Implementation of Hybrid IMRT Breast Planning

Transcription

1 Implementation of Hybrid IMRT Breast Planning Dianne Kearns, Richard Ferguson & Suzanne Smith Dosimetrist Manager Department of Clinical Physics and Bio-Engineering, NHS Greater Glasgow & Clyde

2 Summary Current Breast Techniques Import High Trial Overview Planning Technique Development Case study

3 Current Techniques Full CT planning utilising AAA & forward planned IMRT- available for all patients since 2007 Virtual simulation field placement Isocentric planning Two field breast are symmetric with posterior match plane. There is no superior match plane. START guidelines 40Gy in 15 # Working to ICRU dose constraints 6 or 10MV

4 Current Techniques Three or four field mono-isocentric. Isocentre position is located at sup edge of tangent fields. Tangent sup edge matched to inf edge of S clav / Posterior boost 50Gy in 25 # moving towards 40Gy in 15# Working to 112% dose maximum for the tangential fields 6 or 10MV Max s clav dose of 118% and mid plane dose 90% achieved by beam weight manipulation

5 Current Techniques Full CT with target delineation Multiple options for optimum planning Photon tangentials Mono-isocentric Mono-isocentric with matched electron Electron to whole breast with possibility of matched s clav FAST Forward Trial (20 patients recruited to date) DCIS Trial (3 patients recruited to date)

6 IMPORT High Trial Intensity Modulated and Partial Organ Radiotherapy Dose escalated intensity modulated radiotherapy trial for early breast cancer IMPORT HIGH requires a concomitant 3 level dose distribution to the whole breast with either forward or inverse-planned IMRT. Control Test Arm 1 Test Arm 2 40Gy/15Fr 36Gy/15Fr 36Gy/15Fr Whole Breast 56Gy/23Fr Sequential dose escalation 40Gy/15Fr 48Gy/15Fr Concomitant dose escalation 40Gy/15Fr 53Gy/15Fr Concomitant dose escalation Partial Breast Tumour Bed

7 Technique Appraisal Forward Planned IMRT Time consuming and lacks conformality Inverse Planned IMRT Conformal but longest treatment delivery time Hybrid IMRT Conformal, lowest OAR doses, comparable delivery time with current techniques RapidArc Conformal, fast delivery, lung dose bathing

8 Delineation Ipsilateral & contra-lateral breasts are delineated by screening the breast tissue with pairs of tangential fields with a non-divergent back edge The plan is calculated and the 50% isodose line is converted into a structure The structure is cropped from the skin & lung Contra-lateral breast now delineated The ipsilateral breast volume is amended by the Practitioner to create the PTV WB

9 Delineation Practitioner delineates: Surgical Clips Tumour Bed Partial Breast Heart Ipsilateral Lung Contra-lateral Lung Dosimetrist creates: PTV WB -PTV PB PTV PB - PTV TB Used by DVO for optimisation 50% isodose

10 Delineation Practitioner delineates: Surgical Clips Tumour Bed Partial Breast Heart Ipsilateral Lung Contra-lateral Lung Dosimetrist creates: PTV WB -PTV PB PTV PB - PTV TB Used by DVO for optimisation PTV WB 50% PTV WB -PTV PB isodose

11 Delineation Practitioner delineates: Surgical Clips Tumour Bed Partial Breast Heart Ipsilateral Lung Contra-lateral Lung Dosimetrist creates: PTV WB -PTV PB PTV PB - PTV TB Used by DVO for optimisation PTV PB -PTV TB PTV TB

12 Planning Step One Tangential Fields (Test Arm 1 & 2) 2 Field Tangential 36Gy in 15# Forward planned IMRT used to conform to ICRU Conforming to Trial constraints Ipsilateral Lung <2.5cm in field Isocentre located at the centre of PTV TB where possible

13 Planning Step Two 3 dmlc IMRT Fields (Test Arm 1 & 2) Same Isocentre as tangential plan All fields are have equal gantry angle spacing Plan optimised using tangential plan as a base Utilising the base plan incorporates its distribution when inverse optimising

14 Optimiser Base dose plan

15 Trial Constraints

16 Planning Step Three Composite Plan Composite Final Plan 9 Fields in total 2 Tangential 2 fld in fld 3 dmlc IMRT 2 Iso_Images

17 95% Isodose PTV WB PTV PB PTV TB

18 Case Study Comparison of conventional photon plus electron boost plan with hybrid IMRT performed Left sided volume, 0.5cm from heart Volume of each PTV receiving 95% of prescribed dose Volume of OAR receiving trial dose constraint Technique PTV WB PTV PB PTV TB IL Lung (18Gy) Heart (13Gy) Standard Hybrid

19 Case Study Hybrid PTV TB Standard PTV PB

20 Case Study Lung Standard Heart Hybrid

21 Conclusion New hybrid IMRT technique introduced Three patients treated to date Two test arm two patients (& one ready for treatment) One conventional arm patient Significant improvement in PTV TB conformality Minor differences in OAR doses Class planning solution developed requiring average of 3 iterations Planning time is significantly reduced when compared with forward planned IMRT for test arm patients Reduction in treatment slots