calculation requires good algorithm small fields H. Image guidance required I. Motion management during treatment required 77

78 Why all this technology? Avoid disaster: Posterior lesions Build-up in immobilisation Avoid overlap of beams Dunlap et al IJROBP 2010; 76:796 Common problem in renal irradiation

79

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81 SBRT QA Requirements SIMULATION RT PLANNING IMAGE GUIDANCE Courtesy D Pham

82 reflect PMCC experience not summarize increasing literature White paper endorsed by ASTRO, AAMP, ASRT, AAMD PRO 2012 v2 p.2 National Cancer Action Team, NHS AAPM Task Group Report 101 Med. Phys. 37 p4078

83 QA EQUIPMENT QA 83

84 QA Process: Planning 4DCT phantom 4s cycle, 2cm amplitude right/left sided lesions 4DCT sent to TPS Xio v4.4, superposition conv MIP 4DCT = ITV contour Avg 4DCT = dose calc Plan calculated on phantom Point doses obtained Isodose plane exported 84

85 QA Process: Planning 4DCT phantom 4s cycle, 2cm amplitude right/left sided lesions 4DCT sent to TPS Xio v4.4, superposition conv MIP 4DCT = ITV contour Avg 4DCT = dose calc Plan calculated on phantom Point doses obtained Isodose plane exported lesion 85

86 QA Process: Linac Phantom moving with patientspecific breathing trace Ion chamber measurements stationary moving Film measurements stationary moving Comparison & analysis 86

87 Individual patient QA for first 30 patients Outcomes: all good except for couch attenuation Reduce to 1 in 10 and special cases Summary of QA 87

88 and do not forget imaging QA Home built seesaw phantom for QA (Dunn et al Med Phys 2012)

89 3. Some clinical examples Liver Kidney Spine

90 SABR for liver Australian protocol to come on line through TROG (13.02 LIGHT) Six fractions, NTCP based prescription 60Gy in 6# delivered over 2-3 weeks for mean liver dose < 13.3Gy 51Gy in 6# delivered over 2-3 weeks for mean liver dose Gy 42Gy in 6# delivered over 2-3 weeks for mean liver dose Gy Modelled on experience in Ann Arbor and Princess Margaret Hospital

91 Common issues Patients are non-operable (and not fit for RF or other ablation) Co-morbidities Often large lesions not really stereotactic Motion and immobilisation are challanges

92 Specific challenge Target definition Cannot do 4D CT with contrast MIP concept (or MiNIP) usually not useful Imaging at treatment unit does not allow visualisation of target Fiducials may be helpful

93 SABR for kidney PMCC protocol (FASTRACK, trial registry ID: NCT ) Eligibility Primary single lesion in kidney Up to 5 documented metastasis Up to 10cm in size Dose 26Gy single fx for d < 5cm 42 in 3fx for d > 5cm

94 SABR for kidney PMCC protocol (FASTRACK, trial registry ID: NCT ) Eligibility Why do I fuzz so much about Primary single lesion in kidney clinical trials? Up to 5 documented SABR metastasis not standard of care Up to 10cm in size in many cases Trials ensure standardised practice and outcomes are closely monitored Dose 26Gy single fx for d < 5cm 42 in 3fx for d > 5cm

95 Typical kidney plan 7 to 12 fields

96 Kidney specific issues Use of 18MV for skin sparing Is a small field for 18MV the same as a small field for 6MV? We use 3 x 3 cm2 as minimum field for 6X and 4 x 4 cm2 for 18X

97 Common issues Immobilisation Motion IGRT

98 Image guidance issues Depends on motion pattern

99 IGRT Verification Case Example Patient rotation can potentially affect the dose to OAR. This can exacerbated for contra-lateral organs midline External skin markers changed to counteract rotation effect cm Correction Req d Correction Required: Tan3 = opp/adj = 0.8cm Courtesy D Pham

100 IGRT Verification Case Example 6D couch Patient rotation can potentially affect the dose to OAR. This can exacerbated for contra-lateral organs midline External skin markers changed to counteract rotation effect cm Correction Req d Correction Required: Tan3 = opp/adj = 0.8cm Courtesy D Pham

101 Vertebrae Novel approach to achieve more durable pain relief and response for spinal mets Up to 3 lesions, each lesion up to 2 vertebraes 20Gy single fraction Standard contouring guidelines IMRT essential

102 Cox et al IJROBP, 83 (e ) 2012

103 Vertebrae specific Steep dose gradients Critical structure enclosed by target Good IGRT must include rotation

104 Example Verification of treatment planning system dose calculation around organs at risk for spine SABR TPS: Eclipse v11 Algorithm: AAA v11.02 Calc Grid: 2.5mm x 2.5mm CT Slice: 3/3 IMRT QA performed with further dose gradient testing done

105 dose (Gy) dose (Gy) QA: spatial resolution is everything Coronal Planned Measured position (mm) Planned Measured position (mm)

106 SABR solutions Many Conventional high end linac (Elekta, Varian) Based on conventional linac (Novalis, Elekta, Varian) Helical tomotherapy Special SABR designs (Cyberknife, VERO, )

107 CyberKnife Installations Industrial robot with small linear accelerator (X-Band) Designed specifically for stereotactic applications Image guidance built in

108 Tomotherapy

109 Tomotherapy

110 VERO

111 VERO system Collaboration between Brainlab and Mitsubishi Gimballed linac Dual kv imaging system Ring gantry

112 Cool design

113 Rotating joint for RF

114 4. Where are things heading? From my perspective

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116

117 117

118 A paradigm shift?

119 A paradigm shift?

120 Can we afford this paradigm shift? Better outcomes? Expensive equipment More time for contouring More time for planning More time for QA

121 Can we afford this paradigm shift? Better outcomes? Expensive equipment More time for contouring More time for planning More time for QA New indications Much shorter treatment courses

122 Lievens et al RO 2010: Costing of hypofractionated breast irradiation

123 Medical physics role Provide the technical AND computing tools for applications Advise on their use Understand the clinical need Design and co-ordinate QA activities

124 Technology Patient Clinical Medical Physics

125 so much more to say Training requirements Small field dosimetry FFF, high dose rate Planning tips and tricks Other indications (prostates?) Retreatment

126 High Level Summary Many advances in radiotherapy are related to technological improvements It is essential to evaluate their impact on patient care, clinical outcomes and resources The technological challenges make the involvement of all team members essential Patients will ask for this - we may as well get it right

127 Acknowledgements Yolanda Aarons, David Ball, Jason Callahan, Mathias Bressel, Brent Chesson, Boon Chua, Jim Cramb, Sarah Everitt, Chris Fox, Annette Haworth, Farshad Foroudi, Eric Nguyen, Rebecca Owen, Paul Roxby, Andrea Paneghel, May Whitaker, Scott Williams, Trevor Leong, Kellie Knight, Kate Love, Claire Fitzpatrick, Trish Hubbard, David Willis, Shankar Siva, Aldo Rolfo, Gill Duchesne and many more VARIAN Medical Systems