Multi-Criteria Optimization Volumetric-Modulated Arc Therapy (MCO-VMAT) for Hippocampus Avoidance Whole Brain Radiation Therapy (HA-WBRT)

Transcription

1 Multi-Criteria Optimization Volumetric-Modulated Arc Therapy (MCO-VMAT) for Hippocampus Avoidance Whole Brain Radiation Therapy (HA-WBRT) Stephen Zieminski M.S., RT(T), CMD

2 Learning Objectives Review the utility and dosimetric benefits of multi-criteria optimization (MCO) along with challenges in HA-WBRT Compare HA-WBRT planning metrics for the following modalities: STD (standard)-vmat, MCO-IMRT, MCO-VMAT Discuss the influence of head positioning on the treatment planning process Examine select case studies utilizing the benefits of both MCO and standard optimization (STD) for challenging HA-WBRT scenarios (previous RT and high number of SIB targets) 2

3 Previous HA-WBRT Presentations 2016 AAMD Excellent overview on HA-WBRT and various approaches Hippocampal Sparing: An Advancement to WBRT Timothy Oh, BS, CMD s/file/wednesday/oh.pdf 2015 Plan Challenge Various approaches and TPS(s) from high scorers (Sun Nuclear): SIB whole brain with hippocampal sparing 3

4 Review: Hippocampus Anatomy and Physiology Two halves- Interconnected structure within Limbic system Strong role in consolidation and transition of memory from short-term to long-term memory Spatial memory for navigation and location Alzheimer s usually the first region to become damaged 4

5 Patterns of Care for Brain Metastases Progress Study Two cohorts compared: vs (n=103) 1 year survival rate increased from 15% to 34% Contemporary patients were managed on a much more individualized basis, requiring multidisciplinary case discussion and thorough assessment of prognostic features. Avoiding overtreatment in patients with poor prognosis is as important as aggressive treatment in patients who might survive for several years. Nieder C, Spanne O, Mehta MP, et al. Presentation, patterns of care and survival in patients with brain metastases: what has changed in the last 20 years? Cancer 2011;117:

6 Neurocognitive Function SRS+WBRT vs. SRS alone PURPOSE: To determine how the omission of whole brain radiotherapy (WBRT) affects the neurocognitive function of patients with one to four brain metastases who have been treated with stereotactic radiosurgery (SRS). Mini-Mental State Examination (MMSE) score decline (deterioration) 12 months 24 months 36 months SRS alone 76.1% 68.5% 14.7% SRS+WBRT 59.3% 51.9% 51.9% CONCLUSION: The results of the present study have revealed that, for most brain metastatic patients, control of the brain tumor is the most important factor for stabilizing neurocognitive function. However, the long-term adverse effects of WBRT on neurocognitive function might not be negligible. Aoyama H, Tago M, Kato N, et al. Neurocognitive function of patients with brain metastasis who received either whole brain radiotherapy plus stereotactic radiosurgery or radiosurgery alone. Int J Radiat Oncol Biol Phys 2007;68:

7 Neurocognitive function and quality of life: post WBRT PURPOSE: To examine the relationship between neurocognitive function (NCF) and quality of life (QOL) in patients with brain metastases after whole-brain radiotherapy. Results: Significant correlations with NCF and ADL (activities of daily living) CONCLUSIONS: Neurocognitive function and QOL are correlated. Neurocognitive function scores from previous visits are predictive of QOL. Neurocognitive function deterioration precedes QOL decline. The sequential association between NCF and QOL decline suggests that delaying NCF deterioration is a worthwhile treatment goal in brain metastases patients. Li J, Bentzen SM, Renschler M, et al. Relationship between neurocognitive function and quality of life after wholebrain radiotherapy in patients with brain metastasis. Int J Radiat Oncol Biol Phys 2008;71:

8 Risk Estimation of Perihippocampal Disease Progression post HA-WBRT (RTOG 0933) 1133 metastases, 371 patients (pre-treatment, post-contrast MRIs) Risk estimation in hippocampal avoidance region (hippocampus + 5mm): 8.6% Conclusion: HA-WBRT safe for clinical use (RTOG 0933) Gondi V, Tomé W, Marsh J, et al. Estimated Risk of Perihippocampal Disease Progression after Hippocampal Avoidance during Whole-Brain Radiotherapy: Safety Profile for RTOG 0933; Raditother Oncol. 2010; 95(3):

9 RTOG 0933 & Contour Atlas RTOG 0933 Phase ll Trial of Hippocampal Avoidance During Whole Brain Radiotherapy for Brain Metastases: Eligibility: Neurocognitive Function Assessment (Hopkins Verbal Learning Test, International Shopping List Test, One Card Learning Test) Quality of Life Assessment (FACT-BR, ADL Barthel Index) Karnofsky performancy status 70 (tests functional impairment) Measurable brain metastasis outside a 5-mm margin around either hippocampus (contrast enhanced MRI) Useful Link: Contour Atlas for Hippocampus 9

10 Memory Preservation Outcomes from RTOG 0933 ( ) Used QOL & HVLT-R DR (Hopkins Verbal Learning Test-Revised Delayed Recall), 42 patients from 113 analyzable HA-WBRT (0-4 months) mean relative decline: 7.0% (HBLT-R DR), no QOL loss observed Historical control WBRT (0-4 months) mean relative decline: 30% (HBLT-R DR) 3 patients (4.5%) relapsed in HA area Median survival 6.8 months (62% primary, 7.3% brain metastasis) Two grade 3 toxicities (fatigue & headache), no grade 4 or 5 10

11 Memory Preservation Outcomes from RTOG 0933 ( ) The effect of older age on declining HVLT-R TR and HVLT-R DR scores after HA- WBRT seems consistent with preclinical studies showing an age-dependent inflammatory response of the hippocampal dentate gyrus to WBRT. This finding suggests that patients age 60 years may be a high-risk group of patients for whom neuroprotective interventions beyond HA-WBRT may be required. In addition, higher hippocampal D100% predicted for greater HVLT-R DR decline, suggesting that further lowering the dose to the entire hippocampal neural stem-cell compartment may affect list-learning recall outcomes. 11

12 What is multi-criteria optimization (MCO)? First, a review on what is Conventional (standard) Optimization for inverse planning User sets objectives/constraints (target and OARs) using various weighting priority Optimization is manually adjusted ex. Standard Optimization Iterative approach (trial/error) Highly dependent on planner skillset Optimal plan subjectivity Time required for complex cases, irregular targets and anatomy 12

13 Plan Quality Metric study 2012 The ability of the treatment planners to meet the specified plan objectives (as quantified by the PQM) exhibited no statistical dependence on technologic parameters (TPS, modality, plan complexity), nor was the plan quality statistically different based on planner demographics (years of experience, confidence, certification, and education). Therefore, the wide variation in plan quality could be attributed to a general "planner skill" category that would lend itself to processes of continual improvement where best practices could be derived and disseminated to improve the mean quality and minimize the variation in any population of treatment planners. 13

14 Available Industry Solutions RayStation (Navigational MCO) Eclipse (Knowledge Based Planning), MCO 2017 Pinnacle (Auto Planning) Monaco (Constrained Optimization) Astroid (Navigational MCO p+) ProKnow 14

15 Again, what is multi-criteria optimization (MCO)? Computation of Pareto Plans based on user specification of tradeoff objectives and constraints Pareto Optimal: Unable to improve any one objective without worsening another Pareto Optimal plans create the Pareto Surface Real time navigation of Pareto surface using slider controls 15

16 Example: MCO Pareto Plans and Navigation Tradeoff Objectives + Constraints Navigational Sliders 16

17 17 Anchor Plans with Extreme Tradeoffs, Balance Plan and Auxiliary Plans

18 Brief MGH History: MCO & HA-WBRT 2014: Began MCO-IMRT HA-WBRT 2016: Plan comparison studies (MCO/IMRT/VMAT) 2016: MCO-VMAT HA-WBRT 2014-June 2017: 42 cases (+170 standard conventional WB cases) 18

19 MCO Advantage Studies Craft DL, Halabi TF, Shih HA, Bortfeld TR, Approximating convex Pareto surfaces in multiobjective radiotherapy planning; Med. Phys. 33 (9), 2006; Craft D, Halabi T, Shih HA, et al. An approach for practical multiobjective IMRT treatment planning, Int. J. Radiat. Oncol. Biol. Phys. 2007; (69): Craft DL, Hong TS, Shih H, Bortfeld TR, Improved Planning Time and Plan Quality Through Multicriteria Optimization for Intensity-Modulated Radiotherapy; Int. Jour. of Rad. Onc. Bio. Phys.; 2012; Vol 82, (1), e83-e90 Wala J, Craft D, Paly J, Zietman A, Efstathiou J, Maximizing dosimetric benefits of IMRT in the treatment of localized prostate cancer through multicriteria optimization planning, Med. Dos. 2013; (38): McGarry C, Bokrantz R, O Sullivan JM, Hounsell AR, Advantages and limitations of navigation-based multicriteria optimization (MCO) for localized prostate IMRT planning; Med Dos. 2014; (39): Chen H, Craft DL, Gierga DP, Multicriteria optimization informed VMAT planning. Med. Dos. 2014; 39(1):64-73 Ghandour S, Matizinger O, Pachoud M, Volumetric-modulated arc therapy planning using multicriteria optimization for localized prostate cancer, Jour. of App. Cl. Med. Phys., 2015; 16(3): Kierkels RGJ, Visser R, Biijl HP, et al. Multicriteria optimization enables less experienced planners to efficiently produce high quality treatment plans in head and neck cancer radiotherapy; Bio. Med. Cent.,2015; 10:87, DOI /s

20 MCO Advantage Studies Craft DL, Halabi TF, Shih HA, Bortfeld TR, Approximating convex Pareto surfaces in multiobjective radiotherapy planning; Med. Phys. 33 (9), 2006; Craft D, Halabi T, Shih HA, et al. An approach for practical multiobjective IMRT treatment planning, Int. J. Radiat. Oncol. Biol. Phys. 2007; (69): Craft DL, Hong TS, Shih H, Bortfeld TR, Improved Planning Time and Plan Quality Through Multicriteria Optimization for Intensity-Modulated Radiotherapy; Int. Jour. of Rad. Onc. Bio. Phys.; 2012; Vol 82, (1), e83-e90 Wala J, Craft D, Paly J, Zietman A, Efstathiou J, Maximizing dosimetric benefits of IMRT in the treatment of localized prostate cancer through multicriteria optimization planning, Med. Dos. 2013; (38): McGarry C, Bokrantz R, O Sullivan JM, Hounsell AR, Advantages and limitations of navigation-based multicriteria optimization (MCO) for localized prostate IMRT planning; Med Dos. 2014; (39): Chen H, Craft DL, Gierga DP, Multicriteria optimization informed VMAT planning. Med. Dos. 2014; 39(1):64-73 Ghandour S, Matizinger O, Pachoud M, Volumetric-modulated arc therapy planning using multicriteria optimization for localized prostate cancer, Jour. of App. Cl. Med. Phys., 2015; 16(3): Kierkels RGJ, Visser R, Biijl HP, et al. Multicriteria optimization enables less experienced planners to efficiently produce high quality treatment plans in head and neck cancer radiotherapy; Bio. Med. Cent.,2015; 10:87, DOI /s

21 21 Slade et al. HA-WBRT Survey 2016

22 Slade et al. HA-WBRT Survey (n = 196) Slade, A.S.; Stanic, S.; The impact of RTOG 0614 and RTOG 0933 trials in routine clinical practice: The US Survey of Utilization of Memantine and IMRT planning for hippocampus sparing in patients receiving whole brain radiotherapy for metastases; Contemp. Clin. Trials, 47 (2016)

23 Slade et al. HA-WBRT Survey (n = 196) Slade, A.S.; Stanic, S.; The impact of RTOG 0614 and RTOG 0933 trials in routine clinical practice: The US Survey of Utilization of Memantine and IMRT planning for hippocampus sparing in patients receiving whole brain radiotherapy for metastases; Contemp. Clin. Trials, 47 (2016)

24 VMAT and/or SIB Targets Studies (HA-WBRT) Gutiérrez AN, Westerly DC, Tomé WA, et al. Whole brain radiotherapy with hippocampal avoidance and simultaneously integrated brain metastases boost: A planning study. Int J Radiat Oncol Biol Phys. 2007; (69): Lagerwaard FJ, Van Der Hoorn EAP, Verbakel WFAR, Haasbeek CJA, Slotman BJ, Senan S, Whole brain radiotherapy with simultaneous integrated boost to multiple brain metastases using volumetric modulated arc therapy; Int. J. Rad. Onc. Biol. Phys. 2009; 75(1): Gondi V, Tolakanashalli R, Mehta MP, et al. Hippocampal-Sparing Whole Brain Radiotherapy: A How-To Technique, utilizing Helical Tomotherapy and LINAC-based Intensity Modulated Radiotherapy; Int J Radiot oncol Biol Phys. 2010; 78(4): Hsu F, Carolan H, Nichol A, et al. Whole Brain Radiotherapy with Hippocampal Avoidance and Simultaneous Integrated Boost for 1-3 Brain Metastases: A Feasibility Study using Volumetric Modulated Arc Therapy; Int. J. Rad. Onc. 2010; (76): Wang JZ, Pawlicki T, Rice R, Mundt AJ, Sandhu A, Lawson J, Murphy KT, Intensity-modulated radiosurgery with rapidarc for multiple brain metastases and comparison with static approach; Med. Dos.2012; (37):31-36 Liang X, Ni L, Hu W, Chen W, et al. A planning study of simultaneous integrated boost with forward IMRT for multiple brain metastases; Med Dos, 2013; (38): Cilla S, Deodato F, Digesu C, et al. Assessing the feasibility of volumetric-modulated arc therapy using simultaneous integrated boost (SIB- VMAT): An analysis for complex head-neck, high-risk prostate and rectal cancer cases; Med. Dos.2014; (39): Shen J, Bender E, Yaparpalvi R, et al. An efficient Volumetric Arc Therapy treatment planning approach for hippocampal-avoidance wholebrain radiation therapy (HA-WBRT), Med. Dos. 2015; (40): Lee K, Lenards N, Holson J, Whole-brain hippocampal sparing radiation therapy: Volume modulated arc therapy vs intensity-modulated radiation therapy case study, Med. Dos. 2016; (46):

25 MCO-VMAT HA-WBRT MGH Dosimetry Study Study Features: 30 Gy (whole brain) / 37.5 Gy (SIB targets) feasibility (including SIB targets close to hippocampus), 15 fxs 10 patients (8 SIB, 2 whole brain only) 0-12 SIB targets, variable size and distance to hippocampus 3 Modality comparison: VMAT: MCO vs. STD (standard optimization) MCO: VMAT vs. IMRT 25

26 Materials and Methods Computed tomography simulation Contrast CT MRI axial T2 weighted, gadolinium contrast T1 weighted MR/CT fusion + structure contours using MIM Vista Hippocampal avoidance (HA) avoidance region: 5 mm Secondary 5 mm region (to control dose gradient in HA region) 2 mm PTV expansion: Whole Brain + 2 mm = PTV30 Metastatic lesion + 2 mm = PTV

27 Structures HA-WBRT SIB Structures Optimization Contours A. R+L Hippocampus B. 5 mm Hippocampus Avoidance Area C. CTV30 D. PTV30 (CTV30 + 2mm) E. PTV37.5 (GTV mm) F. Uniform PTV30 (PTV30 PTV37.5) G. Anterior Avoidance Structure H. Central Target I. 2 mm Skin 27

28 Structures HA-WBRT SIB Structures Optimization Contours A. R+L Hippocampus B. 5 mm Hippocampus Avoidance Area C. CTV30 D. PTV30 (CTV30 + 2mm) E. PTV37.5 (GTV mm) F. Uniform PTV30 (PTV30 PTV37.5) G. Anterior Avoidance Structure H. Central Target I. 2 mm Skin 28

29 Structures HA-WBRT SIB Optimization Contours A. R+L Hippocampus B. 5 mm Hippocampus Avoidance Area C. CTV30 D. PTV30 (CTV30 + 2mm) E. PTV37.5 (GTV mm) F. Uniform PTV30 (PTV30 PTV37.5) G. Anterior Avoidance Structure H. Central Target I. 2 mm Skin 29

30 Structures HA-WBRT SIB Structures Optimization Contours A. R+L Hippocampus B. 5 mm Hippocampus Avoidance Area C. CTV30 D. PTV30 (CTV30 + 2mm) E. PTV37.5 (PTV mm) F. Uniform PTV30 (PTV30 PTV37.5) G. Anterior Avoidance Structure H. Central Target I. 2 mm Skin 30

31 Structures HA-WBRT SIB Structures Optimization Contours A. R+L Hippocampus B. 5 mm Hippocampus Avoidance Area C. CTV30 D. PTV30 (CTV30 + 2mm) E. PTV37.5 (GTV mm) F. Uniform PTV30 (PTV30 PTV37.5) G. Anterior Avoidance Structure H. Central Target I. 2 mm Skin PTV37.5 GTV

32 Structures HA-WBRT SIB Structures Optimization Contours A. R+L Hippocampus B. 5 mm Hippocampus Avoidance Area C. CTV30 D. PTV30 (CTV30 + 2mm) E. PTV37.5 (GTV mm) F. Uniform PTV30 (PTV30 PTV37.5) G. Anterior Avoidance Structure H. Central Target I. 2 mm Skin 32

33 Structures HA-WBRT SIB Structures Optimization Contours A. R+L Hippocampus B. 5 mm Hippocampus Avoidance Area C. CTV30 D. PTV30 (CTV30 + 2mm) E. PTV37.5 (GTV mm) F. Uniform PTV30 (PTV30 PTV37.5) G. Anterior Avoidance Structure H. Central Target I. 2 mm Skin 33

34 Structures HA-WBRT SIB Structures Optimization Contours A. R+L Hippocampus B. 5 mm Hippocampus Avoidance Area C. CTV30 D. PTV30 (CTV30 + 2mm) E. PTV37.5 (GTV mm) F. Uniform PTV30 (PTV30 PTV37.5) G. Anterior Avoidance Structure H. Central Target I. 2 mm Skin 34

35 Structures HA-WBRT SIB Structures Optimization Contours A. R+L Hippocampus B. 5 mm Hippocampus Avoidance Area C. CTV30 D. PTV30 (CTV30 + 2mm) E. PTV37.5 (GTV mm) F. Uniform PTV30 (PTV30 PTV37.5) G. Anterior Avoidance Structure H. Central Target I. 2 mm Skin 35

36 RTOG 0933 Phase ll trial: HA-WBRT (30 Gy, NO SIB) & Critical Structure Constraints PTV Acceptable D2% > 37.5 Gy (125%) Unacceptable D2% > 40 Gy (133%) 36

37 Organs at Risk Within PTV30 Brainstem Chiasm Optic nerves (near chiasm) * Necessity in optimization may be optional depending on 37.5 Gy SIB target location or previous irradiation Outside PTV30 Cochleas (study) Lens (study) Eyes Lacrimal Oral cavity 37

38 Treatment Plan Parameters MCO-IMRT: step-and-shoot (SMLC) STD-VMAT + MCO-VMAT VMAT: Dual coplanar arcs (clockwise/counterclockwise of 358, between 181 and 179 ) 3 rd non-coplanar arc 1 to 179 with a 270 couch kick control point every 2 6X (160 MLC) dose grid resolution: cm 3 38

39 VMAT Optimization Course arc segmentation 24 Pre-op: machine constraints are validated (leaf speed, dose, delivery time) MPO to all control points (all machine and user constraints) Fluence map conversion Control points added for final gantry spacing Jaw and passive leaves are positioned 2-4 Control points (user determined) Sorting algorithm to filter out smallest points Convolution dose calculation 39

40 VMAT Optimization STD-VMAT: DMPO (direct machine parameter optimization) algorithm begins coarse arc segmentation 24 deg Converts 2-4 degree control points with machine parameter motion constraints MCO-VMAT: Pareto surface to explore tradeoff objectives to create a navigational state using Pareto plans Pareto database generation 4N 3 unique algorithms: Convex Pareto surface approximation, fluence map optimization (discrete Pareto), DMPO VMAT optimization (see above) Single-value pencil beam kernal (preseg) Intermediate dose (minimize discrepancies in transition) Final dose (collapsed cone algorithm) 40

41 VMAT Dual Arc Feature Same Collimation for 2 Arcs: One set of fluence profiles are optimized while more information from the fluence maps can be kept during leaf sequencing process Potential Advantage: Sequencing stage: 5 control points are created for each initial angle (instead of 2-4) retaining more info from fluence map. Dual Arcs: one arc will focus on the left side of the target and one on the right side, reducing the leaf openings over the OAR (and lowering the dose). OAR OAR 41

42 Dual Arc Feature Same gantry angle at control point Arc 1 Arc 2 42

43 Dual Arc Feature Same gantry angle at control point Arc 1 Arc 2 43

44 44 Cumulative Averages and Standard Deviations

45 Hippocampus Dmean Comparison Comparison of hippocampus Dmean among the three treatment modalities. Patients 1 to 8 were treated with SIB, 9 and 10 with whole brain only. 45

46 Hippocampus Dmean and PTV30 V30 Improved hippocampus mean Significantly improved PTV30 V30(%) 46

47 Modality Isodose Comparisons Patient 3: Most improvement in PTV30 coverage to whole brain PTV 47

48 48 Patient 6 (12 lesions): DVH Comparison per Modality

49 Patient 6: D95 Comparison for 12 Lesions PTV37.5 D95 is compared among the three modalities for each metastatic lesion for patient 6. 49

50 Patient 6: D99 Comparison for 12 Lesions GTV37.5 D99 is compared among the three modalities for each metastatic lesion for patient 6. 50

51 For the students in the room: When Does the Treatment Planning Process Actually Begin? A. When the dosimetrist gets to work B. After morning coffee C. Did it ever end? D. At the time of CT Simulation 51

52 For the students in the room: When Does the Treatment Planning Process Actually Begin? A. When the dosimetrist gets to work B. After morning coffee C. Did it ever end? D. At the time of CT Simulation 52

53 Standard S-Frame, B HH w/ Neutral Position Hippocampus in same axial plane of optics (eye, lens, nerve, chiasm) Less opportunity for coplanar arcs for tight conformal dose Limitations on OAR dose limits/hippo sparing while maintaining coverage Usually less homogeneity in dose 53

54 Standard S-Frame, B HH w/ Neutral Position Optics + Hippocampus: Same Axial Plane Sagittal View 54

55 Standard S-Frame, B HH w/ Chin Tuck Recommendation: To improve anterior target opportunity near hippocampus w/ chin tuck position 55

56 Improved Isodose Distribution Neutral (CTV D %) Chin Tuck (CTV D %) 56

57 Straight Head Position Better Advantage for Vertex Arc for Difficult Central Target area 4.6 cm vs. 5 cm, avoid tilts 57

58 MCO Tradeoff objectives Uniform Dose (Targets) :The objective is met when the entire ROI volume receives a dose equal to the specified dose level Max Dose (OARs) : Objective is met when only the specified % volume of the ROI receives more than the specified Max Dose Equivalent Uniform Dose uniform dose that yields the same radiobiological effect as non-uniform (same fx #) Max EUD (OARs): A>1 Higher doses are given higher weight (hot spots influence EUD). A=1: Corresponds to mean dose AAPM report no

59 Tradeoff objectives to Create Pareto Plans 14 objectives 28 Recommend pareto plans N+1 or 14+1 minimum 59

60 Constraints to Create Pareto Plans Stricter constraints will lead toward a more ideal Pareto surface (particularly the hippocampus) However. Infeasible solutions will require loosened constraint parameters for both targets and OARs These plans usually require more relaxed constraints compared to other plans (tip: 0% 1% on max dose levels) 60

61 61 HA-WBRT after Pareto generation not done yet!

62 62 Lock Target and OAR Navigation Sliders

63 63 Hippocampus OAR slider

64 PTV30 Uniformity Slider (Hippocampus locked) Find balance with All OARs 64

65 First 100 iterations - - CC Final Dose w/ Machine Parameters PTV30 needs improvement Hippocampus not matching Pareto surface 65

66 Next 100 iterations CC Final Dose getting better Improved isodoses Target improved but not matched to PS Hippocampus better (though Dmax and V10 has more potential) 66

67 Options to further Optimize Option #1 Continue with a MCO solution Advantage Adjust navigational state (quick solution) and use more iterations ROI selections emphasize PS match Disadvantage Re-run Pareto plans with adjusted Objectives and Constraints (time consuming) Degeneration of PB model to final dose CC, especially low dose areas Option #2 Combine MCO with Standard Optimization (Hybrid) Advantage Do not need to re-run Pareto plans (time saving) or infeasibilities Additional hippocampus sparing (V10, Dmax) Uses benefits of both features Disadvantage Usually adds more MUs (I ve seen some improvement using stricter iterations to conversion or implementing Intermediate dose) 67

68 Standard Optimization using Mimic Dose (MCO) Mimic dose translate MCO quality parameters by reproducing dose/dvh curves while having the ability to configure dose reference function and add new functions 68

69 MCO-STD vs. MCO (Improvement w/ Hybrid Optimization) MCO-STD MCO Similar CTV coverage Lower exit into Ant Avoidance Improved V10 and Max dose Lower Dmax 9.07 Gy (MCO-STD) vs Gy (MCO) 69

70 MCO-STD vs. MCO (Improvement w/ Hybrid Optimization) MCO-STD 996 MU MCO 949 MU 70

71 Challenging and Unusual Scenarios: Case 1 MCO-VMAT Previous RT (1 year prior): Left Frontal lesion 3DCRT (36 Gy in 12 fxs) 13 metastatic lesions and dura spread 37.5 Gy SIB, whole brain 30 Gy Limit cavity/prior Rx to 60 Gy overlap, 17 Gy HA-WBRT Prior 36 Gy (registered) HA-WBRT SIB 30/37.5 Gy Composite 71

72 Challenging and Unusual Scenarios: Case 1 Prior 36 Gy (registered) HA-WBRT SIB 30/37.5 Gy Composite MCO-VMAT w/ STD OPT -limit hippocampus, ant avoid -ensure dura target coverage -help limit prior cavity HA-WBRT SIB 30/37.5 Gy Composite ~1100 MU (increase) 72

73 Challenging and Unusual Scenarios: Case 2 MCO-VMAT MCO-VMAT HA-WBRT SIB 30/37.5 Gy dose paint, 15 fxs 11 metastatic lesion (1 in brainstem), large volume met 73

74 Challenging and Unusual Scenarios: Case 3 MCO-VMAT 3DCRT 6 months prior Goal: limit overlap ~55 Gy L parietal 39 Gy, 13 fxs MCO-VMAT 30/37.5 Gy Composite 74

75 Conclusion MCO-VMAT improved dosimetry parameters for HA-WBRT SIB compared to STD-VMAT and MCO-IMRT MCO performance and efficiency may encourage clinics to adapt HA-WBRT (Slade et al.) or further complex scenarios (previous RT) Hybrid MCO-STD may improve dosimetric parameters (at cost of higher MU) Dosimetry is sensitive to head position 75

76 Thank you for your attention!!! Thank you to my MGH colleagues Judy Adams CMD Dr. Melin Khandekar MD PhD Brian Napolitano CMD Dr. Helen Shih MD Dr. Yi Wang PhD Dr. Henning Willers MD 76

77 77 Questions???